the life history of the nematode Rughiduscuris acus was followed in the natural environment of the River Bystfice. The incidence, intensity of infection, and also the maturation of the nematode in the definitive host (Saimo truttu m. fario)indicate that the life history of this parasite exhibits an obvious annual cycle, when adult egg-producing female nematodes are present only from May until the beginning of July. This seasonal rhythm is largely due to changes in the food composition of the definitive host, although the effects of other factors cannot be excluded. In the River BystHce the main intermediate hosts of R. ucus are the bullhead (Cottus gobio) and the Siberian sculpin (Cottuspoecilopus) in the trout zone of the river and the stone Ioach (Noernacheilus barbutulus) in the lowland reaches. Larvae of the species Prodiamesa olivacca (Diptera: Chironomidue) were found to act as reservoir hosts for the second-stage larvae of Raphiduscuris acus.

Two echinostome trematodes of the genus Petasiger, P. exaeretus Dietz, 1909 and P. phalacrocoracis (Yamaguti, 1939), parasitising cormorants (Phalacrocoracidae), were found in Phalacrocorax carbo L. from the Czech Republic. Both taxa are redescribed and literary data on their occurence in cormorants are reviewed. The species P. exaeretus appears to be a rather rare species, hitherto recorded in Phalacrocorax carbo in Europe, Kirghizia and Azerbaidzhan. P. baschkirovi Ablassov & Iksanov, 1959 is synonymized with P. exaeretus. P. phalacrocoracis (syn. P. hospitale (Mendheim, 1940) and P. exaeretus auct. nec Dietz, 1909), which has previously been misidentified and erroneously designated as P. exaeretus, appears to be the commonest species of the genus, parasitising cormorants in the Palaearctic Region (Europe, CIS [USSR], Japan) and in Australia. Differential diagnoses of both the above mentioned species are presented.

No abstract

A single third-stage larva of the fish nematode Raphidascaris acus (Bloch, 1779) (body length 1.77 mm) was found in 1 of 775 gammarids Gammarus fossarum Koch examined from the Jihlava River, Czech Republic. This is the first confirmed record of the advanced L, of this species from an invertebrate host, showing that an invertebrate may serve as true intermediate host of this nematode, in addition to lower aquatic vertebrates. Until now, invertebrates have generally been considered as paratenic hosts of the second-stage larvae of R. acus.

NOTERole of Leptodora kindti (Cladocera: Leptodoridae) in the life cycle of Raphidascaris biwakoensis (Nematoda: Anisakidae), a fish parasite in Lake Biwa, Japan