Walking Sideways

Walking Sideways: The Remarkable World of Crabs

JUDITH S. WEIS
Copyright Date: 2012
Edition: 1
Published by: Cornell University Press,
Pages: 256
https://www.jstor.org/stable/10.7591/j.cttn34xc
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    Walking Sideways
    Book Description:

    The world's nearly 7,000 species of crabs are immediately recognizable by their claws, sideways movement, stalked eyes, and thick outer shells. These common crustaceans are found internationally, thriving in various habitats from the edge of the sea to the depths of the ocean, in fresh water or on land. Despite having the same basic body type as decapod crustaceans-true crabs have heavy exoskeletons and ten limbs with front pincer claws-crabs come in an enormous variety of shapes and sizes, from the near microscopic to the giant Japanese spider crab.

    In Walking Sideways, Judith S. Weis provides an engaging and informative tour of the remarkable world of crabs, highlighting their unique biology and natural history. She introduces us to recently discovered crabs such as the Yeti crab found in deep sea vents, explains what scientists are learning about blue and hermit crabs commonly found at the shore, and gives us insight into the lifecycles of the king and Dungeness crabs typically seen only on dinner plates. Among the topics Weis covers are the evolution and classification of crabs, their habitats, unique adaptations to water and land, reproduction and development, behavior, ecology, and threats, including up-to-date research.

    Crabs are of special interest to biologists for their communication behaviors, sexual dimorphism, and use of chemical stimuli and touch receptors, and Weis explains the importance of new scientific discoveries. In addition to the traditional ten-legged crabs, the book also treats those that appear eight-legged, including hermit crabs, king crabs, and sand crabs. Sidebars address topics of special interest, such as the relationship of lobsters to crabs and medical uses of compounds derived from horseshoe crabs (which aren't really crabs).

    While Weis emphasizes conservation and the threats that crabs face, she also addresses the use of crabs as food (detailing how crabs are caught and cooked) and their commercial value from fisheries and aquaculture. She highlights other interactions between crabs and people, including keeping hermit crabs as pets or studying marine species in the laboratory and field. Reminding us of characters such as The Little Mermaid's Sebastian and Sherman Lagoon's Hawthorne, she also surveys the role of crabs in literature (for both children and adults), film, and television, as well in mythology and astrology. With illustrations that offer delightful visual evidence of crab diversity and their unique behaviors, Walking Sideways will appeal to anyone who has encountered these fascinating animals on the beach, at an aquarium, or in the kitchen.

    eISBN: 978-0-8014-6604-5
    Subjects: Zoology

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. List of Vignettes
    (pp. vii-viii)
  4. Preface
    (pp. ix-xii)
  5. Acknowledgments
    (pp. xiii-xvi)
  6. CHAPTER ONE Introducing Crabs
    (pp. 1-22)

    Scientists in a research submarine exploring the deep-sea hydrothermal vents south of Easter Island made an amazing discovery in 2005: on the sea floor they found an unusually large crab (about 6 inches long) with its legs and claws all covered with hair. Then they noticed more of the strange crabs, mostly at depths of about 7,200 feet. Many were hiding underneath or behind rocks, and, at first, all the scientists could see were the hairy tips of their arms sticking out.

    The crabs were living on recent lava flows where warm water seeps out of the sea floor. Hydrothermal...

  7. CHAPTER TWO Habitats
    (pp. 23-43)

    Crabs are found in all kinds of habitats from the shoreline to the deep sea, in marine, estuarine, and freshwater environments, and even on land. Most crabs live in marine and estuarine habitats (which are areas where fresh water and marine water mix, as in river mouths and bays), while only a few specialized ones (e.g., gecarcinids and land hermit crabs) live in fresh water or on land. More species live in shallow water than in the deep sea. Certain groups—namely the grapsids (shore crabs) and ocypodids (fiddler and ghost crabs)—tend to live in shallow and intertidal (shoreline,...

  8. CHAPTER THREE Form and Function
    (pp. 44-61)

    While many aspects of crab anatomy and physiology are similar to those of other animals, some may come as a surprise. Interesting, and sometimes odd, examples in crabs include blue blood, taste buds on their toes, and kidneys in their head!

    When viewed from above, all you can see is the carapace of a crab, but when viewed from underneath (see Fig. 1.2), we can see its major anatomical features—the boundary between the head and thorax, as well as the segments of the thorax and the attachment of the legs to the thorax. The cephalothorax is generally short and...

