Afrolittorina acutispira (E.A. Smith, 1892 )

Reid, DG & Williams, ST, 2004, The Subfamily Littorininae (Gastropoda: Littorinidae) in the Temperate Southern Hemisphere: The Genera Nodilittorina, Austrolittorina and Afrolittorina, Records of the Australian Museum 56, pp. 75-122 : 116-118

Afrolittorina acutispira (E.A. Smith, 1892)

Figs. 17G,H, 25G–N, 26, 27

Littorina acutispira E.A. Smith, 1892: 487–488 , pl. 40, fig. 3 (Green

Point, Watson Bay, Port Jackson , New South Wales; also Parsley

Bay, Port Jackson; lectotype ( Rosewater, 1970: 452) BMNH

1891.11.6.216 (fig. 25L; label: “Port Jackson”), 13 paralectotypes

BMNH 1891.11.6.217–225 (“ Port Jackson ”), 47 paralectotypes

BMNH 1886.7.26.102–111 (“Parsley Bay”), all seen). Melarhaphe acutispira .— Hedley, 1918: M51. Melarapha acutispira .—Iredale & McMichael, 1962: 38. Littorina (? Littoraria ) acutispira .— Rosewater, 1970: 423, 451–

452, pl. 349, fig. 3, pl. 350 (distribution), pl. 351, fig. 1. Littorina (Austrolittorina) acutispira .—Ponder & Rosewater,

1979: 773–774, pl. 1, figs. 1–3. Wilson, 1993: 146, textfig. Nodilittorina acutispira .—Bandel & Kadolsky, 1982: 3. Jansen,

1995: 31, fig. 96. Nodilittorina (? Nodilittorina ) acutispira .— Reid, 1989: 99. Nodilittorina (Austrolittorina) acutispira .— Reid, 2002 a: 154. Afrolittorina acutispira .— Williams et al., 2003. Littorina infans E.A. Smith, 1892: 488 , pl. 40, fig. 4 (Green Point,

Watson Bay, Port Jackson [New South Wales]; 14 syntypes

BMNH 1891.11.6.226–235 ( Fig. 25G), seen). Melarhaphe infans .— Hedley, 1918: M51. Dakin, 1960: 248 (as

Melaraphe ). Melarapha infans .—Iredale & McMichael, 1962: 38. Littorina (? Littoraria ) infans .— Rosewater, 1970: 423, 452, pl.

351, fig. 2.

Taxonomic history. Smith (1892) named this species twice in the same publication, using the name Littorina acutispira for larger elongate shells and L. infans for smaller examples with eroded spires. Owing to their small size, both taxa were neglected by subsequent workers. Rosewater (1970) retained them as separate species. As first revisers, Ponder & Rosewater (1979) established the valid name.

Diagnosis. Shell small, tall-spired, smooth; pale, with brown tessellated or marbled pattern. Penis with rounded, swollen filament; mamilliform gland on narrow lateral branch of base. Pallial oviduct with three consecutive loops of egg groove, in albumen gland, capsule gland and in terminal portion of oviduct.

Material examined. 56 lots (45 AMS, 2 USNM, 9 BMNH), incl. 9 penes, 2 sperm samples, 10 pallial oviducts, 4 radulae.

Shell ( Fig. 25G–N). Mature shell height 2–7.0 mm. Shape high-turbinate to tall-spired (H/B = 1.38–1.84; SH = 1.65– 2.32), but may appear almost globular if spire strongly eroded; spire outline straight; whorls rounded, suture distinct; periphery rounded or slightly angled; small shells translucent, becoming solid. Columella pillar short, straight to slightly concave; columella slightly excavated; sometimes a slight pseudoumbilicus; eroded parietal area absent. Sculpture frequently microscopically smooth, but larger shells may have 11–22 spiral striae or impressed lines on last whorl, striae rarely visible on spire; surface shiny, microstriae absent; growth lines insignificant. Protoconch rarely preserved, 0.29–0.34 mm diameter, 3 whorls, terminated by sinusigera ridge, sculpture unclear. Colour: juveniles brown with spiral white band on base; larger shells cream to brown, usually with darker grey or grey-brown zone from periphery to near suture, entire surface with fine tessellation or marbling of white and pale brown, pattern not highly regular nor aligned into axial stripes, base usually paler; aperture dark brown with basal white band.

Animal. Head and sides of foot grey to black; pigmentation of tentacles varies, may be unpigmented, or with single longitudinal black line or two broad black lines. Opercular ratio 0.45–0.52. Penis ( Fig. 26A–E): filament half total length of penis, swollen with subepithelial glandular tissue, bluntly rounded; sperm groove opens subterminally; single mamilliform gland (and probably also a small patch of subepithelial glandular tissue corresponding to reduced glandular disc, on ventral side of mamilliform gland, visible in histological section only) borne on narrow lateral branch of base; penis unpigmented. Euspermatozoa length unknown; paraspermatozoa ( Fig. 26H,I) elongate-oval, 20–30 µm long, containing single (rarely 2) narrow rod piece, sometimes slightly projecting, cell packed with large spherical granules and one larger oval granule. Pallial oviduct ( Fig. 26F,G) with simple loop of albumen gland, followed by large capsule gland forming a loop (although loop is difficult to distinguish except in juveniles where gland is less swollen); additional simple loop of glandular material between capsule gland and terminal straight portion; copulatory bursa separates in a posterior position and continues back to overlay capsule gland.

