Athanas ivoiriensis, Anker, Arthur & Ahyong, Shane T., 2007

Anker, Arthur & Ahyong, Shane T., 2007, Description of two species in the alpheid shrimp genus Athanas Leach, 1814, with remarks on A. amazone Holthuis, 1951 (Decapoda, Caridea), Zootaxa 1563, pp. 17-30 : 23-28

Athanas ivoiriensis n. sp.

( Figs. 3 , 4)

Type material: Holotype: 1 male, CL 4.0 mm, TL 10.4 mm, MNHN-Na 11278, Côte d'Ivoire ( Ivory Coast), Grand Bassam, depth 20 m, "Benne Aberdeen", coll. P. LeLoeuff, 20 Feb 1970.

Comparative material: Athanas amazone Holthuis, 1951: 1 male, CL 3.2 mm, TL ~ 9 mm, MNHN-Na 8806, off Pointe Noire, Congo, Ombango Sta. 411, between 4°49'S and 4°58'S, dredge, 104 m, 6 Jun 1969; 1 male, CL 5.4 mm, TL 15 mm, MNHN-Na 13708, Banyuls-sur-Mer ( BSM), southern France, 3°13'E, 42°29' N, dredge, 85 m, sand-mud, coll. P. Noël, 6 May 1976, det. P. Noël, 11 May 1976; 1 male, CL 4.9 mm, TL ca. 14 mm, MNHN-Na 13748, Baie de Banyuls off BSM, southern France, dredge, 30 m, mud, coll. Labat, det. P. Noël, 19 May 1976; 1 female (CL and TL not measured), MNHN-Na 13752, off BSM, southern France, dredge, 35 m, coll. Labat, det. P. Noël, 26. May 1977; 1 ovigerous female (CL and TL not measured, carrying around 20 eggs), 1 male, CL 4.0 mm, MNHN-Na 1745, dredge, 43–72 m, off Cap l'Abeille, BSM, southern France, coll. Guille, collection data unknown, det. J. Forest, 1967.

Description: Body elongate, slender. Carapace glabrous, not setose. Rostrum laterally compressed, straight, with acute tip, reaching slightly beyond mid-length of second segment of antennular peduncle ( Fig. 3 A), proximally broadened; rostral carina very feebly marked, posteriorly not reaching beyond rostral base. Extra-corneal spines acute, triangular, almost reaching anterior margin of cornea ( Fig. 3 A, C); infra-corneal and supra-corneal spines absent. Eyes exposed in dorsal and lateral views; cornea well pigmented, anteromesial margin with small process ( Fig. 3 C). Pterygostomial angle rounded, without spine ( Fig. 3 B).

Antennular peduncle with second segment much shorter than dorsally visible portion of first segment, and shorter than third segment ( Fig. 3 A); stylocerite acute, reaching or almost reaching distal margin of second segment ( Fig. 3 A, B); ventromesial carina with well developed, acute spine; outer flagellum biramous, fused portion composed of four segments ( Fig. 3 B). Antenna with basicerite bearing acute ventrolateral spine; scaphocerite exceeding antennular peduncle ( Fig. 3 A), broadly oval, lateral margin straight, anterior margin broadly convex, reaching slightly beyond distolateral spine; carpocerite slightly shorter than scaphocerite ( Fig. 3 B).

Mouthparts without specific features in external view. Third maxilliped slender (Fig. 4J); ultimate segment about 1.3 times as long as penultimate segment and 0.6 times as long as antepenultimate segment; ultimate segment distally unarmed except for stiff setae; lateral plate of coxa as illustrated (Fig. 4K); arthrobranch absent.

Major cheliped slender (Fig. 4A) with basis bearing small exopod dorsally (Fig. 4D) and rounded process with row of curved spiniform setae ventromesially (Fig. 4E); ischium elongate, slightly depressed, slightly shorter than merus, ventromesially depressed; ventral margin irregularly toothed (Fig. 4A), dorsal margin and lateral margins proximally with slender spines (Fig. 4A, B); merus elongate, not expanded, ventromesially depressed, ventrolateral margin irregularly toothed (Fig. 4A); carpus about 3/4 length of merus, distally widening (Fig. 4B), ventral margin with two tubercles (Fig. 4A); chela subcylindrical, slightly compressed, ventral margin of palm with row of blunt tubercles (Fig. 4C), concave proximal to base of pollex; fingers shorter than palm, not gaping (Fig. 4C), tips barely crossing, cutting edges unarmed except for broad, blunt, proximal process on pollex (Fig. 4C).

