Austrolittorina antipodum (Philippi, 1847)

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 : 92-96

Austrolittorina antipodum (Philippi, 1847)

Figs. 4E,F, 9–11

Littorina diemenensis Quoy & Gaimard, 1833: 479–480 (in part; not L. diemenensis Quoy & Gaimard, 1833 = A. unifasciata ). Reeve, 1858: Littorina sp. pl.17, fig. 94 (not Quoy & Gaimard, 1833). Hutton, 1878: 27 (not Quoy & Gaimard, 1833).

Litorina diemensis .—Philippi, 1847:195, Litorina pl. 4, fig. 1 (not L. diemensis Philippi, 1847 , emendation of Littorina diemenensis Quoy & Gaimard, 1833 = A. unifasciata ; in part; includes A. unifasciata ). Weinkauff, 1883:218 (in part;includes A.unifasciata , A. cincta , Echinolittorina novaezelandiae ).

Litorina antipodum Philippi, 1847: 195–196 , Litorina pl. 4, fig. 2 ( New Zealand; lectotype, here designated,Philippi, 1847: Litorina pl. 4, fig. 2; fig. 9D herein). Weinkauff, 1882: 61–62, pl. 8, fig. 4.

Littorina (Melarhaphe) antipodum .—Adams & Adams, 1854: 314 (as Melaraphe ).

Littorina antipodum .— Nevill, 1885: 143.

Littorina (Austrolittorina) unifasciata antipodum .— Rosewater,1970: 423 (as antipoda), 470–471, pl. 359, figs. 6–8, pl. 360, fig. 5, pl.

362 (distribution). Powell, 1976: 87, pl. 16, fig. 12. Powell, 1979: 87, pl. 23, fig. 9.

Nodilittorina (Nodilittorina) antipodum .— Reid, 1989: 99.

Nodilittorina antipodum .—Spencer & Willan, 1996: 18.

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

Austrolittorina antipodum .— Williams et al., 2003.

Littorina caerulescens .— Tenison Woods, 1879: 65–72 (as coerulescens; not Turbo caerulescens Lamarck, 1822 = Melarhaphe neritoides ; in part; includes A. unifasciata , Afrolittorina praetermissa , A. africana , Littoraria mauritiana , M. neritoides ). Hutton, 1880: 79 (not Lamarck, 1822; in part; includes A. unifasciata ). Hutton, 1882: 164, pl. 7, fig. E (radula; not Lamarck, 1822).

Littorina mauritiana .—Smith, 1884: 60–61 (not Phasianella mauritiana Lamarck, 1822 = Littoraria mauritiana ; in part; includes A. unifasciata ). Suter, 1901: 214 (not Lamarck, 1822). Iredale, 1910: 70–71 (not Lamarck, 1822).

Littorina (Melarhaphe) mauritiana .— Tryon, 1887: 247 (as Melaraphe ; not Lamarck, 1822; includes A. unifasciata , A. cincta , L. mauritiana , Echinolittorina ziczac ).

Litorina (Melarhaphe) mauritiana .— Suter, 1913: 188, pl. 38, fig.

28 (not Lamarck, 1822; includes A. unifasciata , L. mauritiana ; as Melaraphe ; as Littorina mauritiana in Atlas, 1915).

Litorina mauritiana .— Bucknill, 1924: 37, pl. 7, fig. 22.

Melarhaphe unifasciata .— Iredale, 1915: 447 (not Littorina unifasciata Gray, 1826 = A. unifasciata ; in part; includes A. unifasciata ). Oliver, 1915: 518 (not Gray, 1826).

Melarhaphe zelandiae .— Finlay, 1928: 241 (not Finlay, 1927 = A. cincta ).

Melarhaphe oliveri Finlay, 1930: 224–225 (Hampden, east coast of South Island, New Zealand; holotype Auckland Museum AK 70456 (formerly TM456) plus 1 paratype AK 72574 (formerly TM456), not seen). Powell, 1937: 67, pl. 9, fig. 12. Powell, 1962: 83, pl. 9, fig. 12 (as Melarhapha). Morton, 1975: fig. 6a–c (radula), fig. 7a,b (stomach).

Melarapha oliveri .— Dell, 1963: 225.

