Pseudodactylogyrus microrchis (Monogenea) on the Gills of Cultured Eels—II Oviposition, Hatching and Development on the Host

Abstract

The influence of water temperature on oviposition, hatching and development of P. microrchis were studied. The results obtained are as follows: 1) The average number of eggs laid by an individual parasite per day was 1.2 at 10°C, 9.6 (4.9–19.0) at 20°C and 7.7 (3.0–9.8) at 28°C, respectively. 2) The oncomiracidium of the species hatched out mostly in 5–8 days at 20°C and 2–5 days at 28–30°C, but did not hatch out at 10°C in the experimental period of 40 days. 3) A Pseudodactylogyrus-free eel (A. anguilla) was brought into contact with the swimming oncomiracidia in a small aquarium, and sequential observations of the young forms attaching to the host were made at 28°C. As a result, the young stages could be divided into 5. Stage 1 (0–1 day after attachment to the host): the shape and the size of the anchor were almost the same as those of the swimming larva (oncomiracidium). Stage 2 (1–2 days): the anchor developed in size. Stage 3 (2–3 days): the bar of the anchor appeared. Stage 4 (3–4 days): the ventral and the dorsal processes of the anchor appeared. Stage 5 (4–6 days): the reflexed part of the ventral process was formed. In 6–7 days after attaching to the host, the worm became adult morphologically, and actually laid eggs. © 1978, The Japanese Society of Fisheries Science. All rights reserved.