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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3069

Sudzuki Minoru; [On the General Structure and the Seasonal Occurrence of the Males in Some Japanese Rotifers VI.]. Zoological Magazine (Dobutsugaku Zasshi) 65(11):415-421, 1956

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17) Brachionus falcatus Zacharias: This species which has been regarded as a subtropico-politan in distribution occurred in the Marsh (M1) in midsummer alone. The species population was found in the latter half of June in 1953, from the beginning of August to the middle of September in '55: while, in the years 1951, '52 and '54 not a single specimen appeared. The mictic females occurred in the middle of June ('53) and the latter half of August ('55) when the water temperature was above 26 degrees C, and the sexual period was observed just after the highest temperature. This species, therefore, seems to be a summer stenothermal and mono-or acyclic form. The male is 110-128 µm in total length, 52-57 µm in body length, 54-63 µm in width, and 54-62 µm in height. Besides the male, two types of the mictic females are figured. 18) Trichocerca pusilla (Jennings): The species was collected from M1 in all seasons save winter, while from R1 only in autumn. The maximum lay in autumn in both spots (M1, R1). The male appeared in M1 from the beginning of September to the middle of November, while, in R1 in the end of October. Monocyclic summer form, but often dicyclic in M1. Males, 55-69 µm in total length, 45-51 µm in body length, 34 µm in width and 27-33.5 µm in height. The Japanese form proved to differ from that of Denmark (Wesenberg-Lund '23) in the following points: it has a motile foot, which reminds one a tap in Gastropus stylifer (W-L '23. Tab.XIII. Fig.3), and is apparently separated from the caudal extremity and provided with the foot-glands; it has a ciliary wreath on the penis, but not the chitinous plate. 19) Trichocerca cylindrica (Imhof): This species, as B. falcatus and F. longiseta, occurred exclusively in M1, and the maximum in general lay from summer to early autumn. The male appeared from late June to the beginning of July ('53, '55), in late July ('53, '54), and in Mid-November ('55). The monocyclic summer form. Total length of the male is 74-92 µm, the body 60-72 µm long, 37.5-42.5 µm wide, and 37.5 µm high. No chitinous plate is observed but the ciliary wreath. The penis somewhat resembles that of Keratella. No foot. Judging from such taxonomic characters as eye, foot and the penis-vas deterens of the male, the writer could not settle this species within the genus Trichocerca.