Friday, May 22, 2009

Basic instincts

This is my housemate's cat, Larry. Larry has had a few bad experiences with cars, so he has to be an indoor cat. At least once a day, he attempts to mate with this knitted patchwork blanket. Given the opportunity, he also likes an encounter with a jumper or scarf (pure wool only, he won't stoop to synthetic fibres).

After servicing the females in his territory, he likes to go hunting. His prey is a length of leopard-spotted synthetic fur with a bunch of feathers attached to the end.

All of Larry's natural impulses and behaviours have to be played out in a completely simulated environment. Sometimes characteristics of household objects (eg. hairy, moving) provide bevhavioural cues, even when, in other ways, that object bears little resemblance to anything a cat would encounter in the wild. It could be said that Larry's blanket-humping is a desparate measure from a domesticated animal. But even wild animals have been known to misread environmental cues.

In the early 1980s, biologists discovered something unusual about the Australian jewel beetle. I could paraphrase these findings, but I think they are best conveyed in the charming deadpan of a scientific paper. Here is an abbreviated version of Dr Trevor J. Hawkeswood's article on the species Julodimorpha bakewelli:

...The males are known to mistake the ends of discarded 'stubby' bottles for females and attempt to mate with them. The first published indication of this phenomenon was Douglas (1984), who published a photograph of a male J. bakewelli attempting to copulate with a 370mL beer bottle in Western Australia.

The 'stubbies' were apparently acting as 'supernormal releasers' for male copulation attempts in that they resembled large females; the shiny brown colour of the glass is similar to the shiny yellow-brown elytra of the female
J. bakewelli. On two occasions, a flying male was observed to descend onto a stubby and attempt copulation, and a search yielded two other stubbies with male beetles, with genitalia everted and attempting to insert the aedagus.

A discarded wine bottle of a different colour brown held no attraction; in addition, rows of regularly spaced, small tubercules around the base of the bottle reflect the light in a similar way to punctuations on the elytra of the beetle; these along with the colour and shape of the bottle may well enhance their resemblance to females.

One of the reasons I find animals interesting is the mystery of what it's like to view the world through their minds. Although I have to take a scientific approach, part of me wants to believe that in some important ways, the minds of animals are not very different from our own. I find it exciting when Larry reads human social cues, or opens doors with his paws, because this behviour seems like evidence of a highly evolved intelligence. But at other times, his actions, like those of the bottle-copulating beetles, seem to be automatic reactions to narrow environmental cues, and not the actions of a thinking being.

The philosopher and mathemetician Rene Descartes thought that animals were 'automata': mere machines whose behaviour was a robotic response to their environment. Sadly, it seems like this view is sometimes correct.

But perhaps this is not the evidence of a vast gulf between human and animal consciousness that it appears to be. Larry's hunting of faux fur and insemination of our woollens may seem like absurd behaviour, and evidence of his lower powers of thought. But what is this animal doing living in our house in the first place? He does no work, contributes no rent, and his food is paid for by humans. By biological definitions, Larry is a parasite, yet we willingly allow him to exploit us.

Modern, urban humans also live in an environment which bears very little resemblance to the environmental conditions under which we evolved. It seems like we too can misdirect our reproductive instincts. Don't worry, this is not a reference to bestiality. I'm referring to zoologist Konrad Lorenz's famous theory on the appeal of domestic pets. Lorenz observed in the 1940s that most pets have large eyes and heads, and shortened noses, all features in common with human infants. He suggesting that these infantile features were responsible for triggering a nurturing response in adults. In the absence of the litter-loads of spawn we would have produced in our wild state, Larry's big eyes, soft fur, and button nose trick us into thinking we are caring for our own baby. Although, if my human child starting doing that to our jumpers, I'd probably put it in a bag and drown it in the creek.

Saturday, May 9, 2009

Brittle Star Photos

Here are some pictures of a brittle star, which were taken by a classmate in my marine zoology subject. Brittle stars are echinoderms, and are related to starfish.

I think this one was about three cm across. These photos were taken by pointing the camera down the microscope lens. The photos down the bottom show the underside of the animal, with its star-shaped mouth visible.

Thursday, May 7, 2009

A Kick up the Blastopore

"When I view all beings not as special creations, but as the lineal descendants of some few beings which have lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled."
-Charles Darwin,
The Origin of Species

In the popular imagination, evolution is an ape with incrementally improving posture. Human beings came from monkeys. Before that, we crawled out of the ocean. But both these primal ancestors are relatively recent arrivals on the earth. Vertebrates are only 400 to 500 million years old. But our ancestors have been around since life first evolved. What did they look like before they developed bony skeletons?

If you trace the evolutionary line back far enough, we are descended from invertebrate animals. So far, I haven't come across any theories on what our invertebrate forebears looked like. Perhaps this is because no one knows. Invertebrates make poor fossils because of their soft, fragile body parts. However, human beings are more closely related to some groups living invertebrates than to others. Perhaps this offers clues as to what our invertebrate ancestors looked like. Try to guess who our closest invertebrate relatives are. Do see any familiar faces below?

What about the molluscs? I hear a lot of stories around the zoology department about octopi in laboratories who wait until their researchers go home, then climb out of their tanks and switch off all the lights in the lab. I'm not sure if these stories are true (perhaps this can be the subject of future blogs), but look at that big brain! Surely the octopus is kin. I'm not too sure about the bivalve, though.

Or what about the platyhelminths? No one really wants to be closely related to a tapeworm, but they can't be discounted.

How about the nematodes? Is that primate-level intelligence brewing behind those unassuming piercing mouthparts?

Or the echinoderms? Sea cucumbers certainly look like a certain part of the primate anatomy, but is this evidence of family ties?

How about the cnidarians, with their very economical use of the same orifice for multiple bodily functions? (see a previous blog). Surely they're not our nearest invertebrate cousins?

The annelids are also contenders. Do you have an inner bloodsucking leech?

My personal favourite would have been the arthropods. There is something familiar about insect faces. You can at least look them in their two eyes, which are located above a mouth, and see something not too different from a basic vertebrate face. Or less different than a blind tube sporting a bunch of piercing hooks, anyway.

But the answer is surprising.

The winner is: ECHINODERMS. Starfish, sea cucumbers, anemones and their ilk are our nearest invertebrate relatives. This does not necessarily mean that our invertebrate ancestors looked like starfish (although part of me really wants to believe they did), but that echinoderms and vertebrates had a more recent common ancestor than vertebrates and any other invertebrate group.

One important piece of evidence for this relationship is as follows. At a very early stage in our lives, all of us (you, me, echinoderms, tapeworms) looked a bit like this:

Before our body plans formed, we were all big, fat, amorphous balls of cells. Those were the days! Our balls of cells each had a little hole called a blastopore in them. In all other groups of animals, the blastopore developed into the mouth of the animal. In vertebrates and echinoderms, it formed the anus. Our guts run in reverse. The thing that sets vertebrates and echinoderms apart is that, compared to other animals, we are all talking out of our arses.