Fiddler Crabs of the World: Ocypididae: Genus Uca

Fiddler Crabs of the World: Ocypididae: Genus Uca

Jocelyn Crane
Copyright Date: 1975
Pages: 765
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  • Book Info
    Fiddler Crabs of the World: Ocypididae: Genus Uca
    Book Description:

    Jocelyn Crane presents a survey of the members of the genusUca, with special reference to their morphology, social behavior, and evolution. Her account is firmly based on numerous field studies along the world's warmer shores and on comparative work in laboratories and museums.

    Originally published in 1975.

    ThePrinceton Legacy Libraryuses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

    eISBN: 978-1-4008-6793-6
    Subjects: Zoology

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Preface
    (pp. v-vi)
  3. Table of Contents
    (pp. vii-x)
  4. List of Figures
    (pp. xi-xiv)
  5. List of Maps
    (pp. xv-xvi)
  6. List of Plates
    (pp. xvii-xx)
  7. Acknowledgments
    (pp. xxi-2)
  8. General Introduction
    (pp. 3-6)

    Any human being who finds a suitable piece of warm shore, sits down, keeps quiet, and watches fiddler crabs must be impressed. Each adult male has one of his claws longer than his body and, when conditions are right, he wields it vigorously in threat and courtship. Sometimes he links claws with another male, in either a strenuous fight or ceremonial encounter.

    Even when he is not socially occupied a fiddler is active, providing only that the tide is out, the day warm, and, preferably, the sun shining. He feeds by straining bits of organic matter from the surface of...

  9. Part One. Systematic Section
    • Introduction
      (pp. 9-13)

      The first paragraphs below concern procedures used in this section. These comments are followed by an annotated list of the topics that will be covered. The section ends with comments on style.

      Every taxonomist who revises a group of animals must ask questions that do not have definite answers. Often the basic query is merely whether to use a particular category above or below the level of a species. For instance, will the division of a complex genus, such asUca,into subgenera be helpful to workers or an inefficient complication?

      A more important example concerns the designation of subspecies....

      (pp. 14-14)

      Brachygnathous crabs with orbits occupying almost entire anterior border of carapace, the front being usually narrow and somewhat deflexed; outer orbital margins often incomplete; eyestalks slender. Palp of third (external) maxilliped articulating at or near antero-external angle of merus; exognath usually slender and often more or less concealed; the maxilliped usually completely covers the large buccal cavity. One cheliped in male often enlarged. Male abdomen narrow.

      Amphibious, burrowing crabs confined largely to the tropics of the world, where they occupy a variety of habitats on shore and in estuaries. Most are gregarious and some genera have complex patterns of social...

      (pp. 14-14)

      Carapace deep, roughly quadrilateral but sometimes almost pentagonal, the regions usually indistinct; front narrow, usually a lobe curved slightly downward between the eyestalks; flagellum of antenna small, folding obliquely or almost vertically; interantennular septum broad; external maxillipeds completely enclosing buccal cavity; exognath always at least partly visible, its flagellum present or absent. Afferent branchial opening, thickly fringed with setae, between bases of 2nd and 3rd pairs of ambulatories. Female gonopore on 3rd segment of sternum.

      One cheliped enlarged in males, often remarkably; chelipeds in females equal or somewhat unequal. Merus of chelipeds and ambulatories always distinctly three-sided at least proximally,...

    • GENUS UCA LEACH, 1814
      (pp. 15-20)

      Brachygnathous crabs differing from all other genera in the enormous size of the male’s major cheliped, the minor cheliped and both in the female being minute.Ucadiffers additionally fromOcypode,the other genus in the subfamily, in having smaller eyes on longer stalks, longer antennae, and shorter ambulatories, while it lacks a stridulating ridge on the ischium of the major cheliped.

      With the characteristics of the subfamily.

      Carapace.Body deep. Carapace subquadrilateral to almost hexagonal, slightly wider than long, never flattened. Front deflexed, moderately to very narrow (about 2.5 to 20 times in breadth of carapace), spatu-Iate to widely...

    • I. Deltuca subgen. nov.
      • [I Introduction]
        (pp. 21-24)

        Ucawith front narrow, antero-lateral margins short to absent, eyestalks slender, postero-lateral striae absent at least in males. Major manus outside rough with tubercles that are usually largest near pollex base; oblique ridge on palm never continued upward around carpal cavity; longitudinal grooves along outside of both pollex and major dactyl. Postero-dorsal surface of ambulatory meri with simple tubercles, not with tuberculate striae vertically arranged. Gill on 3rd maxilliped small, without books. Females with rare exceptions have a pair of enlarged teeth in gape of at least one chela.

        Carapace.Front narrow, narrowest between eyestalk bases, its minimum breadth subequal...

        (pp. 25-28)

        A northern and a southern form are here viewed as subspecies ofUca acuta;one ranges along the coast of China, while the other is known from Singapore and Borneo. Both are mud-livers found near river mouths on banks and flats. Males of some populations in both subspecies have the major manus red, while the carapace in both sexes of the southern form is strikingly reticulated with yellow and black. This form,a. rhizophorae,is also distinguished by having the simplest waving display known in the genus. The entire performance consists only of fast, slight lifts of the flexed cheliped,...

      • 2. UCA (DELTUCA) [ACUTA] ROSEA (TWEEDIE, 1937)
        (pp. 29-31)

        On the western coast of Malaya this pinkish, fragilelooking fiddler lives in sheltered mud close to mangroves. Its populations occur both near stream mouths and, in delta country, in drainage ditches; the water is probably almost always of low salinity, although subject to the usual wide range. At Penang a vigorous population occurred in close proximity to similarly thriving groups offorcipataandtriangularis.Its waving display, poorly known, is wholly vertical and includes jerks.

        Ranging around most of the Bay of Bengal, this species is undoubtedly the western form ofacuta.In the older collections it was identified variously...

        (pp. 32-38)

        From the point of view of a waiting human being, this bluish fiddler seems especially likely to sit indefinitely on the mud without giving any information whatever on the form of his waving display. It is true that when tides are low in the morning a flourishing population may display with energy. Yet even at high intensity these waves look like mere waggings of the claw, intermittent and unimpressive in comparison with the tireless, spacious circlings oflacteanearby.

        U. dussumieriis probably the most abundant and certainly the most widely ranging species of its subgenus, being found near mangroves...

