Surfing The Wierd

Tuesday, January 29, 2008

sites for animals that change gender

  1. Uncovering Sex-change Secrets Of Black Sea Bassthe mechanismsms that determine sex in animals vary widely, involving actions of ... Of Sex (Apr. 5, 2002) — The genetic intricacies of salmon sexes and the ...
  2. Uncovering Sex-change Secrets Of Black Sea Bass

    ScienceDaily (Apr. 12, 2006) — In a former cowshed on the edge of the University of New Hampshire campus, David Berlinsky, assistant professor of zoology, peers into a big blue plastic tub. Inside, black sea bass circle slowly in the dim light. The converted barn is now an aquaculture research facility for the College of Life Sciences and Agriculture, and home to Berlinsky’s latest research.

    Black sea bass feature prominently on many menus, but wild populations of the fish are in decline and their availability is limited. Because of the high demand, they’re a good candidate for aquaculture on the east coast. Except, that is, for one problem: they have a tendency to change sex unpredictably in captivity.

    “In the wild, black sea bass are born as females and turn into males at around two to five years old,” Berlinsky explains. “When you bring them into captivity, they change into males more quickly.” Some captive-born fish emerge as males even before reaching adulthood, devoting energy toward reproductive development and away from growth. Such problems make breeding and growing the fish in captivity a tricky proposition.

    “Black sea bass is a wonderful fish to culture and to eat,” says George Nardi, vice president and director of GreatBay Aquaculture, a commercial fish farm in Newington, NH. But the sex change problem must be tackled if fish farmers are to bring a high-quality fish to market. “We invest in our brood stocks, the parents of the young fish, much as a thoroughbred horse farm invests in mares and stallions,” he says. “It doesn’t do us much good if we always have to go out and get new females.”

    With funding from NH Sea Grant, Berlinsky has teamed with Nardi and GreatBay Aquaculture to study what triggers sex reversal in black sea bass – and how to prevent it. Berlinsky and his colleagues have discovered that fish are more likely to become males if raised at constant temperatures. But temperature is hardly the only factor involved. Sex ratios and density also come into play. Berlinsky’s team found that females were more likely to change sex when no males were present in the tank. Additionally, the fish were more likely to turn into males when kept in crowded tanks.

    Berlinsky is continuing his experiments to clarify the role that water temperature plays and to further understand what factors determine the initial sex of captive-born fish. He’s also collaborating with Canadian researchers to study the underlying biochemical mechanisms that cause the fish to change sex. In female fish, estrogen plays the major role, he said. In males, a steroid hormone called 11-ketotestosterone is involved. The scientists are now studying those hormones as well as the enzymes that control them.

    By turning off estrogen production, Berlinsky says, he can turn a female fish into a male within a week. Giving 11-ketotestosterone to a female converts it into a male. “We’re studying the ways to control the enzymes that control sex reversal,” he explains. “We’re coming at the problem both behaviorally and biochemically.”

    Though he still has details to sort out, Berlinsky believes he has already made important steps. “We have already made progress, determining optimal sex ratios and delaying sex reversal by controlling density,” he notes. “We’ve already made strides toward making black sea bass aquaculture possible.”

    Adapted from materials provided by University of New Hampshire.

  3. Our results indicate that the relative size. of sex change is invariant across all animal ... Figure 2 Animals change sex at the same relative body size. ... - 147k - View as html
  4. ... concentrate on animals it should also be remembered that sex is also important ... It was widely believed that cocks that changed sex and laid eggs were ... - 32k - Cached
  5. Animals that did not copulate did not have distinct sexes in his view. ... change in animals there was no change of chromosomes when the animal changed sex. ... - 83k - Cached
  6. ... for animals that can procreate asexually and animals which change sexes in the ... creatures and creatures that change sexes in the absence of the opposite sex. ... - 167k - Cached

  7. Animals that are labeled male are individuals that changed sex— i.e., those that ... were predictive of which animal changed sex, we ran a logistical regression. ... - 81k
  8. "This suggests that there is a fundamental similarity across all animals ... to change gender when there is a serious imbalance between the sexes and it ...
  9. Species Switch Sex at Specific Size
    Male Today, Female Tomorrow
    Male Today, Female Tomorrow

    Oct. 27, 2003 — Species that automatically change sex do so when they reach nearly three-quarters of their maximum size, neatly proving a cornerstone of evolutionary theory, scientists said.

    Dozens of animal species, from types of fish and crustaceans to mollusks and worms, spontaneously change sex as a result of the pressures for survival and reproduction.

    In the case of the clownfish, a favorite of aquarium-lovers, the gender bending is taken to extremes — males can not only switch to female, but also increase in size to become the alpha-breeder in their piscatorial group.

  10. Biologists David Allsop and Stuart West of Edinburgh University in Scotland studied 77 sex-changing species, ranging from a tiny shrimp, the Thor manningi, to a 1.5-meter (5-foot) fish called a black grouper.

    They found that the creatures swapped gender when they reached 72 percent of maximum size, regardless of mating system, sex-change mechanism and other factors.

    "This suggests that there is a fundamental similarity across all animals ... in the underlying forces that select for sex change," they wrote in Thursday's issue of Nature, the British weekly science journal.

    Under evolutionary theory, an individual is at most pressure to change gender when there is a serious imbalance between the sexes and it has reached an age and size where it can do the switch successfully and contribute quickly to the gene pool.

  11. Animals that did not copulate did not have distinct sexes in his view. ... change in animals there was no change of chromosomes when the animal changed sex. ... - 128k - Cached
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  1. Why write a FAQ about African Dwarf Frogs? What is an African Dwarf Frog (ADF) ... do not change their gender or sex if you have a tank full of only one gender. ... - 89k - Cached
  2. In Depth Information on Common Aquatic Clawed Frogs. For Sale. In Depth African Clawed Frog Diet ... 4-6 months depending on size, gender and age of frog. ... - 39k - Cached
  3. African Union Monitor. 16 Days of Activism Against Gender Violence. Women and Gender ... Is it possible to study climate change effects on things you don't know even ... - 20k - CacV
  4. Vanishing frogs
    ... group of frog-like amphibians that are usually distinguished from frogs by the ... of these animals to adapt to changing conditions has resulted in the large ... - 19k - Cached
  5. Frogs help hunt down the gender benders - 06 June 1998 - New Scientist
    THE spread of sex-change chemicals in the environment could soon be tracked with a test that uses tadpoles and ... from the African clawed frog Xenopus laevis ... - 38k - Cached
  6. Natural Habitat
    African clawed frog site with lots of info. Facts, care instructions, pictures, links. ... states that since African Clawed Frogs are adapted to stagnant ... - 15k - Cached
  7. ... first time in a cold-blooded vertebrate, the South African clawed frog Xenopus. ... Gray's medical work called world-changing. Rains offer hope for bird ... - 47k - Cached
  8. *Click here for a larger view of all the pics on this page.* TANK CARE &nbsp. page created with Easy Designer ... - 23k - Cached
  9. ... symbolic expressions and musical meaning, gender, religion, and social change. ... frogs (the largest frogs in the world) in Cameroon and the African penguins ... - 82k - Cached
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