Afrolittorina praetermissa ( May, 1909 )

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 : 111-116

Afrolittorina praetermissa ( May, 1909)

Figs. 17E,F, 22–24, 25C–E

? Litorina ziczac .—Philippi, 1847: 162–163 (not Trochus ziczac Gmelin, 1791 = Echinolittorina ziczac ; in part; includes E. ziczac ; inclusion in synonymy based on locality Kangaroo Island).

Littorina ziczac .— Tenison Woods, 1879: 69 (not Gmelin, 1791; in part; includes E. ziczac ).

Littorina philippii .— Angas, 1865: 172 [not Litorina philippii Carpenter, 1857 = Echinolittorina apicina (Menke, 1851) ]. Tenison Woods, 1878: 36 (as philippi; not Carpenter, 1857). Gatliff, 1887: 60 (as phillippi; not Carpenter, 1857).

Littorina undulata .— Angas, 1865: 172 (not Gray, 1839 = Littoraria undulata ). Tenison Woods, 1878: 36 (not Gray, 1839).

Littorina paludinella .— Tenison Woods, 1878: 36 (not Reeve, 1857; see Hedley, 1913; Ponder & Rosewater, 1979). Gatliff, 1887: 60 (not Reeve, 1857). Pritchard & Gatliff, 1902: 92 (not Reeve, 1857).

Melarapha paludinella .—Macpherson & Gabriel, 1962: 89 (not Reeve, 1857).

Littorina caerulescens .— Tenison Woods, 1879: 65–72 (as coerulescens; not Turbo caerulescens Lamarck, 1822 = Melarhaphe neritoides ; in part; includes A. africana , Austrolittorina unifasciata , A. antipodum , Littoraria mauritiana , M. neritoides ).

Littorina unifasciata .— Haacke, 1885: 504–505 (not Gray, 1826;

in part, includes Austrolittorina unifasciata ).

Littorina mauritiana .—Tate & May, 1901: 389 (not Phasianella mauritiana Lamarck, 1822 = Littoraria mauritiana ; in part; includes Austrolittorina unifasciata ).

Littorina novaezealandiae “Reeve ” Pritchard & Gatliff, 1902: 91 (unjustified emendation of Littorina novaezelandiae Reeve, 1857 ; not Reeve, 1857 = Echinolittorina novaezelandiae ; in part; includes E. novaezelandiae ).

Litorina praetermissa May, 1909: 57 , pl. 6, fig. 3 (Tasmania; holotype TMAG E353 /7694, fig. 22G, seen; 4 possible paratypes MCZ 23099, seen).

Melarhaphe praetermissa .— Hedley, 1913: 1913 (as Melaraphe ). May, 1921: 47. May, 1923: 49, pl. 22, fig. 18. Cotton & Godfrey, 1938: 10. Macpherson & Chapple, 1951: 118 (as Melaraphe ). Kershaw, 1955: 307 (as Melaraphe ).

Littorina praetermissa .— Guiler, 1958: 139. Wilson & Gillett, 1979: 52, pl. 8, fig. 8, 8a.

Melarapha praetermissa .— McMichael, 1959: 27. Iredale & McMichael, 1962: 38. Macpherson & Gabriel, 1962: 87–88, fig. 116.

Littorina (Littoraria) praetermissa .— Rosewater, 1970: 423, 445– 446, pl. 325, figs. 26, 27, pl. 343, pl. 344, fig. A (radula), B (penis), pl. 345 (distribution).

Littorina (Austrolittorina) praetermissa .—Ponder & Rosewater, 1979: 775, pl. 3, fig. 3 (penis). Ludbrook & Gowlett-Holmes, 1989: 564–565. Wilson, 1993: 146, pl. 18, fig. 4a,b.

Nodilittorina praetermissa .—Bandel & Kadolsky, 1982: 3.

Nodilittorina (? Nodilittorina ) praetermissa .— Reid, 1989: 100.

Nodilittorina (Austrolittorina) praetermissa .— Reid, 2002 a: 154.

Afrolittorina praetermissa .— Williams et al., 2003.

Taxonomic history. This species is common on the shores of southern Australia and Tasmania, so it is remarkable that it was not named until 1909. Before this, it was variously misidentified. The earliest apparent reference to the species is Philippi’s (1847) record of Litorina ziczac from Kangaroo Island in South Australia, collected by Harvey; Philippi’s figure 13 may be this species, but no locality was given. The use of the name Littorina philippii ( Angas, 1865; Tenison Woods, 1878; Gatliff, 1887) is surprising, because this taxon was described from Mexico.