        (pp. 39-43)

        In the southern Philippinesdemanistands out among otherDeltucaboth in color, which is largely a dark red, and in waving display. For the first time in this arrangement of the species ofUca,the pattern includes a raising of the body high on the stretched legs—a character otherwise found only in subgenera showing more advanced social behavior. In another indication of social development,demanioften waves without interruption in continuous series for minutes at a time. This characteristic I have found in no otherDeltuca.

        In Zamboangademaniwas common rather high up on open banks of...

        (pp. 44-47)

        Uca arcuatastands out among otherDeltucain its northern distribution, which lies quite clearly in a band that includes both mainland and islands from Hong Kong to Japan.

        Toward its northern limit the crab hibernates. In northwest Taiwan I found its breeding season well under way in late April, while a month later in south Japan waving had not begun. This breeding pattern, showing local adaptations to temperature, is also characteristic of temperate zone fiddlers in the western Atlantic. The rhythm inarcuataseems to be partly endogenous, judging by the behavior of specimens flown to the crabberies in...

        (pp. 48-51)

        A crab characteristic of the backwaters of river deltas,forcipataextends upstream a little beyond the limits of the mangroves.

        In living crabs the large, spherical eyes and their stalks are sometimes bright scarlet. This characteristic, along with other markings of red or purple, is helpful in distinguishingforcipatafromdussumieri spinata,its frequent sympatric associate among the mangroves near shore; ondussumierired and purplish shades are absent while blue is prevalent. An additional difference among females isforcipata’s habit of building chimneys around their burrows.

        Prompt identification of living crabs is necessary, since so much remains to be...

        (pp. 52-57)

        Wherever it occurs, this species is the most colorful crab in sight. It is usually marked conspicuously with scarlet and often with white and blue as well, the combination being set off by a black carapace.

        Incoarctata,a consuperspecific offorcipata,the chela is equipped only on the dactyl with a hook-like projection, the upper half of the forceps-like specialization found in complete form inforcipata.In the eastern subspecies ofcoarctatathe dactyl’s projection is especially strong, with the pollex end always clearly slender. This combination distinguishes the crab at once fromforcipata,an occasional inhabitant of the...

        (pp. 58-61)

        This large blue fiddler is almost certainly the onlyDeltucathat reaches Africa. It lives characteristically in mangroves along streams well back from the shore, as do all the other members of its superspecies. Inurvillei,however, its niche lies close to low-tide levels.

        In Natal and in Cape Provinceurvilleiis exposed seasonally to chilly weather, although not to the extent of that tolerated, through hibernation, by its northern consuperspecific,arcuata,in Japan. Since both species, without apparent morphological differences, occur also in much warmer climates, comparative study of their range of physiological adaptations to temperature would be of...

    • II. Australuca subgen. nov.
      • [II. Introduction]
        (pp. 62-63)

        Ucawith front narrow, differing most clearly from the related subgenusDeltucaas follows. One posterolateral stria always represented at least by a protuberance, instead of occurring only rarely in males and occasionally in females; a ridge, often with tubercles or granules, always, not sometimes, present on orbit’s floor. Major cheliped with merus having an antero-dorsal crest, but no distal enlarged tooth; manus outside moderately to very smooth, never roughened by large, well-separated tubercles; its largest tubercles near dorsal margin, never around pollex base; pollex without a long lateral furrow and, in distal half, with a large, triangular projection or...

        (pp. 64-69)

        Four closely related forms ofUca,described in the past under various specific names, are here considered as subspecies of the single species,bellator.Only one of them occurs outside Australia, where it is probably restricted to a triangle with angles formed by the Philippines, Borneo, and western New Guinea. The several forms show very minor morphological differences, principally in the armature of the major cheliped and lower orbit. Unlikevocansandlactea,the subspecies are not known to intermingle. Material, however, remains scanty.

        In the form of its waving display,bellatorshows clearly one aspect of the intermediate character...

        (pp. 70-71)

        This AustralianUcais perhaps the most unmistakable of all fiddler crabs, whether watched in action on a mudbank or examined briefly with a lens. During its waving display the small crab shakes all over as the large claw waggles up and down. Only the neotropicalsaltitantagives a similar impression. It seems fitting to give the proposed new species a name signifying “little earthquake.”

        In both sexes the teeth of the small cheliped, always large and serrate, are characteristic, as described below. Unfortunately we have no clue to the uses of this formidable armature, whether in feeding, in stridulation,...

        (pp. 72-74)

        This species, for which the nameUca politais proposed, shows the active, semi-unflexed wave characteristic ofAustraluca.It has, however, none of the speed ofseismella,or the more complete lateralstraight wave-form attained by somebellator.The largest species in the subgenus,politais conspicuous among all Australian fiddlers for the rose pink that often suffuses the claw.

        Except forseismella,it is the onlyUcafound on both the eastern and western coasts of Australia that does not appear to warrant the erection of subspecies.

        Australucawith outer carpus and manus notably smooth even for the subgenus; pollex...

    • III. Thalassuca subgen. nov.
      • [III. Introduction]
        (pp. 75-76)

        Ucawith front narrow, antero-lateral margins short to absent; eyestalks slender; postero-lateral striae absent; no tubercles or other irregularities on orbital floor; suborbital margin erect, not rolled out, its crenellations always distinct and usually strong. Major manus outside rough with moderate to large tubercles; oblique ridge on palm never continued upward around carpal cavity; a long, lateral furrow sometimes present outside pollex, never on major dactyl. Serrations of minor cheliped absent or few and weak. Gonopod always with at least one flange well developed, without a projecting, distal tube; entire terminal portion often twisted. Gill on 3rd maxilliped with up...

        (pp. 77-82)

        A striking red and blue species,tetragononis the most marine of all the genus and has the widest range. From Africa to Tahiti, it often thrives on shores with no more protection than a barrier reef and never lives near muddy river mouths. Althoughchlorophthalmusshares a similar range, that species shows geographical distinctions and the subspecies occur in different biotopes.

        In contrast, the populations oftetragononshow no differences in the material at hand that encourage either the proposal of subspecies or the discernment of clines.

        The populations are locally uncommon, the ecological requirements being obviously more restricted...

