Systematic revision of the Indo-West Pacific bubble-snails of the genus Haloa (Pilsbry, 1921) (Cephalaspidea : Haminoeidae)

The genus Haloa includes dull-coloured species of haminoeid snails inhabiting tidal and shallow waters of the tropical and sub-tropical Indo-West Pacific. This paper reports on the diversity and systematics of Haloa based on the phylogenetic hypothesis generated by Oskars and Malaquias (2019) and on the morphological study of specimens. Shells, external features and anatomical characters from the jaws, radula, gizzard plates and male reproductive system were studied by optical and scanning electron microscopy. The molecular species delimitation method Automatic Barcode Gap Discovery, using DNA sequences of the cytochrome c oxidase subunit I gene, was implemented to aid delimiting candidate species. Thirteen species were recognised as valid, including two new to science, namely Haloa cobbi, sp. nov. and Haloa eora, sp. nov., and one unnamed species herein referred to as Haloa sp. l. Species depict intraspecific variability in their colouration and little character displacement in their anatomy. Shells are of limited taxonomic use; only details of the male reproductive system (e.g. fundus) and the DNA were truly diagnostic. Three species have an Indo-West Pacific distribution and three are restricted to the Indian Ocean. The remaining seven species occur in the Western and Central Pacific Ocean, three of them having geographical ranges restricted to offshore islands.

Automated summary

This paper investigates the diversity and systematics of the Haloa genus, a group of dull-coloured haminoeid snails found in tropical and sub-tropical Indo-West Pacific waters. The study utilizes both morphological and molecular approaches to identify and delimit species. Thirteen species are recognized, including two new species. The study reveals intraspecific variability in colouration and limited character displacement in anatomy. The shells are not reliable for taxonomy, with male reproductive system and DNA sequences providing more diagnostic information. Some species have restricted distributions, particularly in offshore islands.