  9. CHAPTER FOUR Reproduction and Life Cycle
    (pp. 62-84)

    Just about all crabs have distinct male and female forms, and some species show major differences between the sexes. You can tell a crab’s sex by turning it upside down and looking at the abdomen. A mature male’s is narrow and a mature female’s is quite wide (see Fig. 1.2). Some species have additional differences, such as the enlarged claw of male fiddler crabs or the red tips on the claws of female blue crabs. The age and size at which crabs become sexually mature vary among species and geographic location. Some groups of crabs undergo a pubertal molt in...

  10. CHAPTER FIVE Behavior
    (pp. 85-104)

    To study the behavior of aquatic animals, you can either bring them into the lab or watch them in their own environment while snorkeling or scuba diving. Although an enormous amount of information has been learned about the behavior of fish by means of underwater observation, crabs tend to be more secretive and less abundant in coral reefs, where so many of the fish behavior studies have typically been done. In estuaries, the home of many species of crabs, water tends to be murky so underwater observations are difficult at best, and deep-water observations are rare and logistically very difficult....

  11. CHAPTER SIX Ecology
    (pp. 105-128)

    Given the very different habitats in which crabs can be found (see Chapter 2), it is no wonder that their ecology is equally diverse. Following is an overview of these aspects of crab ecology, beginning with the transition from larva to juvenile, and covering hibernation, migrations, navigation, interactions with other kinds of organisms, and the effects of crabs on the environment.

    Larval stages in the plankton are particularly important for the dispersal of most marine invertebrates, including crabs. As discussed in Chapter 4, most crabs hatch into the water as free-swimming planktonic larvae. Since adult crabs generally crawl on the...

  12. CHAPTER SEVEN Crab Problems and Problem Crabs
    (pp. 129-153)

    Crabs, like the rest of us, are affected by diseases, parasites, habitat loss, climate change, and pollution. On the flip side, some crabs cause problems for their neighbors and, in a few cases, for people.

    Crabs are subject to a great variety of diseases from viruses, bacteria, and pathogenic ciliates and amoebas. For example, “gray crab” disease in blue crabs is caused by Paramoeba parasites, resulting in significant mortality. Fungus diseases may infect crabs and especially their egg masses, causing mortality of up to 50% of the eggs. More than thirty viruses have been reported in crabs. Bacterial diseases of...

  13. CHAPTER EIGHT Crab Fisheries
    (pp. 154-181)

    People living on the coast have depended on living marine resources for many thousands of years. Millions earn their living in commercial fisheries, and many people still depend on seafood as their primary source of protein. The very high catch rates of modern industrialized fishing fleets have had widespread effects on fished species, nontarget species, and marine habitats. Overfishing continues to be a major threat to marine ecosystems and vulnerable species throughout the world. Although dwarfed by fisheries for finfish, crab fisheries are important in many countries.

    As early as prehistoric times, blue crabs (Plate 3) were collected for subsistence...

  14. CHAPTER NINE Eating Crabs
    (pp. 182-195)

    Crabmeat, like fish, is a nutritious food, low in calories and fat but high in protein and omega-3 fatty acids, which help prevent heart disease. These fatty acids are especially important for women who are pregnant or breastfeeding because they are needed for their child’s developing nervous system. Omega-3s, which are higher in crabmeat than in shrimp, may also reduce inflammation, enhance immune function, and even lower the risk of certain types of cancer. Crabmeat is also rich in vitamins and minerals, with high levels of vitamin B-12, a vitamin critical for healthy nerve function. The composition of fresh crabmeat...

  15. CHAPTER TEN Crabs and Humans
    (pp. 196-214)

    People most commonly encounter crabs casually on a dinner plate or at the beach (“Ouch, my toe!”). But some people, especially children, find the crabs they encounter at the shore a source of wonder, and scoop them up and put them in plastic pails to study. Others, perhaps some of these same children decades later, spend much of their lives studying various aspects of crab biology, which is called carcinology.

    In a similar manner as a zoo or museum, a public aquarium and a tank in a pet store that sells tropical fish can provide a wonderful learning experience and...

  16. Bibliography
    (pp. 215-224)
  17. Index
    (pp. 225-240)
  18. Color plates
    (pp. 241-248)