Cuapetes seychellensis (Borradaile, 1915)

Marin, Ivan & Sinelnikov, Sergey, 2016, Partial redescription of pontoniine shrimps Cuapetes nilandensis (Borradaile, 1915) and Cuapetes seychellensis (Borradaile, 1915) (Decapoda: Palaemonidae: Pontoniinae) with remarks on taxonomic status of Cuapetes Clark, 1919 and Kemponia Bruce, 2004, Zootaxa 4173 (6), pp. 557-568 : 562-566

Cuapetes seychellensis (Borradaile, 1915)

( Figs. 1 b, 4–6)

Periclimenes (Falciger) seychellensis Borradaile, 1915b: 212 [type locality — Praslin , Seychelles]

Material examined. Western Pacific , South China Sea, Vietnam— 4 ovig, females, pcl. 2.5, 2.6 (dissected), 2.3 and 2.8 mm ( LEMMI), Nhatrang Bay, south to Be River, littoral, 0–2 m, on turtle sea grass Zoostera, coll. I. Marin, 22–25 Nov. 2006 ; Indian Ocean , Madagascar— 1 ovig. female, pcl 2.5 mm (UF 14066), Nose, W of Hellville, 13.4156˚ 48.22465˚, BMADA-0549, MGNW-50, sand flat, sea grass, patch reefs, push net over seagrass, 0–3 m, coll. A. Anker, G. Bakary, F. Michonneau, G. Paulay, T. Werner, 25 May 2008 .

Description. Carapace ( Figs. 1 , 4 a, b) swollen, smooth, with well developed antennal and hepatic teeth, without supraorbital or supraocular teeth; hepatic spine larger than antennal; dorsal margin of carapace with several long simple setae. Rostrum ( Fig. 4 a, k, l) horizontal, compressed, with tip upward, with deep medial part, slightly overreaching antennal scale. Rostral formula 2+7/4, posteriormost tooth slightly separated from remained in dorsal rostral series and posterior to level of hepatic teeth; lateral lamina feebly developed. Orbit feebly developed, inferior orbital angle projecting, rounded.

Abdominal somites smooth; pleurae of abdominal somites I–V rounded, posterolateral angle of abdominal somite V pointed; posterolateral angle of abdominal VI somite rounded ( Fig. 1 b). Thoratic sternites IV ( Fig. 4 m) with spine-like median process perpendicular to sternite and 2 submedial rectangular protuberances); thoratic sternite V with 2 submedial rectangular lobes. Telson ( Fig. 4 g) about 3 times longer than maximal proximal width, tapering anteriorly, with acute, sting-like, distal margin with 2–3 dorsal submedial simple setae ( Fig. 4 h); 2 pairs of large dorsal spines, about 0.15 of telson length, situated at 0.7 and 0.25 of telson length; 3 pairs of posterior spines contain small and slender lateral, long and stout intermediate and slender submediate setose spines which are half of intermediate spines in length.

Eyes ( Fig. 4 c, d) well developed, with semispherical cornea; eyestalk subcylindrical, with marked knob on it medial anterodorsal margin; with accessory pigment spot.

Antennules ( Fig. 4 e) well developed; basal segment slightly less than twice longer than wide, stylocerite well developed, acute, far reaching the midlength of basal segment; with distinct robust submarginal ventral tooth, situated at the middle of medial line of a stalk of basal segment, with acute distolateral tooth and distal medial lobe concave, rounded, bearing long setose setae; intermediate segment stout, as long as wide, with produced inner distal edge bearing long setose setae; distal segment about twice longer than wide. The upper flagellum long and slender, the shorter ramus consists of more than 10 segments with 14 groups of aesthetascs, and longer than free ramus with more than 10 segments. The lower flagellum filiform with more than 12 segments.

Antenna ( Fig. 4 f) well developed, basicerite bearing long sharp distolateral tooth; carpocerite robust, as long as wide; flagellum well developed; scaphocerite slender and far exceeding antennular stalk, about 3 times as long as maximum width, with well developed distolateral tooth, not exceeding the distal margin of the blade.

Epistome unarmed. Mandible robust, without palp; incisor process stout, tapering distally, with 3 terminal marginal teeth; molar process well developed, robust, with 5–6 distal teeth. Maxillula normal; palp well developed, bilobed; the upper lacinia is slightly curved, flaring distally, with strong distal spines; the lower lacinia is slender, distally rounded, with distal setae. Maxilla with well-developed simple palp; endites well developed, distal lobes well developed, slender, furnished with stiff setae; scaphognathite with plumose setae. Maxilliped I with feebly separated well developed endites; palp with medial setose setae; exopod well developed, with large caridean lobe bearing plumose setae; epipod ear-like, well developed. Maxilliped II with exopod well developed; distolateral margin of propodus broadly rounded, with slender setae; dactylus about 4 times longer than broad, with rows of slender serrated and small stout spines along distal margin; epipod subrectangular, well developed; without podobranch. Maxilliped III ( Fig. 3 g) with normal segments; exopod well developed, exceeding the length of ischiomerus; ischiomerus about 4 times as long as maximum width, slightly broader distally, with several spines along lateral margin; the penultimate segment slender, about 4 times as long as wide; the terminal segment slender, about 4 times as long as wide; epipod rounded; arthrobranch well developed.

