bdstaylor's Identifications

Spirostomum ambiguum Ehrenberg, 1834. from the superficial river edge benthos of the freshwater segment of the estuarine Peconic River. Imaged in Nomarsdki DIC on Olympus BH2S using Splanapo 20 0.70 and SPlanapo 40 0.95 objectives plus variable phone camera cropping on Samsung Galaxy S9+. The cell measures 960 um in length. The peristome is 2/3 the length of the body with the cytostome at the posterior 2/3 location. There is a large terminal contractive vacuole with a long collecting canal reaching almost the anterior end of the cell. The macronucleus is moniliform forming a chain of connected elongate spindle shaped macronuclear nodules beginning at the anterior 40% of the cell length and extending almost to the posterior end.

"Spirostomum ambiguum Ehrenberg, 1834. [syn: Trichoda ambiguum Müller, 1786; S. ambiguum var. major Roux, 1901] 900 m several mm long. Length: width ratio about 9-17. 15-25 kineties on each side; heterogeneous, numerous (4-5) CG rows per stripe. Peristome always longer than 1/2 of the body length, often reaching 2/3. CV much shorter than body length, rarely exceeding 1/10. The color depends on cytoplasmic granules. Moniliform MAC with 12-50 (avg. 15-25) nodules not exceeding 35 45 m in length when stained by Feulgen reaction. Numerous (up to 100) MICs 1-2 m long. Mono phyletic. Only found in freshwater. Reported in central and northern Europe, England, Russia, central Africa, USA, Jamaica, India and Japan. It sometimes harbors prokaryotic symbionts in the MAC. Spirostomum ambiguum is a well-defined, easily recognizable morphospecies whose monophyly is also strongly supported by molecular sequences" (1).

"Differential diagnosis
1) Size in vivo 1-000-4000 x 48-100 um, mostly 1200-2000 um. Visible with the naked eye as a white thread. Very flexible and contractile, shortens to approximately 390-430 x200-220 um. Contracted cells cigar-shaped.
2) Shape slender to moderately broad worm-shaped, more or less parallel-sided, 10-17 times longer than wide. Front end rounded, rear end truncated. Slightly flattened laterally. Ventral side in area of ​​the mouth entrance slightly bulging.
3) Macronucleus moniliform or rosary-shaped, consists of 10-50, mostly 15-20 ellipsoids, about 18-53 x 12-24 um large nodes that form a long band that approaches the dorsal side. The number of nodes correlates positively with the age of the cell (REPAK & ISQUITH L974).
4) Contractile vacuole at the posterior end, with a long collecting duct extending forward along the dorsal side which sometimes shows ampullary extensions.
5) Close under the pellicle there are many spherical, spherical, yellowish granules arranged in elongated bands of 4-5 rows each which give the cell a yellowish to brownish color.
6) About 70-90 slightly spiraling rows of cilia, consisting of basal bodies arranged in pairs are constructed, but only the front one has a cilium.t
When the cells contract (startle reaction), the rows of eyelashes spiral around the body.
7) The adoral membrane zone extends from the anterior end to the posterior third (about 65-70 % of the body length) and turns to the right at the lower end. Parallel to the adoral membranelle zone a non-ciliated oral groove, which is bordered on the right by an undulating membrane.
8} Movement hatching, worm-like crawling and writhing. Fluidity with longitudinal rotation axis, with the front end describing a cone-shaped body of revolution. In the plankton falling floating with inclined longitudinal axis" (2).

"Spirostomum ambiguum is easy to recognize because of its size and shape, but the differentiation with S. minus causes considerable difficulties. There are many shape variations which occur, size and shape are not reliable distinguishing features. Usually S. minus is significantly slimmer and almost never reaches a length of 1 mm, while S. ambiguum is more compact, stockier and over 1 m long. Only the length of the adoral membrane zone in relation for body length (S. ambiguum: 65-70 %; S. minus: 35-50%) remains reasonably reliable distinguishing feature, but here too the differences do not seem to be too pronounced. Furthermore, the ciliates S. semivirescens have a similar size and shape (up to 2 mm, very slender, adoral membrane zone up to 50 % of body length, green through symbiontic algae) and Homalozoon vermiculare (up to 1.5 mm, 5-21 contractile vacuoles along the dorsal side, mouth small and only at the front end) as well as microturbellaria and nematodes. The characteristics 1,3 and 7 are particularly important for identification" (2).

1. Focusing on Genera to Improve Species Identification: Revised Systematics of the Ciliate Spirostomum Vittorio Boscaroa,1, Daniela Carducci, Giovanna Barbieri, Marcus V.X. Senra, Ilaria Andreoli, Fabrizio Erra, Giulio Petroni, Franco Verni, and Sergei I. Fokin. Protist, Vol. 165, 527–541, August 2014
2. FOISSNER W., BERGER H. & KOHMANN F. (1992): Taxonomische und ökologische Revision der Ciliaten des Saprobiensystems - Band II: Peritrichia, Heterotrichida, Odontostomatida. – Informationsberichte des Bayer. Landesamtes für Wasserwirtschaft, 5/92: pp 317-25.