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Malformed Frogs

Malformed Frogs: The Collapse of Aquatic Ecosystems

Michael Lannoo
Copyright Date: 2008
Edition: 1
Pages: 288
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  • Book Info
    Malformed Frogs
    Book Description:

    The widespread appearance of frogs with deformed bodies has generated much press coverage over the past decade. Frogs with extra limbs or digits, missing limbs or digits, or misaligned appendages raise an alarming question: "Are deformed humans next?" Taking a fresh look at this disturbing environmental problem, this reference provides a balanced overview of the science behind the malformed frog phenomenon. Bringing together data from ecology, parasitology, and other disciplines, Michael Lannoo considers the possible causes of these deformities, tells which frogs have been affected, and addresses questions about what these malformations might mean to human populations. Featuring high-quality radiographic images,Malformed Frogssuggests that our focus should be on finding practical solutions, a key component of which will be controlling chemical, nutrient, and pesticide runoff into wetlands.

    eISBN: 978-0-520-94253-0
    Subjects: Biological Sciences

Table of Contents

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  1. Front Matter
    (pp. i-viii)
  2. Table of Contents
    (pp. ix-x)
    (pp. xi-xiv)
    (pp. xv-xvi)
    (pp. 1-6)

    As a cultural phenomenon it began in the summer of 1995 in south-central Minnesota, with school kids on a field trip.² While exploring a rural wetland, Cindy Reinitz and her junior high school students discovered a large number of northern leopard frogs (Rana pipiens) that were having trouble jumping. When normal frogs with two good hind legs jump they maintain control in the air and land on their hands and their chest. But the leopard frogs these kids were finding had missing legs or missing parts of legs, and when leopard frogs with only one good leg jump, they often-times...

    (pp. 7-20)

    The word “malformation” literally means “bad form.” Bad form in most animals means an unintended lack of symmetry, or an imbalance in structure, color, or other quality. A lack of symmetry can arise through one of three mechanisms:²

    GeneticGenes are flawed, or the expression of genes during development is flawed. Albinism (in which animals have white bodies and pink eyes) is a familiar genetically determined malformation. Albinism is often caused by a mutation that results in the failure of embryonic neural crest cells to migrate. Similar genetic mutations in northern leopard frogs produce blue or partially blue axanthic individuals...

  7. Plates
    (pp. None)
    (pp. 21-84)

    In an attempt to organize, and to correlate effect with cause, malformations, whether human, frog, or otherwise, have tended to be divided into types. Malformation types are almost always based on: (1) structures absent or reduced, (2) structures duplicated (or multiplied), and (3) structures present but otherwise abnormal (e.g., eye position, jaw shape, limb shape, skin color, pigment pattern). Definitions of malformed frogs have been provided by Carol Meteyer and her colleagues.² The team we assembled in 2001 to re-examine the hottest of the Minnesota malformed frog hotspots slightly modified this terminology,³ which is in turn slightly modified and presented...

    (pp. 85-104)

    In amphibian conservation biology, the term “hotspot” is used in two contrasting ways. One way, with a good implication, is to denote a site or a region with high amphibian richness. These places are usually located in tropical or subtropical ecosystems and are often the focus of intense conservation efforts. The second use of the term “hotspot,” and the way I use it here, is much less desirable and indicates a site with a large number or percentage of malformed animals. The Minnesota Pollution Control Agency, for example, defined a wetland as a hotspot if, at any time when it...

    (pp. 105-110)

    The year 2006 marked the 300th anniversary of known published observations of malformed frogs. The recognition that malformed frogs preceded the beginning of the Industrial Revolution by about 150 years and preceded modern agricultural techniques (including the application of pesticides) by about 250 years has led many people to deduce that there are natural causes of frog malformations. Indeed there are.

    In his treatise on the history of malformed amphibians, Martin Ouellet² lists several natural causes of malformations.

    WoundingWounds from failed predation attempts (“bites and mutilations”) and leech (Erpobdella octoculata) parasitism can lead to either missing limbs or parts...

    (pp. 111-178)

    There has been nothing tidy about the malformed frog investigation. Examining the field, some workers have chosen terms like the “complexity of deformed amphibians”² or an “eco-devo riddle”³ as descriptors. At face value this is true, but I gently disagree that we need more data. The data necessary to achieve a solution to this problem are right in front of us, but at the scale of individual research papers they are often hard to see.

    Since the publication of Bill Souder’s “A Plague of Frogs”⁴ (the paperback edition, published by the University of Minnesota Press in 2002, contains an epilogue...

    (pp. 179-188)

    The fear that what was happening to frogs could happen to humans is the major reason why the malformed frog problem tipped in 1996. As with many ways of thinking about malformed frogs, the logic behind this concern is sound. Something in the water is causing frog malformations; developmental systems are conserved across vertebrates; therefore, if it’s happening to frogs it could happen to us. Given this, it becomes useful to review human malformations (congenital anomalies) in light of frog malformations.

    The rate of congenital anomalies in humans varies slightly from continent to continent and region to region, but globally...

    (pp. 189-202)

    Why is it that when human congenital malformations are addressed, the full suite of abnormalities and the full range of causes are considered, but when addressing malformations in frogs, the focus is typically only on single causes and their effects on hindlimbs, and then often only on hindlimb polymely? In almost every publication devoted to amphibian declines, we read that amphibians are “canaries in the coal mine,” sensitive indicators of environmental health. To fully understand the role of amphibians as bioindicators, it would be wise to consider both the breadth and the depth of their sensitivity.

    There is a curious...

    (pp. 203-216)

    Amphibian malformations are not evenly distributed across taxa. As mentioned in Chapter 1, amphibian malformations tend to be frog malformations. A quick count shows that 52 of 105 U.S. frog species (50%) had documented malformations compared with 19 of 188 U.S. salamander species (10%).

    The frog genera with the highest rates of documented malformations include:Ascaphus(1 of 2 species or 50%),Bufo(10 of 23 species or 43%),Acris(2 of 2 species or 100%),Hyla(7 of 10 species or 70%),Osteopilus(1 of 1 species or 100%),Pseudacris(8 of 14 species or 57%),Gastrophryne(2 of...

  15. NOTES
    (pp. 217-264)
  16. INDEX
    (pp. 265-270)
  17. Back Matter
    (pp. 271-273)