Echinolittorina peregrinator, Reid, 2011

Reid, David G., 2011, 2974, Zootaxa 2974, pp. 1-65 : 11-15

Echinolittorina peregrinator new species

( Figures 2, 3, 4A–D, 5)

Littorina meleagris — Rosewater & Vermeij, 1972: 67–69, map 1, figs 1, 2 (in part, includes E. meleagris (Beck in Potiez &

Michaud, 1838)). García-Talavera, 1983: 42 (in part, includes E. meleagris ). Fernandes & Rolán, 1993: 34 (not Beck in

Potiez & Michaud, 1838). Littorina (Fossarilittorina) meleagris — Rosewater, 1981: 29–30, pl. 1C, 3C (operculum) (in part, includes E. meleagris ). Littorina aff. meleagris — Gofas, Afonso & Brandão, 1987: 129 (not Beck in Potiez & Michaud, 1838). Nodilittorina (Fossarilittorina) meleagris — Reid, 1989: 98 (in part, includes E. meleagris ). Nodilittorina meleagris — Reid, 2002a: 259–281 (in part, includes E. meleagris ). Echinolittorina meleagris — Williams et al., 2003: 83 (in part, includes E. meleagris ). Robin, 2008: 113, fig. 8 (not Beck in

Potiez & Michaud, 1838). Echinolittorina meleagris B— Williams & Reid, 2004: 2227–2251, fig. 6A (map). Williams & Duda, 2008: fig. 1 (phylogeny). Echinolittorina (Fossarilittorina) meleagris B— Reid, 2009: 16–22, figs 1, 37 (phylogeny).

Types: Holotype BMNH 20110090 ( Fig. 2B); 3 dry paratypes BMNH 20110091; 50 alcohol paratypes BMNH 20050373; Old Ningo , 30 km east of Accra, Ghana.

Etymology: Latin, one who travels about (a masculine noun, used in apposition as a specific name), in reference to trans-Atlantic dispersal by which this species was derived.

Taxonomic history: This species was first recorded in West Africa by Rosewater & Vermeij (1972), who considered the western Atlantic E. meleagris to be an amphi-Atlantic taxon. It was at first distinguished as E. meleagris B in molecular studies ( Williams & Reid 2004; Williams & Duda 2008; Reid 2009). The name L. meleagris was incorrectly applied to small specimens of E. pulchella by Bernard (1984).

Diagnosis: Shell small; smooth except for microstriae and one incised peripheral line; pseudumbilicus; brown with aligned array of white spots and sometimes a sutural white band. Penis simple, tapering, no obvious glands, closed sperm duct. Ghana to Angola. COI: GenBank AM941712 , FN298399 .

Material examined: 18 lots (including 11 penes, 1 sperm sample, 8 pallial oviducts, 1 spawn sample, 4 radulae).

Shell ( Fig. 2): Mature shell height 1.9–7.9 mm. Shape high turbinate to elongate (H/B = 1.31–1.60, SH = 1.48–2.00); spire whorls rounded; suture distinct; spire profile straight; shoulder sometimes thickened; periphery rounded or slightly angled. Columella long, straight or slightly convex at midpoint, narrow, slightly flattened at base; deep pseudumbilicus as wide as columella; no eroded parietal area. Sculpture absent but for fine spiral microstriae over entire surface (making surface dull) and single incised line just above periphery. Protoconch not seen. Ground colour brown to black, paler on base, with white spots (or backward-pointing triangles) regularly arranged in prosocline and opisthocline series; spots anastomose at suture to give larger spots or short axial dashes, or a continuous broad white band from suture to shoulder ( Fig. 2H, I); spots anastomose into oblique axial lines on base; in dark shells spots are small or absent except at suture and on base; rarely entire shell may be yellow brown with irregular paler marbling or zigzags ( Fig. 2C, D); aperture brown with external pattern showing through, pale zone at base (rarely forming a distinct band); columella brown.