Taxonomic history. There has been a long history of inclusion of this species as a single taxon with the Australian A. unifasciata , and sometimes also with other superficially similar white-shelled littorinids (see Taxonomic History of A. unifasciata ). Quoy & Gaimard (1833) listed the locality New Zealand for their species L. diemenensis and therefore evidently considered the Australian and New Zealand species to be the same (although the name has now been restricted to A. unifasciata ). This concept was followed by Philippi (1847), although in addition he introduced Litorina antipodum for smaller, taller-spired, less markedly striated shells with a dark peripheral band, found in New Zealand. This name was almost entirely neglected for 120 years (exceptions were Weinkauff, 1882; Nevill, 1885), until used as a subspecies of L. unifasciata by Rosewater (1970). Instead, the species was generally combined with A. unifasciata under the name L. mauritiana (Smith, 1884; Suter, 1901, 1913; Iredale, 1910; Bucknill, 1924). Following Iredale (1915), the name Melarhaphe unifasciata was briefly used in New Zealand ( Oliver, 1915). Iredale (1915) had also suggested that “the Neozelanic shell may prove subspecifically separable”, which induced Finlay (1927) to introduce the new name M. zelandiae . However, as Finlay (1930) later confessed: “Owing to a curious and unpardonable misconception of species I described the wrong shell” (the description applied to the other New Zealand littorinid, A. cincta ). He therefore introduced yet another name, M. oliveri , for the present species, which was widely used in New Zealand (e.g., Powell, 1937, 1962; Dell, 1963). This was superseded by the older name L. unifasciata antipodum following the revision by Rosewater (1970). The taxon was given full specific status in the worldwide family list of Reid (1989), although the anatomical evidence justifying this decision was not presented. Rudman (1996) noted that the differences between the egg capsules of A. unifasciata and A. antipodum supported separate species status for both.

No type specimens of Litorina antipodum are known to exist, and to obviate any further confusion as to the identity of the taxon Philippi’s (1847) figure is here designated lectotype. The shape and coloration of the shell leave no doubt as to its identity ( Fig. 9D). The specific epithet is a noun in the genitive case, not an adjective that should agree in gender with the feminine generic name (e.g., Rudman, 1996).

It may be noted that Littorina novaezelandiae Reeve, 1857 was mistakenly said to come from New Zealand in its original description; it is a valid species of Echinolittorina that is endemic to Sri Lanka ( Reid, 2001).

Diagnosis. Shell small, usually tall-spired, often smooth; white with broad band of blue-grey above periphery. Penis with smooth, slightly swollen filament; glandular disc and mamilliform gland on base. Pallial oviduct with two consecutive loops of egg groove, in albumen and capsule glands.

Material examined. 76 lots (15 AMS, 18 USNM, 14 BMNH, 4 IRSNB, 4 ZMA, 1 MNHNP, 1 NMW, 19 MNZ), including 11 penes, 5 sperm samples, 7 pallial oviducts, 3 radulae.

Shell ( Fig. 9). Mature shell height 5.4–13.7 mm. Shape highturbinate to tall-spired (H/B = 1.36–2.20; SH = 1.43–2.63, exceptionally 3.22); spire outline straight to slightly convex; whorls gently rounded, suture slightly impressed, periphery slightly angled; solid. Columella pillar short, slightly concave; columella slightly excavated; small eroded parietal area sometimes present. Sculpture of 9–12 approximately equidistant primary spiral grooves (incised lines) may be present above periphery, continuing faintly on base, but frequently surface is almost smooth; microstriae absent; surface, especially spire, often eroded; growth lines weak. Protoconch rarely preserved, about 3 whorls, 375–425 µm length, sculptured by spiral rows of minute tubercles ( Pilkington, 1971). Colour white, with broad spiral bluegrey band above periphery; rarely grey-black with white base, or almost entirely white with faint grey band; small juveniles entirely black or brown, with spiral white line on base; aperture dark brown with basal white band.

Animal. Head, tentacles and sides of foot black. Opercular ratio 0.47–0.61. Penis ( Fig. 10A–E): filament 0.5 total length of penis, smooth, bluntly pointed, slightly swollen, sperm groove opens slightly subterminally; single large, often narrow, mamilliform gland and adjacent large flap of penial glandular disc borne together on short lateral branch of base; penial base often with black pigment. Euspermatozoa 75– 82 µm; paraspermatozoa ( Fig. 10H,I) spherical, 11–14 µm diameter, containing large spherical granules and a curved, twisted or torus-shaped rod body. Pallial oviduct ( Fig. 10F) with simple loop of albumen gland, followed by large, almost circular loop of capsule gland, within which portion adjacent to egg groove (translucent capsule gland) is differentiated as a ring; copulatory bursa confined to straight section of pallial oviduct, opening near anterior end.

