Three new and five known species of Diplopeltoides Gerlach, 1962 (Nematoda, Diplopeltoididae) from Sweden, and a revision of the genus

Abstract

Abstract. Eight species of Diplopeltoides are described from the Swedish west coast. Diplopeltoides suecicus sp. nov. has the cuticle with longitudinal striation visible only under SEM; cuticular plate underlying the cephalic cuticle around the amphid present; cephalic sensilla 4-6 µm long; amphid an inverted U-shape; wide space between amphidial branches areolated; spicules 27-31 µm long; gubernaculum with caudal apophysis. Diplopeltoides longicaudatus sp. nov. is characterized by a cuticle without longitudinal striation; cuticular plate underlying cephalic cuticle around amphid present; cephalic sensilla 13 µm long; amphid an inverted U-shape; narrow space between amphidial branches not ornamented; spicules unequal in size, 27-31 µm long; gubernaculum absent; midventral precloacal cuticular ridge present. D. grandis sp. nov. is characterized by a cuticle with longitudinal striation; cuticular plate underlying cephalic cuticle around amphid present; cephalic sensilla 18.5 µm long; amphid an inverted U-shape; wide space between amphidial branches punctate. The following taxonomic changes are proposed:

Neodiplopeltula gen. nov. from the west coast of Sweden and reappraisal of the genus Diplopeltula Gerlach, 1950 (Nematoda, Diplopeltidae)

“…The 'Traditional' focus lies on male characters in species descriptions and diagnoses of genera, and the partial or complete ignorance towards the morphology of female reproductive system causes taxonomic and nomenclatorial problems in those cases where higher classification of taxa relies on female-specific characters. The genus Diplopeltula is but one example (see detailed discussions in Holovachov et al 2009;Leduc 2013;Holovachov 2017;Holovachov & Boström 2017). Of course, it would not be such an issue if the type material for such 'troublesome' taxa were preserved and available for restudy.…”

“…Secretory- (Southern, 1914) gen. et comb. nov. and generic diagnosis (this publication), Diplopeltula Gerlach, 1950 based on the type species D. breviceps Gerlach, 1950, andDiplopeltoides Gerlach, 1962 based on the type species D. ornatus (Gerlach, 1950) and emended generic diagnosis in Holovachov & Boström (2017).…”

“…The new genus differs from all other taxa currently included in the family Diplopeltidae (Holovachov 2017) in having amphids in the shape of an elongated loop, a well-developed subcylindrical stoma and outstretched ovaries. It is proposed in order to accommodate a number of species previously placed in the genus Diplopeltula and to solve a long lasting taxonomic conundrum (Vincx & Gourbault 1992;Holovachov et al 2009;Holovachov 2017;Holovachov & Boström 2017). The description of Diplopeltula breviceps, type species of the genus Diplopeltula, does not include clear descriptions of several important taxonomic characters (see Table 1) and the absence of such data prevents an unequivocal placement of the species D. breviceps and the genus Diplopeltula in the classification system of Nematoda.…”

“…Taxonomic instability of the genus is further sustained by the fact that the original description of the type species Diplopeltula breviceps Gerlach, 1950 does not include clear descriptions of characters currently considered diagnostic at the genus and family level, such as the exact structure of the pharynx or of the female reproductive system (Table 1), and because the type material was not preserved by S.A. Gerlach. As a result, the genus Diplopeltula recently underwent several taxonomic revisions, with more and more species being moved to other known and newly proposed genera (Holovachov et al 2009;Leduc 2013;Holovachov 2017;Holovachov & Boström 2017). In this manuscript we propose to move all the remaining properly described species from the genus Diplopeltula to a new genus Neodiplopeltula gen. nov., treat both Diplopeltula breviceps and D. longiceps Gerlach, 1950 as species inquirenda et incertae sedis, treat Diplopeltula ostrita Boucher &Helléouët, 1977 andD.…”