Rhynchelmis malevici Sokolskaya 1983

Rhynchelmis malevici (Sokolskaya, 1983)

We have not had an opportunity to examine material of this species. The original description is detailed, but reexamination of some anatomical details would be useful. The R. brooksi spermathecae are described as having a frontal diverticulum from the ampulla (Holmquist 1976), which bears some similarity to the frontal diverticula of R. (Rhynchelmis) species. However, there is no mention of such a structure in the R. malevici description, despite the stated differences being limited to the unforked chaetae, the genital pores on the chaetal line (instead of slightly medial), and nephridia on 6/7. It is not clear whether the description of R. malevici (Sokolskaya 1983) was based on more than the holotype, but as noted by Fend & Brinkhurst (2000), the listed characters are either very difficult to see, or subject to intraspecific variation.

In the analysis of Kaygorodova & Liventseva (2007) R. malevici clusters with the Nearctic saxosa, alaskana and brooksi. According to their character matrix, it shares 50 character states with R. saxosa but differs from it by 12, but the relationship between this quartet and other potential Rhynchelmoides group species was not firmly established. This is clearly a Rhynchelmis s. lat. taxon, but of undetermined subgeneric affilition. Sokolskaya (1983) attributed this species to Rhynchelmoides based on its lack of R. (Rhynchelmis)- like, curled longitudinal muscles, and presumably the lack of an anterior vas deferens. The thick spermathecal ducts resemble those of R. brooksi and most Rhynchelmoides group species. Nevertheless, possible apomorphies shared with R. brooksi could be used to define a separate species group. The atria are divided into three approximately equal sections, with the ectal part rather muscular, the median section with thick glandular epithelium, and the ental part thin-walled and covered with prostate glands. The vasa deferentia join the atria in the ental part, rather than in the ectal part, as in typical Rhynchelmoides group species.

Pseudorhynchelmis Hrab ĕ, 1982

sensu Kaygorodova & Liventseva, 2007; Martin & Kaygorodova, 2008 Type species: Rhynchelmis olchonensis Burow & Koshow, 1932

Included species: Pseudorhynchelmis alyonae ( Martin & Kaygorodova, 1998), P. o l c h o n e n s i s (Burow & Koshow, 1932), P. paraolchonensis (Giani & Martinez-Ansemil, 1984), P. parva (Michaelsen, 1905), P. semernoyi Martin & Kaygorodova, 2008, and P. s h a m a n e n s i s (Martin & Kaygorodova, 1998). Several Baikal species were originally described as having a spermatheca-gut connection, but were unavailable for study by us. Pseudorhynchelmis spermatochaeta (Semernoy, 1982), P. anomala (Semernoy, 2004), P. dissimilis (Semernoy, 2004), and P. minimaris (Semernoy, 2004) may well be attributed to Pseudorhynchelmis, as proposed by Kaygorodova & Liventseva, particularly if the reported association between the spermathecae and the gut proves to be erroneous (Martin & Kaygorodova 2008). The validity of one additional species, P. dissimilis (Semernoy, 2004) has been questioned by Martin & Kaygorodova (2008).

Pseudorhynchelmis is not formally defined here, because distinct synapomorphies have proven elusive (Kaygorodova & Liventseva 2007, Martin & Kaygorodova 2008), and the original descriptions of most species do not cover all of the potentially apomorphic characters discussed below. A working diagnosis for the genus was provided by Kaygorodova & Liventseva (2007), largely based on the absence of R. (Rhynchelmis) apomorphies. Martin & Kaygorodova (2008) used a “weight of evidence” approach to define the group, citing previous molecular and ultrastructural studies to support the weak morphological evidence.