Helicarion Férussac, 1821

Hyman, Isabel T. & Ponder, Winston F., 2010, A morphological phylogenetic analysis and generic revision of Australian Helicarionidae (Gastropoda: Pulmonata: Stylommatophora), and an assessment of the relationships of the family 2462, Zootaxa 2462 (1), pp. 1-148 : 22-23

Helicarion Férussac, 1821

Helixarion Férussac, 1821: 20 . Amended to Helicarion: ICZN, 1992 , Opinion 1678. Type species Helicarion cuvieri Férussac, 1821 (SD: Thon 1829).

Helicarium Agassiz, 1846: 174 (nom. nov. for Helicarion Férussac, 1821 ).

Description. External morphology: Shell reduced, 3.0–3.2 whorls, glossy, spire and apex flattened. Protoconch sculptured with incised spiral grooves and teleoconch with microscopic spiral grooves. Whorl profile rounded above and below evenly convex periphery. Internal walls of early whorls complete; umbilicus closed. Animal with moderately large mantle laps, not fused, uniform in colour. Mantle lobes small to medium, not fused. Caudal apparatus as for family; caudal foss vertical slit in tail.

Mantle cavity: Mantle cavity roof with visible minor blood vessels; pigmentation of white spots or absent.

Digestive system: Oesophageal crop present.

Genital system: Carrefour and talon both embedded in albumen gland. Free oviduct short; capsular gland present; internal longitudinal pilasters absent ( Helicarion cuvieri ) or present ( H. mastersi ). Bursa copulatrix inserted on vagina, short, less than half spermoviduct length; duct of bursa copulatrix wide, distinguishable from bursa copulatrix, internally with longitudinal pilasters. Vagina very short, internally with longitudinal pilasters. Epiphallus enters penis through simple pore; penis internally with diagonal V-shaped bumpy ridges, pilasters absent, diverticulum on penis absent. Penial sheath enclosing complete penis ( H. mastersi ) or only base of penis ( H. cuvieri ); penis retractor muscle attached to epiphallus. Epiphallus simple internally ( H. mastersi ) or with longitudinal pilasters ( H. cuvieri ). Epiphallic retractor caecum absent. Flagellum present; flagellum and distal part of epiphallus with internal cryptae forming external projections. Spermatophore soft capsule with firm tail pipe open at one end, tail pipe short and spiralling, sculptured with long branching spines.

Radula ( H. cuvieri data from Kershaw 1979): Relatively long and narrow. Central tooth with small ectocones; mesocone lanceolate, shorter than tooth base. Lateral and marginal tooth fields distinguishable. Lateral teeth with endocones smaller than central tooth ectocone, ectocone equal in size to those on central tooth, mesocones shorter than tooth base. Marginal teeth with endocones absent, ectocones approximately same length and breadth as mesocone ( H. mastersi ) or shorter than mesocone ( H. cuvieri ), not subdivided into extra teeth.

Remarks. The first Helicarionidae described were Helicarion cuvieri and Fastosarion freycineti , both originally placed in the genus Helicarion ( Férussac, 1821) . Many species have subsequently been included in this genus from Australia and elsewhere. However, currently only six species from southeastern Australia (Tasmania, Victoria and New South Wales) are included ( Smith et al. 2002). Three of these species have been described by Kershaw and co-authors ( Dartnall & Kershaw 1978; Kershaw 1979, 1980, 1981). Kershaw (1981) also redescribed the genus to include semislugs with no stimulator, epiphallic retractor caecum or elaborate atrial diverticulum, but possessing a coiled flagellum that produces an elaborate spermatophore and sometimes a small fleshy penial papilla.

In Smith (1992), R.C. Kershaw synonymised genera Desidarion and Luinarion Iredale, 1933 with Helicarion . Both of these were introduced as monotypic genera, for Desidarion dispositus Iredale, 1941 and Luinarion castanea ( Pfeiffer, 1853) respectively. As well as Luinarion and Desidarion, Schileyko (2002b) placed non-Australian genera Platycloster Hasselt, 1824 and Laconia Gray, 1855 in synonymy with Helicarion and listed the range of the genus as including Java, Papua New Guinea and New Caledonia as well as Australia. This was followed by Smith et al. (2002).

