Notes on Some Nematodes from Fresh-Water Fishes

Observations on the morphology of Truttaedacnitis clitellarius and T. lebedevi (Nematoda: Cucullanidae) from acipenserids and synonymy of the two species

“…Skrjabina (1974) distinguished T. clitellarius from T. lebedevi by the presence of four pairs of unequal sized post-anal papillae in T. clitellarius, as opposed to five pairs of equal sized post-anal papillae in T. lebedevi. However, it is evident from our study that the papillar arrangements of the two species are identical, including the position of the phasmids, which were not mentioned by Ward & Magath (1917) and apparently misplaced in the diagram of Skrjabina (figure 48, page 84, of Skrjabina, 1974). The sizes of the caudal papillae (excluding the papilliform phasmids, which are always the smallest) are frequently uniform in T. lebedevi, while displaying much variability in T. clitellarius.…”

“…Skrjabina (1974) also considered the spicule size of T. clitellarius diagnostic, and this is stated as being 1.6 rnm as opposed to 1.1 mm for T. lebedevi. The data for T. clitellarius were apparently obtained from the original description of Ward & Magath (1917). Although we were unable to locate the type-material (J.R. Lichtenfels, pers.…”

“…Three species of Truttaedacnitis Petter, 1974 are recognised as being specific for acipenserids (sturgeon): T. lebedevi (Skrjabina, 1966) (= T. sibiricus Finogenova, 1967; see Skrjabina, 1974) is specific for freshwater acipenserids in Siberia and the Amur River drainage; T. sphaerocephala (Rudolphi, 1809) commonly parasitises anadromous/estuarine sturgeons in Europe and North America (Skrjabina, 1974;Appy & Dadswell, 1978); and T. clitellarius (Ward & Magath, 1917) has only been reported in lake sturgeon in North America (Hoffman, 1967;Margolis & Arthur, 1979;Choudhury & Dick, 1993). Of these three species, T. lebedevi and T. sphaerocephala have been fairly well described (Tornquist, 1931;Skrjabina, 1974).…”

“…However, an examination of the morphology of T. clitellarius and a re-examination of T. lebedevi indicated the two species are morphologically more similar than previously thought (Skrjabina, 1974). In view of the incomplete description of T. clitellarius by Ward & Magath (1917) and the close similarity with T. lebedevi, we redescribe T. clitellarius, add to the information on T. lebedevi and re-evaluate the relationship between the two species.…”

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Truttaedacnitis clitellarius (Ward & Magath, 1917) (Nematoda: Cucullanidae) is redescribed from the lake sturgeon Acipenser fulvescens from North America and compared with T. lebedevi (Skrjabina, 1966) from the Siberian sturgeon A. baeri. Studies on the morphology and morphometrics of the two species reveal considerable overlap with unique shared characters, such as the previously unreported position of the excretory pore at the level of the pseudobuccal capsule and arrangement of caudal papillae.

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