Second pereiopod slender, relatively short (Fig. 4F); ischium shorter than merus; carpus five-segmented, first article as long as four others combined; ratio of carpal segments (from proximal to distal) approximately: 5: 1: 1: 1: 2.5; chela simple, longer than distal carpal article, fingers longer than palm. Third pereiopod slen- der, relatively short (Fig. 4G); ischium armed with one ventrolateral spinform seta; merus and carpus unarmed; propodus unarmed except for slender distal spiniform seta (Fig. 4H); dactylus about 0.7 length of propodus, simple, slender, slightly curved.

Pleura of first to fourth abdominal somites with rounded posteroventral angles; pleuron of fifth somite with angular posteroventral angle; sixth somite with articulated triangular flap posteroventrally ( Fig. 3 D). Second pleopod with appendix masculina exceeding appendix interna, tip with at least five spiniform setae (Fig. 4I). Uropod with protopod ending distally in one larger acute and one smaller subacute lobe ( Fig. 3 E); diaeresis straight, lateral spiniform seta small ( Fig. 3 E). Telson oval-rectangular, distally tapering, with two pairs of dorsal spiniform setae ( Fig. 3 E); posterior margin medially convex, with two pairs of slender posterolateral spiniform setae, mesial almost three times as long as lateral ( Fig. 3 E). Gill formula typical for genus (see under previous species).

Colour in life unknown. Size: CL 4.0 mm, TL ca. 10.4 mm.

FIGURE 4. Athanas ivoiriensis n. sp., male, holotype, CL 4.0 mm, MNHN-Na 11278, Grand Bassam, Ivory Coast. A – left cheliped, dorsomesial view; B – same, lateral view; C – same, detail of carpus and chela; D – same, detail of coxa and basis, lateral view; E – same, ventromesial view; F – second pereiopod, lateral view; G – third pereiopod, lateral view; H – same, dactylus; I – endopod of second pleopod, mesial view; J – third maxilliped, lateral view; K – same, detail of lateral plate. Scale bars = 1 mm.

Etymology: The new species’ name is derived from the French name of the West African country of Ivory Coast ( République de Côte d’Ivoire), where the type locality of this species (Grand Bassam) is situated.

Type locality: Grand Bassam, situated about 40 km east of Abidjan, Côte d’Ivoire ( Ivory Coast), West Africa.

Habitat: The single specimen was collected from 20 m, possibly on mud-sand bottom.

Distribution: Presently known only from the type locality off Ivory Coast, West Africa.

Remarks: With 10.4 mm TL the holotype of A. ivoiriensis n. sp., is possibly a relatively young individual. Furthermore, it lacks the right cheliped, although the corresponding coxa is as robust as that of the detached left cheliped, indicating that the difference in size between the two chelipeds may not be so strong. Athanas ivoiriensis n. sp., is closely related to A. amazone , but can be separated from A. amazone by (1) the absence of an infra-corneal spines or angles; (2) the much stouter antennular peduncles; (3) the distinctly longer stylocerite, reaching the distal margin of the second segment of the antennular peduncle; (4) the much shorter carpocerite, not reaching the distal margin of the scaphocerite blade; and (5) the different proportions and shape of the (possibly major) cheliped, which shows more similarities to the chelipeds of A. phyllocheles and A. sydneyensis n. sp. (cf. Fig. 1 D, E, 2).

Athanas amazone ( Fig. 5 ) was reported from depths ranging between 40 and 155 m, from Nigeria ( Holthuis 1951), Togo, Congo ( Crosnier & Forest 1973), Cape Verde ( Türkay 1982), Morocco ( Garcia Raso 1996), and throughout the Mediterranean Sea: Spain, France, Italy, Greece, Israel and Turkey ( Holthuis & Gottlieb 1958; Crosnier & Forest 1973; Kocataş 1981; Koukouras et al. 1992; Froglia & Argenti 1993; García Raso 1996; Atkinson et al. 1997; Froglia & Atkinson 1998; see also d’Udekem d’Acoz 1999). Holthuis & Gottlieb (1958) and Crosnier & Forest (1973) noted some variation in the development of the infra-corneal spines; the relative length of the stylocerite (compared to the distal margin of the first segment of the antennular peduncle); the length of the carpocerite (compared to the scaphocerite); and the shape of the chelipeds. Banner & Banner (1983) were "not convinced that the specimens of A. amazone described and depicted [referring to Holthuis, 1951; Holthuis & Gottlieb, 1958; Crosnier & Forest, 1973] are as mature as our holo- and allotype [of A. phyllocheles ], for even sexually mature males and females may not have yet developed the proportions and shape of ultimate condition of the chelipeds". Nevertheless, the holotype of A. amazone is an ovigerous female, although its small size (TL 7 mm) suggests that it must be a young female. The mostly fragmentary specimens reported from Israel ( Holthuis & Gottlieb 1958) were 4–10 mm in TL. Banner & Banner (1983) noted: "perhaps the Mediterranean specimens may be found to be a different species on the basis of their chelipeds, and the specimens described by Crosnier & Forest different enough on the basis of their carpocerites that they may in the future be considered to be three separate species".

