Ceradocus shoalsi, Appadoo, Chandani & Myers, Alan A., 2006

Appadoo, Chandani & Myers, Alan A., 2006, Melitids (Crustacea: Amphipoda) of the genera Ceradocus and Mallacoota from Rodrigues Island (Indian Ocean), Zootaxa 1370, pp. 1-22 : 2-6

Ceradocus shoalsi sp. nov.

Figures 1–3

Type material. HOLOTYPE. Male, 4 mm, from Iles des Fou, (19 ° 39.527 ’ S, 63 ° 23.752 ’E), Rodrigues at depths of 8 m on Lithophyllum sp., M. Richmond, 21 September 2001, AM P 73596 .

PARATYPES. 1 male, 3.5 mm, AM P 73597 , 1 female, AM P 73598 , same data as holotype. 1 male, AM P 73599 , 2 females, Passe Coco, reef off Port Mathurin, 19?° 40.282 ’S, 63 ° 25.378 ’E, Rodrigues, 9 - 6 m SCUBA from dead coral on reef slope, N. Bruce, 22 September 2001.

Description. Male length, 4 mm. Head with subocular notch; eyes round with discrete ommatidia. Antenna 1 peduncle article 1 with few stout robust setae on posterior margin; article 2 longer than 1; article 3, 0.2 x article 1; accessory flagellum 4 -articulate; primary flagellum damaged. Antenna 2 peduncle 2.5 x as long as flagellum; gland cone of article 2 extending the length of article 3; article 4, 1.4 x longer than article 5; flagellum 6 -articulate. Mandible palp 3 -articulate, article 1 with distal cusp, article 2 longest and 3.3 x article 1, with long setae on lateral margins and short setae on medial face, article 3 shortest and 0.7 x the length of article 1. Maxilla 1 inner lobe with 11 setae. Maxilla 2 outer plate with distal setae, inner plate with distal setae, inner marginal setae and an oblique row of setae. Gnathopod 1 coxa as broad as long, antero-distal margin produced; basis robust, 1.9 x as long as broad, posterior margin with long setae; carpus 1.8 x as long as broad with groups of medial setae, anterior margin sparsely setiferous, posterior margin densely setose; propodus 0.8 x length of carpus with a few medial patches of setae, palmar margin oblique with short setae; dactylus with short setae on inner margin. Gnathopod 2 asymmetrical. Small gnathopod 2 (left or right) coxa subrectangular, 1.3 x as long as broad; basis 3 x as long as broad with few long setae on posterior margin; carpus 1.5 x as long as broad, propodus 1.6 x length of carpus, palm transverse with numerous robust setae on palmar margin; dactylus fitting palm, with short setae on inner margin. Large gnathopod 2 (left or right) coxa subquadrate; basis 2.5 x as long as broad; carpus triangular, 2.5 x as broad as long; propodus 1.5 x as long as broad, palmar margin transverse and characterised by a medial V-shaped excavation, two semi-circular shallow indentations followed by a thumblike process on postero-distal margin, inner margin of thumb-like process with short setae; dactylus short, 0.9 x length of palmar margin and fitting excavation of thumb-like process. Pereopod 3 coxa subrectangular, 1.1 x as broad as long, ventral margin with few slender setae; basis slender with short robust setae on anterior margin and groups of long setae on posterior margin; propodus subequal to carpus; dactylus margins smooth. Pereopod 4 coxa 0.9 x as long as broad with few setae, other features similar to pereopod 3. Pereopod 5 slender, coxa bilobed; basis 2.2 x as long as broad, postero-distal margins sharply produced, anterior margin with robust setae, posterior margin with small setae; propodus 1.2 x length of carpus; dactylus slender. Pereopod 6 slender, coxa 1.2 x as broad as long with one seta on distal margin; basis 2 x as long as broad, posterior margin sharply produced; propodus subequal to carpus, anterior margin with strong patches of setae; dactylus slender and similar to that of pereopod 5. Pereopod 7 similar to pereopod 6, but basis is distally less produced than basis of pereopod 6 and more slender 2.4 x as long as broad. Pleonites 1–3 strongly toothed. Epimeron 1 and 2 with two teeth on postero-distal margin. Epimeron 3 with 2 teeth on postero-distal margin, irregular teeth on distal margin and 6 well-defined teeth on medial distal margin. Urosomites 1–2 (from male, 3.5 mm) without teeth. Uropod 1 (from male, 3.5 mm) rami subequal, 0.9 x length of peduncle. Uropod 2 (from male, 3.5 mm) outer ramus weakly serrated, 1.1 x inner ramus, 1.2 x length of peduncle. Uropod 3 missing. Telson cleft to half its length, telsonic lobes well separated, with robust setae on outer margin.

Female: 4 mm, ovigerous. Same data as holotype. Gnathopod 1 coxa 1.2 x as long as broad, antero-distal corner produced, distal margin with short setae; basis 3.6 x as long as broad; carpus 1.9 x as long as broad; propodus 1.6 x as long as broad, palmar margin oblique, with few patches of slender setae. Gnathopod 2 asymmetrical. Gnathopod 2 (small), coxa 1.3 x as long as broad; basis 2.6 x as long as broad; carpus 1.6 x as long as broad; propodus 1.4 x as long as broad, palm transverse, palmar margin with short slender setae and robust setae, one large robust setae at postero-distal corner; dactylus fitting palm. Gnathopod 2 (large) coxa 1.1 x as broad as long, basis 3.2 x as long as broad, carpus triangular 1.5 x as broad as long, propodus massive 1.5 x as long as broad, palmar margin transverse, lined with short slender setae and robust setae, and a thumb-like process at postero-distal corner; dactylus shorter than length of palm.

Remarks. Ceradocus shoalsi sp. nov. closely resembles C. mahafalensis Ledoyer (1979) described from Madagascar. However, it differs from the latter in the more transverse palm of the larger gnathopod 2, and in the smooth or only weakly serrated margins of the basis of pereopods 5–7. The present species also resembles C. mahafalensis var. incisa of Ledoyer (1978) described from Mauritius, however the same differences as with C. mahafalensis are noted. The presence of teeth on the urosomites 1 and 2 of C. mahafalenis var. incisa are not noted in the current species. However, it is important to note that the specimen of C. mahafalenis var. incisa of Ledoyer (1978) were larger (5.5 mm) as compared to the present species where specimen examined are 3.5–4 mm.

Distribution. Rodrigues Island, Indian Ocean

Etymology. Named after the Marine Research Centre “Shoals Rodrigues” where the collection programme was organised.

Figures

FIGURE 1. Ceradocus shoalsi sp. nov., male holotype, 4 mm, Ile des Fou, AM P 73596. Scales: a = 1 mm (whole animal), b = 0.5 mm (A 1, A 2, rG 2), c = 0.2 mm (enlargement of rG 2), d = 0.2 mm (lt G 2).

FIGURE 2. Ceradocus shoalsi sp. nov., male holotype, 4 mm, Ile des Fou, AM P 73596; female paratype, 4 mm, Ile des Fou, AM P 73598. Scales: a = 0.5 mm (P 5, P 6, P 7, female P 7), b = 0.1 mm (MX 2), c = 0.2 mm (Md, D 7, T), d = 0.2 mm (P 3, P 4, U 1, U 2), e = 0.1 mm (D 4).

FIGURE 3. Ceradocus shoalsi sp. nov., female paratype, 4 mm, Ile des Fou, AM P 73598. Scale bar = 0.2 mm (G 1, ltG 2, rG 2).