Helicarion nigra (Quoy & Gaimard, 1832)

Hyman, Isabel T & Köhler, Frank, 2018, Reconciling comparative anatomy and mitochondrial phylogenetics in revising species limits in the Australian semislug Helicarion Férussac, 1821 (Gastropoda: Stylommatophora), Zoological Journal of the Linnean Society 184, pp. 933-968 : 950-962

publication ID	https://doi.org/10.1093/zoolinnean/zly017
persistent identifier	https://treatment.plazi.org/id/03E487A3-FF87-C464-FF06-B0E3FB99FA86
treatment provided by	Plazi
scientific name	Helicarion nigra
status

Treatment

Helicarion nigra View in CoL – Smith, 1992: 234.

Material examined

Types: Neotype of H. cuvieri : MNHP no number ( Needles picnic ground, S of Strathgordon Road, SW TAS) ( Kershaw, 1979).

Lectotype of Vitrina nigra : MNHP no number ( Western Port , Vic) ( Kershaw, 1981).

Holotype of H. leopardinus : AM C.101141 (Ourimbah Scrubs, NSW).

Holotype of H. mastersi callidus : AM C101138 ( Twofold Bay , NSW) . Non-type material: See Supporting Information ( Table S1).

Description

External morphology: Shell greenish gold to orange-brown, 2.7–3.5 whorls. Body colour variable, ranging from cream to black, often speckled with orange, cream or brown. Shell lappets sometimes dark bordered, sometimes with two to three pigmented warts. Tail with a moderately strong keel, usually paler than body colour.

Genital anatomy: Penis generally slender, tubular, of variable length, occasionally slightly swollen proximally. Penial interior sculptured with nine to 50 rows of papillose ridges arranged in a deep V shape. Penis-to-epiphallus ratio variable, 0.18–1.31; epiphallus entering penis apically or laterally. Flagellum with internal cryptae. Spermatophore variable, with nine to 20 spines.

Remarks

Helicarion cuvieri has previously been recorded only from Tasmania, where it is widespread ( Fig. 6 View Figure 6 ). Here we expand the delineation of this species to include populations from eastern Victoria and southeastern NSW. This species and its congener, H. mastersi , are both highly variable in body size and colour, making it difficult to distinguish them reliably. Helicarion cuvieri generally has a uniform body and sole colour in darker shades ranging from grey to orange-brown and black, with dark eye tentacles. In specimens with a contrasting pale sole (clades E, F and G), the tail tip often has a dark vertical stripe. Three pigmented warts are often (but not always) present on the shell lappets, and the tail has a longer keel. Helicarion mastersi has no pigmented warts, generally paler coloration, with pale eye tentacles in shades of cream, pink, grey and brown, deepening on the tail, and has a pale sole contrasting with its body colour. The two species can be distinguished morphologically by the spacing of the internal penial lamellae; H. cuvieri has fewer, coarser lamellae arranged in a deep V shape, whereas H. mastersi has more numerous, finer lamellae arranged in a shallower V shape.

Within H. cuvieri there are eight morphologically distinct subclades (clades A–H), which are morphologically distinct; these are described below.

specimens with 13–16 spines, formula (2, 2, 9, 3); Brown Mountain specimens with 20 spines, formula (4, 11, 1, 4) ( Figs 10, 11A–C View Figure 11 ).

Remarks

Clade A comprises all Tasmanian specimens along with one population from the Otway Ranges in Victoria and another population from Brown Mountain in NSW. There is a wide range of colour variation seen in clade A, including the only known orange forms of Helicarion . The two geographically isolated populations differ anatomically from the rest of the clade. Semislugs from the Otway Ranges have a much simpler spermatophore, with nine simple spines, in contrast to the ten to 16 more complex spines seen in Tasmanian specimens. Likewise, specimens from Brown Mountain in NSW have a much more complex spermatophore than Tasmanian specimens, with 20 spines in total, including a higher number of branching spines; this population also has a slightly longer penis. These differences probably reflect the isolation of these geographical areas. There may also be a connection with altitude, because both regions have a relatively high elevation.