        (pp. 83-84)

        This elusive species appears to be known from less than a dozen preserved specimens. I was unable to find it in northwest Taiwan at the type-locality in its only known habitat. According to Takahasi (1935), it lives on muddy shores near low tide level in the neighborhood of a river.

        The species obviously belongs withtetragononandvocansin the subgenusThalassuca;its differences from both, equally obviously, are of specific rank. It seems likely thatformosensisis the northern, allopatric representative oftetragonon,a species that has not been recorded in this latitude. Because of the scanty material, it...

        (pp. 85-95)

        This Indo-Pacific fiddler is undoubtedly one of the most abundant in the world. Because of its exposed habitat,vocansis also one of the easiest to find and observe. Populations thrive in the sandy mud along the edges of protected bays. Although the crabs are most numerous near river mouths, freely surging tides seem essential. This species lives closer to lowtide levels than doeslactea,its usual associate, although the populations are often mixed in the middle levels.

        Throughout most of its wide rangevocanscan be recognized promptly by the yellow to orange red color on the lower manus...

      • [IV. Introduction]
        (pp. 96-97)

        Ucawith front moderately wide; antero-lateral margins always distinct, short to moderate, posteriorly rounded; no ridge, mound, or tubercles on orbital floor; suborbital margin with crenellations minute or absent except near outer angle. Major manus outside with very small, close-set tubercles except dorsally; dorsal margin externally with a beaded keel; a depression with definite edges outside pollex base; tuberculate predactyl ridges on palm strongly divergent; no long furrows on pollex or dactyl. Posterior merus of minor cheliped without tubercles in vertical rows. Gill on 3rd maxilliped large, with distinct books. Female never with an enlarged tooth in cheliped gape.


        (pp. 98-104)

        Uca chlorophthalmusis one of those species, prevalent in the Indo-Pacific, that combine vivid color with persistent lethargy. Nevertheless its morphology and display both show characteristics intermediate between those of the Indo-Pacific narrow-fronts and the broad-fronts of the world.

        In both males and females the colors are unfading scarlet red, blue, blue green, and white, usually in a striking mixture, although sometimes the entire crab is scarlet. An individual, either male or female, often lives in the same burrow for days or weeks. The waving periods seem regularly to be confined to two or three days of spring tides, with...

        (pp. 105-108)

        Uca inversa,likechlorophthalmus,shows characteristics of both morphology and waving display that are intermediate between those of Indo-Pacific narrow-fronts and the remaining subgenera ofUca.

        In contrast to the situation inchlorophthalmus,individualinversadevote a relatively large amount of time to waving display, while strictly agonistic behavior also appears more prevalent. Unfortunately the social behavior of the African form is known only in outline, while the eastern subspecies has been observed in life during part of a single low tide, and then before it was recognized. The use of the large tooth at the tip of the major...

    • V. Boboruca subgen. nov.
      • [V. Introduction]
        (pp. 109-111)

        LargeUcawith front of intermediate width; pile prevalent at least on ambulatories, often on carapace; 3rd and 4th ambulatory meri wide; major manus appearing smooth, never rough with large tubercles; fingers usually long and slender, never broad and flat; eyes never with styles; gonopods with subequal flanges, large thumb, little torsion; female gonopore without marginal tubercle.

        With the characteristics of the genus (p. 15).

        Carapace.Front barely of moderate width, narrowest below eyestalk bases, its breadth between them about twice or less width of erected eyestalk at its base, in front of which the halves of the distal margin...

        (pp. 112-115)

        As mentioned above in the description of the subgenusBoboruca,certain characteristics ofUca thayerisuggest a closer kinship with Indo-Pacific subgenera than with the American groups. Most of them are concerned with social behavior, the unusual aspects being the infrequency ofthayeri’s waving display; the hours of waving, with their concentration near sunrise and sunset; the almost vertical wave, without special behavior during high intensity courtship; the low general level of social activity; and the female's habit of constructing chimneys. In contrast, the male's attraction of the female to his own burrow, as well as morphological details such as...

    • VI. Afruca subgen. nov.
      • [VI. Introduction]
        (pp. 116-117)

        Front moderate tending toward narrow. Carapace and pterygostomian region covered with large, wellseparated tubercles; dorso-lateral margins extending back almost to posterior carapace border; a large, sharp tubercle on orbital floor near inner corner; spoon-tipped setae on 2nd maxilliped with a pointed process at base of each spoon. Major cheliped: manus rough; fingers flattened, the pollex broader.

        With the characteristics of the genus (p. 15).

        Carapace.Front barely of moderate width, narrowest below eyestalk bases, its breadth between them about twice basal breadth of erected eyestalk, each half of distal margin obliquely converging to the usual slightly excavate tip. Orbits straight...

      • 18. UCA (AFRUCA) TANGERI (EYDOUX, 1835)
        (pp. 118-124)

        Uca tangeriholds a number of distinctions that are rare or unique among fiddlers. It is the only member of the genus found in Europe and probably the only one that lives in west Africa. Its range extends farther from north to south—a distance, measured around the bulge of the continent, of more than 9,500 kilometers—than that of any otherUca.In spite of the lack of competition from other fiddlers, it maintains a complex waving display unchanged from one end of this vast strip to the other; whatever the function of waving patterns in helping among sympatric...

    • VII. Subgenus Uca Leach (sensu Bott, 1954)
      • [VII. Introduction]
        (pp. 125-127)

        Ucaof moderate to large size. Front extremely narrow, its distal end abruptly somewhat wider; eyestalks strikingly slender; eye on major side sometimes with a terminal style, unique in the genus; lower edge of eyebrow absent; no elevation on orbital floor. Major cheliped with oblique ridge sometimes continued up around carpal cavity ; no beaded ridge along upper edge of cavity, which always continues unimpeded toward dactyl base; no long furrow on pollex or dactyl; pollex with ventral carina. Spoon-shaped tips on setae of 2nd maxilliped each with a proximal projection. Gill on 3rd maxilliped large, with books.

        With the...

      • 19. UCA (UCA) PRINCEPS (SMITH, 1870)
        (pp. 128-132)

        One of the most interesting observations that has been made on the biology ofUca princepsis the fact that waving display in one population is different in details of posture and in timing from that of several others. Comparison of specimens from Panama City, Panama, and from Puerto Bolivar, Ecuador, the two localities where I have observed displaying males, shows no morphological indication whatever that two subspecies are concerned. Several differences between the populations, aside from their wave forms, were noticed. First, the displaying crabs seen in Panama, although of mature proportions, were much smaller than those in Ecuador;...

