Austropeplea subaquatilis (Tate, 1880)

Figs 4 A, C, E, 5 A, C, 6 A, C, 7 A

Material examined.

Specimens from “Drain M” near Princes Highway in Thornlea, South Australia, Australia, and their artificially bred offspring.

Description.

Shell (Fig. 4 A) medium in size (up to 12.5 mm in height), ovate, with low, narrow conical spire and strongly inflated last whorl. Shell wall thin, fragile in some specimens. Whorls (4.0– 4.5 in number) rounded, slightly convex, separated by a shallow, slightly oblique to nearly straight suture. Last whorl comprises ~ 0.9 of shell height. Shell surface smooth, somewhat shiny, light brown to nearly colourless, covered by collabral growth lines. Aperture pyriform, with evenly rounded basal and palatal margins, posterior corner forming angle with last whorl. Peristome sharp, not expanded but columellar lip reflexed and attached to back of last whorl. Parietal callus thin but distinct, extending to last whorl far beyond inner lip. Columellar fold weakly developed. Umbilicus covered by inner lip, closed or very narrow (slot-like).

Head-foot (Fig. 4 C, E) typical of family. Foot broad, reaching 1.5–2 × shell height when fully extended, light grey with sparse white freckles (observed when living). When stimulated, considerable quantities of mucus produced and covers entire body. Tentacles shield-shaped (Fig. 4 E), twice as long as wide (observed when living). Mantle light grey with large black blotches on pallial roof. Mantle collar (Fig. 4 E) reflexed and attached to shell, extended as thin flap on both sides to enclose shell fully or largely in mature individuals. Closed edge of mantle collar situated along midline of animal, forming marginal fold near shell apex. Mantle covering visceral coil with band-like black pigment in mature individuals (Fig. 4 C); disconnected from pigmentation on pallial roof, and readily lost in preserved specimens.

Central nervous system typical of family (Fig. 5 A). Cerebral ganglia with regular borders, pale yellow (fresh). Commissural lobule distinct, white, approximately equal to cerebral ganglia in size.

Pulmonary roof (pallial complex) (Fig. 2 C) with heart and kidney in their typical positions for family. Kidney spindle-shaped, thin-walled, with transversely pleated lining of sinuate tube visible through transparent wall, proximal part opposite anterior pericardium. Ureter short, urinary opening not observed.

Prostate pear-shaped, with single internal fold. Sperm duct long and thick, equal to or slightly longer than oothecal gland in length. Praeputium (Fig. 6 A) light greyish-white, cylindrical, tapers towards proximal end, distal part folded near male genital opening. Bulbous termination of praeputium distinct in lighter colour to white, equal to or wider than narrowest part of praeputium. Penis sheath narrow, shorter than praeputium, proximal part slightly inflated. ICA 1.34 to 2.02. Spermatheca (Fig. 6 C) spherical, duct short, not exceeding length of spermatheca, width approx. 0.1 of its length.

Radula of the haplolateral multidentate type (Fig. 7 A). Radular formula 28 - C- 28 to 32 - C- 32. Teeth in same row bend upward to margin. Central tooth small, bicuspid, asymmetrical, right cusp significantly larger than left. Lateral teeth pairs 1–8 ~ 11 tricuspid, middle cusp largest, left cusp larger than right, rarely with denticle situated on the right basal side; pairs 9 ~ 12–28 ~ 32 with four or five cusps.

Remarks.

The name A. subaquatilis (Tate, 1880: 103, pl. 4, Fig. 5 A – C) is here tentatively considered to be the species name for South Australian Austropeplea populations following Ponder et al. (2024). This species was described based on type material collected from the River Torrens in Adelaide and are not aware of it having been found from type locality in recent years (Z. - Y. Chen, unpublished data). A currently recognised synonym, A. aruntalis Cotton & Godfrey, 1938 (replacement name for Limnaea papyracea Tate, 1880: 103, pl. 4, Fig. 6 A, B), may represent a valid species name for the South Australian Limestone Coast population, from which the specimens in this study were collected, if future studies reveal consistent differences between populations of the two forms.

Distribution.

South-eastern South Australia and western Victoria (Ponder et al. 2024).