Spawn and development. Spawn ( Fig. 10G) a transparent pelagic capsule 200–250 µm diameter, containing a single ovum 80 µm diameter, capsule with hemispherical dome sculptured by 3 concentric rings, peripheral ridge and a basal circumferential flange; development planktotrophic, inferred planktonic life of 1–2 months; spawning season November to March (at Otago; Pilkington, 1971).

Radula ( Fig. 4E,F). Relative radular length 2.0–2.5. Rachidian: length/width 1.13–1.33; major cusp elongate, rounded or slightly pointed at tip. Lateral and inner marginal: major cusps large, elongate, bluntly rounded at tip. Outer marginal: 6–7 cusps.

Habitat. Throughout much of New Zealand, especially in the north, this species is abundant on rocky shores from the top of the littoral fringe to the upper part of the barnacle zone ( EHWST to MTL). Juveniles occur below adults, often among barnacles. The upper limit depends upon shade and spray, so that on the most strongly exposed, shaded vertical cliffs, it can reach 12 m above EHWST. It is less common on sheltered shores, scarce in extreme shelter, and absent where water is turbid. Shaded rock faces are favoured; on sunny faces, it occupies cracks and crevices and it may occur in shallow, high-level rock pools ( Dellow, 1950; Knox, 1953; Foster, 1966; Morton & Miller, 1968). In the south of South Island A. antipodum is less common and occupies a more restricted vertical range, confined to the littoral fringe, and its distribution is shifted towards more sheltered shores ( Batham, 1956, 1958; Morton & Miller, 1968; Pilkington, 1971). At Rangitoto Island (near Auckland), it has been recorded among Salicornia and lava blocks on stiff mud ( Powell, 1933a). The diet included black lichens, diatoms, Ulva and Enteromorpha ( Powell, 1933a; Morton, 1975). It is frequently sympatric with A. cincta (see Habitat of A. cincta for comparison).

Range ( Fig. 11). New Zealand, Chatham Islands, Kermadec Islands. This species occurs around the entire coastline of North and South Islands, and is also recorded from Stewart Island (Ringaringa, 46°44'S 168°09'E, MNZ M019600), Snares Islands (North Island, 48°02'S 166°36'E, MNZ M015474), Chatham Islands (Waitangi Bay, 43°57'S 176°33'W, MNZ M110471; Powell, 1933), Three Kings Islands (Great Island, 34°09'S 172°09'E, MNZ 049237) and Kermadec Islands (Raoul Island, 29°16'S 177°55'W, MNZ M 214380, AMS). The species is reported to be rare in the Kermadec Islands ( Iredale, 1910; Oliver, 1915; Brook, 1998); it is likely that only chance migrants reach these islands and that the population is not self-sustaining.

Remarks. Although superficially similar to the Australian A. unifasciata , these two species should not be confused. Austrolittorina antipodum is smaller, reaching only 13.7 mm in height ( A. unifasciata attains 24.9 mm), more tall-spired, the spiral striae are less marked and often obsolete, microstriae are absent, the peripheral blue-grey band is more conspicuous, and the penial filament is shorter and not wrinkled. In addition, their ranges are allopatric. Throughout most of its range A. antipodum is sympatric with A. cincta , although it has a more northern distribution. The latter is readily separated by the brown spiral lines of its shell and larger size (to 20.2 mm); anatomically the two are similar, the penial filament of A. cincta being only slightly more pointed.

Occasionally shells of A. antipodum are found that are extremely elongate (H/B up to 2.21, SH up to 3.22; Fig. 9J); by analogy with other species (see Remarks on Afrolittorina knysnaensis ) these probably represent specimens infected with trematode parasites, although this has not been confirmed by dissection.

Molecular data have shown that A. antipodum and A. cincta are sister species, with an estimated divergence time of more than 10 million years. Possible causes of this speciation are unknown; it is too recent to be ascribed to the Oligocene transgression that greatly reduced the land area of New Zealand (Cooper & Millener, 1992). In turn, this pair is sister to the pair A. unifasciata plus A. fernandezensis , with a separation estimated as 23–44 million years ( Williams et al., 2003). This is younger than the attainment of the present width of the Tasman Sea, implying that dispersal took place from Australia to New Zealand.