Several authors used the name Littorina paludinella for a juvenile form of this species that is a small, low-spired shell of brown colour with a pale basal band ( Tenison Woods, 1878; Gatliff, 1887; Pritchard & Gatliff, 1902; Macpherson & Gabriel, 1962). However, Hedley (1913) examined the types of Reeve’s species and found that they were a hydrobiid from Tasmania, as subsequently confirmed (Ponder & Rosewater, 1979; Ponder et al., 1993).

This species has sometimes been considered as a striped form of the sympatric Austrolittorina unifasciata ( Tenison Woods, 1879; Haacke, 1885; Tate & May, 1901; see Taxonomic History of A. unifasciata ).

Diagnosis. Shell moderately large, patulous to high-turbinate, periphery rounded, usually sculptured with incised spiral lines; pale, with brown tessellated or marbled pattern. Penis with rounded, slightly swollen filament; mamilliform gland and glandular disc on base. Pallial oviduct with three consecutive loops of egg groove, in albumen gland, capsule gland and in terminal portion of oviduct.

Material examined. 64 lots (45 AMS, 7 USNM, 9 BMNH, 1 ZMA, 1 MNHNP, 1 NMW), including 8 penes, 4 sperm samples, 6 pallial oviducts, 3 radulae.

Shell ( Figs. 22, 25C–E). Mature shell height 8.2–19.4 mm (down to 3 mm, Nwe, 1974). Shape patulous to highturbinate (H/B = 1.13–1.60; SH = 1.20–1.95); spire outline slightly concave; whorls well rounded, suture distinct, periphery rounded or slightly angled; moderately solid. Columella pillar straight to slightly concave; columella excavated; sometimes a slight pseudoumbilicus (frequent in juveniles); eroded parietal area absent. Sculpture of 13– 16 primary spiral grooves above periphery, remaining as approximately equidistant incised lines, continuing faintly on base; periphery sometimes marked by a slightly raised rib; secondary division occasionally increases spiral lines to up to 22 above periphery on last whorl; prominence of spiral lines varies, juveniles are usually smooth and lines often become obsolete on last whorl; microscopically, surface is shiny with only faint spiral microstriae; spire usually eroded; growth lines may be strong at end of last whorl. Protoconch rarely preserved, about 0.34 mm diameter, 3 whorls. Colour whitish, cream or pale blue-grey; pale grey brown to dark brown pattern, finely tessellated or marbled, often aligned to form oblique axial stripes or zigzags, occasionally spiral lines; juveniles dark brown with white spiral band on base, pattern of additional pale bands and marbling appearing only on and after whorl 3 of teleoconch; aperture dark brown with basal white band.

Animal. Head and sides of foot black; tentacles with two broad longitudinal black stripes, fusing distally, sometimes completely fused to give black tentacles. Opercular ratio 0.46– 0.52. Penis ( Fig. 23A–E): filament 0.4–0.5 total length of penis, bluntly rounded, smooth, slightly swollen; sperm groove open to filament tip; single large mamilliform gland and adjacent smaller lobe of penial glandular disc borne together on lateral branch of base; penis unpigmented; penis regresses to a stub outside May–October breeding season ( Nwe, 1974). Euspermatozoa 61–66 µm; paraspermatozoa ( Fig. 23J,K) spherical to oval, 13–21 µm diameter, containing large spherical granules and one (or up to 6) small, rectangular or irregular rod-bodies that are hexagonal in section and do not project from cell. Pallial oviduct ( Fig. 23F,G) with simple loop of albumen gland, followed by large, almost circular loop of capsule gland, opaque pink, within which central portion adjacent to egg groove and distal portion are differentiated as reddish translucent capsule gland; 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 albumen gland.

Spawn and development. Spawn ( Fig. 23I) a transparent pelagic capsule 240–300 µm diameter containing a single ovum 80 µm diameter, capsule hat-shaped with waved concentric ring on crown and wide peripheral brim; development planktotrophic; females mature July–September in vicinity of Adelaide ( Nwe, 1974). Pelagic spawn also observed by F. Murray (quoted in Pilkington, 1971).

Radula ( Fig. 17E,F). Relative radular length 4.1–7.6. Rachidian: length/width 1.16–1.53; major cusp elongate, rounded at tip. Lateral and inner marginal: major cusps large, elongate to rectangular, rounded to truncate at tip. Outer marginal: 7–8 cusps (12, Nwe, 1974).