      • 20. UCA (UCA) [MAJOR] HETEROPLEURA (SMITH, 1870)
        (pp. 133-135)

        Among the six members of the subgenus,heteropleurais the smallest, the most vigorous in waving display, and the most abundant. The bright orange on its lower manus and pollex, combined with its general appearance, flattened claw, size, and habitat, all make this species a close parallel to one of the Indo-Pacific narrow-fronts,(Thalassuca) vocans.The displays of the two forms, however, are wholly unlike, each showing characteristics typical of its own part of the world (p. 533).

        Members of the narrow-fronted subgenusUcawith fingers of major cheliped moderately slender and the pollex not pitted. Short ocular style occasional...

      • 21. UCA (UCA) [MAJOR] MAJOR (HERBST, 1782)
        (pp. 136-139)

        Ucamajor is a moderately large fiddler that seems to be uncommon. Only scattered individuals have been observed and collected from single localities, and apparently no large population of the species has ever been reported.

        Its closest relations appear to beheteropleuraandstyliferain the eastern Pacific. The problem of the contrasting gonopods in these species is considered on p. 127.

        The species for many years was known by the name of its synonym,heterochelos.

        Large, narrow-frontedUcawith fingers of major chela tapering, not broad and flat and not touching except distally. Differs fromU. heteropleuramost distinctly...

        (pp. 140-142)

        When in full display color a maleUca styliferais one of the most striking fiddlers in the world, the shiny white of his carapace being set off by an orange and yellow cheliped and bright purple legs. The yellow phase that precedes the white seems to human eyes no less notable. This large species, although uncommon, would be a convenient subject for experimental work on color changes and their relation, if any, to social behavior.

        Comments on styles will be found on p. 455.

        Uca styliferaandheteropleuraappear to be so closely related and are so closely sympatric...

      • 23. UCA (UCA) MARACOANI (LATREILLE, 1802-1803)
        (pp. 143-149)

        Uca maracoaniand a related species,ornata,are both notable for large size and a heavy claw with broad, flat fingers. Their displays are equally unusual. At high intensity the great claw is lifted above the body and balanced high overhead, the divergent fingers pointing toward the sky; then, while the whole cumbersome appendage revolves, the chela describes wide circles for long seconds at a time.

        It is interesting that two other, less specialized members of the subgenus,princepsandstylifera,in their high intensity display closely resemble the low intensity simplicity of the more specializedornataandmaracoani.


      • 24. UCA (UCA) ORNATA (SMITH, 1870)
        (pp. 150-153)

        Because of the broad fingers of its claw,Uca ornataprobably attains a greater weight than any other fiddler, although in dimensions it resembles its close relation,maracoani insignis,and is surpassed by(Afruca) tangeri.

        Both its habitat and the form of its display are probably adaptations connected with the lopsided distribution of its weight. When mature it occurs, at least in Panama when breeding, on the inshore edges of mudflats which are so moist that at most low tides the surface remains semi-liquid ooze. From this substrate the crabs may derive some support during their vigorous display. The situation...

    • VIII. Subgenus Minuca Bott, 1954
      • [VIII. Introduction]
        (pp. 154-157)

        Very small to largeUcawith front wide to very wide; except inpygmaeaandpanamensisanterolateral margins long and curving posteriorly, not sharply angled. Eyestalks short, their diameter large, almost filling orbits; suborbital crenellations small, often obscured by pile except near outer angle. No special armature on lower proximal palm and on anterior surface of carpus of 1st major ambulatory. Major manus with tubercles on upper half moderate, never very small; except inbrevifronscarpal cavity with beaded edge on upper margin, the cavity never extending distally. Small cheliped always with gape narrow, minutely serrate. Gonopod with flanges well...

        (pp. 158-160)

        Uca panamensisis the only fiddler adapted by both morphology and behavior to a stony habitat. It occurs only at the ends of beaches, where sand so often gives way to rocky headlands. The fiddler depends on stones and small rocks for protection, dodging around and beneath them, or freezing motionless in their shelter for minutes at a time. Its variable colors, ranging widely from light to dark, are always in general accord with the local substrate. The carapace is unusually flat for aUca,in apparent adaptation to sheltering under stones. Burrows, insofar as they have been sampled, are...

      • 26. UCA (MINUCA) PYGMAEA CRANE, 1941
        (pp. 161-162)

        A very small species with paedomorphic characteristics,Uca pygmaeais known from few specimens and has not been observed alive before capture.

        Front wide; orbits extremely oblique. Major pollex with a deep, narrowly triangular furrow supraventrally at its base; palm without oblique, tuberculate ridge, the area being granulate; manus greatly tumid; no backwardly directed heel. Gonopod with anterior flange projecting clearly beyond posterior flange; inner process moderately thick and broad.

        With the characteristics of the subgenusMinuca(p. 154).

        Carapace.Front only moderately wide in the subgenus, contained about 4 times in width of carapace between antero-lateral angles, which are...

      • 27. UCA (MINUCA) VOCATOR (HERBST, 1804)
        (pp. 163-167)

        LikeUca thayeriin the subgenusBoborucaandmaracoaniinUca,the two forms ofvocatorare divided by the Isthmus of Panama and yet are so similar that there seems to be no justification for giving them the rank of separate species.

        The fragility of the characteristic pile on the carapace has led to confusions of identification on both coasts. As in (Amphiuca)chlorophthalmus,variations in the form of the gonopod are prevalent, particularly in the Pacific. Since differences occur, as in chlorophthalmus, even within the same populations, further allopatric subdivisions are not indicated, at least on the basis...

        (pp. 168-172)

        Until its recent description by Holthuis, specimens of this widespread and very common species,Uca burgersi,were usually identified asU. mordax.Although minor morphological differences and distinct ecological preferences were sometimes apparent, the characteristics were all so variable that there was overlap in at least parts of the ranges, and no division into two species seemed practical. The difficulties extended then, and still do, even to their waving displays, which in the details so far known are indistinguishable; even the morphology of the gonopods is such that the two forms cannot be decisively identified by that means; their geographical...

