Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University Volume 17 Issue 1
1978-08-10 発行

Gamogenetic Forms of Evadne tergestina CLAUS (Branchiopoda, Cladocera) of the Inland Sea of Japan

Onbé, Takashi
A redescription is given of the gamogenetic forms of Evadne tergestina CLAUS (Branchiopoda,Cladocera) in somewhat more detail than in previous publications, based on the specimens collected on September 11-13, 1973 at several stations in the central Inland Sea of Japan. The adult male is provided with a pair of testes, each lobe of which terminates through a seminal duct in a long, tapering penis situated just behind the last thoracic leg. The terminal seta on the endopodite of the 1st thoracic leg is modified into a sharp, recurved hook, with 2 ventral setae also differentiating into very strong, falciform bristles. The gamogenetic female has a large resting egg, which looks dark in transmitted light, and an opening, the vagina, on the shell surface behind the caudal furca. These characteristics are similar to those in other podonid species. The number of gamogenetic forms in the total population on these dates varied considerably according to the stations, ranging from 2.7% to 23.3%, of which males comprised 2.2-12.5% and females with resting eggs, 0-12.4%. There seems to be a clear tendency for resting eggs to be formed in larger individuals.