Echinolittorina caboverdensis, Reid, 2011

Reid, David G., 2011, 2974, Zootaxa 2974, pp. 1-65 : 24-26

Echinolittorina caboverdensis new species

( Figures 8–10, 11A–D)

Littorina guttata — Reeve, 1857: Littorina sp. 76, pl. 14, fig. 76 (not Litorina guttata Philippi, 1847 = E. meleagris ). Locard, 1897: 493 (not Philippi, 1847). Nobre, 1909: 35 (not Philippi, 1847).

Litorina punctata — Weinkauff, 1878: 36 (in part, includes E. punctata ). Weinkauff, 1883: 221 (in part, includes E. punctata ).

Melarhaphe punctata — Rochebrune, 1881: 280 (not Gmelin, 1791; as Melaraphe ).

Littorina (Melarhaphe) punctata — Tryon, 1887: 248, pl. 44, fig. 61 (in part, includes E. punctata , E. pulchella , Littoraria intermedia , Littoraria cingulifera ; as Melaraphe ). Saunders, 1977: 11 (not Gmelin, 1791; as Melaraphe ).

Littorina punctata — Locard, 1897: 492–493 (in part, includes E. punctata ). Nobre, 1909: 34 (in part, includes E. pulchella ; not Gmelin, 1791). Melvill & Standen, 1913: 341 (not Gmelin, 1791). Nicklès, 1950: 48–49 (in part, includes E. punctata , E. pulchella ). Marche-Marchad, 1956: 42 (in part, includes E. punctata , E. pulchella ). von Cosel, 1982a: 16 (not Gmelin, 1791).

Littorina (Austrolittorina) punctata — Rosewater, 1970: 423, 474–476, pl. 367 (map) (in part, includes E. punctata , E. pulchella , E. soroziczac and probably Afrolittorina knysnaensis and L. saxatilis ). Rosewater, 1981: 24–26 (in part, includes E. punctata , E. pulchella , E. soroziczac ). Guerreiro & Reiner, 2000: 65, fig. (not Gmelin, 1791).

Nodilittorina (Echinolittorina) punctata — Reid, 1989: 99 (in part, includes E. punctata , E. pulchella ).

Nodilittorina punctata — Buys, 1991: pl. 4, fig. 3 (not Gmelin, 1791). Rolán, 2005: 57, figs 140, 141 (in part, includes E. punctata , E. pulchella ).

Nodilittorina aff. punctata — Reid, 2002a: 261.

Echinolittorina aff. punctata — Williams et al., 2003: 83.

Echinolittorina punctata B— Williams & Reid, 2004: 2227–2251, fig. 6E (map). Williams & Duda, 2008: fig. 1 (phylogeny; as E. punctata A in error).

Echinolittorina (Amerolittorina) punctata B— Reid, 2009: figs 1, 37 (phylogeny; in fig. 1 as E. punctata A in error).

Litorina pulchella — Reibisch, 1865: 131 (not Dunker, 1845).

Littorina pulchella — Stearns, 1893: 333 (not Dunker, 1845). Burnay & Monteiro, 1977: 23–24, fig. 11 (not Dunker, 1845).

Types: Holotype BMNH 20110116 ( Fig. 9L); 13 dry paratypes BMNH 20110117 ( Fig. 9G–K); 33 alcohol paratypes BMNH 20110118; Baia do Canto , Boavista, Cape Verde.

Etymology: Latin, from the islands of Cape Verde.

Taxonomic history: This species was first noticed by Reeve (1857), but he misidentified it as L. guttata (a synonym of E. meleagris ). Reeve did not introduce this epithet as a new name (contra Rosewater 1970: 476). Following Reeve (1857), Locard (1897) and Nobre (1909) both used this name for specimens from the Cape Verde Islands, while also listing L. punctata from the same locality. Subsequent authors almost all identified the Cape Verde species as punctata , although a few used the epithet pulchella ( Reibisch 1865; Stearns 1893; Burnay & Monteiro 1977). It was first suggested to be distinct on the basis of genetic ( Backeljau et al. 2001) and shell characters ( Reid 2002a), and this was confirmed by additional DNA sequence analysis ( Williams & Reid 2004; Williams & Duda 2008).

Monterosato introduced many infraspecific names and in HUJ there are specimens from his collection labelled Melarapha punctata verdensis Monterosato ; this appears to be an unpublished manuscript name (fide Mienis, 1975: 29).

Diagnosis: Shell tall, with 9–14 faint striae above periphery or smooth; pale orange to dark brown with regular tessellation of white to grey spots and sometimes pale bands. Penis bifurcate, with smooth tapering filament, mamilliform penial gland and glandular disc of similar size on side branch of base. Cape Verde Islands. COI: Gen- Bank AJ623033 , AJ623034 .

Material examined: 12 lots (including 9 penes, 6 pallial oviducts, 4 radulae).

