Towards a sound definition of Skeneidae (Mollusca, Vetigastropoda): 3D interactive anatomy of the type species, Skenea serpuloides (Montagu, 1808) and comments on related taxa
2016
Haszprunar, Gerhard | Kunze, Thomas | Bruckner, Martin | Hess, Martin
The family Skeneidae, originally characterized by their minute size, lack of nacre and a rhipidoglossate radula, is an example of a polyphyletic assemblage. Most ‘skeneimorph’ species are based on the shell, sometimes the radula and rarely features of the external body. Data on internal anatomy are almost entirely lacking. In order to provide a complete anatomical data set with histological information, we applied serial semithin sectioning and 3D reconstructions to describe and visualize the anatomy of the type species of Skeneidae, Skenea serpuloides (Montagu, 1808). In addition, comparative data are provided for three other Skeneidae, Skenea profunda Friele, 1879; Dillwynella lignicola Marshall, 1988 and Dillwynella voightae Kunze, 2011 as well as for a tiny turbinid-like species, Lodderena minima (Tenison-Woods, 1887). We diagnose Skeneidae as trochoidean vetigastropods with combined epipodial sense organs (ESOs), neck lobes, eyes with a closed vesicle and the diagnostic propodial penis. Other features include simultaneous hermaphroditism with distinct testis/vas deferens and ovary/oviduct, a urogenital opening with the right kidney and a distinct seminal receptacle. Several features of Skeneidae are explained by dwarfing through progenesis, and accordingly, we interpret paedomorphosis of various characters. In contrast, L. minima has a true hermaphroditic gland, but lacks of propodial penis and a receptaculum. Also, molecular data support an exclusion of Lodderena from the Skeneidae.
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