Habitat. In South Australia (Womersley & Edmonds, 1958; Nwe, 1974) and Victoria (Bennett & Pope, 1953) A. praetermissa is less common than the abundant Austrolittorina unifasciata ; it occupies the lower littoral fringe (overlapping with, but lower than A. unifasciata ) and favours more sheltered habitats, where it is found on a variety of hard substrates including wooden piers, and occurs in shaded crevices. Juveniles occur lower, in the upper barnacles zone (Bennett & Pope, 1953; Ponder & Rosewater, 1979). Reports of the habitat of A. praetermissa in Tasmania confirm that it occurs slightly lower on the shore than A. unifasciata and often in more cryptic microhabitats; however, it is said to predominate at wave-exposed sites, especially on cliffs with intense spray ( Guiler, 1952b,c; Bennett & Pope, 1960; Newman, 1994; contrary report by Guiler, 1955, suggests possible confusion of names of taxa). Of these two, only A. praetermissa occurs on the cold, strongly exposed west coast of Tasmania, where it is found over the whole rock surface (Bennett & Pope, 1960).

Range ( Fig. 24). Southern Australia, from southwestern WesternAustralia toTasmania and southern New South Wales. The main centre of distribution of this species is from the Eyre Peninsula ( SA) along the coastline of Victoria to Wilsons Promontory, the islands of Bass Strait and the entire coastline of Tasmania. Several records are outside this range, all of which are of small numbers of juvenile or small shells. To the west, it is recorded from Point Sinclair, SA (32°06'S 133°00'E, AMS C390493, juveniles); Lion Island, Recherche Archipelago, WA (33°53'S 122°01'E, AMS C69337, 7 specimens, max. H = 8.5 mm); near Esperance, WA (33°51'S 121°53'E, AMS C390482 and C390490, 1 and 4 juveniles); Nine-Mile Beach, Esperance, WA ( BMNH 20030447, 10 specimens, max. H = 4.8 mm); Hopetoun, WA (33°57'S 120°07'E, AMS C390489, 2 juveniles); south of Cowaramup, WA (33°52'S 115°05'E, AMS C390491, 1 juvenile). The species has not previously been recorded from Western Australia (unless the record of Melarhaphe undulata from King George Sound by Hedley, 1916, might possibly have been A. praetermissa ). A recent record from the vicinity of Perth, WA (A. Cummings, pers. comm.; figured by Schneider, 2003: fig. 1) is based on a worn specimen of Echinolittorina vidua (Gould, 1859) .To the east the two records from southern NSW are from Twofold Bay (37°05'S 149°54'E, AMS C356463, 2 juveniles) and Burrill Lake (35°23'S 150°27'E, AMS C427919, 1 juvenile). This confirms the occurrence in NSW recorded by Bennett & Pope (1960) and Macpherson & Gabriel (1962, as Melarapha paludinella ), although this was denied by Ponder & Rosewater (1979).

Remarks. This species shows considerable variation in shape, from low-spired and patulous ( Fig. 22C) to highturbinate ( Fig. 22B); possible correlation of this variation with habitat has not yet been investigated. Small shells are dark brown with a pale basal band ( Fig. 25C–E) and do not show the typical marbled pattern of the adults; this has led to some taxonomic confusion (see Taxonomic History above). These juveniles should not be confused with any other species; at a similar size (3–4 mm) the shells of the sympatric Austrolittorina unifasciata are blue-grey with fine brown spiral lines ( Fig. 25A,B). In southern NSW the distribution just overlaps that of Afrolittorina acutispira , but that small species has a more tall-spired shell ( Fig. 25G– N). Adult shells of A. praetermissa can usually by distinguished from Austrolittorina unifasciata by the presence of a brown pattern of marbling, tessellation or stripes on the shell of the former; the penial filament is shorter in A. praetermissa and the pallial oviduct shows three consecutive loops of the egg groove, not two.

The present records extend the known range of this species into WA and NSW for the first time, but these outlying records are all of small or juvenile shells and might represent occasional long-distance dispersal events that do not result in permanent colonization.

This species is a characteristic member of the cool- temperate component of the southern Australian fauna (Bennett & Pope, 1953, 1960). Its predominance on waveexposed shores in Tasmania, but preference for cryptic microhabitats on sheltered shores in Victoria and South Australia, might suggest habitat restriction in the warmer parts of its range.

Molecular data have shown that A. praetermissa and A. acutispira are sister species, with an estimated time of more than 10 million years since divergence ( Williams et al., 2003). Molecular estimates of age in the absence of fossil calibration are approximate, but this estimate appears to rule out divergence to the east and west of Tasmania during Pleistocene low sealevel stands when Bass Straight was dry (for examples of this common pattern see Wilson & Allen, 1987). The almost complete allopatry between this pair, despite the old divergence time, is noteworthy.As in other sister-species pairs of southern littorinines that occupy the same land masses ( Austrolittorina antipodum and A. cincta in New Zealand; Afrolittorina africana and A. knysnaensis in southern Africa), the ecological and geographical separation between these two species appears to be along an axis of temperature.