Animal ( Fig. 3): Head ( Fig. 3B) black, usually with unpigmented stripe across snout; tentacle pale around eye with two longitudinal black stripes extending to a black dot at tip; sides of foot black. Opercular ratio 0.35–0.41. Penis ( Fig. 3A–G): wrinkled base merges into simple strap-like filament with pointed tip; vas deferens closed as a superficial duct (running from anterior end of open prostate, across right side of head, to tip of penial filament); penis unbranched and lacking mamilliform glands or penial glandular disc, but with small, slightly raised pad on inner side at junction of filament and base; penis unpigmented except at base. Euspermatozoa 65 µm; paraspermatozoa ( Fig. 3L) contain an elongate-fusiform rod-piece 22–30 µm long with pointed to rounded ends, projecting from cell, which is packed with round granules. Pallial oviduct ( Fig. 3H–J): copulatory bursa separates near anterior end of straight section and extends back to two-thirds or full length of straight section; at half length or further back the straight section contains an opaque cream or reddish gland around the egg groove (this does not appear to be an extension of the small translucent capsule gland). Spawn ( Fig. 3K): an asymmetrically biconvex pelagic capsule about 250 µm diameter with broad peripheral rim slightly overhanging base, dome-shaped upper side sculptured by 2 concentric rings, containing single ovum about 80 µm diameter (personal observation: Accra).

Radula ( Fig. 4A–D): Relative radula length 1.13–1.76. Rachidian: almost square, length/width 0.94–1.22; major cusp broad, tip pointed. Lateral and inner marginal: 4 cusps, tip of major cusp rounded to slightly truncate. Outer marginal: 5–8 cusps; no flange on outer side of base.

Range ( Fig. 5): Ghana to northern Angola; São Tomé and Principe; Annobón (Pagalu) I. Range limits: Takoradi, Ghana ( BMNH 20050395; USNM 707154); Lomé, Togo ( MNHN); Cap Esterias, Libreville, Gabon ( MNHN); Pointe Indienne, Pointe-Noire, Congo ( BMNH 20110097); Futungo, Luanda Prov., Angola ( MNHN); Annobón I., Equatorial Guinea ( BMNH 20110098); Bom Bom I., Principe I., São Tomé and Principe ( BMNH 20110099); Lagoa Azul, São Tomé I., São Tomé and Principe ( BMNH 20110095).

Habitat: Abundant in shallow pools and depressions, with filamentous green algae, brown alga Ralfsia and barnacles, on outcrops of beachrock and sandstone, on moderately exposed sandy coasts with moderately turbid water (personal observation, Ghana). In algal turf in low-intertidal echinoid zone, and in shallow high-intertidal pools ( Ghana; Rosewater & Vermeij 1972).

Remarks: As discussed by Reid (2009) this species does not show diagnostic morphological differences from its western Atlantic sister taxon E. meleagris ; sperm, oviduct, radula and egg capsule do not differ significantly, and the penis and shell are similar in both. The penes of E. meleagris illustrated by Reid (2009: fig. 4) are mostly smaller and more slender, and the basal pad is barely visible; it is not known whether this is a consistent difference or if penial size and shape could change with reproductive condition. The shell colour form with a broad white sutural band ( Fig. 2H, I) has been observed only in E. peregrinator . The western and eastern species were first suggested to be distinct ESUs on the basis of 12S sequence data by Williams & Reid (2004). Addition of COI sequence data showed them to be sister taxa, with an average K2P genetic distance for COI of 4.53% ( Williams & Duda 2008; Reid 2009); this exceeds the lowest values (2.61–2.70%) reported for sister ESUs that are considered to represent distinct biological species ( Reid 2009). The widely disjunct distribution makes continuing gene flow very unlikely, and the present species is therefore treated as distinct from E. meleagris .

The oldest known collections of this species date from the Atlantide expedition of 1946; this, together with its patchy distribution and occurrence at the port of Takoradi, led Rosewater & Vermeij (1972) to suggest the possibility of introduction on shipping from the western Atlantic. The genetic distance from E. meleagris is inconsistent with recent migration or transport across the Atlantic. This small species was probably simply overlooked by earlier collectors.

This species is superficially similar to the three members of the E. punctata group and E. soroziczac ( Figs 6, 9, 12, 14, Table 1); these are all much larger, but confusion is possible with small examples of the sympatric E. pulchella and E. soroziczac . Shells of E. peregrinator possess only a single narrow spiral groove above the periphery, whereas in the others there are more than 9 grooves. A pseudumbilicus is present only in E. peregrinator . Anatomically, all three are distinct.