      • 29. UCA (MINUCA) [MINAX] MORDAX (SMITH, 1870)
        (pp. 173-175)

        Although large populations ofUca mordaxapparently live only far upstream in tropical rivers, a few individuals sometimes mingle with or adjoin populations ofburgersiandrapaxin lagoons and estuaries close to the open sea.

        The species has the broadest front in the entire genus, a fact which is a reminder that we still do not have any idea of the adaptive value of wide fronts, since their increase, particularly inMinuca,is necessarily at the expense of the length of the eyestalks (p. 452).

        The puzzling relationship ofmordaxtoburgersiis reviewed as a whole on p....

      • 30. UCA (MINUCA) [MINAX] MINAX (LE CONTE, 1855)
        (pp. 176-179)

        This large fiddler,Uca minax,is more completely confined to the temperate zone than any other member of the genus, since even the ranges ofpugnax, pugilator,andarcuataextend into the subtropics of Florida and China. For this and other reasonsminaxwould repay more special study than it has yet received. For example, the crabs seem to be as well adapted to fresh water as their close allopatric relations,mordax,in the rivers of the tropical Atlantic mainland, and brevifrons in the tropical Pacific; yet, of the three, only the integument ofbrevifronsis particularly fragile, while that...

        (pp. 180-182)

        Once in Costa Rica I saw a fiddler up a tree. She was sitting at eye level on a branch, her coral red carapace set off by the glossy green of a jungle vine behind her. Her perch was surrounded by forest, no stream was close by, and the shore was at least a kilometer away. She was the only tree-climbingUcaI ever saw. The fact that the forest had been soaked the night before by the first heavy rains of the season helps explain the crab’s location, as does the preference ofUca brevifronsfor water apparently wholly fresh...

        (pp. 183-189)

        Uca galapagensishas long been better known under the early name ofmacrodactylus.As with a number of species in its subgenus, its morphological idiosyncrasies have led to cumulative confusions. On the one hand, its variability and changes during growth invited nomenclatural splitting. On the other, valid species distinctions, as well as bases for subspecies, appear minor and difficult to recognize without series of specimens which were usually unavailable to workers in the group; these conditions led to confusions with other species.

        U. galapagensisis morphologically so similar torapax,its close allopatric relation in the tropical Atlantic, that single...

        (pp. 190-199)

        A waving male Uca rapax stands out among other fiddlers on any shore in his range by the numerous small jerks dividing the raising of his large cheliped. Almost always they number at least 8; sometimes they reach more than 30. Nothing else about his appearance is striking. His carapace never changes to shining white; his major claw is never colorful, the lower manus achieving at most a rather dull orange; his size is small to medium; and the tempo of the display, especially at low intensities on chilly mornings, has a soporific effect on the watching ethologist. In fact...

        (pp. 200-205)

        A small fiddler with an often lethargic display,Ucapugnax is the most abundant of its genus on the eastern coast of the United States. From Cape Cod to northern Florida it often associates more or less closely with (Celuca)pugilator,althoughpugnaxoccurs typically on muddy substrates, whilepugilatorlives on sandier strips of shore. Throughout these latitudes waving members of the two species can be distinguished in the field, even at a considerable distance, by the slower, less frequent display of pugnax, the waving always showing distinct traces of jerks.

        The degree and directions of circularity in the waves...

      • 35. UCA (MINUCA) ZACAE CRANE, 1941
        (pp. 206-208)

        Uca zacaeat the moment appears to be a somewhat unimpressive member of its subgenus. The crabs are almost the smallest in the group, dark in color, with only a single jerk in their waving display, infrequent drumming, minimal combats, and a known range covering a short strip of coast Nevertheless a few populations observed briefly in life were all easily accessible, crowded, lively, and showing hints of aggressive behavior that nowadays would demand analysis. These fiddlers will certainly repay some concentrated attention.

        Front wide; orbits strongly but not extremely oblique, with antero-lateral margins short but definite. Outer major pollex...

        (pp. 209-210)

        A small crab with an almost cylindrical body,Uca subcylindricais a challenging species of which we know almost nothing. So far we have no information whatever on the living fiddler, and only a handful of preserved specimens, all from southern Texas and northern Mexico.

        In addition to an unusually rounded body, this fiddler has a gonopod of striking form. The proportions of the parts are so distorted from their customary arrangements that it is not at all certain that the species should be included in the subgenusMinuca.Once we have learned something of its display and other characteristics,...

    • IX. Celuca subgen. nov.
      • [IX. Introduction]
        (pp. 211-219)

        Very small to moderate-sizedUcawith front moderate to wide; anterolateral margins varying from short to long but always posteriorly angled, not curving. Carapace profile strongly arched (except ininaequalisand allies) and sometimes fully semi-cylindrical. Eyestalks of moderate length and diameter, not nearly filling orbits; suborbital marginal crenellations, although rarely absent, usually definite and often large throughout, never obscured by projecting setae. Special armature sometimes present on lower proximal palm and anterior surface of 1st major ambulatory; carpal cavity often with beaded ridge on upper margin; cavity sometimes extended distally; major pollex sometimes with ventral carina; tip of major...

        (pp. 220-222)

        Living close to fresh water,U. argillicolahas striking paedoraorphic characteristics of shape and armature along with a persistently pale color. On my second visit to the type locality in Pacific Costa Rica, it was clear that the nameargillicolais partially unsuitable, since the species is not confined to clay substrates.

        As yet we have learned nothing about its social behavior. Even the general waving pattern is unknown, in spite of observations which supplemented a week’s sporadic observation of field populations with two months’ close checking of a small group brought to the Trinidad crabberies. At the time of...

      • 38. UCA (CELUCA) PUGILATOR (BOSC, 1802)
        (pp. 223-228)

        Probably more biologists know the sand fiddler,U. pugilator,by name than any otherUcaexcept its familiar associate,pugnax.For many years the two species have provided much of the material for experimental work on crustacean hormones and biological rhythms. During the first half of this centurypugilatorwas already suspected of signaling to females by drumming on the ground, and throughout the 1960s the species was a chief subject of pioneer experiments on acoustical signaling in the genus. Recently we have learned that this species, as well as the eastern Atlantictangeri,both use a sun compass in...

        (pp. 229-231)

        This species, along with the west African tangeri, extends farther south than any other Atlantic members of the genus.U. uruguayensis,a distinct form known only from southern Brazil and Uruguay, belongs to a group of five allopatric forms and five other closely related species that occur in the tropics of both the Atlantic and Pacific shores of America.

