Molecular Identification of Two Strains of Third-Stage Larvae of Contracaecum rudolphii Sensu Lato (Nematoda: Anisakidae) From Fish in Poland

Abstract

Contracaecum sp. larvae (L3) from fish were identified using nucleotide sequences of the internal transcribed spacers ITS-1 and ITS-2 of the ribosomal DNA. The nematode larvae originated from fish in a freshwater situation (crucian carp Carassius carassius, from Selment Wielki Lake in Mazury, northeastern Poland) and a brackish-water region (Caspian round goby Neogobius melanostomus from the Baltic Sea, Gdafisk Bay at the Polish coast). Two strains (Contracaecum rudolphii A and B) of Contracaecum rudolphii senso lato, a parasite common at the adult stage in fish-eating birds, were identified. In fish from the freshwater site, only the strain temporarily designated C. rudolphii B was identified; in the brackish-water region, both strains were found, suggesting that fish serve as paratenic host for both genotypes. Contracaecum rudolphii sensu lato has been recorded in several species of fish-eating birds in Poland, particularly in the great cormorant, Phalacrocorax carbo, in which the abundance is highest. The results, although based on a restricted number of larvae, suggest that the life cycles of both genotypes can be completed in the Polish region and that at least one of them, C. rudolphii B, can develop both in fresh and brackish water.

In vitro infection experiments with eggs of the nematode Contracaecum rudolphii Hartwich, 1964 (sensu lato) targeting aquatic insect larvae (Odonata: Coenagrionidae and Libellulidae; Trichoptera: Integripalpia) as possible intermediate hosts

“…Those authors explained the high infection intensity of the crucian carp with larval C. rudolphii (c. 500 individuals) by the fact that the fish could have consumed mature nematode females. Both the observations reported by Szostakowska and Fagerholm (2007) and those described in this paper may be taken as evidence that eggs, in addition to larvae, are dispersive stages of C. rudolphii, and that the eggs may develop in the intermediate host's intestine.…”

“…Under natural conditions, the libellulid larvae show a stronger association with the benthic environment than the coenagronidae larvae do; the latter are more associated with aquatic plants. Szostakowska and Fagerholm (2007) contend that also fish may be the first intermediate hosts of the nematode. Those authors explained the high infection intensity of the crucian carp with larval C. rudolphii (c. 500 individuals) by the fact that the fish could have consumed mature nematode females.…”

“…Under natural conditions, benthic invertebrates may come into contact with the nematode eggs, expelled with cormorant feces and subsequently sinking to the bottom. According to Szostakowska and Fagerholm (2007), eggs of C. rudolphii may be a source of infection for some fish.…”

Infestation of the black cormorants (Phalacrocorax carbo sinensis L. 1758) from the colony on the Selment Wielki, with the nematode Contracaecum rudolphii Hartwich, 1964 (Nematoda, Anisakidae)

“…While in the cormorant stomach, the larvae moult for the last time and mature. The literature survey revealed a single paper only on the nematode's presence in fish in Poland (Szostakowska & Fagerholm 2007). On the other hand, many years of studies failed to demonstrate the presence of the parasite's larvae in those fish species that contribute most to the black cormorant diet (Dzika 2003, Rolbiecki 2003.…”

Infection rates and prevalence of metazoan parasites of the non-native round goby (Neogobius melanostomus) in the Baltic Sea

“…However, C. rudolphii found in this study in Danish and Lithuanian round gobies is an avian parasite, maturing primarily in cormorants (Szostakowska & Fagerholm, 2007, 2012. Cormorants have been known to prey actively on round gobies where they co-occur, e.g.…”