The absence of an epiphallic retractor caecum and the presence of an extremely short vagina, a coiled flagellum with internal cryptae and a spiralling spermatophore with long branching spines are characteristic of five genera found in southeastern Australia ( Helicarion , Mysticarion , Parmavitrina , Peloparion and Brevisentis ). Amongst these, Helicarion can be distinguished by the internal sculpture of the penis, which is made up of V-shaped diagonal papillate ridges [present at least in H. cuvieri , H. mastersi , H. rubicundus Dartnall & Kershaw, 1978 , H. nigra (Quoy & Gaimard, 1832) ] and the presence of at most a very small penial papilla or verge (absent in H. cuvieri , H. mastersi , H. rubicundus ; present in H. nigra ). The other genera have longitudinal or circular pilasters or pustules and, in some taxa, a more substantial verge is present ( Mysticarion , Brevisentis ). In addition, the spermatophore of Helicarion can be distinguished from that of Brevisentis , Mysticarion and Peloparion by its tighter coiling and the presence of longer branching spines that cover the whole tail pipe (the morphology of the spermatophore is unknown in Parmavitrina ). Species of Brevisentis and Mysticarion generally have less reduced shells than Helicarion , while species of Peloparion have more reduced shells and Parmavitrina species have shells with a similar degree of reduction to those of Helicarion but are thicker and much larger.

Luinarion , Desidarion , Platycloster and Laconia are not treated as synonyms of Helicarion in this study. Examination of Desidarion dispositus showed that it shares the characteristics of the other five southeastern Australian genera (short vagina, no retractor caecum, coiled flagellum with external cryptae, spinose spermatophore). However, it differed from Helicarion , Mysticarion , Parmavitrina , Peloparion and Brevisentis in the internal anatomy of the penis and the structure of the flagellum and spermatophore. The interior of the penis consisted of longitudinal pilasters at the base and irregular round pilasters at the apex, whereas there are diagonal rows of pustules in species of Helicarion . In addition, the flagellum showed large cryptae at the epiphallus end but very few cryptae at the proximal end, again differing from Helicarion . Finally, the branching spines of the spermatophore were split at the base into two major branches, the tip of each branch was dark brown in colour (contrasting with the golden-brown colour of most of the spermatophore) and there was a single long spine at the apex. None of these characteristics were observed in the spermatophores of species of Helicarion . Given these differences, Desidarion is retained as a separate genus.

Specimens of Luinarion castanea were not available for dissection. The only existing specimens appear to be the syntypes of L. castanea and its synonym, Helicarion thomsoni Ancey, 1889 , despite intensive enquiries and a search of the Western Australian Museum collection (S. Slack-Smith, pers. comm.). The type locality of L. castanea is given only as southern Western Australia; however, the type locality of ‘H’. thomsoni (Geographe Bay, Western Australia) has been well sampled (S. Slack-Smith, pers. comm.). Therefore, it appears possible that either L. castanea is extinct or extremely rare, or that the original locality was given in error and the species does not occur in that part of Western Australia. In either case, there is insufficient information or material available to make a judgement as to whether or not this species should be included in Helicarion and we treat this taxon as incertae sedis.

Platycloster is from Maluku ( Indonesia) ( Beck 1837) and has been synonymised with Microcystis Beck, 1837 by previous authors ( Thiele 1929 –1931; Zilch 1959). Laconia was first placed in synonymy with Helicarion by Zilch (1959). No justification for the synonymy was given by any previous authors. Material of this genus could not be examined and there is no information published on its anatomy. There is no justification for placing it in synonymy with Helicarion and we therefore treat it as incertae sedis pending the availability of further data. This limits Helicarion to five Australian species, ranging from Tasmania to northern New South Wales.