Ceradocus (Denticeradocus) greeni, Appadoo & Myers, 2005

Appadoo, C & Myers, AA, 2005, Amphipods of the Genera Ceradocus, Dulichiella, Melita and Nuuanu (Crustacea: Melitidae) from Mauritius, Indian Ocean, Records of the Australian Museum 57, pp. 221-236 : 222-225

Ceradocus (Denticeradocus) greeni n.sp.

Figs. 1–3

Ceradocus sp. 1 Appadoo & Steele 1998: 639.

Type material. HOLOTYPE 3, 5.2 mm, AM P60865, at depths of 0.5–2 m living on coral rubble and Pocockiella variegata , Flic-en-Flac (20°16.5'S 57°21.7'E), Mauritius, C. Appadoo, 9 November 1998. PARATYPES: 233, 2♀♀, AM P60866, same data as holotype; 1♀ from coral rubble and Pocockiella variegata , Flic-en-Flac, 3 March 1998; 1 juv. from coral rubble and Pocockiella variegata , Flic-en-Flac, 9 November 1998; 13, 4♀♀, 2 juv. from coral rubble, Padina sp. and Pocockiella variegata , Flic-en-Flac, 5 April 1999; 733, 5♀♀ from coral rubble, Padina and Pocockiella variegata , Flic-en-Flac, 10 December 1999; 333, 3♀♀, 1 juv. from coral rubble, Padina sp. , Pocockiella variegata and Turbinaria ornata , Flic-en-Flac, 27 January 2000.

Description. Male length, 6.2 mm. Head with subocular notch; eyes round with discrete ommatidia. Antenna 1

peduncle article 1 with stout robust setae on posterior margin; article 2 longer than 1; article 3, 0.3× article 1; accessory flagellum 5-articulate; primary flagellum 14- articulate.Antenna 2 peduncle 3× as long as flagellum; gland cone of article 2 extending to 0.7× the length of article 3; article 4 slightly longer than article 5; flagellum 11- articulate. Mandible palp 3-articulate, article 1 with medial cusp, article 2 longest and 2.5× article 1, with long setae on lateral margins and short setae on medial face, article 3 shortest and 0.6× the length of article 1. Maxilla 1 inner plate triangular with plumose setae; outer plate with terminal serrated robust setae; palp 2-articulate with double-row of terminal setae. Maxilla 2 outer plate with distal setae, inner plate with distal setae, inner marginal setae and an oblique row of setae. Lower lip with rounded mandibular lobes. Maxilliped palp 4-articulate, article 2 longest and 2.2× article 1. Gnathopod 1 coxa 1.3× as long as broad, anterodistal margin produced into a lobe, posterodistal margin notched; basis slender, slightly less than three times as long as broad, anterior margin with short robust setae, posterior margin with long setae; carpus with groups of medial setae, anterior margin sparsely setiferous, posterior margin densely setose; propodus subequal in length to 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, slightly longer than broad, distal margin with a notch and a few setae; basis 2.5× as long as broad, posterior margin with strong patches of setae; merus anteroventral and posterodistal corners sharply produced; propodus 2× as long as broad, 1.3× carpus, palm oblique with short robust setae and a few groups of long setae; dactylus slender, inner margin with short setae. Large gnathopod 2 (left or right) coxa subrectangular, ventral margin notched and with 2 setae; basis 2.5× as long as broad; merus posterodistal corner sharply produced; carpus triangular, slightly more than 1.5× as broad as long; propodus robust, slightly over 1.5–1.75× as long as broad, palm oblique, distal margin with a process close to base of dactylus with stout robust setae followed by an excavation and a triangular process with fine setae and robust setae at the posterodistal margin; dactylus robust and fitting into the triangular process of propodus. Pereopod 3 coxa subrectangular, almost as broad as long, ventral margin with 1 long seta and a few short-setae at the anteroventral corner; basis slender with short robust setae on anterior margin and groups of long setae on posterior margin; propodus subequal to carpus; dactylus with a distinct unguis and anterior margin with one plumose seta and posterior margin with 3 setae. Pereopod 4 coxa posteriorly excavate, 0.7× as long as broad with one long seta and a few short setae on the anterodistal corner, other features similar to pereopod 3. Pereopod 5 slender, coxa bilobed; basis 1.8× times as long as broad, anterodistal and posterodistal margins sharply produced, anterior margin with robust setae, posterior margin weakly serrated and with small setae; propodus subequal to carpus; dactylus slender. Pereopod 6 slender; basis similar to that of pereopod 5, but posterior margin more deeply serrated; 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 and narrower than basis of pereopod 6; propodus slightly longer than carpus. Pleonites 1–3 strongly toothed. Epimeron 2 with one tooth on posterodistal margin and a few irregular teeth on distal margin. Epimeron 3 with 2 teeth on posterodistal margin and 5 teeth on distal margin. Urosomite 1 and 2 each with 7 dorsal teeth. Uropod 1 peduncle, 1.3× outer ramus with a stout robust seta on medial outer margin; outer ramus slightly shorter than inner ramus. Uropod 2 peduncle 0.7× inner ramus; inner and outer rami subequal, armed with robust setae, margins of rami with very short fine robust setae. Uropod 3 peduncle inner margin with numerous robust setae; rami spatulate, equal in length to each other, twice as long as peduncle; outer ramus outer margin with long robust setae; inner ramus outer margin with numerous robust setae; rami with stout terminal robust setae. Telson deeply cleft; telsonic lobes well separated, with a pair of plumose setae on outer margin, notched at apex, with outer tooth produced and inner tooth vestigial, apices with one long and a few short setae.