        Some share similar structures, apparent acoustical equipment, on the lower part of the major palm and on die 1st ambulatory, and all have characteristic combat armature on the claw.

        Front moderately wide. 1st ambulatory in male on each side with a...

        (pp. 232-235)

        Although the form here designatedU. crenulata crenulatastill occurs in southern California on the Pacific coast of America, it has become scarce. Certainly it is the onlyUcanow found in the eastern Pacific north of the Mexican border. The few biological observations were made before the middle of this century (p. 233). We know nothing of the biology of the form here regarded as a subspecies,c. coloradensis,and restricted to the Gulf of California.

        Front moderately wide. Major cheliped with upper part of manus bent over moderately to sharply, its top more or less flattened, with a...

        (pp. 236-239)

        Two forms hitherto considered separate species,Uca speciosaandU. spinicarpa,are here classed as subspecies, since the chief specific characters have proved to be unreliable. Both are known principally from the subtropical and warm temperate shores of the United States of America, although one extends south to Yucatan. At least in Floridaspeciosauses sound production in nocturnal courtship, a behavior pattern that is proving to be common among species from higher latitudes (pp. 238, 501).

        Front broad; anterolateral margins straight, sharply angled posteriorly. Major cheliped with oblique, tuberculate ridge present on palm and continued strongly upward around carpal...

        (pp. 240-243)

        Among tropical Atlantic fiddlers, displaying males ofcumulantaandleptodactylaalone are known to build hoods. As in the other hood-building forms, only some members of a few known populations construct them.

        Within its range,Uca cumulantais always the smallest fiddler in a mixed population, the otherCeluca, leptodactyla,preferring sandier habitats. Found on muddy banks near low-tide levels,cumulantais usually recognizable at once in the field through the bright blue green carapaces of most displaying males.

        Crab size small, front moderately broad; anterolateral margins straight, sharply angled posteriorly. In male, no abdominal segments fused; 1st ambulatory with...

        (pp. 244-246)

        A very small, partly white fiddler,Uca batuentahas a waving display of special interest. The conspicuous drumming motions that end most individual waves rarely or never actually touch either the ground or the carapace. These vibrations should, it seems, be considered a ritualization of a common acoustic mechanism, the major-manus-drum. This component occurs in proven functional form in two other members of the same superspecies,speciosaandcumulanta,in both of which tape recordings have been secured.

        During each wave,batuentaholds its cheliped for an instant at the highest point attained, a habit that usually distinguishes it easily...

        (pp. 247-250)

        A strikingly small species,U. saltitantashows in several particulars the highest degree of development in its general group. This group comprises both the members of its tropical eastern Pacific alliance and of the superspeciescrenulata.The outstanding specializations ofsaltitantainclude its strongly semicylindrical carapace, which doubtless assists in moisture conservation during long periods of vigorous display on dark mudflats in blazing sunshine; a uniquely shaped pollex, yet to be observed during combat; the highest degree of display whitening; the fastest single waves in the group and among the fastest in the genus; and the greatest number of waves...

        (pp. 251-253)

        Small, waving fiddlers showing greenish blue when seen from the front should turn out to beUca oerstedi.At high intensity the display of this species includes a component apparently unique in the genus, the vibration of the first ambulatories; their meri appear to human eyes to be particularly vivid, approaching peacock blue. This exhibit of intense hue through a motion of display makes a good example of the untouched opportunities for experimental work on the possible functions of color in social behavior.

        This species is the third member of the local alliance.

        Front moderately broad; antero-lateral margins long, strongly...

        (pp. 254-257)

        U. inaequalis,the fourth of the species in the local alliance, is small and largely brown, the distinguishing tufts of pile on the carapace often hidden in life by clinging mud.

        According to present knowledge,inaequalisappears more prone to combat than its close relations; before encounters and between rounds the opponents sometimes wave in alternation, in a fashion similar to that oflactea perplexain New Guinea and Fiji; at these times palm-leg rubbing is also prevalent,inaequalisbeing provided with armature that is moderately well developed but not as striking as in musica.

        For a long time I...

        (pp. 258-260)

        Notable for slender legs and small size,Uca tenuipediswas unknown in life until von Hagen (1968.2) found it in Peru. Now, thanks to his work on its waving display, we have behavioral evidence that it should be considered a member of the group composed ofcrenulataand its allies, in accordance with its morphological characteristics of form and armature.

        Front moderately broad. Ambulatories unusually slender in both sexes; antero-lateral margins long, slightly diverging, posteriorly angled. Carapace without pile. No oblique ridge on major palm; pollex very broad at base. Gonopod with large flanges but thumb represented by an oblique...

      • 48. UCA (CELUCA) TOMENTOSA CRANE, 1941
        (pp. 261-263)

        Uca tomentosais one more small fiddler that seems clearly, if not closely, related to the superspeciescrenulata.This one has no outstanding morphological peculiarities, is dull in color, and has confusingly various amounts of pile on its carapace. The unique male holotype ofU. mertensiBott, 1954, and the series from Peru referred tomertensiby von Hagen, 1968.2, are examples oftomentosa.Von Hagen’s field work has provided basic data on tomentosa’s color and waving display.

        Front moderately wide. Major pollex not unusually broad proximally and without a strong projection on prehensile edge. 1st ambulatory on major side...

        (pp. 264-266)

        Von Hagen’s publication of the type description ofU. tallanicaadds one more species, notably small and remarkably interesting, to this group of closely related forms. For years it seemed unwise to base a new species on the few imperfect male specimens I collected in Ecuador. Now the nametallanicais available, based on a series from Peru. In the following description I have combined von Hagen’s data with that from the Ecuadorian specimens; the details of the armature and gonopod, however, are derived entirely from the latter.

        Front moderately wide. Major cheliped with a small, pilous depression with definite...

      • 50. UCA (CELUCA) FESTAE NOBILI, 1902
        (pp. 267-270)

        The fingers of the major cheliped inUca festaeattain record lengths in relation to the size of the crab, although the armature shows no uncommon peculiarities. Notes made many years ago in Ecuador indicate that fighting was more prevalent, during those particular low tides, than in any other species I have encountered. Our present knowledge of combat components leads to the expectation that the long fingers will prove to be concerned with some combat characteristic, as well as with any physical and psychological advantages of large size and high visibility (p. 487). A possibly related point in the crab’s...

