Two rotifers - info and photo added

[dy5]

One collection site this summer was especially rich in micro creatures. These two rotifers, in particular, caught my eye.

The first photo is Monommata sp. which was quite common. Very graceful and calm usually, but capable of sudden, violent jumps.

The rest of the photos are of Microcodon sp. Didn't see many of these, and they were only in the samples for a week or so. Fast, lunging movement made it a challenge to photograph, as did its geometry. It took about 350 photos to get these three and just a few other reasonable images. Fascinating creatures that could star in a sci-fi horror film.

This is a view looking at the back (dorsal) side of the rotifer focused on the red eyespots. Portions of the back side and edges of the corona are visible.

Now looking at the front of the animal focused on the mouth in the center. The corona, with the rows of cilia that create the feeding current, is roughly circular, but not a flat disk. In fact, it's curved enough so some parts are completely out of focus. The rotifer swims with the corona facing forward. The colors from the eyespots and other structures show through the semi-transparent body.

An oblique view of the corona with only a small portion in focus. The white bumps lined up around the mouth are the bases of the cilia.

A view similar to the 2nd Microcodon photo, but a different focal plane. The flash just happened to catch this yellow object hovering over the rotifer's mouth. Could be a food item just before ingestion. However, it was in three frames taken a couple of seconds apart - food would be gone more quickly than that. My guess is that a potential food item was pulled in by the current, but was too big for the mouth.

Cheers, David

Nikon 80i microscope and D850 camera, DIC, high-speed flash.

[Sym P. le]

Thanks for posting these. I'm not familiar with microscopic life forms other than what's posted here. I just want to be clear about something for my own understanding. The colours are real?

[dy5]

Yes, the colors are real. Eyespots as in rotifers and copepods are often bright red because of the photopigment or for other reasons (think of the colored eye shine of many mammals caused by the tapetum lucidum that enhances sensitivity). Some of the Microcodon had a large, brilliant orange structure (an egg?).

As an aside:
My goal - as with others on the forum - is to present an image that conveys as accurately as possible what I see under the microscope. Sometimes the color balance of an image may be off, but that affects the whole image and is generally obvious.

[dy5]

Looking at the Microcodon photos after a few days, I realized that without a sense of the whole animal, they are more like abstracts than animal photos. So, I added some description and another photo to the original post hoping that might help.

But probably not. These guys are strange, and their body shape is hard to get across in photos. There aren't many photos of Microcodon on the web, and none I found helped much.

I did come across a wonderful monograph on rotifers from 1898 (http://www.rotifera.hausdernatur.at/Rot ... eLeman.pdf). The plates at the end are full of detailed drawings that are very pretty. There are several drawings of Microcodon that that do help somewhat with the anatomy. That monograph also suggests what a challenge those early naturalists faced and how amazingly well some of them succeeded. Imagine the time and effort drawing by hand what we capture digitally in a fraction of a second.

Cheers, David

[Sym P. le]

Thanks for posting the link. Now I also understand why those plates are coloured.