To: RobBerdan, Charlie Guevara, PNWmossnerd
From: Jim Kirk, aka gastrotrichman
Thanks for the links. I looked at your website and your gastrotrich piece. Very nice images. You could easily capture sets of images that would allow you to identify gastrotrichs to species.
I’m not familiar with the Axioscope A1. Given the price, I’m guessing it is an “infinity tube length” scope. But it does make nice images.
I remember you from another microscope forum about a decade ago. Nice to meet again. I’ve pasted your points below with some thoughts.
1) Do you serendipitously encounter varied Genus/species of gastrotrichs...or do you have predictable locals to collect from to encounter your variety of gastrotrichs? I have encountered perhaps five species of these elongated 'porkypines' ( vertebrate conceit...whoops).
I’ve been focused on gastrotrichs for just over a decade … basically, since retiring. Early encounters were somewhat serendipitous, but gastrotrichs are so widespread that diligent searching will reveal them in almost any aquatic environment. In the last few years I’ve focused almost exclusively on gastrotrichs in moving water; seeps, streams, small rivers. Gastrotrich species diversity and population density seem to be lower in moving water habitats, but those habitats have been less studied than standing water habitats, and therefore invite attention.
2) Do you go to any particular current listserves of meiofauna biologists to opine your ID's with images included..or do you mostly yourself posit an ID and have your sources to bolster your opinion?
I rely primarily on the scientific literature for identifications. I’ve collected much of the world literature on freshwater gastrotrichs. Identifications of species are often challenging, particularly in the large genus Chaetonotus. Molecular methods are frequently used by modern workers, but there are so many descriptions that predate molecular methods that morphological identifications are still necessary (and of course desirable for those of us addicted to light microscopy).
3) I fancy my next upgrade will be a DIC system, I'm curious about your stand. Do you have the DIC sequence of objectives on your nosepiece which you are quite satisfied with...or do you have an eye out to aquire a specific DIC objective for your stand?
I have two DIC scopes. I first bought a Leitz Orthoplan with “Interf.-Kontrast S.” As I recall, the oil top lens gives the DIC condenser a numeric aperture of 1.3. The DIC objectives are all Leitz (170mm tube length) and include a 25x 0.50, a 40x 0.65, and a 100x 1.30 … all cemented in what is presumably their original factory position in the nosepiece so that the objective prism has the appropriate orientation relative to the condenser prism. My other DIC scope is a Nikon Microphot. The DIC condenser has a top lens that yields a numeric aperture of 1.4. Since the Nikon DIC system does not have a prism associated with each objective, it is possible to use virtually any 160mm tube length objective of the appropriate magnification. My Microphot DIC objectives are all Nikon and include a 20x 0.75, 40x oil 1.0, 60x oil 1.4, and 100x oil 1.4. None are branded as DIC objectives, but I’ve yet to see a strain-related problem with the images they produce. So far the Microphot produces better DIC images than the Orthoplan, which may be due to the superior (i.e., larger numeric aperture) Nikon objectives, operator (me) error with the Orthoplan, or a combination of both. Note that I have not seen a Labophot-Optiphot-Microphot DIC condenser with an oil top lens (oil top lenses are available for later Nikon DIC condensers), so immersion oil incursion into the condenser lens assembly is a risk. However, “oiling the condenser” is essential for better images.
4) Is the water table under your coverslip a fleeting moment prior to specimen squash...or does your DIC protocol permit a water film thickness tolerable for your live gastrotrichs?
I have a “typical” protocol for examining gastrotrichs for identification. I put a small bead of petroleum jelly on three edges of a 22 x 22mm No. 1 or 1.5 coverslip, put a very small drop of 1 percent magnesium chloride in the center of the coverslip, transfer a live gastrotrich to the drop with an Irwin loop, and carefully set the coverslip, petroleum jelly beads down, on a clean slide. The magnesium chloride anesthetizes most gastrotrichs; the concentration sometimes needs to be reduced to keep some gastrotrichs from rolling into a tight ball. Once the gastrotrich has stopped swimming, I carefully press down on the coverslip to slightly compress the specimen. Too much compression will cause the specimen to burst. Too little compression will yield images that may be difficult to use for identification. If you want to observe the gastrotrich alive, substitute water in place of the magnesium chloride, limit compression, and be patient. The reason for a very small drop is to keep the gastrotrich near the center of the coverslip and away from the edges. Toward the end of a viewing session, I sometimes run a small amount of dilute aceto-orcein under the open edge of the coverslip to bring out small scales that may not be visible otherwise, even with DIC. Every gastrotrich worker seems to have his or her own protocol. Permanent mounts of gastrotrichs are reputed to degrade over time, so that essential morphological features are lost … consequently, temporary mounts documented with good photomicrographs and line drawings are typical for gastrotrich descriptions.
Howdy. I toyed with mosses in the distant past … even took a few identification courses in Portland, Eugene, and Berkeley. But gastrotrichs got under my skin.
I’d be interested in hearing what you do with mosses.
Bausch & Lomb MicroZoom