Redescription of Rhabdochona cotti (Nematoda, Rhabdochonidae) from Cottus caeruleomentum (Teleostei, Cottidae) in Maryland, USA, with remarks on the taxonomy of North American Rhabdochona spp.

Abstract

The nematode Rhabdochona cotti Gustafson, 1949 is redescribed from specimens collected from the intestine of the blue ridge sculpin Cottus caeruleomentum (a new host record), a recently described fish species, from Little Fishing Creek in Maryland, USA. The measurements of these specimens, collected in November 2005, are generally smaller than those reported in the original description of R. cotti, this being probably associated with the nematode's seasonal maturation cycle or the different host species. As revealed by SEM, the deirids of R. cotti are simple (not bifurcate), in which this species differs from almost all North American congeners. Of these, simple deirids, filamented eggs and a rounded tail tip in females occur only in Rhabdochona longleyi, but it distinctly differs from R. cotti in the smaller number of anterior prostomal teeth (6 vs. 14). Rhabdochona rotundicaudatum is considered a junior synonym of Rhabdochona cascadilla; numerous specimens of the latter were collected from Semotilus atromaculatus, Luxilus cornutus and Notropis rubellus from the type locality (Eramosa River, Ontario, Canada) (unpublished). Rhabdochona paxmani and Rhabdochona salmonis are synonymized with Rhabdochona kisutchi, whereas Rhabdochona californiensis is considered a junior synonym of R. cascadilla. The need of a taxonomic revision of North American species of Rhabdochona is stressed.

Some aspects of the taxonomy, biology, possible evolution and biogeography of nematodes of the spirurine genus Rhabdochona Railliet, 1916 (Rhabdochonidae, Thelazioidea)

“…Moreover, three North American species of Rhabdochona described by Maggenti et al (1992), R. californiensis, R. paxmani and R. salmonis, which were considered by Mejía- Madrid et al (2007a) to be valid, have recently been synonymized with previously described species R. cascadilla Wigdor, 1918 or R. kisutchi Margolis, Moravec et McDonald, 1975 (see Moravec andMuzzall 2007). It is worth mentioning that these synonymized species were placed in other clades in the above mentioned analysis than those with which they were synonymized.…”

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“…Endoparasites were placed in separate Petri dishes with physiological saline and immediately observed. Parasite preparations were conducted according to methods indicated by Paradiznik and Radujkovic (2007) for digeneans, Moravec and Muzzall (2007) for nematodes, Yurakhno (1988) for myxosporeans, Özer et al (2014) for cestodes, Lom and Dykova (1992) for trichodinids, All parasite species were examined and identified using a phase contrast Olympus microscope (BX53) equipped with a digital camera (DP50) and hand drawing attachment (U-DA). Identification keys were also used (Gaevskaya et al, 1975, Bray and Gibson, 1990, Dmitrieva and Gerasev, 1997, Lom and Dykova, 1992.…”

Biogeographic Hierarchical Levels and Parasite Speciation

“…A phylogenetic and historical biogeographical analysis of Rhabdochona species is now due mainly because the systematic research on the whole genus is reaching a stage of maturity that is reflected in the stabilization of species rate discovery (Mejía-Madrid, unpublished data), and because of the quality of new descriptions and redescriptions (Sánchez-Álvarez et al, 1998;Caspeta-Mandujano & Moravec, 2000Mejía-Madrid & Pérez-Ponce de León, 2003;Mejía-Madrid et al, 2007a;Moravec & Muzzall, 2007;Moravec et al, 2011). Such detailed morphological descriptions are essential for a clear distinction between species.…”

“…The American species are completely represented in the present analyses, but I include representative species distributed worldwide, with the exception of R. papuanensis Moravec, Ríha & Kuchta, 2008. The historical biogeographic analysis presented here is based on the updated matrix used for generating the phylogenetic framework of Rhabdochona spp. presented in Mejía-Madrid et al (2007a) with additional character coding derived from recently redescribed species from the Americas and Asia (Moravec & Muzzall, 2007;Moravec, 2010;Moravec, et al, 2011; Figure 1). The results presented herein represent a new phylogenetic framework for Rhabdochona spp., with two outstanding characteristics: the phylogeny is fairly well resolved and the degree of resolution is higher than that previously recovered.…”