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Cohnilembus verminus (O. F. Müller, 1786) from an increasingly putrid 5 day old sample taken from the coarse sand intratidal benthos of marine extuary Acabonac Harbor at Louse Point launching ramp. A shiny thin biofilm developed on the surface of the specimen container due to putrefaction of a small marine snail and some algal clumps that were left to rot giving rise to several saprobic species. As mentioned by Song (2000), C. verminus shows great variation in size and this is reflected in my sample with individuals ranging from 37.5 um up to 75 um. I find the membranelles mesmerizing and extraordinarily delicate.

Genus Cohnilembus Kahl, 1931; Cohnilembus verminus (O. F. Müller, 1786) Syn. Lembus punctatus Kahl, 1928; Lembus reesi Kahl, 1931.

"Description. Size highly variable, in vivo 40-130 x 6-20 µm, depending evidently on population rather than nutrition state: in one population mostly more than 100 µm in length, while in others seldom over 80 µm. Length: width in slender population about 7-10:1, in thick populations ca 5-6:1. Outline basically very slender, spindle-shaped or fusiform with anterior portion considerably narrowed and tapering, both ends pointed. Cross section circular, yet in starved (?) specimens much flattened (likely bilaterally) so that the cells sometimes make a fold-up or twisted appearance. Buccal field narrow, about 2/5 to over 1/2 of body length. Pellicle smooth. Extrusomes spindle-like, about 1 µm long, sparsely arranged beneath pellicle, which are recognised from life only at high magnification" (1).

"Cytoplasm colourless and hyaline, always containing several to many large (2-4 µm across), shining greenish granules. Food vacuoles large and few in number, containing possibly bacterial. Contractile vacuole small, located caudally or slightly subcaudally near ventral margin of cell with frequent pulsation (about several seconds intervals). Macronucleus large, elongate to oval in shape, centrally located with many to numerous nucleoli, which are often irregular-shaped after protargol impregnation. Single micronucleus close to macronucleus" (1).

"Cilia more or less sparsely arranged, 7 to 10 µm in length, single caudal cilium about 15 µm long. Cilia of membrane/ membranelles about 12-15 µm in length. Movement not very active, swimming snake-like or slightly zig-zag, moderately fast; in culture usually motionless for a long time or gathered together on sediment (food) as shown in Fig. 4 B. When disturbed, swimming for a short distance and then motionless again" (1).

"Somatic kineties longitudinal, extending over entire length of body. Unlike in most other scuticociliates, among these “mixed” kineties each composed of often only a few to several dikinetids at anterior end, while in most portion with monokinetids. Along buccal field, kinety left of oral area (SKn) membranelle-like, consisting of densely arranged paired basal bodies, adjacent to membranelle" (1).

"Buccal apparatus highly specialized. Membranelle 1 (M1) occupying about 4/5 of buccal length, one-rowed in most portion; its posterior portion splitting into 3 groups, each with 3 basal bodies. Most part of M1 adjacent to densely-ciliated kinety n (SKn), both of which form together the prominent “undulating membranes”. Membranelle 2 and 3 close to M1, relatively small and each with about 5-8 basal bodies. Paroral membrane (PM) on right of shallow buccal cavity, short and gently curved, extending anteriorly to about level of M2; its anterior half one-rowed, posterior with zig-zag structure. Scutica (Sc) Y-shaped, consisting of about 3 pairs of basal bodies" (1).

"As revealed in previous work, this species appear very much size- and shape-variable and may exhibit rather different appearances in vivo, but after impregnation, all share the same patterns of the silverline system and infraciliature (Kahl 1931; Borror 1963; Thompson 1964, 1968; Jones 1974; Foissner 1976; Foissner et al. 1982; Ströder 1991, master thesis; Hu et al. 1996). Based on the body shape and the general appearance from life, two marine slender Lembus-species described by Kahl, L. punctatus Kahl, 1928 and L. reesi Kahl, 1931 should be compared. The former has a narrowed posterior end (similar to the thicker form of the Qingdao population) with relatively shorter buccal field. Considering the fact that the body shape of Cohnilembus verminus is highly population-dependent, it is reasonable to come to the conclusion that Kahl’s L. punctatus represents only a form-variation and should be thus conspecific with the former. Lembus reesi is characterized by the distinctly smaller cell size (ca 30 µm long) as described originally (Kahl 1931). However, the minimum size of some starving cells of the Qingdao-population could be-during culture-only 30-40 µm long, therefore, Lembus reesi should be possibly synonymized with Cohnilembus verminus" (1).

1. Morphological and Taxonomical Studies on Some Marine Scuticociliates from China Sea, with Description of Two New Species, Philasterides armatalis sp. n. and Cyclidium varibonneti sp. n. (Protozoa: Ciliophora: Scuticociliatida) Weibo SONG. Acta Protozool. (2000) 39: 295 - 322

Magnification of photo: 400×
Habitat: very dark, muddy sludge near the edge of a pond.
Photo taken with a Celestron PentaView Digital Microscope. According to their website, the FOV (i.e. the diagonal width) at 400× is 150 µm.
https://www.celestron.com/blogs/knowledgebase/what-is-my-digital-microscopes-field-of-view

1000x + phonezoom. Saltwater marsh sample that has been closed on my desk, accumulating algae for months. Super super fast, spins as it swims & can swim backwards! Weird. The jar isn’t too biodiverse anymore, a few tiny flagellates and ciliates, nematodes, and of course an abundance of algae, fungi & methane-producing anaerobic bacteria. When I popped the jar open, it made a hiss & my partner asked, “did you fart???”

Mag. 100x (1), 400x (2)
Bryozoan survival and proliferation "pod":
https://en.wikipedia.org/wiki/Statoblast --and-- http://www.bryozoans.nl/statoblasts/en/statoblast_intro.html

• A pond-side water sample was taken on 05/29/2022 using a 10µ dip net to enrich for microbes. Air temp. 76°F.

Was not moving.
Seemed to be filled with the same organisms featured in these observations:
https://www.inaturalist.org/observations/112352855
https://www.inaturalist.org/observations/112352929
https://www.inaturalist.org/observations/112352993

Collected from fish tank rocks.
First two pics are 250x magnification, others are 1000x.