Kamaka appendiculata sp. nov.

(Figs 2–5)

Kamaka sp. 2 Angsupanich et al., 2005: 375.

Material examined. Holotype: male, 2.1 mm (OMNH-Ar-7750), Outer Songkhla Lagoon (Fig. 1 A; 07°08'47''N, 100°33'15''E), 1.2 m deep, brown soft clay, 30 psu in salinity, 12 Oct. 2008, coll. S. Angsupanich. Allotype: female, 1.7 mm (OMNH-Ar-7751), same data as holotype. Other paratypes: 2 males, 1.9, 1.7 mm (OMNH-Ar-7752, 7753); 1 male and 2 females, 2.1, 2.0, 1.8 mm (PSUZC-CR0224 to 0226); 7 males and 4 females, 1.8–2.0, 1.7–2.3 mm (PSUZC-CR0227, 0228; not dissected), same data as the holotype.

Description. Male [based on holotype, 2.1 mm (OMNH-Ar-7750), and paratype 1.9 mm (OMNH-Ar- 7752) for pereopod 5]. Body (Fig. 2) slender, smooth. Eyes medium-sized. Antenna 1 (Fig. 3 A) with ratio of lengths of peduncular articles 1–3 1:0.9:0.7, peduncular article 1 with 1 penicillate and 1 simple setae at ventrodistal corner; flagellum with 5 medium-sized articles and 1 tiny distal article, articles 2–5 each with aesthetasc at ventrodistal corner. Antenna 2 (Fig. 3 B, B1) with article 2 bearing ovoid lamellate appendix mediodistally, ratio of lengths of peduncular articles 3–5 1:2.2:1.7; flagellum with 4 medium-sized articles and 1 tiny distal article, tip of article 4 with several setae.

Upper lip (Fig. 3 C) with a hollow on ventral margin, bearing short thin setae. Mandible (Fig. 3 D, D1, E, E1) with each incisor bearing 4 cusps; left lacinia mobilis with 5 cusps, right 3 cusps; palp article length ratio 1:1.6:1.7, articles 1–3 with 0, 1 and 11 setae, respectively. Lower lip (Fig. 3 F) with mandibular process short, central part of outer lobe with a roundish cavity-like structure, apical parts of inner and outer lobes covered with thin setae. Maxilla 1 (Fig. 3 G, G1) with outer plate bearing 10 robust setae apically; tip of palp article 2 with 4 robust and 2 thin setae. Maxilla 2 (Fig. 3 H) with both plates setose apically. Maxilliped (Fig. 3 I) with inner plate bearing several thick plumose setae distally; outer plate with 8 medial robust setae.

Gnathopod 1 (Fig. 4 A) with coxal plate roundish-trapezoidal, posteroventral corner rounded, bearing 9 fine setae and 1 robust seta on anterior/ventral and posterior margins, respectively; basis with 3 long setae posteriorly; carpus with many thick setae and several normal setae on posterior margin and medial surface, respectively; propodus setose anteriorly and posteriorly; dactylus with denticle on posterior margin. Gnathopod 2 (Fig. 4 B) with coxal plate roundish, bearing 2 ventral setae and 1 posterior robust seta (lost); basis elongate, posterodistal corner with short seta; merus short, posterodistal corner rounded; carpus triangular; propodus enlarged, with long acute process on posteroproximal corner, posterior margin of main part with many setae, posterior margin of process with several setae; dactylus elongate, strongly curved posteriorly, anterior and posterior margins each with several setae.