Female: length, 4.9 mm. Gnathopod 1 coxa 1.2× as long as broad, anterodistal margin produced, posterodistal margin with a notch; basis slender, posterior margin with long setae, anterior margin with short robust setae; merus produced at posterodistal corner; carpus subequal to propodus with groups of medial setae, ventral margin setose; propodus 2.3× as long as broad, anterior margin with 5 groups of setae, palm oblique with fine setae and short robust setae and stout robust setae on medial face. Gnathopod 2 coxa 1.2× as long as broad, distal margin with a notch and a few setae; basis 3.1× as long as broad, anterior margin with robust setae, posterior margin with groups of long setae; carpus 0.75× length of propodus; propodus 2.2× as long as broad, palm with short robust setae and patches of fine setae, with stout robust setae on inner medial face.

Habitat. In the subtidal at depths of 0.5 to 2 m, occurring mostly on coral rubble and the associated brown alga, Pocockiella variegata .

Remarks. Ceradocus greeni n.sp. is assigned to the subgenus Denticeradocus because pleonites 1–3 are multidentate dorsally. This species is distinguished from Ceradocus hawaiensis J.L. Barnard (1955) recorded from Mauritius by Ledoyer (1978), by having the larger male gnathopod 2 with an oblique palm lacking many tooth-like processes. The species differs from Ceradocus mahafalensis Ledoyer (1978) var. incisa , reported from Mauritius, which also has an oblique palm in the larger male gnathopod 2, by the broadly sinuous palmar border, with a distal process with robust setae as opposed to a palmar margin with a deep medial incision. Urosomites 1 and 2 each have 7 teeth in Ceradocus greeni n.sp. instead of 5 and 4 respectively in Ceradocus mahafalensis var. incisa and C. mahafalensis from Madagascar ( Ledoyer, 1979).

Ceradocus greeni shares with C. spiniferus Ledoyer (1973) , C. tattersalli Ledoyer (1982) and C. serratus ( Bate, 1862) , the multidentate pleonites and oblique palm in the large male gnathopod 2. However, the shape of the larger gnathopod 2 propodus palm separates it from these three species. Ceradocus serratus lacks the smooth excavation and the triangular process, C. spiniferus has a convex palmar margin and a small U-shaped excavation and C. tattersalli lacks the triangular process and has a palm with numerous robust setae.

Two other species of Ceradocus with multidentate pleonites 1–3 and oblique palm in the male gnathopod 2 are Ceradocus (Denticeradocus) oxydus Berents (1983) and Ceradocus (Denticeradocus) yandala Berents (1983) . The shape of the large male gnathopod 2 is the distinguishing feature. Ceradocus oxydus lacks an excavation in the palmar margin which is convex with numerous robust setae. Ceradocus greeni differs from C. yandala by having a gentle excavation on the male gnathopod 2 without any mid-palmar sinus, C. yandala has a quadrate mid-palmar sinus.

Type locality. Flic-en-Flac , Mauritius .

Distribution. Mauritius.

Etymology. This species is named after Prof. John Green of Memorial University of Newfoundland for his help in the field to one of authors (CA) during an initial study on amphipods from Mauritius in 1995.