TABLE 2. Variation among specimens of A. amazone (A–E), compared to A. ivoiriensis n. sp. (F). Athanas amazone : A – adult male (MNHN-Na 13748) from Banyuls-sur-Mer, southern France ( Fig. 5 A, B); B – adult male (MNHN-Na 8806) from Pointe Noire, Congo (cf. Crosnier & Forest 1973, fig. 48; Fig. 5 C–H); C – possibly immature male from Israel (cf. Holthuis & Gottlieb 1958, fig. 4); D – ovigerous holotype female from Nigeria (cf. Holthuis 1951, fig. 23); E – adult ovigerous female (MNHN-Na 1745) from Cap l'Abeille near Banyuls-sur-Mer, southern France ( Fig. 5 H). Athanas ivoiriensis n. sp.: F – holotype male (MNHN-Na 11278) from Ivory Coast ( Figs. 3 , 4). Abbreviations: S1-2, S2-3 = limits between 1st and 2nd and 2nd and 3rd segments, respectively; Sc. = scaphocerite; Tb. = tubercle;> = exceeding; <= not reaching.

Species A. amazone A. ivoiriensis A series of A. amazone is deposited in the MNHN, Paris. The differences between the MNHN specimens, those reported by Holthuis (1951), Holthuis & Gottlieb (1958) and Crosnier & Forest (1973), and A. ivoiriensis n. sp., are summarized in Table 2. It shows that some features, e.g., the length of the carpocerite, the shape of the merus and the chela of the major cheliped, and the slenderness of the minor cheliped, may indeed be sexually dimorphic and/or age-dependent. However, more material with information on colour patterns and ecology is needed to conclude about the taxonomic status of A. amazone .

Interestingly, at least in A. amazone and A. ivoiriensis n. sp., the ventromesial portion of the basis of the major and minor chelipeds bears a peculiar process furnished with a comb-like row of slender, curved spiniform setae (Fig. 4E, 5F). The process on the right cheliped is thus juxtaposed to that on the left cheliped. The function of these structures, if there is any, remains unknown.

Figures

FIGURE 1. Athanas sydneyensis n. sp., female, holotype, CL 4.8 mm, AM P 62764, Hawkesbury River, New South Wales, Australia. A – frontal region, lateral view; B – same, dorsal view; C – right antennule and antenna, dorsal view; D – right cheliped, lateral view; E – merus and ischium of right cheliped, mesial view; F – left cheliped, lateral; G – merus and ischium of left cheliped, mesial view; H – right second pereiopod, lateral view; I – right third pereiopod, lateral view; J – tail fan, dorsal view; K – tailfan, right lateral view. Scale bar: A, B, D – H, J, K = 1.0 mm; C, H = 0.5 mm.

FIGURE 3. Athanas ivoiriensis n. sp., male, holotype, CL 4.0 mm, MNHN-Na 11278, Grand Bassam, Ivory Coast. A – frontal region, dorsal view; B – same, lateral view; C – same, detail of rostrum and eyes; D – sixth abdominal segment and tail fan, right lateral view; E – tail fan, dorsal view. Scale bars = 1 mm.

FIGURE 5. Athanas amazone Holthuis, 1951: male, CL 4.9 mm, MNHN-Na 13748, Banyuls-sur-Mer, southern France: A – habitus; B – major cheliped, chela and distal carpus, mesial view; male, CL 3.2 mm, MNHN-Na 8806, Pointe Noire, Congo: C – major cheliped, chela and distal carpus, ventral view; D – same, ventromesial view; E – same, dorsomesial view; F – same, basis and ischium, ventromesial view; G – same as B, fingers in slightly different angle (entire cheliped illustrated by Crosnier & Forest 1973, fig. 48); ovigerous female, CL not measured, MNHN-Na 1745, Cap l'Abeille, Banyuls-sur-Mer, southern France, H - minor cheliped, lateral view. Scale bars = 1 mm.