The Glycymerididae (Mollusca: Bivalvia) of the NE Atlantic and the Mediterranean Sea 1 2 Frank Nolf and Frank Swinnen 1 Pr. Stefanieplein, 43/8 B-8400 Oostende, Belgium [email protected] 2 Lutlommel, 10B, B-3920 Lommel, Belgium [email protected] Keywords: Glycymeris, GLYCYMERIDIDAE, Madeira and the Canaries. Glycymeris arabica BIVALVIA, MOLLUSCA, Mediterranean Sea, NE (H. Adams, 1871) is a Lessepsian immigrant Atlantic. from the Red Sea, only known from a few specimens in Israel. In the present paper we will Abstract: In a previous paper, published in extensively compare and illustrate these species. Neptunea, 12(2), the endemic West African representatives of the genus Glycymeris were Diagnosis: treated. The new species Glycymeris The family GLYCYMERIDIDAE is a very puzzling rafaelmesai Nolf & Swinnen, 2013 was family as many “common” species are introduced, together with the diagnosis of misunderstood, even those from the another unknown species from Angola. The Mediterranean Sea and the NE Atlantic. present paper will treat the East Atlantic and Most of them have a cancellate microsculpture. Mediterranean species of the genus Glycymeris. The periostracum of European species with fine Some of these species also occur along the separated hairs is in contrast with the West coasts of NW Africa, Madeira and the Canary African species of Glycymeris which all have a Islands. distinctly velvety periostracum. The size varies from 30 mm (Glycymeris vanhengstumi) to 120 Abbreviations: mm (Glycymeris bimaculata). They live from CFN: Private collection of Frank Nolf subtidal to deep water shallowly burrowed in (Oostende, Belgium). sandy, gravelly or muddy bottoms. Shells are CFS: Private collection of Frank Swinnen equivalve, often equilateral, circular or (Lommel, Belgium). subcircular, occasionally posteriorly angled, H.: Height. usually thick, occasionally rather smooth L: Length. (Glycymeris nummaria) or slightly ribbed with a radial or cancellate microsculpture. Umbones are Introduction: In the NE Atlantic and the opisthogyrate and the ligament condition is Mediterranean Sea the family GLYCYMERIDIDAE is amphidetic or prosodetic. The hinge plate carries is only represented by the genus Glycymeris and two series of taxodont teeth. There is no pallial contains five different species: Glycymeris sinus. The interior is porcellaneous and the inner bimaculata (Poli, 1795) restricted to NW ventral margin is strongly crenulated. Morocco, the Mediterranean Sea from Spain, Italy to Turkey and Israel, Glycymeris glycymeris The microsculpture of every European (Linnaeus, 1758) which occurs from Norway to Glycymeris is unique for each species and is the E Atlantic coasts of the Iberian Peninsula, the typically not very variable. This offers us a good western Mediterranean Sea (from Spain to Sicily identification tool when we fail to use the other in the east), the Azores, Madeira, the Canary characteristics which are not constant enough to Islands and Morocco, Glycymeris nummaria distinguish the different species. The (Linnaeus, 1758) in the Canaries, Gibraltar, the microstructure is linked to the implantation of the Alboran Sea, the Marmara Sea, Israel and the hairs. Smooth shells carry a very fine NE Atlantic coast of Morocco, Glycymeris pilosa periostracum or none at all. (Linnaeus, 1767) throughout the Mediterranean The outline is mostly not a good characteristic to Sea from Spain, Italy to the Aegean Sea, Israel distinguish the different species. It partially and the Levant Sea, the Atlantic coasts of depends on the kind of substrate in which the Morocco and Western Sahara and finally a specimen is buried. In hard substrates recently described species Glycymeris specimens tend to be more oblique as the vanhengstumi Goud & Gulden, 2009, from Neptunea, 12(3) 1 November 2013 1 mantle gest damaged during the burrowing Periostracum: remaining bristles at the margins, process. but mostly absent. Although the umbo in Glycymeris is always Colour: Shell externally white with beige, dark opisthogyrate, which means that the beaks are brown to reddish brown tessellate markings or turned to the posterior end of the valves, some with larger coloured areas. Internally usually with European species such as G. bimaculata, G. a dark brown-black posterior-ventral area. nummaria, and the Lessepsian immigrant G. Measurements: 20-30 mm. arabica may have slightly orthogyrate umbones. Habitat: It lives in shallow water sandy bottoms. The height and width of the ligamental area are In the Mediterranean dredged at about 50 m variable within each species, depending on the depth. growth stage of the individual specimens. The Remarks: In the Red Sea (from Suez to Aden) a ligamental condition in European species may be second, very similar species