A new species of <i>Pachycordyle</i> (Hydrozoa, Clavidae) from Lake Biwa (Japan), with remarks on this and related Clavid genera

Abstract

SUMMARY:The history of research on species of Pachycordyle and related genera is discussed. A description and differential diagnosis of a new species, Pachycordyle kubotai, is presented. Hydroid colonies, hydranths, and gonophores of this species are described in detail. Peculiarities of medusoid development and oocyte maturation are analyzed. The genus Pachycordyle is rediagnosed and an identification key to species assigned to it is provided. Clavopsella is regarded as congeneric with Pachycordyle. Thieliana is established as a new genus for species subsequently and erroneously assigned to Clavopsella. The taxonomic status of species referable to Thieliana is discussed. Justification is provided for our position that these genera belong to the family Clavidae. Characteristics of genera assigned to the family Clavidae are summarized. Data on the geographic distribution and ecology of the species of Cordylophora, Pachycordyle, and Thieliana, referred here to the subfamily Cordylophorinae, are presented.

Cnidarian fauna of relict Lakes Baikal, Biwa and Khubsugul

“…Pachycordyle kubotai Stepanjants et al (2000b) ( Fig. 1f) Weakly branching stems; each branch terminates by polyp and beneath it a zone of budding of 1-2 gonophores-eumedusoids; up to 17 filiform tentacles, arranged in 3-4 rows in the upper part of polyp head around hypostome.…”

“…In Lake Biwa only one species of hydra, Pelmatohydra oligactis and a representative of the family Clavidae (Athecata) described as a new species Pachycordyle kubotai (Stepanjants et al, 2000b) are known. In the Atlas ''The Plankton of Lake Biwa'' (Negoro, 1982) an indistinct photo of a medusa is given, but identification from this is impossible.…”

“…In the Atlas ''The Plankton of Lake Biwa'' (Negoro, 1982) an indistinct photo of a medusa is given, but identification from this is impossible. The medusa might be referred to the genus Craspedacusta (Limnomedusa), but may also be a free medusoid stage of Pachycordyle kubotai (Stepanjants et al, 2000b).…”

Global diversity of inland water cnidarians

“…Molecular data have yet to be published for Cordylophora, Pachycordyle, or Australomedusa, but they are classified in the anthoathecate group Filifera. There may have been multiple invasions of freshwater within Cordylophorinae, as most species within the group are adapted to brackish conditions (Stepanjants et al 2000). Molecular data from the 18S ribosomal gene have been gathered for Polypodium, but this gene has undergone such a high rate of divergence in Polypodium, that it appears to be an unreliable indicator of its phylogenetic position (Kim et al, 1999).…”

“…It has been recorded sporadically but widely in freshwater on all continents except Antarctica (Folino, 2000). Pachycordyle kubotai is known only from Lake Biwa in Japan (Stepanjants et al, 2000).…”