Members of this clade are microsympatric with Attenborougharion rubicundus in southeastern Tasmania but can be distinguished by their smaller size and generally uniform cream to dark brown coloration, in contrast to the two-toned burgundy and green coloration of A. rubicundus .

CLADE A

( FIGS 6 View Figure 6 , 7A View Figure 7 , 8A–C View Figure 8 , 9 View Figure 9 , 10, 11A–C View Figure 11 )

Diagnosis

External morphology: Shell golden amber, 2.7–3.5 whorls ( Figs 7A View Figure 7 , 8A–C View Figure 8 ). Body cream, orange, grey or dark brown, often speckled with orange, cream or brown. Eyestalks blue-grey to black. Shell lappets dark bordered, with three pigmented warts, two on right lappet, one on left lappet, with black pigmentation in grey specimens and orange pigmentation in orange-brown specimens. Tail with a moderately strong keel, usually paler than body colour ( Fig. 9 View Figure 9 ).

Genital anatomy: Penis medium length, tubular, occasionally slightly swollen proximally. Penial interior with ~14–16 lamellae. Penis-to-epiphallus ratio of 0.41–0.84; epiphallus enters penis apically or slightly laterally. Spermatophore variable; Otway Ranges specimens with nine spines, formula (0, 7, 2, 0); Tasmanian

CLADE B

( FIG. 12 View Figure 12 )

Diagnosis

External morphology: Shell golden amber, 3.1 whorls. Body and sole a uniform dark grey (in alcohol). Shell lappets darker, black bordered, with three pigmented warts, two on right lappet, one on left lappet. Tail keeled. Fig. 12 View Figure 12

Genital anatomy: Penis moderately long, tubular, slightly swollen proximally. Penial tunica covering approximately four-fifths of penis. Penial interior with ~12 lamellae. Penis-to-epiphallus ratio of 0.53; epiphallus enters penis slightly laterally. Spermatophore with 15 spines, formula (3, 5, 5, 2).

Remarks

Clade B is represented by only a single specimen from Alpine NP in Victoria. This specimen is distinguished by its very dark body colour, the presence of pigmented warts on its shell lappets, and the moderately long penis with very few penial lamellae. Further collecting in the Alpine NP and adjacent high-altitude parts of Victoria and southern NSW is necessary to understand this clade better .

SPECIES LIMITS IN HELICARION SEMISLUGS 955

CLADE C

( FIGS 6 View Figure 6 , 7B View Figure 7 , 8D–F View Figure 8 , 13A View Figure 13 , 14 View Figure 14 )

Diagnosis

External morphology: Shell golden, 3.3 whorls ( Figs 7B View Figure 7 , 8D–F View Figure 8 ). Body and sole dark grey-brown (in alcohol); in life with a speckled appearance. Lappets narrow, lacking pigmented warts, dark bordered. Left lappet with dark streaks on inside. Mid field of sole slightly paler ( Fig. 13A View Figure 13 ).

Genital anatomy: Penis long, slender, proximally swollen, swollen portion folded over. Penial tunica covering approximately three-quarters of penis. Penial interior with ~25 lamellae. Penis-to-epiphallus ratio of 0.74; epiphallus also folded. Spermatophore of 12 spines, formula (1, 4, 6, 1) ( Fig. 14 View Figure 14 ).

Remarks

Clade C is known only from Mitchell River NP ( Fig. 6 View Figure 6 ). No material was available to measure; however, based on the limited material available members of this clade appear to be relatively small, similar in size to members of clade G from the Blue Mountains. Clade C semislugs can be distinguished from other clades of H. cuvieri by their longer penis and epiphallus, both of which are folded.

CLADE D

See clade H below.

CLADE E

( FIGS 6 View Figure 6 , 7C View Figure 7 , 8G–I View Figure 8 , 11D–F View Figure 11 , 13B, C View Figure 13 , 15 View Figure 15 )

Diagnosis

External morphology: Shell amber to orange-brown, 2.8–3.4 whorls ( Fig. 7C View Figure 7 , 8G–I View Figure 8 ). Body grey or pale brown to black, colour deepening on tail and neck, with a vertical dark stripe at tail tip; sole generally paler than body. Shell lappets with three pigmented warts in Victorian populations ( Fig. 13B, C View Figure 13 ).

