The world’s tiniest land snails from Laos and Vietnam (Gastropoda, Pulmonata, Hypselostomatidae)

Barna Páll-Gergely,Menno Schilthuizen,András Hunyadi,Adrienne Jochum,Ábel Szabó,Aydin Örstan,Jaap J Vermeulen,Katja Anker,László Dányi

doi:10.1163/18759866-bja10025

Abstract

Abstract Two new, extremely small land snail species, Angustopila coprologos Páll-Gergely, Jochum & Hunyadi n. sp. and Angustopila psammion Páll-Gergely, Vermeulen & Anker n. sp. are described from northern Vietnam and northern Laos, respectively. The former is characterized by a rough surface sculpture and bears tiny mud granules arranged in a pattern of radial lines on its shell surface. The latter species is the new global record-holder of the tiniest land snail title, with a shell width of 0.6–0.68 mm and a shell height of 0.46–0.57 mm. These measurements surpass the former records of Angustopila pallgergelyi and Acmella nana.

Highlights

The evolutionary drivers of extremely small body size in invertebrate animals remain contentious in evolutionary biology because it is the point where both adaptive opportunities and physical/physiological constraints begin to clash
Morphology of the granules Shells of living Angustopila coprologos n. sp. individuals and freshly dead shells possess rounded or elongated granules on the shell, arranged in radial lines starting from the umbilicus up to the dorsal shell surface
We describe two even smaller members of this genus: Angustopila coprologos n. sp. with a shell width of 0.66– 0.76 mm and a shell height of 0.49–0.58 mm and a second new species, Angustopila psammion n. sp

Summary

Introduction

The evolutionary drivers of extremely small body size in invertebrate animals remain contentious in evolutionary biology because it is the point where both adaptive opportunities and physical/physiological constraints begin to clash. For example, extremely small body size, down to 0.3 mm, enables specialisation on parasitizing the small eggs of small-bodied hosts (Van der Woude & Smid, 2017). In soil invertebrates, such as mites and páll-gergely et al. Since the shell is the only rigid element of a snail’s body, its size and shape will be the factor that determines the 3-dimensional spaces in which subterranean snails can feed Another evolutionary driver of reduced body size, which may act in conjunction with ecological competition, may be the opportunity to escape from predators that preferentially target larger prey items (e.g., Suchmann & Sullivan, 2000)

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