﻿Rediscovering the dancing semislug genus Cryptosemelus Collinge, 1902 (Eupulmonata, Ariophantidae) from Thailand with description of two new species.

Arthit Pholyotha,Somsak Panha,Chirasak Sutcharit

doi:10.3897/zookeys.1076.75576

Abstract

Knowledge of Thai semislugs remains scarce, especially the dancing semislug genus Cryptosemelus. Prior to the present study, only a single species has been recognized with little available information. To address this knowledge gap, we surveyed for semislugs in western and southern Thailand, which yielded three species belonging to the genus Cryptosemelus. The little-known type species C.gracilis is redescribed herein, including a comparison with the type specimens. Two additional species, C.betarmonsp. nov. and C.tigrinussp. nov., are described as new to science. All three species are characterized by differences in their genital anatomy, especially with respect to anatomical details of the penis, epiphallus, and spermatophore. In addition, C.tigrinussp. nov. differs from C.gracilis and C.betarmonsp. nov. in the mantle color pattern.

Highlights

Becoming a slug through the reduction of the shell has occurred multiple times among the stylommatophoran land snails; this has occurred frequently within the limacoid snail families Ariophantidae Godwin-Austen, 1883, Helicarionidae Bourguignat, 1877, and Urocyclidae Simroth, 1889 (Solem 1966; Hausdorf 1998; Hyman et al 2007; Hyman and Köhler 2020)
Located in the center of the Indo-Burma biodiversity hotspot (Myers et al 2000), Thailand harbors a large number of snails, slugs, and semislugs belonging to the Ariophantidae and Helicarionidae (Solem 1966; Panha 1996; Hemmen and Hemmen 2001), of which several semislug genera have never been systematically revised since the seminal work of Solem (1966)
The three character states of (i) reduced shell, (ii) presence of the stimulator with a calcareous dart, and (iii) attachment of the penial retractor muscle directly to the epiphallus rather than to the epiphallic caecum are characteristic for members of the Ostracolethinae, family Ariophantidae (Hausdorf 1998)

Summary

Introduction

Becoming a slug through the reduction of the shell has occurred multiple times among the stylommatophoran land snails; this has occurred frequently within the limacoid snail families Ariophantidae Godwin-Austen, 1883, Helicarionidae Bourguignat, 1877, and Urocyclidae Simroth, 1889 (Solem 1966; Hausdorf 1998; Hyman et al 2007; Hyman and Köhler 2020). Collinge (1902) only gave a very brief description without providing any details on the genitalia, which bear important characters in semislug taxonomy (Blanford and Godwin-Austen 1908; Solem 1966; Hyman and Ponder 2010; Hyman and Köhler 2020) This monotypic genus was described based on specimens collected during the ‘The University of Cambridge Expedition to the North-Eastern Malay States and Upper Perak’, known as the ‘Skeat Expedition, 1899–1900’ (Gibson-Hill et al 1953), which visited a region situated in southern Thailand and the northern part of the Peninsular Malaysia. Cryptosemelus has been referred to as the ‘dancing semislug’ because of the fidgety or dance-like movement that it makes when it is disturbed or attacked (Collinge 1902)

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