Bothriembryon (Bothriembryon) sophiarum, Whisson, Corey S. & Breure, Abraham S. H., 2016

Whisson, Corey S. & Breure, Abraham S. H., 2016, A new species of Bothriembryon (Mollusca, Gastropoda, Bothriembryontidae) from south-eastern Western Australia, ZooKeys 581, pp. 127-140 : 129-134

Taxon classification Animalia Stylommatophora Bothriembryontidae

Bothriembryon (Bothriembryon) sophiarum sp. n. Figs 1and 3, 4, 5, Table 1

Type material.

Holotype. Western Australia, Nullabor Plain, Baxter Cliffs near Burnabbie Ruins, 32°07'30"S, 126°20'45"E, V. Kessner collector (ex J. Hemmen collection) 6 October 1989, dry, WAM S66478. Paratypes (from type locality) WAM S66479 (2 dry specimens) and RMNH.334653 (2 dry specimens); Western Australia, Nullabor Plain, Baxter Cliffs near Burnabbie Ruins, 32°07'30"S, 126°20'45"E, V. Kessner collector, 6 October 1989, WAM S30768 (6 dry specimens), AM C.477954 (3 dry specimens), RMNH.334654 (1 dry specimen).

Other material examined.

Western Australia: Israelite Bay, W.G. Buick Collection No. 13096, Pre June 1992, WAM S7972 (2 dry specimens); Israelite Bay area, start of cliffs at E end, Point Culver area, A. Longbottom, 21 October 1983, WAM S7977 (46 dry specimens); Nuytsland Nature Reserve, Toolina Cove, A. Cummings, 31 August.2010, WAM S64829 (4 preserved specimens); Top of Toolina Cliff, J. Lowry, 07 November 1966, WAM S7978 (8 dry specimens); Nuytsland Nature Reserve, Baxter Cliffs, near Baxter Memorial, A. Cummings, 30 August 2010, WAM S64824 (6 preserved specimens); South of Baxter Memorial, 50 feet from edge of cliff, P. Bridge and B. Robinson, 19 December 1966, WAM S7968 (6 dry, 24 preserved specimens); 38 km S of Caiguna, sea cliff top, K.A. Lance, 07 January 1976, WAM S7966 (25 dry specimens); S of Caiguna, between the Baxter Memorial and coast, P. Bridge and B. Robinson, 19 December 1966, WAM S7971 (8 dry specimens); S of Caiguna; near coast, B. Robinson, April 1966, WAM S8006 (2 dry specimens); 6 km SE of Baxter Memorial, top of Baxter Cliffs, A. Saar and K. Lance, 07 January 1976, WAM S7970 (10 dry, 4 preserved specimens); Twilight Cove, on cliff slope east of the cave, J. Lowry, 05 November 1966, WAM S7973 (33 dry specimens); 13 miles SE of Cocklebiddy, 7 miles N of Eyre, K. Thies, 21 May 1971, WAM S7974 (12 dry specimens); Eyre Homestead, escarpment face, W. Humphreys, March 1985, WAM S7969 (1 dry specimen); 14 miles ESE of Cocklebiddy, on face of Hampton Escarpment, A. Baynes and W. Youngsen, 04 September 1969, WAM S8031 (25 dry, 2 preserved specimens); Eyre, foot of escarpment, E. Sedgwick, August 1977, WAM S8053 (8 dry specimens); Baxter Cliffs 1.3 km E of Burnabbie Ruins, 32°07'6.54"S, 126°21'4.50"E, R. Phillips, 6 March 2015, WAM S67680 (1 wet specimen).

Diagnosis.

A slender shell characterised by plicate teleoconch whorls, often with pillared sculpture formed from incised spiral lines which become less frequent on the body whorl, and a strongly crenulate suture.

Description.

Shell morphology. Shell slender, mostly turriform, diameter 4.7-6.7 mm (mean 5.5 mm, sd 0.45), height 12.7-24.4 mm (mean 16.2 mm, sd 2.39) with 6.20-8.50 whorls (mean 7.05, sd 0.63) and a H/D ratio of 2.4-3.8 (mean 2.9, sd 0.26), rimate (Table 1, Suppl. material 1). Protoconch of 1.80-2.45 whorls (mean 2.18, sd 0.14) with very short, separate oblique wrinkles extending from suture before reticulating into a dense pattern of uniform punctated thimbles (honeycomb pattern). Teleoconch consisting of slightly convex, but regularly rounded plicate whorls, sculptured with narrow, crowded (often bifurcate) flattened or slightly raised axial ribs that are smooth and often translucent. The axial ribs become irregularly spaced on the last whorl, fading away towards the lower part of the whorl. Axial ribs usually crossed by only a few (mean 5.0, sd 1.0 on penultimate whorl) faint incised spiral lines creating a pillared sculpture that becomes less obvious on the body whorl. Suture irregularly but strongly crenulate formed from axial ribs terminating as large, rectangular nodules at the suture line, with a single nodule often forming from multiple axial ribs. Colour reddish-brown at the protoconch, the teleoconch cream with irregular blotches of reddish- to greyish-brown. Aperture relatively small, skewed elongate-ovate, lip thin, simple, basal margin slightly angular at the transition to the columellar margin, which is triangular dilated above; parietal callus thin and transparent.

