Turn to the weird side of science

[The Straight Story]

Alan Boyle writes:Caterpillars who whistle? Crickets with giant cojones? Help us decide which scientific tales from the past year are worthy of the Weird Science Awards.

This year's nominees have to meet a high standard for scientific weirdness. Weirdies from past years include glow-in-the-dark cats, glow-in-the-dark puppies, reattached rabbit penises and a 2,700-year-old pot stash.

Fortunately, we have some good precedents to follow: The Ig Nobel Prizes, announced in September, included some choice slices of scientific weirdness — and we've included one of the Ig-winners on our 30-choice menu (the one about the slime mold). The aim of the Ig Nobels, administered by Marc Abrahams of the Annals of Improbable Research, is to recognize "research that makes people laugh and then think." That's a fine criterion for our Weirdies as well. But you could also consider scientific tales that make you laugh, and then make you ask, "What were they thinking?"


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Other criteria include things that make you go "Ewww," such as the story about crickets with huge testicles ... or make you go "Auugh," such as the chicken-or-egg study ... or make you go "Hmmm" and reflect upon the foibles of human or animal nature, such as the tale of the chimp who was forced to stop smoking. (That's a double-header selection, as you'll see below.)



http://cosmiclog.msnbc.msn.com/_news/2010/12/23/5698471-turn-to-the-weird-side-of-science

[mike_c]

1. regarding cricket testes....

First, let me say that I NEVER thought I would ever type that subject line on DU, or anywhere for that matter, LOL.

It's easy to anthropomorphize factoids like "a species of cricket has testes that account for 14% of it's body mass" but it's a bad idea. The truth is that crickets have "large" testes because they have a very different mating system than mammals. To begin with, they do not transfer sperm directly during copulation-- crickets package their sperm in a spermatophore that they transfer to females. The spermatophore itself is largely produced by reproductive accessory glands, not the testes, but since female reproductive systems have to hold the whole spermatophore anyway, the use of a spermatophore partly focuses male natural selection on the ability to pack lots of spermatozoa into the package. This, in turn, favors large testes to produce that abundant sperm. Also, crickets have relatively short reproductive lives-- they are sexually mature only during the last life history stage and typically have 5-7 immature stages which don't reproduce, and during which males have vanishingly small, undeveloped testes. Finally, assembling and filling a spermatophore takes physiological time, quite a bit more than the refractory period between copulations in mammals, reducing the number of POSSIBLE mating opportunities to relatively few during the short reproductive lifetime of adult male crickets. So selection once again favors large testes producing great amounts of sperm during the relatively brief and infrequent mating opportunities most male crickets can ever hope for.

On the female side, things are even more un-mammal-like. Female insects receive sperm internally just like mammals, often by intromission but other times not-- sometimes spermatophores are essentially "handed off" to females who place them into their reproductive tracts themselves. Most crickets probably copulate.

That's where the resemblance ends, however. If some male crickets have the largest testes, I can tell you-- from having looked inside many a cricket myself-- that females have correspondingly large ovaries that occupy most of their abdominal volume (and females are typically larger than males). However, they don't produce millions of eggs-- rather, each egg is relatively large and yolky. More to the point though, is that female insects store sperm internally after mating, sometimes for quite long periods (think of a social insect queen in the Hymenoptera, for example, who might use sperm stored from a single mating to fertilize eggs for a year or more). They store sperm in a sac-like structure called a spermatheca and release it, a few spermatozoa at a time, as each egg slides past the opening of the spermathecal duct on it's way down the oviduct and into the ovipositor chute. Thus, selection again favors the production of lots of sperm so that females can fertilize greater numbers of eggs over a longer period following each mating. The spermatophore itself, that contained those spermatozoa (and usually some important pheromones, too) before they were deposited into the spermatheca, is often absorbed by females or directly eaten-- it is usually quite nutritious and represents a considerable transfer of nutrient reserves from males to females at a time when they need it most to complete maturation of their eggs. With the extra nutrients, females can produce more eggs, but fertilizing them requires more sperm, stored for longer-- again, selection favors males with large testes who can produce that additional sperm.

So the "eww" factor is only appropriate when we anthropomorphize crickets and try to interpret their anatomy in terms of familiar selective forces. No, a pair of 28 lb testes dangling between my legs doesn't sound like an adaptive feature, no matter how much I might giggle about the possibilities. But for crickets, selection has optimized their reproductive fitness by favoring the insect equivalent. When you want to really give a guy credit, tell him that he's hung like a cricket!