Spawn and development. Pelagic egg capsules 169–188 µm diameter (similar to those of Austrolittorina antipodum illustrated by Pilkington, 1971), containing single eggs 75– 93 µm diameter; development planktotrophic; breeding season October/November to March/April (Underwood & McFadyen, 1983).

Radula ( Fig. 17G,H). Relative radular length 1.21–1.67. Rachidian: length/width 1.12–1.47; central cusp long, sharply pointed, smaller pointed cusp on either side. Lateral: small inner cusp and three well-developed pointed cusps. Inner marginal: four well-developed pointed cusps. Outer marginal: 6–9 cusps.

Habitat. This species is one of the most abundant molluscs on the rock platforms of New South Wales ( Dakin, 1960; Underwood, 1981), although often overlooked because of its small size. In a detailed study of its population dynamics Underwood & McFadyen (1983) recorded densities of up to 70000 m –2 at the highest levels of the littorinid zone on platforms in Botany Bay. The highest densities were found on an exposed shore, in areas where barnacles provided crevices for protection from waves. On a sheltered shore, most snails were found in shallow pools with Enteromorpha . In southern Queensland the species is also found among barnacles and in shallow pools ( Johnston, 1917), and occupies a zone between high water of neap tides and mean sea level ( Endean et al., 1956), below that of the larger littorinids.

Range ( Fig. 27). Southeastern Australia from New South Wales to southern Queensland. This species is frequent along the entire coastline of New South Wales, the southernmost record being from Eden (37°04'S 149°54'E, AMS C357489 ). In Queensland it is common as far north as Noosa Heads (26°23'S 153°09'E, AMS C388093 ) and there are isolated records further north from Pialba, Hervey Bay (25°18'S 152°50'E, AMS C390527 ), Facing Island (23°49'S 151°22'E, AMS C390516 ), Gladstone (23°51'S 151°15'E, AMS C018502 ) and Yeppoon (23°9'S 150°46'E, AMS C390525 ). A record based on a single shell from Hayman Island ( AMS C390526 ) requires verification .

Remarks. Afrolittorina acutispira is an abundant species throughout most of its range. Its small size and tall-spired, patterned shell readily distinguish it from the sympatric Austrolittorina unifasciata , and its habitat in pools, among algae and in barnacles is generally lower on the shore. At a similar size, juvenile shells of Austrolittorina unifasciata are blue-grey, with fine brown spiral lines ( Fig. 25A,B). Juveniles of Afrolittorina praetermissa are brown with a basal pale band, like those of A. acutispira , but are broader ( Fig. 25C–E), and that species is rare in southern New South Wales.

In the southern parts of its range, L. acutispira could be confused with Laevilitorina mariae (Tenison Woods, 1876) , which occurs among algae on littoral rock platforms, although it is uncommon in New South Wales (Ponder & Rosewater, 1979). That species is of similar elongate shape, up to 3.4 mm in height, translucent brown in colour, with a pale spiral band on the base, however the columella is narrow and not excavated and the apex is bluntly rounded, with a bulbous protoconch 0.43 mm in diameter of 1.5 whorls (indicating nonplanktotrophic development) ( Fig. 25F).

The radula looks markedly different from those of other species of Afrolittorina , Nodilittorina and Austrolittorina , owing to the more equal size and sharply pointed tips of all cusps. However, these characteristics are typical of both juveniles and small species in other littorinine genera, including Peasiella (Reid & Mak, 1998) , Littorina (Reid, 1996) and Echinolittorina ( Reid, 2002 a, as Nodilittorina ), and are therefore interpreted as an allometric consequence of small size, perhaps connected with a different diet or feeding mechanism in small snails.

ACKNOWLEDGMENTS. This study was supported by a research grant from the Natural Environment Research Council (GR3/ 12977 to D.G. Reid and D.T.J. Littlewood). We thank the many colleagues who have loaned specimens for this study from museums around the world: I. Loch (AMS), R.N. Kilburn (NM), B.A. Marshall (MNZ), P. Greenhall (USNM), V. Héros (MNHNP), G. Marska (SAM), H.-J. Niederhöfer (SMNS), S. De Grave (OUM) and E. Turner (TMAG). Specimens were kindly supplied to us by J.D. Taylor (BMNH), E. Glover (BMNH), W.F. Ponder (AMS), D.R. Bellwood (Townsville), J. Austen (Hobart) and M. Kelly (Auckland). The photographs of shells were by H. Taylor (BMNH Photography Unit).