Siong Kiat Tan

Molluscs for Sale: Assessment of Freshwater Gastropods and Bivalves in the Ornamental Pet Trade

The ornamental pet trade is often considered a key culprit for conservation problems such as the introduction of invasive species (including infectious diseases) and overharvesting of rare species. Here, we present the first assessment of the biodiversity of freshwater molluscs in the ornamental pet trade in Singapore, one of the most important global hubs of the ornamental aquarium trade, and discuss associated conservation concerns. We recorded freshwater molluscs from ornamental pet shops and major exporters including non-ornamental species (e.g., hitchhikers, molluscs sold as fish feed). We recorded an unexpectedly high diversity—59 species—of freshwater bivalves and gastropods, with the majority (38 species or 64%) being from the Oriental region. In addition to morphological examination, we sequenced the DNA barcode region of mitochondrial CO1 and 16S genes to provide molecular data for the confirmation of the identification and for future re-identification. DNA barcodes were obtained for 50 species, and all but four were separated by > 3% uncorrected pairwise distances. The trade has been considered a main introduction pathway for non-native species to Singapore, and we found that out of 15 species in the trade as well as in the wild in Singapore, 12 are either introduced or of unknown origin, representing almost half of the known non-native freshwater molluscs in Singapore. Particularly prevalent are non-ornamental species: six hitchhikers on aquarium plants and six species sold as fish feed. We found that a quarter of the trade species have a history of introduction, which includes 11 known or potentially invasive species. We conclude that potential overharvesting is difficult to assess because only half of the trade species have been treated by IUCN. Of these, 21 species are of Least Concern and three are Data Deficient. Our checklist, with accompanying DNA barcodes, images, and museum vouchers, provides an important reference library for future monitoring, and constitutes a step toward creating a more sustainable ornamental pet trade.

Limicolaria flammea (Müller, 1774), another potentially invasive African land snail in tropical Asia

The pulmonate land snail, Limicolaria flammea (Müller, 1774), is native to West Africa and its invasive potential is hitherto unknown. We report this species in Asia, specifically on the tropical island of Singapore. The presence of this alien species is of grave concern because its congener (L. aurora) has invaded the French West Indies and the confamilial giant African land snail (Achatina fulica) has colonized the globe to an extent where it is regarded as one of the worlds worst 100 invasive alien species. In order to curb the spread of L. flammea into the native forests in Singapore, local authorities should start employing mechanical eradication methods (e.g., handpicking). We hypothesize that L. flammea arrived together with an exotic plant species, whose identity and import origin must be determined urgently to prevent the spread of this species into the rest of tropical Asia.

Integrative taxonomy of the genus Onchidium Buchannan, 1800 (Mollusca, Gastropoda, Pulmonata, Onchidiidae)

Abstract In an effort to clarify the species diversity of onchidiid slugs, the taxonomy of the genus Onchidium Buchannan, 1800 is revised using an integrative approach. New, fresh specimens were collected in a large number of places, including type localities. The genus Onchidium is redefined here as a clade including only three species which are strongly supported by both morphological and molecular data. All three species were already named: the type species Onchidium typhae Buchannan, 1800, Onchidium stuxbergi (Westerlund, 1883), and Onchidium reevesii (J.E. Gray, 1850). With the exception of a re-description of Onchidium typhae published in 1869, all three species are re-described here for the first time. First-hand observations on the color variation of live animals in their natural habitat are provided. The anatomy of each species is described. Important nomenclatural issues are addressed. In particular, Labella Starobogatov, 1976 is regarded as a junior synonym of Onchidium and Labella ajuthiae (Labbé, 1935) and Onchidium nigrum (Plate, 1893) are regarded as junior synonyms of Onchidium stuxbergi. The nomenclatural status of several other species names is discussed as well. Many new records are provided across South-East Asia and precise ranges of geographic distributions are provided for the genus Onchidium and its three species. Distinctive features that help distinguish the genus Onchidium from other onchidiids are provided, as well as an identification key for the three species.

The Taxonomy, Distribution and Introduction History of the Earliest Reported Alien Freshwater Mollusc in Singapore — Sinotaia guangdungensis (Gastropoda: Viviparidae)

Freshwater fauna introductions in Singapore have been relatively well documented (Yeo & Chia, 2010), but the origins of many alien species, such as freshwater molluscs are unconfirmed (Tan et al., 2012). Among the known introduced molluscs, the South American Pomacea canaliculata is perhaps the most notorious owing to it being a widespread and major agriculture pest (Joshi & Sebastian, 2006). However, P. canaliculata is a relatively recent introduction to Singapore (since 1980s; Tan et al., 2012) compared to Sinotaia guangdungensis (Kobelt, 1906) (Viviparidae), which was first recorded in the 1950s (as Vivipara polyzonata by Johnson, 1957), making it the earliest reported introduced freshwater mollusc here. The taxonomy of Sinotaia guangdungensis has been confusing, resulting in the species being referred to by different names. Following Johnson (1973), the species has been known in Singapore as Angulyagra polyzonata (and subsequently as Taia polyzonata in Clements et al., 2006; Tan et al., 2012); however, the name Taia polyzonata appears to have been used almost exclusively in Singapore and neighbouring Malaysia (e.g., Palmieri et al., 1980; Sengupta et al., 2009; Tan et al., 2012). Shea (1994) re-identified the species in Singapore as Bellamya heudei guangdungensis, by differentiating it from Angulyagra polyzonata, and although Shea’s correction was noted by Chan (1997), this name has been overlooked in Singapore to date. Sinotaia guangdungensis is rarely documented in its native region in southern China (Shea, 1994) and little else is known about the species. Therefore, an account based on specimens collected in Singapore can conMALACOLOGIA, 2014, 57(2): 401408

A revision of Peronina Plate, 1893 (Gastropoda : Euthyneura : Onchidiidae) based on mitochondrial and nuclear DNA sequences, morphology and natural history

Abstract. Peronina Plate, 1893 is a genus of onchidiids that live on the mud in mangrove forests. Peronina can be identified in the field by the lung opening at the margin between the ventral hyponotum and the dorsal notum, and by the distinctive scalloped notum edge. This genus was previously known only from the holotype of the type species, Peronina alta Plate, 1893, from eastern India. Onchidium tenerum Stoliczka, 1869 is moved to Peronina and applies to the same species as Peronina alta. Peronina species are described using an integrative approach (natural history, comparative anatomy and DNA sequences). Mitochondrial COI and 16S sequences and nuclear ITS2 and 28S sequences are used to independently test species boundaries. Mitochondrial sequences yielded three units separated by a large barcode gap, but nuclear sequences yielded two units. Because these two units are congruent with differences in the male copulatory apparatus, they are accepted as species. Explanations for highly divergent COI haplotypes within one species are discussed. Peronina tenera (Stoliczka, 1869) is distributed in the Bay of Bengal and the Strait of Malacca, while P. zulfigari Goulding & Dayrat, sp. nov. is endemic to the Strait of Malacca. The two species differ internally but are cryptic externally.

On the identities of the molluscan names described in A Short Zoology of Tahiti in the Society Islands by Anthony Curtiss in 1938 (Mollusca: Cephalopoda, Gastropoda)

Anthony Curtiss described two species of cephalopod and nine species of gastropod molluscs from Tahiti. Herein, we discuss and determine the identities of these eleven names. Ten of these names are considered to be junior subjective synonyms of well-known taxa, and one an unavailable name.