occurs: Glycymeris amphidetic (G. arabica, G. bimaculata), slightly adenensis Jousseaume in Lamy, 1916. prosodetic (G. nummaria, G. glycymeris, G. vanhengstumi) or clearly prosodetic (G. pilosa). Glycymeris bimaculata (Poli, 1795) The ligamental area can be ornamented with (Pl. II, Figs 5-6; Pl. III, Figs 7-10; grooves. Muscle scars are distinct, the anterior Pl. IV, Figs 11-12; Pl. V, Figs 13-16) scar (rounded triangular) being different from the posterior scar (rather oval). The anterior muscle = Arca bimaculata Poli, 1795 scar is narrower than the posterior one. The = Pectunculus stellatus (Gmelin, 1791) lower part is obliquely truncated. The posterior = Pectunculus siculus Reeve, 1843 muscular scar is nearly circular but the lower part = Pectunculus pilosus var. philippii Pallary, 1912 is narrowing below. = P. stellatus var. mediterranea de Gregorio, 1892 Type Family GLYCYMERIDIDAE Newton, 1916 = P. stellatus var. pervalida de Gregorio, 1892 Glycymeris da Costa, 1778 = P. stellatus var. umbonata de Gregorio, 1892 = Pectunculus bimaculatus var. crassa Koch & Type species: Arca glycymeris Linnaeus, 1758 Pallary in Pallary, 1900 (by absolute tautonomy: ICZN Opinion 1414 - 1986). Geographic distribution: South Portugal, NW Morocco, the Mediterranean Sea, from Spain, Glycymeris arabica (H. Adams, 1871) Italy to the Bosporus, Greece, Turkey and Israel. (Pl. I, Figs 1-4) Shell: very large, heavy and thick, not as globose as Glycymeris pilosa. = Axinaea (Pectunculus) arabica H. Adams, Outline: almost circular. 1871 Beaks and umbones: raising a little above the = Pectunculus savignyi P. Fischer, 1871 ligamental area. Very slightly opisthogyrate, nearly orthogyrate, Geographic distribution: originally in the Ligamental condition: amphidetic, fairly high western Indian Ocean, Red Sea: Gulf of Suez. and broad. Especially in thick and heavy Introduced in the Mediterranean Sea (Israel) via specimens a number of chevron shaped grooves the Suez Channel. Till 2003 only known from one (about 5) are very clear. record in 1977 (Dor, Israel). At present also Microsculpture: Many narrow and distinct found at Palmahim lagoon (Israel). radiating ribs are separated by very fine grooves. Outline: equivalve, inequilateral, subcircular, Concentric cords are obsolete and often with posterior margin subangular. The anterior repressed, resulting in an undulating sculpture of margin is protruding, giving the shell a somewhat irregular lines. oblique shape. This distortion together with the Periostracum: dark brown, nearly black short inflated shell and the small size are diagnostic bristles follow the concentric ribbing more than features for this species. Very slightly the radial striae covering most parts of the opisthogyrate, nearly orthogyrate. valves, especially at the ventral side, the anterior Hinge: Small strongly arched taxodont teeth, and posterior margins. The bristles are shorter with up to 12 teeth anteriorly and up to 14 teeth than in G. glycymeris and G. pilosa. posteriorly. Colour: yellow, orange to brown. Often with Ligamental condition: amphidetic, very narrow alternating yellow and brown concentric rings. and small. Interior mostly paler than in G. pilosa. In fact the Microsculpture: about 30 low ribs with narrow name ‘bimaculata’ was derived from the white interspaces. All ribs incised by radial grooves. blotch at the beaks. However, this is not a Inner margin crenulated. constant characteristic feature: it is not always Neptunea, 12(3) 1 November 2013 2 present and it can also be discovered in G. Geographic distribution: the Hebrides, Faroe pilosa. Young specimens are paler than adults. Islands, N Norway, North Sea, Scotland, the Measurements: 80-120 mm. English Channel, Ireland, E Atlantic, the Bay of Habitat: In shallow water buried in sand or Biscay, the Azores, Madeira and the sandy mud bottoms. Mediterranean Sea (from the Alboran Sea, Spain, France to Italy). This is in fact a typical NE Remarks: Atlantic species, only occasionally found in the This species is the largest glycymeridid among Mediterranean. the European species within this family. It can be Shape and outline: Valves thick and solid, but differentiated from other European Glycymeris by thinner and lighter specimens are commonly its shell which is even heavier than in G. pilosa, found depending upon the locality. Shells may be the central umbones, the colouration and the inflated or compressed, with a circular or broader hinge line. The number of radiating obliquely subovate outline. Often posteriorly striae and concentric grooves is larger than in G. elongated. pilosa, resulting in a denser reticulating network. Beaks and umbones: very opisthogyrate. Umbones clearly behind the middle of the Pallary (1912) made a mistake in mentioning ligamental area.