Tuesday, December 26, 2023

The Ongoing Birdbath Fauna Check



Continuing with some backyard biology, with a focus on the microscopic fauna of our birdbath. Here are a couple of YouTube videos, made four plus years apart, but I can assure you that just about any time I look at our birdbath contents under the microscope, the community of organisms is pretty similar, especially with the rotifers and Vorticella, at least as long as the heater is in there in the winter. If we clean it out in the summer, it usually takes a couple of weeks before the community starts to reappear. And where do these organisms come from? I have no idea, but there is a lot of bird traffic in that water, and birds pick up all kinds of dirt, especially the robins who are messing around in the mulch, leaves, and grass continuously. Some of you may be able to put a name on the rotifer, but rotifer identification has always been far beyond my abilities, even though in another life, I might study them instead of parasites. However, the ones you see in these videos are the same kind that show up month after month, year after year.

Video link to Birdbath Dec 20, 2015


Video link Birdbath April 23, 2020


The two main characters in these videos, the rotifers (telescoping inverts with prominent cilia fields at their anterior ends, looking like wheels that give them their names), and the single-celled, bell-shaped, and stalked Vorticella, are filter feeders, generating water currents that sweep in small particles, e.g., bacteria, that are their food. In the rotifers, sometimes you can see a constantly moving chewing device, the mastax, which usually you must dissect out in order to accurately identify the species. One of the rotifers in this week’s video is also pregnant and you can see the egg inside her. Rotifers are notorious for having mostly female populations, and producing two kinds of eggs, one of which is relatively resistant to environmental conditions, the other of which hatches quickly and produces more females. These eggs hatch into males only during times of environmental stress and mating results in these resistant eggs. No metaphorical possibilities here at all for my writer friends.

The genus Vorticella was officially described by Christian Gottfried Ehrenberg, in 1838, in his classic two-volume set: Die Infusionsthierchen als vollkommene Organismen (liberal translation: Little beasts of infusions as complete organisms.) Infusions, as presented in a previous mailing, are mixtures of water and vegetation that have been allowed to blossom over time. The UNL library has a set of Ehrenberg’s volumes in Special Collections. When I was teaching Invertebrate Zoology, we would go over there to look at the folio-sized publications, with pages turned by the gloved hand of a staff member. The students (and I too!) were always stunned at the beauty, detail, and scholarship, given that these drawings were produced with 1838 optical technology. It’s a big-time lesson in observation. I’ve attached a pdf version of his drawings of Vorticella.

On other matters, filter feeding, like you’re seeing in these videos, has a long and glorious history in the animal kingdom. Oysters and clams are filter feeders, but so are brachiopods, which are truly prominent in the fossil record over the past several hundred million years. The structures used to generate currents and trap particles differ from group to group, but are obviously effective at collecting those life-sustaining particles that are simply (“”) floating around in the environment. Again, obvious metaphorical possibilities for my writer friends.

If you’re interested, here are a couple of links to Ehrenberg. I’ve had the privilege, and experienced the wonder, of going into the Linda Hall Library in Kansas City; highly recommended if you are in the vicinity.


Linda Hall Library in Kansas City