Going through the July 13 issue of Current Biology, I was struck by just how many interesting things you can learn from a single issue of a journal:
- From a review of the new book Butterflies: Messages from Psyche, by Philip Howse: The Atlas moth (Attacus atlas) evolved the image of a snake head at the tip of each wing; the moth flicks its wings when disturbed to mimic a snake’s swaying motion.
- The eyed hawk moth (Smerinthus ocellata) has wing patterns that look like the face of a fox. Could this be aggressive mimicry of a mammal, evolved to frighten predators?
- Fungus-growing ants use bacteria (which produce antibiotics) to keep down the parasites in their fungus gardens. The ants also exhibit “proactive hygiene,” grooming themselves compulsively before entering the garden chamber of the nest. They groom themselves longer if they’re more contaminated by microbes, but don’t groom when there is no fungus growing in the garden.
- Adult mongooses crack bird eggs by either biting them or throwing them against rocks. Some scientists made artificial eggs and watched how adults opened them while juveniles were nearby. Two to four months later, the juveniles were presented with fake eggs. Surprisingly, they used whichever opening method—either biting or throwing—that they had witnessed much earlier. According to the authors, this is the first evidence in any animal for “social learning involved in the transmission of behavioral variants between individuals.” I don’t know enough about things like primate behavior to judge if this is true.
- Cleaner fish, who remove parasites from other “client” fish (thereby getting a meal) in a famous example of mutualism, have evolved independently many times. One species (L. dimidatus) eats 1200 parasites per day, most of them isopods. When fish are caged and not allowed access to cleaners, the isopods can increase more than fourfold on the fish’s body in 12 hours, and can kill it. But who cleans the cleaner fish? Answer: they clean each other.
The bluestreak cleaner wrasse, Labroides dimidiatus (left) cleaning a “client,” a Pacific sailfin tang (Zebrasoma veliferum). Photo (in the journal) by Karen Cheney
- This is relevant to our discussion of senescence. In an intruigingly-named dispatch called “Behavioral ecology: the menopausal aphid glue-bomb” (who wouldn’t read a dispatch with a title like that?), William Foster highlights some nice work—published in the same issue—by Keigo Uematsu and colleagues from the University of Tokyo. The gall-forming aphid Quadrartu yoshinomiya is clonal: females produce exact genetic copies of themselves via parthenogenesis. (Galls are bizarre growths on plants that are induced by insects themselves; the evolution of gall making is another fascinating evolutionary tale.) The aphids have an unusually long life span, hanging around well after they stop reproducing. It turns out that post-reproductive (“menopausal”) aphids cluster around the opening of the gall (through which the aphids exit), and secrete a glue when a predator (e.g., a ladybug) is nearby. This glue gums up both the aphid and the predator, dooming both to death. The authors do a bunch of experiments supporting their idea that this “altruistic” behavior, which really does keep down predators, has evolved via kin selection. The aphids are, after all, clonal, so when an individual dies as a glue bomb, it’s really helping save exact copies of its genome. This is analogous to sterile worker bees dying after they sting an enemy (the sting pulls out the worker’s innards), thereby saving their future-queen sisters, with whom they share three-quarters of their genes.
Aphid gall on evergreen witch-hazel (Distylium racemosus). The meonopausal glue-bomb aphids are clustered around the gall entrance, waiting to bomb predators. Photo by Harunobu Shibao.
C. Wingless adult aphids secreting glue (scale: 0.5 mm). D. Wingless adults (arrows) stuck with glue to a doomed predatory ladybug larva.
These are only about half of the articles/dispatches I read in this issue, and this is but single issue of a single journal—there are dozens of journals relevant to evolutionary biology. And this is why it’s so much fun to be a biologist. Not only do we get to find out stuff in our own labs, but we get to read about all the cool stuff that other people have found out. In other words, every day we go to work expecting to learn about new marvels of nature. And those marvels are, apparently, inexhaustible. Imagine getting paid to do this!
Now many of these articles are also of interest to laypeople who are curious about science, but how many laypeople read scientific journals? Most of those journals are expensive, arcane, and can’t be seen online for free. I can’t do posts like this every day, so if you’re a parent, and want your kids to have as much fun as we do, by all means expose them to biology when they’re young.
Oh, and congratulations to Geoff North and his team at Current Biology for keeping the journal a repository of not only good science, but good stories as well.
p.s. The latest (July 27) issue of Current Biology contains a nice “quick guide” to pycnogonids, or sea spiders, by our own pinch-blogger Matthew Cobb. Pycnogonids are bizarre marine arthropods that appear to be all legs and no body:
The pycnogonid Colossendeis gigas perched on an anemone, Liponema brevicornis, 2893 meters down in Monterey Submarine Canyon, CA, USA. Photo (c) 2005 MBARI.