Quid estClea helena?Evidence for a previously unrecognized radiation of assassin snails (Gastropoda: Buccinoidea: Nassariidae)

Abstract

The genus Clea from SE Asia is from one of only two unrelated families among the megadiverse predatory marine Neogastropoda to have successfully conquered continental waters. While little is known about their anatomy, life history and ecology, interest has grown exponentially in recent years owing to their increasing popularity as aquarium pets. However, the systematic affinities of the genus and the validity of the included species have not been robustly explored. Differences in shell, operculum and radula characters support separation of Clea as presently defined into two distinct genera: Clea, for the type species Clea nigricans and its allies, and Anentome for Clea helena and allies. A five-gene mitochondrial (COI, 16S, 12S) and nuclear (H3, 28S) gene dataset confirms the placement of Anentome as a somewhat isolated offshoot of the family Nassariidae and sister to the estuarine Nassodonta. Anatomical data corroborate this grouping and, in conjunction with their phylogenetic placement, support their recognition as a new subfamily, the Anentominae. The assassin snail Anentome helena, a popular import through the aquarium trade so named for their voracious appetite for other snails, is found to comprise a complex of at least four species. None of these likely represents true Anentome helena described from Java, including a specimen purchased through the aquarium trade under this name in the US and one that was recently found introduced in Singapore, both of which were supported as conspecific with a species from Thailand. The introduction of Anentome “helena” through the aquarium trade constitutes a significant threat to native aquatic snail faunas which are often already highly imperiled. Comprehensive systematic revision of this previously unrecognized species complex is urgently needed to facilitate communication and manage this emerging threat.

Assassin snails (Anentome helena) as a biological model for exploring the effects of individual specialisation within generalist predators

“…A. helena snails appear only to feed on prey less than twice its own wet weight. Furthermore, recent work suggests that A. helena might be a species complex [ 28 ].…”

“…A. helena (von dem Busch in [ 26 ], Nassariidae, previously also known as Clea helena ) is a fresh water snail [ 27 , 28 ]. It actively hunts other freshwater snails and worms, but also scavenges on dead fish [ 29 , 30 ].…”

Mitogenomic phylogeny of mud snails of the mostly Atlantic/Mediterranean genus Tritia (Gastropoda: Nassariidae)

“…For instance, the species of the genus Bullia are the most conspicuous surfing organisms of the swash zone of many sandy beaches in the southern hemisphere, and some species of Nassarius and Tritia display dense populations in estuaries and coastal lagoons. Several species have adapted to brackish water, and a few have successfully conquered freshwater habitats in South East Asia (Strong et al., 2017). Due to their abundance, nassariids have been well studied from different points of view.…”

Elemental analyses reveal distinct mineralization patterns in radular teeth of various molluscan taxa

“… ? Taeniogloss 2 + 1 + C + 1 + 2 1,2,3 – – – – Anentome helena (von dem Busch, 1847) 2 + 1 ZMH 122792 Pet shop Summer 2019 Gastropoda, fish eggs, shrimps, carrion 70 , 71 Soft to solid Stenogloss 1 + C + 1 1 2097 244 511,668 61 2 2102 241 506,582 60 3 2189 261 571,329 61 Buccinum undatum Linnaeus, 1758 2 + 1 ZMH 122793 Biologische Anstalt Helgoland, Germany May 2021 Polychaeta, fish eggs, bivalves, carrion, etc 72 Soft to solid Stenogloss 1 + C + 1 1 9660 1420 13,717,200 59 2 9641 1396 13,458,836 60 3 9701 1486 14,415,686 …”