Monday, December 22, 2008

California dreaming

I was supposed to fly out to visit family in California for the holidays, but the nor-easter that blew through Sunday has adjusted our schedule rather dramatically. Our flight's been postponed 5 days. On the bright side, I love the white Christmas in Maine. It's also Nina's birthday, and Isaac Newton's, too, so there's much to celebrate. Unfortunately, my husband traveled a few days earlier to spend extra time with his mom and to work on a paper with a colleague in San Diego, so he's already been out there for some time. I keep reminding myself that we spent the first year of our marriage on separate coasts, while I was finishing grad school and he was starting up at COA. This helps put one Christmas 22 years later into perspective.

Friday, December 19, 2008

ant brains

Winter break and holiday plans aside, I'm already thinking about the parasites tutorial I'll be teaching next term. Carl Zimmer's book, Parasite Rex, makes the case very persuasively: parasites are so much more than grotesque little footnotes in life's pageant. They are major players in the ecology and evolution of many species. Of course, in addition to their ecological and evolutionary heft, many of them exhibit some really weird and creepy lifestyles. One of the most disturbing tricks that some parasites have developed is that of mind control. An infected host's behavior is altered by the parasite in a way that increases the ability of the parasite to complete its lifecycle. In many cases, parasites gain access to the final host, where reproduction occurs, by first infecting an intermediate host that is later eaten by the final host. Any behavior by the intermediate host that makes it more likely to be eaten benefits the parasite (but not the intermediate host, of course). Some parasites are able to manipulate theirs hosts, actually causing them to engage in reckless behavior. Pill bugs harboring acanthocephalan parasites may spend more time in dryer places and even prefer walking around on whiter surfaces.  This may not sound like especially exciting risky behavior, but compared to the safety of  the dark, moist leaf litter, where healthy pill bugs prefer to be, the infected pill bugs are more easily seen by birds, which gobble up the pill bugs and serve as the final host of their parasites.
Mind control of ants by liver fluke parasites has been colorfully presented in this video.

Thursday, December 4, 2008

Endangered Marine Invertebrate

A physicist friend recently sent me a link to 20 strange and exotic endangered species, saying that the list was "sufficiently yucky and biological" to appeal to me, and it got me thinking about endangered marine invertebrates. The white abalone is the only marine invertebrate that's been listed as endangered under the Endangered Species Act. "Only one? Those marine inverts must be in pretty good shape," you might be tempted to surmise. But you're more sophisticated than that, so you probably wouldn't. There is a long list of assaults on marine invertebrate species: habitat loss, overharvesting, invasive species, disease outbreaks, pollution, global climate change, and more. Most marine invertebrates just haven't been studied in sufficient depth to be listed as endangered, and there are only a handful that are considered to be "threatened" or "species of concern," which are lesser categories than "endangered." To read more about threatened and endangered marine species, you can find plenty here.
White abalone have suffered dramatically from overharvesting. Here's the somewhat oversimplified ecological tale: Usually as population size goes down, individuals enjoy enhanced rates of growth and reproduction, because competition between individuals decreases as populations shrink. But there's a limit. When populations get extremely small (and what's extreme will vary with the ecology of each species), individuals may suffer reduced rates of growth and reproduction. If you do better with some neighbors around, the benefits of reduced competition that come with a shrinking population ultimately lead to other challenges, the most obvious being finding a mate. The general phenomenon of individuals doing worse as population size gets even smaller is called the Allee effect. This is what happened to white abalones. Mating in abalones is not a particularly touchy-feely process. Males and females shed gametes directly into the ocean where fertilization and subsequent embryonic and larval development occur. Fertilization cannot happen if spawning partners are too far away from each other; even a few meters can result dilution of gametes that is severe enough to eliminate the possibility of fertilization. Moving adult abalone closer to each other in the field, as well as spawning them in the lab to produce offspring are management measures that are being taken to rescue this species from the threat of extinction. There's plenty to read about regarding sustainable seafood (white abalone clearly not included) at this month's Carnival of the Blue.