      • 51. UCA (CELUCA) HELLERI RATHBUN, 1902
        (pp. 271-273)

        Uca helleriappears to be endemic in the Galapagos, and remains the only species in the genus with a distribution confined to a small group of islands. Few specimens have been collected, and information on its biology appears to be lacking. Films of waving fiddlers, lent by visitors, do not show the display characters clearly enough to describe them.

        Front moderately broad. Orbits oblique; anterolateral margins short, not at all divergent. Major cheliped with the minute tubercles on outer manus and triangle on proximal palm in a reticulate pattern; oblique tuberculate ridge strong but apex low; pollex not unusually wide,...

      • 52. UCA (CELUCA) LEPTOCHELA BOTT, 1954
        (pp. 274-274)

        This little-known species,Uca leptochela,has been recorded from El Salvador. It appears to be closely related toUca dorotheae.A similar form, established as a subspecies, was collected in the Galapagos.

        Apparently about as indorotheae,except for a narrower gape on the minor cheliped and, on the gonopod, a wider distal pore that lacks a marginal protuberance (data from Bott, 1954, Text Fig. 20 and Bott, 1958, Text Fig. 2). Armature, if any, on anterior aspect of 1st ambulatory unknown.

        (Data from Peters, 1955: 441.) About as indorotheae,with a distinct pause at the peak; the tempo,...

        (pp. 275-277)

        Uca dorotheaeappears to hold an interesting position in the subgenus, intermediate between members of the group that includes the superspeciescrenulatawith its allies and that composed ofbeebeiandstenodactylus.Although in the most specialized parts of its armature, on the upper manus and anterior ambulatory,dorotheaeresemblesbeebei,its more basic structures, as well as the form and tempo of its waving display, have more in common with, for example,cumulantaor festae. Its closest relation may well prove to be the Salvadorean form ofleptochela,at present poorly known.

        Likebeebeiand several otherCeluca,displaying...

      • 54. UCA (CELUCA) BEEBEI CRANE, 1941
        (pp. 278-281)

        Adapted to a number of common habitats,Uca beebeiis probably the most abundant of all the fiddlers within its range, even though its local populations are often rather small. As withlacteain the Indo-Pacific, several dozen individuals sometimes thrive on bits of suitable shore only a few meters long.

        In most places, green on the carapace and purplish brown on the lower cheliped distinguish displaying males at a glance among any variety of species. The extremely rapid, simple, “beckoning” wave makes an even better recognition mark, reliable even in populations in which display white is prevalent. Once it...

        (pp. 282-285)

        A striking sight when he is in full display, a maleUca stenodactylusoften races to and fro, holding a great pink claw high overhead or stretching it to the side as he chivies a small female toward his burrow.

        One of the most interesting aspects of the species is the coincidence of much of its range with that of its closest relation,beebei.Often, as in the alliance that includesbatuentaand its relations, the species mingle at least marginally in the same biotope. Understandably they have been confused in collections, or not given full specific status because of...

        (pp. 286-291)

        Among the species of the subgenusCelucarecognized in this study, onlytriangularisandlacteaoccur in the Indo-Pacific. The species contrast with each other in several ways, forming a classic example of differences that occur between related forms sharing broadly coincident ranges.

        Whilelacteathrives in a variety of biotopes flooded regularly by tides of high salinity,triangularisin any locality lives only in one or two secluded habitats that are normally cut off from marine tides and often watered only by scarcely brackish streams. Nevertheless populations of both species sometimes intermingle marginally and most are subject to mixing...

      • 57. UCA (CELUCA) LACTEA (DE HAAN, 1835)
        (pp. 292-303)

        One temptation in this study is to write aboutUcalactea in superlatives. Among fiddlers these small crabs have one of the four widest ranges on earth. They form perhaps the most abundant species. They vary the most widely in often bright and complex color patterns. Above all they present us with more challenges, as they unfold the refinements of their social behavior, than any other fiddler I know.

        A report on these behavior patterns, particularly those of agonistic behavior, will be published separately; it is too detailed for appropriate inclusion here and, moreover, includes the results of recent field...

        (pp. 304-307)

        Uca leptodactyla, uruguayensis,andmajorare the only Atlantic species that attain the dazzling white shown by a number of forms in other parts of the tropics. Also,leptodactylaand two otherUca, minaxandcumulanta,are the only builders of hoods in the Atlantic. As a final distinction,leptodactylashares with the north temperatepugilatora preference for sandier, saltier habitats than those frequented by otherUcaon the east coast of America.

        Front moderately wide; carapace strongly arched. Anterior side of 1st ambulatory in male without a row of tubercles or a ridge on any segment. Major cheliped...

        (pp. 308-310)

        Uca limicolais known only from a few specimens, a brief observation in Panama, and two filmed sequences. On this evidence it lacks outstanding peculiarities; morphologically its close relationship toleptodactylain the Atlantic seems clear.

        Front moderately wide; carapace strongly arched. Major cheliped with gape moderate, both fingers slender and tapering, the few enlarged teeth scarcely larger than the rest; no parallel ridges on triangle of lower palm. In both sexes outer suborbital crenellations gradually, not abruptly, enlarged, with spaces between them; largest beside channel. Gape of small chelae moderate with serrations very small to absent. Gonopod with a...

        (pp. 311-313)

        Usually found on somewhat sandier, more open shores than mostUca, deichmannisometimes lives in close association with two other commonCeluca, oerstediandbeebei.The waving displays of this trio can often be compared without even shifting focus, giving in capsule form an example of the obvious differences in display rhythm among the wealth of sympatric species that occur in the eastern Pacific. The pause atdeichmann’spoint of highest reach, the lack of pause in beebei combined with its more horizontal wave, andoerstedi’sslower, widely circling motion of the cheliped make each species unmistakable.

        Front moderately broad;...

      • 61. UCA (CELUCA) MUSICA RATHBUN, 1914
        (pp. 314-318)

        The outstanding structural characteristic of both subspecies ofUca musicais a distinctive stridulating mechanism. This consists of parallel striations on the manus and a row of tubercles on the 1st ambulatory, their positions being characteristic of less remarkable armature in a number of otherCeluca.Althoughm. terpsichoreshas been observed in life, the functioning of this apparatus, presumably in the component termed the palm-leg-rub, has not yet been observed or recorded.U. m. terpsichoresis also remarkable for fashioning the most perfectly shaped hoods known in the genus. These structures are also the largest in comparison with the...