Animal external morphology. Body and foot sculptured with regular honeycomb pattern. Upper body and tentacles dark brown to black with an olive to green foot base and sides, the latter relatively wide (Fig. 3A).

Genital morphology. (Based on micro-CT images, see Figs 4 A–B, 5 A–E) Phallus gradually becoming narrower, with the distal part of the epiphallus and the proximal part of the flagellum subcylindrical. Distal part of penis lumen star-shaped (five-legged), lined with a high epithelium and gradually changing into the epiphallus, of which the narrow lumen is also star-shaped. Near the transition to the flagellum the lumen becomes three-legged star-shaped with five very narrow side-branches; more proximally the lumen is rectangular with five very narrow side-branches. The vagina is externally swollen, internally the lumen is elongated and undivided in its distal part, becoming forked at the tail-ends near the split into the spermathecal duct and spermoviduct. The spermathecal duct is comparatively broad with a club-shaped bursa copulatrix. The spermoviduct is slender (as far as traceable). In 3D (Fig. 4A) the genitalia are extruded outside the body of the animal; the female part cannot be traced towards its distal end, the phallus is heavily curled towards its distal end.

Distribution.

Western Australia; along the escarpment and cliff tops of the Baxter Cliffs and Hampton Ranges from the Point Culver area eastward to the Burnabbie Ruins, a linear distance of about 180 kilometres (Fig. 2). Museum records (WAM S7972) suggest it might occur further westward to Israelite Bay (townsite) but the veracity of the location data is questionable.

Habitat.

Very open, low coastal scrub on limestone cliff-edge or slope scattered (often densely) with low limestone rocks and stones. Dominant plant species were Westringia dampieri , Correa backhouseana var. coriacea and Carpobrotus virens and very occasionally Melaleuca and Eucalyptus trees. In dry conditions living specimens are commonly found in rock crevices or fissures; under stones or around tree roots, and occasionally in litter. When wet, crawling snails have been observed on soil and stones and on branches of scrub (Fig. 6).

Remarks.

Bothriembryon (Bothriembryon) sophiarum can be distinguished from most other Bothriembryon species by its shell morphology, notably its slender turriform shape and a teleoconch sculpture of coarsely plicate whorls and strongly crenulate sutures. Most Bothriembryon species are ovate to elongate-conical in shape and have a teleoconch sculpture of faint or narrow axial growth lines. The nearby Bothriembryon (Bothriembryon) perditus Iredale, 1939 has similar shell morphology but its shell is much broader being elongate-conical in shape and has sutures which are more finely crenulate. The other nearby species Bothriembryon (Bothriembryon) gratwicki (Cox, 1899) is similar in shape but its shell is broader and usually more elongated, with a coarse nodulose teleoconch sculpture (Fig. 2). Only one fossil species occurs nearby, Bothriembryon kremnobates Kendrick, 2005 which is found further east on the Roe Plain and is ovate-conical in shape. Anatomically Bothriembryon (Bothriembryon) sophiarum differs only slightly from known Bothriembryon (Bothriembryon) species which have a long, narrow spermathecal duct and a short rounded bursa copulatrix. The short and broad spermathecal duct and relatively broad, elongate bursa copulatrix of Bothriembryon (Bothriembryon) sophiarum agrees more with Bothriembryon (Tasmanembryon) tasmanicus ( Kershaw 1986, Breure 1978). However in this paper we have tentatively placed Bothriembryon sophiarum in the subgenus Bothriembryon on account of its shell morphology and its geographical proximity to other members of the same subgenus. The specimens examined have their genitalia somewhat extruded, hence the male and female genital pores seem to be separated; in other preserved, non-extruded specimens these pores are united inside the atrium (Fig. 4A). It is interesting to note that Bothriembryon (Bothriembryon) sophiarum specimens from Point Culver (WAM S7977) at the western edge of its range, are slightly taller (mean height 20.3 mm, sd 2.11) with a higher H/D ratio (mean 3.4). This collection is a large series (n = 46) and most likely represents population variation due to local environmental conditions, a common occurrence within Bothriembryon as suggested by Main and Carrigy (1953).

Etymology.

Named in honour of Sophie Jade Whisson, first daughter of the senior author and Sophie J. Breure, spouse of the second author; noun in plural genitive case.