Genital anatomy: Penial interior of few (nine to 13) lamellae arranged in deep V-shaped rows. Penis size and epiphallus entry variable: penis-to-epiphallus ratio of 0.44–0.50, epiphallus entering penis apically (Victorian populations and Flinders Island)’ penis-to-epiphallus ratio of 0.18–0.36, epiphallus entering laterally (Nadgee NR, Burragorang, Mt Kelgoola and Mt Coricudgy); or penis-to-epiphallus ratio of 0.83, epiphallus entering laterally (Wyong, Wombeyan Caves). Flagellum with prominent internal cryptae, corresponding to ten to 13 robust branching spines on spermatophore; spermatophore formula (2–3, 4–10, 0–7, 0–2) ( Figs 11D–F View Figure 11 , 15 View Figure 15 ).

Remarks

Clade E includes material from Victoria, including the type locality of H. niger . However, H. niger as previously understood contained all Victorian populations and Flinders Island (Tas). In contrast, clade E does not three pigmented warts on their shell lappets and in the presence of a medium-length penis with the epiphallus entering apically. Populations from Nadgee Nature Reserve (the type locality of H. mastersi callidus ), Burragorang, Mt Kelgoola and Mt Coricudgy all have a very short penis, the shortest observed in Helicarion to date, with the epiphallus entering slightly laterally. Finally, specimens from Wyong and Gosford (representing H. leopardinus ) and from Wombeyan Caves have a relatively long, broad penis with a slightly lateral epiphallus entry point. These differences are significant; however, there is only slight genetic differentiation, and one of the three groups thus delimited (the short penis group) is paraphyletic. Furthermore, there are some strong characters uniting the three groups, including a penial interior with a small number of relatively large internal lamellae, and the presence of a robust spermatophore with 13–16 spines, most highly branched. It is also possible that the penial differences are attributable to reinforcement, because the clades exhibiting a very short penis are all in close proximity to another clade (see Taxonomic Preamble).

Kershaw (1981) described a small penial papilla in H. niger ; this has not been observed in any specimens in the present study.

contain all Victorian populations; in fact, from Victoria, only populations from Wilsons Promontory (the type locality) and the Central Highlands are included. Several populations from south-eastern NSW are also included ( Fig. 6 View Figure 6 ). The resulting distribution, the largest of any H. cuvieri subclade, contains several large gaps, notably between Wilson’s Promontory in Victoria and Nadgee Nature Reserve in NSW, and between Nadgee Nature Reserve and Wombeyan Caves. It is probable that further collecting will extend the known range of clade E still further and may somewhat reduce the size of the gaps in its distribution .

In addition to the largest distribution, this taxon also exhibits the most anatomical variation seen in any Helicarion clade. The Victorian populations (including Flinders Island; equivalent to H. niger s.s. and forming a monophyletic group) are significantly larger than the NSW specimens, and also differ in exhibiting

CLADE F

( FIGS 6 View Figure 6 , 7D View Figure 7 , 8J–L View Figure 8 , 11G–I View Figure 11 , 16A–C View Figure 16 , 17 View Figure 17 )

Diagnosis

External morphology: Shell golden amber, 3.0–3.5 whorls ( Figs 7D View Figure 7 , 8J–L View Figure 8 ). Body cream to pale grey or brown, colour deepening on tail and neck, with a white to pale pink sole. Shell lappets with one to three pigmented warts (one or two on right lappet, one on left), less visible in pale specimens ( Fig. 16A–C View Figure 16 ).

Genital anatomy: Penis long, slender, penis-to-epiphallus ratio of 0.29–0.87, epiphallus entering laterally or apically. Penial interior of 12–21 lamellae arranged in deep V-shaped rows. Spermatophore of 11–17 branches, with a gap after the second or third branch ( Figs 11G–I View Figure 11 , 17 View Figure 17 ).

Remarks

Clade F is distributed in southeastern NSW and eastern Victoria. Members of this clade are very similar in external morphology to members of the neighbouring clade E and to pale specimens of clade A. All three taxa are large semislugs with two or three pigmented warts on their shell lappets. Anatomically, semislugs belonging to clade F can be distinguished from members of clade E by their longer penis relative to the epiphallus, with a larger number of penial lamellae.

