biological oddities, including the naughty bits

Last night I gave a talk up in Auckland, on various biological oddities (mostly from the animal kingdom and, all right, mostly to do with s*x). You can slip a lot of serious science in once the audience’s attention has been captured by the naughty bits! (I would hate folks to think that biologists are totally obsessed with s*x. This is not true. But related stories do tend to focus the attention.)

Anyway, I was chatting sbout it with some of our grad students this morning and they said, oooh, we wouldn’t might reading more about that. Various people (including me & Grant) have blogged them all before, so I’ll bring all the links together in one place but won’t fill in too many of the gaps.

First up, zombies! More particularly, the use of the z-word to capture public attention & direct it to a serious subject: modelling (& more recently, how to deal with) the spread of infectious disease. The outcome of the modelling work was brought to the world’s attention by a paper with the eye-catching title, When zombies attack. More recent advice on getting through an infectious disease outbreak – things like stocking up on food & water & staying home – was presented by the US Centres for Disease Control under the heading: Preparedness 101: Zombie Apocalypse. (The daughter, who pays attention to such things, felt the advice was sadly lacking in that it doesn’t actually say anything about how to dispose of the zombies who might actually get into your house. Practicalities, people!)

This naturally segued into the tale about zombie ants – zombified by a parasitic fungus. Parasites can have quite marked effects on their hosts’ behaviour – changes that maximise the reproductive success of the parasite. I first got interested in this topic years ago, when I read Carl Zimmer’s excellent book, Parasite Rex. In the case of the ants (Camponotus leonardi), infection with the fungus Ophiocordyceps unilateralis causes the ants to leave their usual habitats, hang upside down off leaves or stems, bite on to the plant – & die. Then when the fungus produces a fruiting body it can rain down spores onto the heads of unsuspecting ants passing underneath.

Then we moved on to the slightly risque stuff, beginning with the interesting observation that female crayfish release urine during courtship. This influences the males’ behaviour & allows the females to assess the quality of her suitors. The original report includes a link to a video – using fluorescent dyes allowed the researchers to visualise the timing of urine release & so relate this to the more obvious behaviour patterns displayed by their subjects.

Couldn’t leave out the tree shrews living in montane forests in Borneo, who use the ‘pitchers’ of some pitcher plant species as toilets. This is qutie a cool example of coevolution, where Nepenthes lowii plants gain up to 100% of their nitrogen requirements from shrew faeces, while Tupaia montana (the shrew) gains sugars from licking the plant’s nectaries, enticingly displayed on the inside of the pitcher’s lid. (Well, enticing if you’re a shrew…)

Also in the forest, we have fruit bats. As Ed Yong describes, in one species of fruit bat, the duration of copulation is affected by whether or not, & how long, the female licks the male’s penis during copulation! Presumably this would have an impact on mating success. (In empid flies, for example, duration of mating is affected by the size of the food gifts that males bring for females, & longer copulations tend to produce more offspring.)

On the other hand, duration of copulation would have no impact at all on breeding success in the sole recorded example of homos*xual necrophilia, involving two mallard drakes (one of them very very dead). Not that this stopped the living drake from mating vigorously with the corpse – for 75 minutes!!

Mallard drakes are randy little beggars, with their activity extending to forced copulations with hapless females. This is usually later in the season & often involves multiple drakes, & can be so physical & prolonged that the females may drown. This promiscuous behaviour in waterfowl has a morphological correlate. Males of highly promiscuous species, where there are high levels of sperm competition, have long & tightly coiled penises (matched by long & tightly coiled vaginas in the females). At the other end of the spectrum are the monogamous species like black swans, who are much less-well endowed in the genital department. Females in the promiscuous species are able to control who they mate with by contracting or relaxing muscles that allow them to shorten the vagina, so that in a forced copulation the male may not actually be successful in passing on his genes, as his sperm may not be deposited high enough in the female’s reproductive tract.  Fascinating stuff – & caught on film (again, hat tip to Ed Yong).

As you may imagine, the discussion after last night’s talk was extremely animated 🙂