抄録
Abstract: The life history of the luminescent crustacean Vargula hilendorfii(Ostracoda: Myodocopida), which mainly inhabits sand/mud bottoms near the seashore, was investigated in Amakusa, Kyushu, Japan from April, 2000, to March, 2001. The species was collected from a beach monthly or semi-monthly using sledge nets. Ovigerous females occurred from April to ctober, and juveniles were collected from May to December. In winter, most V. hilgendorfii collected were adult females, which suggests that females that had copulated survive until spring. Brood size averaged 50-58 eggs in most months but was slightly smaller in April(41eggs). In the laboratory, juveniles that were released from the marsupium reached maturity in 50-55 days. We also investigated the occurrence of the crustacean ectoparasite Onisocryptus ovalis(Isopoda: Epicaridea)in V. hilgendorfii Male O. ovalis invaded female hosts, consumed host eggs, changed sex to be come female, produced eggs, and died after hatching of the eggs. The percentage of female hosts parasitized by O. ovalis was low(0-24%)from summer to autumn, but increased greatly(36-91%)from winter to spring, primarily because of a shortage of hosts. Usually one or two male parasites were found to occupy one host, and only one of them changed sex; from winter to spring, however, up to eight male parasites were found on a single host and a maximum of five changed ex.
