PATELLA SWAKOPMUNDENSIS new sp.

(Gastropoda: Patellidae: Patella)

Description of a new Patellidae species from Namibia and north-western South Africa

Werner Massier, Swakopmund, Namibia

ABSTRACT: Description of a well-known but undescribed Patella sp. from Namibia and the north-western coast of South Africa.

INTRODUCTION: This widely distributed species has been considered part of Patella miniata, Born, 1778, by most scholars (Koch, 1949, Christiaens, 1973, Powell, 1973, Kilburn & Rippey, 1982, Steyn & Lussi, 1998). In their work “Marine Shells of South Africa”, page 16, no. 41, Steyn & Lussi display the unnamed species as P. safiana Lamarck, 1819.

In their excellent publication, Ridgway, Branch, Stewart & Hodgson, 2000, point out the differences between specimens of P. miniata collected in South Africa up to Kommetjie on the Cape Peninsula, and specimens collected further north of the Atlantic coast. They refer to this sp. as P. cf. miniata.

However, they only obtained samples from two populations: Groen River (30º49'59S 17º34'01E) of the north-western Cape of South Africa and Swakopmund in central Namibia. The author collected this species in 14 areas of Namibia – from Lüderitz in the south (26º38'18S 15º05'22E ) to Möve Bay in the north (19º22'40S 12º42'34E).

Penrith & Kensley, 1970, carried out research further north at Rocky Point (18º59'83S 12º28'62E), but failed to find the species. The author of this article continued the search from Rocky Point up to the Angolan border, but this also proved fruitless.

Ridgway et al. did not differentiate between P. cf. miniata and P. adansonii Dunker, 1853. Having collected samples on the entire Namibian coastline and into southern Angola, I could establish that these are indeed two different species. P. adansonii’s habitat does not extend to Namibian waters. The author could only find it in southern Angola. The differences to P. cf. miniata are consistent. The specimens found are consistent with the photographs of the syntypes of P. adansonii in the “Museum für Naturkunde” in Berlin. I firmly believe that this shell should not be confused with either P. cf. miniata or P. safiana.

Ridgway et al. consider P. safiana to be only from Angola. In fact, I found the species in northern Namibia as far south as Cape Cross (22º03'57S 14º12'46E). From here up to Möve Bay the distribution areas of P. safiana and the new species overlap. The closest relative of the new species is P. miniata.

Hodgson, Ridgway, Branch & Hawkins, 1996m, state that patellid limpets in each of these geographical centres have unique sperm:

N. E. Atlantic/Miditerranean centre,

East Atlantic centre, incl. S. W. coast of southern Africa ,

Indo-Pacific centre, incl. S. E. coast of southern Africa.

I quote: “An examination of spermatozoa of one patellid from Namibia and one from southern Angola (both initially identified as Patella miniata), has revealed that their sperm are distinctly different, as well as being different to that of P. miniata from South Africa.”¹

One can conclude that the species found in Namibia remains unnamed. I propose naming it

Patella swakopmundensis new sp.

DESCRIPTION: The shape of the shell is ovate to elongated ovate. It is moderately large and relatively thin and light considering its size. The external sculpture consists of radial ribs of various strengths. Several weak ribs are located between the strong ribs. A rib of medium strength separates the weak ribs. The number of uninterrupted weak ribs varies from one to three. These external ribs give the margin a crenulated appearance.

The external pattern consists of beige to brown radial streaks on a lighter background. Almost all specimens are covered with a calcified layer which obscures most of the pattern, which is visible internally. The shell is moderately high with the apex at the posterior third of its length. The height can vary greatly, depending on the environment.

The holotype displays a vivid internal pattern covering part of the muscle-scar. The central blotch is dark orange in colour with some glossy white on the periphery. However, in some specimens the internal pattern consists of a relatively narrow rim along the margin, displaying the full extent of the muscle-scar. The central blotch can be either orange, white or made up of smaller blotches of various colours. The internal pattern comes in many colours, incl. rare cases of purple or grey.

HABITAT: In the littoral zone on submerged rocks which are heavily overgrown. They are not found on exposed rocks.

TYPE LOCALITY: Swakopmund (22º41'39S 14º31'24E) on the central coast of Namibia.

DISTRIBUTION: From Möve Bay (19º22'40S 12º42'34E) in northern Namibia to Groen River

(30º49'59S 17º34'01E) on the western coast of South Africa.

TYPE MATERIAL:

ETYMOLOGY: Named after the type locality Swakopmund, where a large colony of this species is present.

MATERIAL EXAMINED: A series of 130 specimens was studied.

COMPARATIVE EXAMINATION: The closest relative is doubtlessly P. miniata.

P. swakopmundensis new sp. is on average smaller, higher and more elongated than P. miniata, but very flat specimens do occur. P. miniata clearly has a broader shell. The average ratio L/W for

P. swakopmundensis new sp. is 1.33 and for P. miniata 1.27.

The external ribs are stronger in P. miniata and therefore produce a more pronounced marginal crenulation. The ribs are pinkish to reddish-brown in P. miniata, but beige to brown in P. swakopmundensis new sp. The central blotch of P. miniata is white or patterned. It is orange or partly orange in most specimens of P. swakopmundensis. In some cases it is pure white or a mixture of smaller blotches of varying colours. The internal pattern of P. miniata is always pink or reddish-brown, whereas these colours do not occur in P. swakopmundensis new sp.

Distinguishing the new sp. from P. safiana and P. adansonii is comparatively easy. P. safiana is a much larger shell, and slightly broader and flatter. The external ribs are stronger. The internal pattern is restricted to a narrow rim along the margin, leaving the largest portion of the interior white. In most species the pattern of this rim consists of short double streaks. Occasionally the internal pattern continues close to the central blotch. The external streaks of P. safiana are distinctly darker.

I am confident that P. adansonii is a valid species and can be distinguished from P. swakopmundensis new sp. and P. safiana. It is a flat shell with a black interior pattern, consisting of broad streaks, which are noticeably absent in the other species. It is much smaller than P. safiana and on average smaller than P. swakopmundensis new sp., but the size range of the latter does overlap. The geographic ranges of P. adansonii and P. swakopmundensis new sp. are well separated.

Acknowledgements: I would like to thank Matthias Glaubrecht and Lothar Maitas of the “Museum

für Naturkunde” of the Humboldt-Universität zu Berlin and Emilio Rolan of Vigo, Spain, for making the photographs of the syntypes of P. adansonii available.

Bibliography:

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