Materials Characterization

The species of two gastropod superfamilies, i.e. Pupilloidea and Enoidea, that have been recorded in Bhutan, are described and illustrated. Five families with ten species in total are dealt with. Three species are described as new to science, viz. Pupisoma (P.) paroense Gittenberger et Leda, n. sp., Pseudonapaeus occibhutanus Gittenberger, Gyeltshen et Sherub, n. sp., and Laevozebrinus parvus Gittenberger, Gyeltshen et Leda, n. sp. Distribution maps are presented for all the species. Some biogeographical considerations are added.

The Balkan region is inhabited by hundreds of endemic species of freshwater molluscs but the information on their distribution, as well as that on the distribution of more common and widespread species, is still insufficient; most areas have no complete inventories of their mollusc faunas. The Zrmanja is one of the largest rivers in the Adriatic part of Croatia. Its freshwater molluscs were studied in the last decade, resulting in a substantial body of distributional data. The main objective of this study was to summarise and analyse the recent distributional information on its freshwater molluscs, with special reference to endemic or threatened species. In total 33 freshwater mollusc species were found in the Zrmanja River and its tributaries at 73 sites. The middle section of the Zrmanja River and its largest tributary, the Krupa River, were the richest studied parts. Dalmatinella fluviatilis Radoman, Tanousia zrmanjae (Brusina) and Islamia zermanica Radoman, endemic to the Zrmanja catchment area, were found in the middle and lower sections of the river. Their occurrence is scattered and limited in area; T. zrmanjae is probably on the verge of extinction. The occurrence of the endemic Belgrandiella kusceri (Wagner), Hadziella sketi Bole and Kerkia sp. in springs or underground waters and an abundant population of Unio elongatulus C. Pfeiffer in the Zrmanja and Krupa Rivers is also noteworthy. The area can be regarded as an important part of the Balkan region, one of world’s hotspots of global biodiversity. Although it is protected, there are still anthropogenic factors that are negatively affecting or may affect the mollusc assemblages.

Olividae are marine gastropods living as predators or scavengers on soft sediments. The complex prey handling behaviour of large predatory species includes the storage of food in a pouch formed temporarily by bending and contraction of the posterior foot. Such metapodial pouches had been observed only in Olividae that lack an operculum, prompting the hypothesis that the folding of the metapodium into a pouch biomechanically required the absence of the operculum. Here we report metapodial pouch formation in an operculate olivid, Callianax biplicata (formerly Olivella biplicata). Since the operculum is too small to close the shell aperture in mature C. biplicata, a protective function seems unlikely. The operculum may rather serve as an exoskeletal point for muscle attachment, but may also represent a ‘vestigial organ’ in the process of evolutionary reduction, or an ontogenetic remnant functional at early life stages but not at maturity. Consequently, our observations refute the notion that only inoperculate olivids can form pouches, but not necessarily the idea that the ability to form a metapodial pouch evolved in parallel with operculum reduction

Two species of cuttlefish: Sepia robsoni (Massy) and Sepia faurei Roeleveld, are redescribed based on sexually mature males and females of both species. They were previously known only from their holotypes: male and female, respectively. They belong to a distinct group of small-sized sepiids, all near-endemics of southern African waters. The knowledge of the systematics and biology of this group is still limited despite the long time since the first description (1875). This is because, inter alia, of their small size: not larger than 4 cm mantle length at maturity. Twenty-one individuals of S. robsoni described here were scattered from Port Nolloth area to the Tsitsikamma coast (bottom depth <37–449 m). Eight known individuals of S. faurei came from the eastern Agulhas Bank (bottom depth 116–184 m). S. robsoni can be identified by extremely thinly calcified cuttlebone (transparent); smooth skin of dorsal mantle and head; tips of first pair of arms thick, finger-like, devoid of suckers. S. faurei can be distinguished by the following combination of characters: thick, heavily calcified cuttlebone but with flat and fused inner cone; skin of dorsal mantle and head very densely covered by characteristic warts; thin, whip-like tips of first pair of arms devoid of suckers. All described specimens of both species are deposited in the South African Institute of Aquatic Biodiversity (SAIAB) and in Iziko, South African Museum (SAMC).

The history of malacological exploration of Siberia, made in 1932 and 1933 by the malacologist Alan Mozley, then affiliated with the Smithsonian Institution, USA, is given, with a discussion of his contribution to the knowledge of taxonomy, biogeography and ecology of freshwater and terrestrial molluscs of Northern Asia. The type specimens of the Siberian species and subspecies, described as new by Mozley, are illustrated, with remarks on the current taxonomic status of these taxa. A social-historical context of Mozley’s trip to Stalin’s Russia is also provided, including its connection to the prosecution of Nikolay Vavilov, a key opponent of “Lysenkoism”.

Cepaea nemoralis is a recently introduced species on Öland. Discounting an early and debateable record, the species has been recorded only in the 21st century, despite intensive earlier faunistic surveys. A recent survey has yielded records from the whole length of the island (137 km), but the majority of known populations are in its southern half, most particularly around the settlements of Mörbylånga, Gräsgård and Färjestaden. Populations are usually in anthropogenic habitats. Most appear small and isolated by less disturbed areas. Nearly all samples are polymorphic for both colour and banding morphs, and the variation among populations is low when compared with similar sets from other places where recent colonisation has occurred. There is no latitudinal variation in morph frequencies, nor is any spatial autocorrelation apparent. While a relatively uniform and rigorous selection regime could account for the patterns seen, a single initial introduction followed by transport of propagules large enough to minimise founder effects is also possible.

The Mediterranean Massylaea vermiculata (O. F. Müller) is reported from Slovakia for the first time (two sites), and from Hungary for the first time since the 1980 record. There is a reason to suspect the existence of further, yet undetected, specimens or even populations in Central Europe. Based on the dynamics of similar invasions of terrestrial molluscs, we expect that in 2–3 decades the species may become locally abundant and widespread in both the Hungarian and the Slovak capitals.

Sinanodonta woodiana (Lea) and Corbicula fluminea (O. F. Müller) are among the most invasive aquatic molluscs found in Europe. Both species were recorded in the Adriatic part of Croatia for the first time in 2019 although in the Danubian Croatia they were more common. An abundant population of S. woodiana was found in an oxbow of the Cetina River; mussels with shell length of ca. 12–17 cm dominated. A population of C. fluminea was recorded in the freshwater section of the Zrmanja River above the Jankovića Buk waterfall which forms the border between the brackish and the freshwater sections of the river. Possible pathways of their introduction and reasons for their rare occurrence in contrast to the Danubian Croatia are discussed.