VMartin
Posts: 525
Joined: Nov. 2006
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Alan Fox at Evolution of the thorse:
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Your assertion led me to google and I came across this. It seems someone is testing the idea that undescended testicles result in sterility in the Florida panther. There is lots more on sperm viability and temperature control of the testes.
It seems to me differential temperatures and sperm viability are measurable, and a resultant hypothesis, (sperm survives better at a slightly lower temperature than normal internal body temperature in mammals) is quite testable
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Your article states:
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Semen quality and endocrine and reproductive functions have been shown to be adversely affected in some inbred lines of several species, including mice, cats, 2 lion subspecies and cheetahs (Wildt 1994). Comparative reproductive analyses of seminal traits in five feline species, revealed that Florida panther males display some of the poorest seminal quality traits ever recorded for any felid species or subspecies (Barone et al., 1994). Total motile sperm per ejaculate in the Florida panther is 18-38 times lower than in other puma subspecies, 30-270 times lower than in other felids and 30 times lower than in the cheetah. Although cougars and other large felids tend to produce high proportions of morphologically abnormal sperm, the Florida panther has a significantly greater frequency of malformed spermatozoa (average 93.5% per ejaculate) than any other subspecies; particularly noteworthy was a 42% incidence of acrosomal defects, a trait that renders sperm deficient in fertilization potential (Barone et al., 1994). Seventy-five percent of the sperm exhibit severe deformity and are classified as having primary abnormalities (Roelke 1990). Compared to Felis concolor from Texas, Colorado, Latin America, and North American zoos, the Florida panther has lower testicular and semen volumes, poorer sperm progressive motility, and more morphologically abnormal sperm, including a higher incidence of acrosomal defects and abnormal mitochondrial sheaths (Barone, et al. 1994).
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Somehow I couldn't find there anything about descended testicles, could you? Yet 93,5 % of malformed spermatazoa obviously do not affect fitness of Florida panther. Much ado about nothing.
I don't know if you have followed the entire discussion here about the issue. The problem is that birds having temperature 42 grad Celsius do not have descended testicles.
And lower temperature of sperms in descended testicles might be the result of descent, adaptation to lower temperature, not the cause of it. This mistake of reasoning is common amongst neodarwinists
(and behavorial ecologists especially).
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I could not answer, but should maintain my ground.-
Charles Darwin
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