Pereiopod I ( Fig. 5 a) slender; basis about as long as wide; ischium about 3 times as long as wide; merus about 6 times as long as wide; carpus about 10 times as long as wide in distal part, slightly tapering proximally; palm about twice longer than wide, subcylindrical, with long and slender setae along its ventrolateral margin ( Fig. 5 b); fingers simple, slender, about 5 times as long as wide, with acute tips and straight cutting edges.

Pereiopod II similar in size and shape; with slender segments ( Fig. 5 c); basis equal in length and width; ischium about 4 times as long as maximal width; merus unarmed, about 6 times longer than wide; carpus about 5 times as long as wide, flared distally, with straight, unarmed distal margins ( Figs. 5 d, e); palm subcylindrical, about 3 times as long as maximal width; fingers simple, slender and straight, about 5 times as long as wide, with acute tips and straight cutting edges ( Fig. 5 f).

Pereiopod III ( Fig. 5 g) stout; basis about as long as wide; ischium about 5 times as long as wide; merus about 6 times as long as wide; carpus about 3 times as long as wide, with projected distodorsal margin; propodus about 6 times as long as wide, with ventral margin bearing 4 single and 1 paired ventral spines and a pair of distoventral spines; dactylus ( Fig. 5 h) moderately robust, about 4.5 times as long as maximum width, tapering distally, with stout curved unguis, one preterminal dorsal straight setae. Pereiopods III–V similar.

Pleopods of abdominal somite V very small and stout. Uropods ( Fig. 4 j) slightly exceeding telson; lateral border of uropodal endopod with small distal tooth and mobile spine, bearing small setae along it lateral margin.

Coloration. The body transparent, scaphocerites, carapace, dorsal and ventral surface of abdominal segments and uropods covered with grey, brown and black chromatophores ( Fig. 6 ). Eyes with 2 dark brown bands. Segments of pereiopods I and II transparent, with bands of brown and grey chromatophores on medial segments. Eyes yellow-grayish.

Remarks. Some differences were found in rostral formula of collected specimens. One of female from Nhatrang Bay possesses rostral formula — 2+6/4 while another have rostral formula — 2+5/4. Thus, rostral formula 2+5–7/4. Additionally, one of females from Nhatrang Bay showed only one medial setose spine while others possess two normal spines.

The species can be clearly separated from relatively and sometimes sympatric C. nilandensis by the following morphological features: 1) the presence of a small knob on eyestalk of eyes, 2) the absence of supraorbital tooth on carapace, 3) deeper rostrum and 4) stouter ambulatory pereiopods, especially dactylus of pereiopod III.

Habitat. The species inhabits muddy shallow Zostera grass beds ( Fig. 6 c) being, possibly, scavenger or micropredator. It is interesting that the species was absent in “clean”, without muddy cover, Zostera bushes growing between coral rubbles in highly washed zone. Camouflage coloration of the species is clearly adapted to conceal the silhouette in muddy habitats rather than on green sea grass leaves ( Marin & Savinkin, 2007; Marin, 2012). The other pontoniine species described from the same habitat is Phycomenes sulcatus ( Duris, Horka, Marin, 2008) ( Duris et al., 2008; Bruce, 2008).

Distribution. Widely distributed Indo-West Pacific shallow water species, known from Red Sea to Mozambique, eastward to Indonesia, Papua, Australia, New Caledonia, and Marshall Islands.

Figures

FIGURE 1. Cuapetes nilandensis (Borradaile, 1915), ovigerous female, general lateral view, Madagascar (a) and Cuapetes seychellensis (Borradaile, 1915), ovigerous female, general lateral view, Nhatrang Bay, Vietnam (b).

FIGURE 3. Cuapetes nilandensis (Borradaile, 1915), alive coloration: a, b — male and ovigerous female from Nhatrang Bay, Vietnam; c — ovigerous female from GBR of Australia; d — ovigerous female from Madagascar (leg. A. Anker).

FIGURE 4. Cuapetes seychellensis (Borradaile, 1915), ovigerous female, Nhatrang Bay, Vietnam: a, b — carapace; c, d — eye; e — antennula; f — antenna; g — telson; h — distal margin of telson, ventral view; i — dorsal spine of telson; j — uropods.

FIGURE 5. Cuapetes seychellensis (Borradaile, 1915), ovigerous female, Nhatrang Bay, Vietnam: a – pereiopod I; b — chela of pereiopod I, ventral view; c — pereiopod II; d, e — carpo-propodal articulation of pereiopod II; f — chela of pereiopod II; g — pereiopod III; h — dactylus of pereiopod III.

FIGURE 6. Cuapetes seychellensis (Borradaile, 1915), alive coloration, ovigerous female, Nhatrang Bay, Vietnam.