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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Stylaria

Stylaria Lamarck, 1816 (ref. ID; 1257, 3692, 6913)

Family Naididae (ref. ID; 1928, 5869, 5939, 6451, 7854)

Family Naididae: Subfamily Naidinae Lastockin, 1924 (ref. ID; 1257)

ref. ID; 1663

Anterior end forming a proboscis. Dorsal setae beginning on IV, V or VI. Fewer setae, mostly less than 10 per bundle. (ref. ID; 1663)
  1. Stylaria fossularis Leidy, 1852 (ref. ID; 1923, 3692, 7854)
  2. Stylaria lacustris (Linnaeus, 1767) (ref. ID; 1257, 1663, 1923, 2780, 3692, 6913, 7098, 7854) reported year? (ref. ID; 1928, 3446, 5869) reported author and year? (ref. ID; 5939, 6451)
  3. Stylaria lomondi (ref. ID; 1928)

Stylaria fossularis Leidy, 1852 (ref. ID; 1923, 3692, 7854)

Descriptions

Proboscis projects from the apex of the prostomium. (ref. ID; 1923)

Remarks

Respecting the authority of Michaelsen (1900), several authors have regarded S. fossularis as an intraspecific form of S. lacustris. Sperber (1948) listed characters different in these species. I did not find any difference in size between them, noted by Sperber (1948), as my S. fossularis had ventral chaetae about 100-150 µm long and hair chaetae 140-820 µm, which was well within the variation limits of S. lacustris. The shape of the prostmium was certainly different, conical in S. fossularis and bilobate in S. lacustris, without any intermediate forms. (Di Persia 1975 described variations of the prostomium in S. lacustris, from lobate to rectangular, but never conical like in S. fossularis. According to my own experience, a rectangular prostomium occurs in the early separated zooids of S. lacustris). Ventral crotchets of S. fossularis, although curved in thier proximal portion (well figured by Liang 1962), had no broken appearance characteristic of S. lacustris. The atrium of the mature individual was distinctly divided into the ampulla and the ejaculatory duct (the duct being inconspicuous after Sperber 1948), both about 90 µm long. Vas deferens entered the atrium between the ampulla and the duct, outside the atrial prostatic layer, as noted by Sperber (1948) in the case of S. fossularis. Thus S. fossularis and S. lacustris appear to be two different sympatric taxa in the study area. (ref. ID; 7854)

Examined materials

Three specimens were found in three different samples from the rivers of Razdol'naja and Rakovka. One of them, collected on 20.10.1989 as mature, was studied on sections. (ref. ID; 7854)

Stylaria lacustris (Linnaeus, 1767) (ref. ID; 1257, 1663, 1923, 2780, 3692, 6913, 7098, 7854) reported year? (ref. ID; 1928, 3446, 5869) reported author and year? (ref. ID; 5939, 6451)

Descriptions

Proboscis inserted in a notch in the prostomium. (ref. ID; 1923)

Remarks

Common and abundant at vegetated localities throughout the lake. Although Stylaria fossularis differs from S. lacustris by lacking an invaginated lobe on the prostomium bearing the proboscis (Chen 1940), both have been regarded as a single species (e.g. Brinkhurst 1971). Dipersia (1975) (cited in Brinkhurst 1986) demonstrated that the proboscis characteristic could change in culture. The form of proboscis in all the Lake Biwa specimens examined corresponds to S. fossularis type, i.e., an invaginated lobe has never been seen. (ref. ID; 7098)