 |
| Varadia amboliensis Bhosale, Thackeray, Muley et Raheem in Bhosale, Saadi, Wade, Thackeray, ... et Raheem, 2021. |
ABSTRACT
We here describe a new Indian helicarionoidean genus, Varadia Bhosale & Raheem gen. nov., containing the single species Varadia amboliensis Bhosale, Thackeray, Muley & Raheem gen. et sp. nov. This new semi-slug is endemic to the northern and central Western Ghats and is primarily a forest-living species. We describe and figure the shell, reproductive system, radula, spermatophore and external morphology of this new species, and detail its known distribution. We explore its relationships to other helicarionoideans using phylogenetic analyses of DNA sequence data for part of the ribosomal RNA gene cluster and discuss the morphology of the new genus in relation to other, primarily South Indian, helicarionoidean taxa. Based on characters of the reproductive system, particularly the male genitalia and the gametolytic sac, we provisionally place Varadia gen. nov. in the Macrochlamydinae (Ariophantidae). This is consistent with the results of our molecular phylogenetic analyses. The combination of large size, broad, densely tuberculated shell lobes and a shell with ca 4 whorls and a disproportionately large body whorl makes V. amboliensis gen. et sp. nov. unique among the helicarionoidean taxa of the Western Ghats. The new semi-slug is also highly distinctive in the morphology of its male genitalia.
Keywords: Varadia amboliensis gen. et sp. nov., Macrochlamydinae, taxonomy, phylogenetics, ribosomal RNA gene cluster
 |
| Live individual of Varadia amboliensis from the site near Amboli waterfall. Image: O. Yadav. |
Phylum Mollusca Linnaeus, 1758
Class Gastropoda Cuvier, 1795
Subclass Heterobranchia sensu Bouchet et al., 2017
Order Stylommatophora sensu Bouchet et al., 2017
Superfamily Helicarionoidea Bourguignat, 1877
Family Ariophantidae Godwin-Austen, 1888
Subfamily Macrochlamydinae Godwin-Austen,1888
Varadia Bhosale & Raheem gen. nov.
Diagnosis: Only known large semi-slug species from the Western Ghats having broad shell lobes (covering nearly all of the dorsal shell surface when fully extended) and a depressed, discoid shell with a large body whorl. Shell thin, glossy golden brown, with 4–4½ rapidly increasing whorls and barely raised spire. Extensive, largely free penial sheath enclosing substantial part of male genitalia. When sheath is in situ and penis in relaxed state, male genitalia constitute a single elongate, irregularly-shaped mass, with all of penis and epiphallic caecum, most of epiphallus and part of flagellum enclosed by sheath; only vas deferens and most of flagellum is visible outside intact sheath. Penial sheath divisible into thick proximal part and thin distal part, with transition between these two parts occurring between distal penis and epiphallic caecum. With penial sheath removed, following evident: region extending from penis to epiphallic caecum long and cylindrical, with distinctive S-shaped bend in penis and associated band of muscle running along length of penis; proximal ¾ of epiphallus held in long, conspicuous loop; and penial retractor muscle with two branches, one inserting subterminally on epiphallic caecum and one inserting on apex of loop of epiphallus. Inner wall of penis divisible into three regions: proximal penis (one major and several minor longitudinal pilasters), mid-penis (several minor longitudinal pilasters) and distal penis (a few minor pilasters with associated regular transverse ridges in interspaces). Inner wall of epiphallic caecum shows one long major longitudinal pilaster, a large mass of reticulate ridges proximally and several minor longitudinal pilasters distally. Gametolytic gland elongated and long; gametolytic sac 3–3.5 times as long as gametolytic duct. Amatorial organ absent. Spermatophore consists of elongated, soft capsule and long tail-pipe, with U-shaped bend at capsule–tail-pipe junction and funnel-like opening at tip of tail-pipe; surface smooth apart from four ribs running obliquely along length of tail-pipe and short spines near end of tail-pipe.
Etymology: The new genus is named in honour of the herpetologist Dr Varad Giri, who has made a major contribution to the modern study and conservation of the Indian herpetofauna; masculine.
Varadia amboliensis Bhosale, Thackeray, Muley & Raheem gen. et sp. nov.
Etymology: Named after the type locality, Amboli, in the Sindhudurg District of southern Maharashtra, India. In recent years, Amboli has emerged as a hotspot for the discovery of new species (particularly reptiles and amphibians) in the northern Western Ghats.
Amrut R. Bhosale, Ahmed J. Saadi, Christopher M. Wade, Tejas U. Thackeray, Asif S. Tamboli, Suhas K. Kadam, Dipak V. Muley and Dinarzarde C. Raheem. 2021. Varadia, A New Helicarionoidean Semi-slug Genus from India’s Western Ghats (Stylommatophora: Helicarionoidea). European Journal of Taxonomy. 757(1), 50-79. DOI: 10.5852/ejt.2021.757.1413