This clade contains four well-supported, morphologically distinct subclades. The major differences lie in the spermatophore and flagellum, particularly in the presence of a large gap in the pattern of spermatophore spines in populations from Mt Gulaga and Tallaganda NP, with some variation also present in the penis shape and length. However, the genetic distances between the subclades are low and indicative of their rather recent evolutionary origin and potentially incomplete lineage differentiation. We are also unsure whether the anatomical differences are truly indicative of reproductive incompatibility.

CLADE G

( FIGS 6 View Figure 6 , 7E View Figure 7 , 8M–O View Figure 8 , 16D, E View Figure 16 , 18 View Figure 18 )

Diagnosis

External morphology: Shell golden, 3.2–3.6 whorls ( Figs 7E View Figure 7 , 8M–O View Figure 8 ). Body cream to dark grey, darker on tail; lappets dark edged, lacking pigmented warts ( Fig. 16D, E View Figure 16 ).

Genital anatomy: Penis very long, slender, swollen medially; proximal end similar in width to epiphallus; penis-to-epiphallus ratio of 1.08–1.31, epiphallus entering penis laterally through simple pore. Epiphallus with an extra fold. Interior of penis with numerous lamellae (~50), slightly deeper and more folded in narrow proximal portion. Bursa copulatrix with a very long duct, duct longer than bursa. Spermatophore with 14 evenly spaced branching spines of decreasing complexity; formula (1, 9, 2, 2) ( Fig. 18 View Figure 18 ).

Remarks

This clade is distributed in the Blue Mountains NP, including Mt Wilson, Mt Tomah Botanic Gardens and Katoomba ( Fig. 6 View Figure 6 ). Specimens from Jenolan Caves probably also belong to this clade. A separate taxon, clade E, is found further south in Burragorang.

Members of clade G are significantly smaller than members of clade A and H. mastersi . These semislugs can be distinguished from other subclades of H. cuvieri by their extremely long penis, with a distinctive shape and relatively numerous penial lamellae.

CLADE H

( FIGS 6 View Figure 6 , 7F View Figure 7 , 8P–R View Figure 8 , 16F View Figure 16 , 19 View Figure 19 )

Diagnosis

External morphology: Shell greenish gold, 3.0–3.4 whorls ( Figs 7F View Figure 7 , 8P–R View Figure 8 ). Body grey, with deeper grey-black wrinkles and black eyestalks. Shell lappets and mantle lobes speckled grey, dark bordered, without pigmented warts. Sole a uniform grey ( Fig. 16F View Figure 16 ).

Genital anatomy: Penis long, slender, subdivided into two portions, with distal portion covered by penial tunica. Penial interior with wavy, pustulose lamellae arranged in a V shape in distal portion; proximal portion with deep, distinct, less pustulose lamellae arranged in much deeper V shape (close to longitudinal). Total number of lamellae ~14–16. Penis-to-epiphallus ratio of 0.79; two arms of epiphallus twisted around one another. Flagellum with internal cryptae. Spermatophore of 19 spines, formula not recorded, most spines with multiple branches ( Fig. 19 View Figure 19 ).

Remarks

Clade H is known only from the Brindabella Range ( Fig. 6 View Figure 6 ). Helicarion specimens have also been collected at other sites in and around the ACT, including Tidbinbilla Nature Reserve, Namadgi National Park and Tantangara Mountain, but the identity of these specimens has not been confirmed. Specimens from Wee Jasper at the northern tip of the Brindabella Range are very similar in external morphology and in genital morphology, with the same overall pattern of a two-chambered penis but with a shorter penial complex and fewer spines on the spermatophore. This degree of variation is consistent with the population-level differences observed in other clades, and it is likely that the Wee Jasper population forms part of clade H despite not grouping together on the molecular tree.

Members of clade H are unique in their grey speckled appearance and greenish golden shell. They are significantly smaller than all other Helicarion semislugs. Their penial anatomy is highly distinct, particularly in the presence of very deep, nearly longitudinal lamellae in the proximal portion of the penial interior. The large number of spermatophore spines also helps to distinguish this clade.