1972 Volume 7 Issue 1 Pages 6-14
In 14 previous papers, we reported on various stages of the life cycle of Callotetrarhynchus nipponica (a tentative name proposed by us). That is: Procercus with a cephalic organ, “borer” and scolex anlage, is parasitic on the abdominal body cavity ofEngraulis japonica; Procercus developes into Plerocercus with the scolex in the body cavity ofSeriola quinqueradiata or some other teleosts; Adult are found in the valvular intestine of Scoliodon walbeemi, a kind of requiem shark; Oraly administered plerocercus can develope into the adult in the valvular intestine ofTriakis scyllia under experimental conditions; Fertilized eggs are spawned from the gravid proglottides when the latter escape from the intestine into the sea; Ciliated coracidia liberate from theoperculated eggs.
In the present study efforts were made to clarify the processes of the development from coracidium to procercus. The results were as follows;1)9, 066 copepods of 15 genera collected from 4 different areas in the Bungo Channel and its adjacent seas were examined for stages following the coracidium. The result was negative.2)Copepods of 11 genera, Cladocera and zoea staged larvae, 1, 728 in total, collected from the stomachs of 150 Engraulis japonica(spring hatched group and 37 months old)caught in the Uwa sea were similarly examined.The result was negative, too.3)About 10 thousands coracidia were made in contact with 106 Tigriopus japonicus and the other 87 copepods of 9 species in beakers contained 1, 000 ml of sea water. Coracidia were not ingested by the copepods within 5 days. 4)About 800Engraulis japonica of 6.211.8cm in body length caught in the Sagami bay and 5 Triakisscyllia of 53.679.5cm in total length which had been artificially infected with the adults of C. nipponica were kept in the same aquarium. 325 anchovies were examined for procercus through 50 days with negative results.
Consequently the complete life cycle ofC. nipponica is still unknown, but we believe that our studies on the present species may give leading informations concerning the life cycle of Trypanorhyncha.