A new species of marine cercaria, possibly belonging to the family Acanthocolpidae, was found in the digestive gland of the spindle shell Fusinus perplexus and the specific name Cercaria itoi is proposed. C. itoi is a distome and biocellate cercaria with a long simple tail, five pairs of penetration gland cells, I-shaped excretory vesicle, 66 flame cells on each side and peculiar structures of comma- to sausage-shaped minute bodies, probably cystogenous glands, filled in the hindbody posterior to the acetabulum. The cercaria develops in redia, but its maturation of the cercaria occurs in the digestive gland of the host, after the immature cercariae leave the redia.
There was no mortality in ayu (Plecoglossus altivelis) which had mean body weight of 4.2 or 9.2 g during the rearing period after direct immersion in underground water containing lyophilized formalin-killed cells or sonicated cells of Vibrio anguillarum. A high level of protection against vibriosis was found in fish immersed directly in 0.94 or 9.4 (wet) g/l lyophilized or sonicated bacterin. The efficacy was no different for fish with a mean body weight of 4.2 g immersed for 1, 3, or 10 min in 1 (wet) g/l lyophilized bacterin. The duration of protective immunity in fish with a mean body weight of 8.0 g lasted 60 days after direct immersion in 0.94 or 9.4 (wet) g/l of lyophilized bacterin.
A new mytilicolid copepod, Trochicola japonicus, parasitic in the intestine of the short neck clam, Tapes philippinarum, from Lake Hamana (semi-enclosed coastal bay) is described for both female and male.
Argulus americanus WILSON 1902 was found on the bowfin, Amia calva, imported from Wisconsin, U. S. A. Eggs laid in a plastic container hatched in 35-37 days at 15°-16°C. Hatched larvae were experimentally infected to a cichlid, Tilapia mossambica. The larvae kept at 23°-26°C grew from 0.6-0.7 mm in total length on Day 0, to 2.5-3.5 mm on Day 20, to 4.5-5.8 mm on Day 40, and a single female larva grew to 6.9 mm on Day 70. Females laid eggs on Day 49 and Day 53. Male specimens on Day 7 and Day 26 are illustrated.
The parasitic copepod, Pennella sp., was found on the saury, Cololabis saira (BREVOORT), from the western and central North Pacific Ocean and the Okhotsk Sea in 1981 and 1982. It is supposed that the parasite population in the western Pacific area has recently increased.