Pereopods 3 and 4 (Fig. 4 C, C1, D, D1) with coxal plates roundish, each bearing 4 ventral setae and 1 posterior robust seta; basis of pereopod 3 with 2 long setae; meri with several setae at anterodistal corners; dactyli short. Pereopod 5 (Fig. 4 E) with coxal plate wide, anterior lobe with several setae on ventral margin, posterior lobe with short plumose seta at posteroventral corner; basis slightly expanded, anterior margin with 1 plumose and 3 simple setae, anterodistal corner with 3 simple setae, posterior margin with 1 plumose and 2 simple setae; merus with thick seta at posterodistal corner; carpus with 1+3 robust setae; propodus with 1+2 robust setae and 1 apical plumose seta. Pereopod 6 (Fig. 4 F) with coxal plate narrow, anterior margin with long robust seta, posteroventral corner with short plumose seta; basis slightly curved posteriorly, anterior margin with 5 plumose and 3 simple setae, anterodistal corner with 2 simple setae, posterior margin with 2 plumose and 3 simple setae; merus with anterodistal robust seta and posterodistal long seta; carpus with 3 posterodistal robust setae; propodus with 1+1+1 robust setae, distal end with 1 long and 2 short simple setae and 1 plumose seta; dactylus curved.

Pleon 2 with 2 plumose setae ventrally (Fig. 5 A). Pleopod 3 shortest (Fig. 5 B–D); peduncles of pleopods each with several plumose setae and 2 coupling hooks; outer rami shorter than inner, outer rami of pleopods 1–3 with 7, 6 and 6 articles and inner rami with 5, 4 and 4 articles, respectively. Uropod 1 (Fig. 5 E) with peduncle bearing 3 robust setae on dorsal surface; outer ramus shorter than inner, outer ramus with 3 marginal and 4 terminal robust setae, inner ramus with 2 marginal and 4 terminal robust setae. Uropod 2 (Fig. 5 F) with peduncle bearing robust seta each on dorsal and medial surface; outer ramus shorter than inner, outer ramus with 3 marginal and 4 terminal robust setae, inner ramus with 2 marginal and 4 terminal robust setae. Uropod 3 (Fig. 5 G) with peduncle bearing 1 fine seta and 1 distal robust seta on medial margin; ramus short, distal end obtuse, with 2 thick and 3 normal setae. Telson (Fig. 5 H) short, not coalesced with urosomite 3; dorsodistal margin with 2 and 1 short setae, lateral margins each with 2 penicillate setae.

Female [based on allotype, 1.7 mm (OMNH-Ar-7751)]. Generally similar to male except for antenna 2, gnathopods and oostegites. Antenna 2 (Fig. 5 I) with more slender peduncle lacking lamellate appendix. Gnathopod 1 (Fig. 5 J) with coxal plate smaller than that of male. Gnathopod 2 (Fig. 5 K) with coxal plate roundish-square, bearing 5 ventral setae and 1 posterior robust seta; basis bearing 4 setae on anterior margin, posterior margin with long seta, posterodistal corner with 3 setae; merus relatively long, distal end truncate; carpus roundish triangular, anterior margin and medial surface weakly setose; propodus setose posteriorly, palm oblique, defined by small robust seta; dactylus slender; oostegite on gnathopod 2 small, with single long seta. Pereopod 7 (Fig. 4 G) with coxal plate weakly lobate, anterior margin with robust seta, posteroventral corner with short plumose seta; basis almost linear, anterodistal corner with simple seta, posterior margin with plumose seta; merus with seta on anterodistal corner; carpus with 2 robust setae distally; propodus with 2 anterodistal robust setae, posterodistal end with 3 long simple setae and 1 plumose seta; dactylus curved.

Shape change in male antenna 2 and gnathopod 2 with growth. Paratype, 1.7 mm (OMNH-Ar-7753): lamellate appendix on peduncular article of antenna 2 small (Fig. 5 L); propodus proper, posterior process and dactylus of gnathopod 2 shorter than those of the holotype (Fig. 5 M).

Etymology. Referring to the appendix on peduncular article 2 of male antenna 2.

Remarks. The ovoid lamellate appendix on peduncular article 2 of male antenna 2 is a unique character that all other Kamaka species do not possess, although the shape of male gnathopod 2 of this new species resembles that of Kamaka biwae and K. morinoi.

Distribution. Outer Songkhla Lagoon (present study) and Middle Songkhla Lagoon (Angsupanich et al., 2005).