Shell ( Fig. 9): Mature shell height 5.0–13.9 mm. Shape tall-spired (H/B = (1.42)1.58–1.91, SH = (1.58)1.67– 2.03); spire whorls gently rounded; suture distinct; spire profile straight; periphery of last whorl rounded or slightly angled. Columella hollowed and slightly pinched at base; eroded parietal area absent. Some specimens show 1–2 conspicuous growth interruptions on last whorl. Sculpture of 9–14 faint spiral striae or weak incised lines above periphery of final whorl (on spire whorls the 1–2 anteriormost are covered by suture; about 9 faint primary grooves visible on small shells, but indistinct); sometimes 1 or 2 secondary lines appear (by interpolation or division) near periphery on last whorl, 1–9 faint lines may be visible below periphery; sculpture frequently obsolete or absent; a slightly enlarged peripheral rib is rarely present; spiral microstriae absent, surface shiny. Protoconch not seen. Ground colour pale orange, olive brown or black brown, with regular opisthocline series or regular tessellation of small grey to white spots; colour often paler in bands at suture, periphery and on base; pale shells sometimes show darker broad grey to brown spiral band from shoulder to periphery and narrow dark band on base; aperture dark brown to black with pale band at base; columella pale brown.

Animal: Head black, no unpigmented stripe across snout; tentacle black, pale around eye and at tip; sides of foot grey to black. Operculum: opercular ratio 0.34–0.40. Penis ( Fig. 10A–C): filament gradually tapering to pointed tip, 0.6–0.7 total length of penis, sperm groove ends terminally; mamilliform gland approximately same size as penial glandular disc, which projects as a lobe, borne together on short projection of base; penis unpigmented or slightly pigmented at base. Sperm not seen. Pallial oviduct ( Fig. 10D, E): first loop of albumen gland small; copulatory bursa separates at posterior end of straight section and extends back almost to albumen gland. Spawn not known; pelagic capsules predicted from form of pallial oviduct ( Reid 2002a).

Radula ( Fig. 11A–D): Relative radula length 2.68–4.94. Rachidian: length/width 1.34–1.91; major cusp narrow, tip pointed. Lateral and inner marginal: 4 cusps, tip of major cusp bluntly rounded or rounded; major cusps sometimes enlarged and outer cusps reduced to denticles ( Fig. 11C, D). Outer marginal: 7–9 cusps; usually with 8– 9 cusps and prominent flange on inside and outside of base; sometimes slightly narrowed and with 7 cusps ( Fig. 11C, D).

Range ( Fig. 8): Restricted to Cape Verde Archipelago. Range limits: Salamansa, São Vicente ( BMNH 20110119); Curral, Santa Luzia ( BMNH); Mordeira Bay, Sal ( BMNH); Baia do Canto, Boavista ( BMNH 20110118); Praia, São Tiago ( MNHN); Brava ( MNHN); São Nicolau ( von Cosel 1982a); São Antão ( von Cosel 1982a).

Habitat: Common on basalt rock at top of eulittoral and in littoral fringe, on moderately sheltered and exposed shores.

There are few literature reports of the habitat of this species in Cape Verde. Morri et al. (2000) reported it in the splash zone and in a supralittoral pool. Otero-Schmitt (1993) mentioned it only on sheltered rocky shores.

Remarks: The shell shows a greater diversity of colour forms that the other members of the E. punctata group, with pale and banded shells relatively common ( Fig. 9B, C, G, J). Some specimens have been seen in which a pronounced colour change occurs at a growth interruption ( Fig. 9C), implying that colour pattern is not entirely under genetic control. There is slight sexual dimorphism, shells of males being smaller with a larger aperture ( Fig. 9G–J, female; Fig. 9K, L, male).

The identification of the three members of the E. punctata group has been discussed in the remarks on E. punctata and is summarized in Table 1. There is a striking convergence between shells of this species and some tallspired colour forms of Littorina scutulata Gould, 1849 ( Reid 1996: fig. 20) from the northeastern Pacific, but in the latter the spotting is less discrete and regular, and the basal white band in the aperture is absent.

The first hint that E. caboverdensis was distinct from Mediterranean specimens of E. punctata was the observation of the divergence of their 18S rRNA sequences ( Winnepenninckx, Reid & Backeljau 1998; Backeljau et al. 2001). This was supported by the characteristic narrow, smooth shell of Cape Verde specimens ( Reid 2002a). In a phylogenetic analysis of three genes the COI tree showed reciprocal monophyly of E. punctata and E. caboverdensis , and results for 12S rRNA and 28S rRNA were consistent (but with poor support) ( Williams & Reid 2004). Analysis of additional COI sequences showed reciprocal monophyly for each of the three species of the E. punctata group, but did not resolve their relationships ( Reid 2009: fig. 37). A three-gene analysis of a smaller number of samples showed E. caboverdensis as the sister taxon of the pair E. punctata and E. pulchella ( Williams & Duda 2008; Reid 2009; note error in former reference, and Reid 2009: fig. 1, in which the taxa E. punctata A and B were transposed). Average K2P genetic distances for COI are 6.44% between E. caboverdensis and E. pulchella , and 5.95% between E. caboverdensis and E. punctata . These distances are greater than the minimum (2.61–2.70%) reported for sister ESUs that are regarded as distinct biological species ( Reid 2009). The distinctive shell of E. caboverdensis implies possible nuclear genetic differentiation and therefore supports its recognition as a species.