Redescription of Tubulideres seminoli Sørensen et al., 2007 and notes on Wollunquaderes majkenae Sørensen & Thormar, 2010 (Kinorhyncha, Cyclorhagida): Morphology, postembryonic development, life cycle, and new characters

Abstract The morphology and postembryonic stages of the Kinorhyncha Tubulideres seminoli and Wollunquaderes majkenae as well as the assumed mouth cone weir and the outer oral styles of adult Antygomonas paulae and Semnoderes sp. are re-examined with light microscopy. Tubulideres seminoli is redescribed. The study was initiated by the older and very recent findings of more than one adult life history stage in Kinorhyncha such as in species of Antygomonas , Campyloderes , Cateria , Centroderes , and Zelinkaderes . Preliminary observations in 2012 had shown that several specimens of T. seminoli and W. majkenae revealed a slightly different character set than female and male specimens, so this material was suspected to represent possibly another adult life history stage. Earlier juvenile specimens of both species are described here in more detail. Characters discriminating earlier juvenile stages from the last juvenile stage and these from the adult stage are compared among Kinorhyncha. During this study, evidence suggested that the potential adult specimens more probably represented the last juvenile stage of T. seminoli and W. majkenae . In Tubulideres seminoli , several morphological characters were previously interpreted differently or overlooked like the assumed mouth cone weir, placids separated from the trunk in a specific arrangement, trunk segments 2–11 revealing a single tergal plate, whose lateral ends meet midventrally, female-specific gland cell outlets, and type-5 sensory spots. The gland cell outlets on segments 8 and 9 consist of a circular area with micropapillae at the surface, a strongly sclerotized tube through the trunk cuticle, and a bulbous subcuticular structure; similar gland cell outlets were previously reported from female specimens of species of Centroderes . The findings in T. seminoli and W. majkenae prompted also re-examination of the assumed mouth cone weir and the outer oral styles of adult Antygomonas paulae and Semnoderes sp. Characters of the outer oral styles, placids, and postembryonic stages are re-evaluated and compared among Kinorhyncha.