      • 62. UCA (CELUCA) LATIMANUS (RATHBUN, 1893)
        (pp. 319-321)

        The major cheliped of adultUca latimanusclosely resembles the claws of most half-grown fiddler crabs. The entire appendage is short, its manus broad and thick; the palm practically lacks an oblique ridge and the stumpy fingers are not only straight but far shorter than the palm, while the gape is a narrow slit edged with feeble tubercles. In all other characteristics of both morphology and behavior, this species is one of the most advanced in the genus. Everyone with an interest in the relation of structure to function can only await with impatience some knowledge of combat techniques in...

      (pp. 322-328)

      This section has three divisions. The first gives an annotated list of species names which cannot be placed satisfactorily, whether as valid species or as synonyms; it includes comments on geographical records where they are concerned in the discussion of the unacceptable names. The second section lists questionable geographic records alone, each under the name of a species here regarded as valid. In each of these two sections the forms are listed alphabetically under the name of the species, with a crossreference, when pertinent, to other comments in the text. The last division lists several specimens ofUcaof special...

  10. Figures
    (pp. 329-408)
  11. Maps
    (pp. 409-429)
  12. Part Two. Toward an Evolutionary Synthesis
    • Chapter 1. Zoogeography
      (pp. 431-439)

      Fiddler crabs, comprising the homogeneous genusUca,are widely distributed throughout the tropics and subtropics of the world. Nine subgenera, totaling 62 species, are recognized in this contribution. More than two-fifths of these species are found only along the coast of the tropical eastern Pacific. Less than one-third occur in the entire Indo-Pacific region from East Africa to the Marquesas. On most coasts from one to three species extend into temperate regions.

      The puzzles of the origins ofUcadistribution yield both clues and permanent uncertainties in abundance. The clues, as usual, encourage hypotheses, while the uncertainties promptly reduce most...

    • Chapter 2. Ecology
      (pp. 440-447)

      Almost all adult fiddler crabs live in the intertidal zones of sheltered bays and estuaries, digging and feeding in sandy mud and muddy sand throughout the warmer parts of the world. These habits show basic demands for tidal action, for a soft and nutritious substrate, and for warmth.

      As usual inUcabiology, each of these needs turns out to have wide variability, and all illustrate well the capacity of the genus to adapt to a wide range of conditions.

      In this chapter the chief physical and biological factors in their environments will be examined. Because of the overlapping and...

    • Chapter 3. Structures and their Functions
      (pp. 448-470)

      In live fiddler crabs structure and function are challenging subjects that continue to provide biologists with a series of surprises. This chapter concerns selected morphological characteristics and their relations to certain ecological requirements and behavior patterns.

      Most of the characters discussed are external and include all of those most typical of the genus. Where our knowledge is severely limited, as with antennae and antennules, the structures are briefly mentioned to underline our ignorance. The survey includes the range of variation, post-larval development, apparent adaptive values, and the functional relation, in social behavior, of the parts to one another. Descriptions of...

    • Chapter 4. Non-Social Activities
      (pp. 471-475)

      The behavior of fiddler crabs may be roughly divided into maintenance activities, defenses against predators, and social patterns. As usual in such classifications, and particularly in any subdivision ofUca,the dividing line is movable and a number of activities are multifunctional. Burrows provide an example. Seldom dug by the current occupant, they are nevertheless kept clear and, if necessary, enlarged by that individual. The burrows probably originated as an underwater defense against fish and other predators and continued as protection also against desiccation, heat, and terrestrial enemies during low tide, as the ancestors of fiddler crabs assumed an increasingly...

    • Chapter 5. Components of Social Behavior
      (pp. 476-508)

      In fiddler crabs, social behavior consists almost altogether of agonistic activities, their ritualized derivatives, and courtship. Most but not all aggressive behavior, whether ritualized or not, is also clearly connected with reproduction. With two exceptions—droves and synchronous waving—none of the patterns shows collaboration between more than two crabs in a joint activity. Fiddler crabs neither dig communal burrows, for example, nor threaten predators in unison. There is no trace of the group territoriality found especially in some mammals, where an area is defended by its inhabitants from trespass by another group of conspecifics. Furthermore, since the larvae are...

    • Chapter 6. Territoriality, Functions of Combat and Display, and the Origins of Social Patterns
      (pp. 509-525)

      The last chapter examined aspects of social behavior which could be objectively described. In colloquial brief, it dealt with thewhatsandwhensof these patterns. This chapter, in contrast, deals with thewhat forsand thehow comes,which, together, constitute the whys. Both subjects obviously demand speculation, which in many contributions can be quarantined at the end. In this discussion such a course would be illogical and confusing, since the heart of the subject consists of speculation. Therefore I have tried simply to base most non-factual statements directly on objective knowledge which is either reviewed in the same...

    • Chapter 7. Speciation, Phylogeny, and Directions of Evolution
      (pp. 526-536)

      InUcathe evidence on evolutionary trends remains indirect. Fossils are confined to three specimens, one of them a dactyl, while in related groups they are similarly rare. Genetics is untapped. Even the indirect evidence is restricted, since our knowledge of comparative development, basic physiology, sense organs, and neurophysiology is rudimentary or wanting. Experimental work on behavior is starting, but has scarcely begun to extend to the comparative approach; only several releasers have been studied experimentally.

      On the other hand, both morphology and behavior have yielded information of aid in working out the probabilities of fiddler crab descent. Wide distribution,...

  13. Plates
    (pp. 537-588)
  14. Appendixes
    • Appendix A. Material Examined
      (pp. 591-614)
    • Appendix B. Keys
      (pp. 615-631)
    • Appendix C. Tables
      (pp. 632-663)
    • Appendix D. Field Methods and the Maintenance of Fiddler Crabs in Captivity
      (pp. 664-677)
    • Appendix E. Conventions, Abbreviations, and Glossary
      (pp. 678-692)
  15. Bibliography
    (pp. 693-716)
  16. Indexes
  17. Back Matter
    (pp. 737-737)