Ref ID : 3067
Sudzuki Minoru; [On the General Structure and the Seasonal Occurrence of the Males in Some Japanese Rotifers IV]. Zoological Magazine (Dobutsugaku Zasshi) 65(1):1-6, 1956
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This paper is a part of the study on the general structure and the seasonal occurrence of the male rotifers, dealing with two species, Filinia longiseta (Ehrbg.) and Asplanchna sieboldii (Leydig), collected from Urawa (M1). 13) Filinia longiseta: Perennial. In winter the present species occurred as a mystacina-maior-like form having short spines, while, in summer, as a limnetica-like form having long ones. The mictic females did not appear in some definite periods of year; in 1952 they occurred once from summer to fall, in 1953 at the end of autumn; while, in 1954 only the D-Female females appeared at the end of April, lasting to the middle of May (the Male-Female females were not collected in spring). The mictic females occurred at the beginning of November and again at the end of December; in 1955 only the Male-Female females occurred already from the end of January to the end of February with a mixmum, then in the middle of March and April respectively and again in the end of May (in these periods the D-Female females did not appear). The cyclicity, therefore, could not be given with certainty. From the fact mentioned above it seems probable that there is not a very close relationship between the occurrence of the males and the seasons, and that between the mictic females Male-Female and D-Female there are certain differences as to their habitats. Since difference between the males of mystacina-maior-like and limnetica-like species was scarcely recognizable, chiefly the males of the former was figured. Total length 78-112 µm, body length 90-95 µm, body width 45-58 µm. 14) Asplanchna sieboldii: In males as well as in females, there are observed some differences between the specimens collected from Urawa and the so-called sieboldii reported by Wesenberg-Lund et al. concerning the number and arrangement of flame bulbs, distribution of the protonephridia and muscles, etc. Therefore, the specimens from Urawa might be treated here as a new sub-species, A. sieboldii urawaensis. This subspecies occurred twice a year: at the end of May and from the end of August to October; the population, however, was almost always small and nothing like a maximum was observed. The specimens collected usually belonged to the mictic females and were without exception of a saccate form, and never revealed a tendency to trimorphic development. Dicyclic. Body 342 µm in length, 218-180 µm in width, but even among the males hatched at the same time from the same mother were found some individual variations: for example, 194 µm by 103-253 µm by 157 µm (May 26). Syntype in the Zool. Inst. of Tokyo Kyoiku University: Preparat-No. Z.I.T.K.D. 5350.