On the bionomics ofCrepidostomum metoecus(Braun, 1900) andCrepidostomum farionis(Müller, 1784) (Trematoda: Allocreadiidae)

Abstract

The life-cycles of the two species ofCrepidostomumoccurring in a stream in North Wales are investigated. Both species share the same arthropod and definitive hosts, viz.Gammarus pulexandSalmo trutta, respectively, but have different molluscan hosts, viz.:Lymnaea peregraforC. metoecusandPisidium casertanumforC. farionis.C. metoecusandC. farionishave annual cycles, hence periodicity of occurrence in their hosts. InC. metoecusthe dynamics of occurrence in the three hosts are correlated. The inverse relationship inG. pulexandS. truttaas well as the existence of a time-lag of 3–4 months between the establishment of this worm inG. pulexand inS. truttaare discussed.Neither premunition nor age-resistance occurs in the parasitization ofS. truttaandG. pulexbyC. metoecus. The increase in the rate and degree of infestation with the age and length of fish, except in the oldest and longest group, is shown to be due to trophic factors.C. metoecusis more abundant and widely distributed in the stream thanC. farionis. This fact is associated with the occurrence of their molluscan hosts.Experimental observations were made on the stages in the life-history ofC. metoecus, including the mode of emergence of the cercaria, invasion of shrimps and encystment, as well as development of the metacercariae inG. pulex.More cercariae are shed by day and at higher temperatures, and they live for about 5 days at 8 °C. The metacercaria undergoes considerable development before becoming infective.C. metoecusdoes extensive damage toL. peregra, has no observed ill-effect on trout, and apparently affects the life-span of shrimps adversely only in cases of very heavy infestations.The non-parasitization ofCottus gobioby the two flukes is probably due to the prevailing ecological factors.My thanks are due to Professor H. B. N. Hynes and Dr J. C. Chubb for many helpful criticisms at all stages of this study; to Miss Joan Venn for helping with the sampling programme; and the Commonwealth Scholarship Commission in the United Kingdom for financial support.

Distribution and Seasonal Abundance of Trematode Parasites (Trematoda: Allocreadiidae: Crepidostomum spp.) in burrowing-mayfly nymphs (Ephemeroptera: Ephemeridae: Hexagenia spp.) from Connecting Rivers of the Laurentian Great Lakes

“…Parasite transmission and mayfly emergence that occurs in June and July in the St. Marys River begins during a period of rapidly rising water temperatures. Other researchers have observed similar associations between parasite and host lifecycles, parasite transmission, and water temperature (Awachie, 1968;Hazen & Esch, 1977;Esch & Hazen, 1982).…”

“…Various studies have suggested that metacercariae may impair body functions and cause non-lethal impacts to mayfly nymphs through decreased proteins, muscle, fat reserves, nerve ganglia, and gonadal tissues which could contribute to retarded growth, declined health, and increase mortality by other factors (Awachie, 1968;Olsen, 1974;Chambers et al, 1975;Knowles & Hall, 1976;Hominick & Welch, 1980;Moravec, 1982). Chambers et al, (1975) found substantial reductions in hemolymph proteins in heavily infected nymphs with metacercarial intensities ranging between 16 and 116 per nymph.…”

Parasitofauna study of the brown trout,Salmo trutta(Pisces, Teleostei) from Corsica (Mediterranean island) rivers

“…Many studies already listed the parasitic trout species, C. metoecus, in different European countries and particularly in Ireland (Holland & Kennedy, 1997), England, Sweden (Corbett, 1955), Poland or Czech Republic (Slusarski, 1958) and North Eastern Finland (Rahkonen & Valtonen, 1989). Considering its important geographical distribution (Chubb, 1979), this parasite must have diverse intermediate hosts (Awachie, 1968) according to the biotope which its definitive host colonizes. The presence of the nematode, R. gnedini is well known in Salmo trutta.…”

Parasites Communities in Brown Trout Salmo Trutta (Pisces, Teleostei) from Corsican Rivers

“…Many studies already listed these parasitic species of trout in different European countries and particularly in Ireland [12], England, Sweden [8], Poland or Czech republic [21]. Considering its important geographical distribution [6], this parasite must have diverse intermediate hosts [2] according to the biotope which its definitive host colonizes. Presence of the nematode, R. gnedini is well known in Salmo trutta.…”