Caridina rapaensis Edmondsonı 1935

Mazancourt, Valentin de, Marquet, Gérard & Keith, Philippe, 2019, Revision of freshwater shrimps belonging to Caridina weberi complex (Crustacea: Decapoda: Atyidae) from Polynesia with discussion on their biogeography, Journal of Natural History 53 (13), pp. 815-847 : 832-838

Caridina rapaensis Edmondsonı 1935

( Figure 6 )

Caridina rapaensis Edmondson 1935: 12 , 14, Figure 5 (a – h) page 15; Marquet 1988, 1991: 130; Poupin 1998: 8; Keith and Vigneux 2002: 125, photos 3 & 4; Keith et al. 2002: 40 – 41; Keith et al. 2013, p. 78 – 79.

Material observed

Type material. Holotype: 1 ♀, cl 4.7 mm, 1934, a freshwater stream, Rapa Island , French Polynesia, Mangarevan Expedition coll., BPBM 53933.

Paratype: 1 ♀, cl 5.0 mm, same data as holotype, BPBM 53694 .

Other material. 1 ♂, cl 3.3 mm, 15 June 2001, 27°35.919 ′ S 144°20.392 ′ W, Panui stream, Rapa Island , French Polynesia, altitude 18m, G. Marquet coll., MNHN-IU-2016-11768; 1 ♂, cl 3.4 mm, same data as previous, MNHN-IU-2016-11769 (DNA: CA2114 ); 1 ♀, cl 4.8 mm, same data as previous, MNHN-IU-2016-11770; 1 ♀, cl 5.2 mm, same data as previous, MNHN-IU-2016-11771 (DNA: CA2115 ); 1 ♀, cl 6.0 mm, same data as previous, MNHN-IU -2016-11772 (DNA: CA2111 ); 2 ♂, cl 2.5 – 2.9 mm and 2 ♀ ovig, cl 4.0 – 4.6 mm, 2 May 1986, 22°26.240 ′ S 151°22.243 ′ W, Tevaovai stream, Rurutu Island, French Polynesia, altitude 52m, G. Marquet coll., MNHN-IU-2015 – 1921.

Comparative material. Type material

Caridina parvirostris De Man, 1892 .

Syntypes: 2 ♀, cl. 3.1 – 3.2 mm, river near Bombang, Flores Island, Indonesia, M. Weber coll., MNHN-IU-2015-1748; 1 ♀, cl. 4.2 mm, same data as for previous, MNHN-IU-2015-1754 .

Caridina weberi var. keiensis Roux, 1911

Lectotype: 1 ♀ ovig. cl 5.7mm, 5 June 1908, Warka, Grand Kei Island , Indonesia, H. Merton coll., NMB 6.IV.b.

Paralectotypes: 2 ♂ cl 2.6mm, 1 ♂ 6.IV.b, same data as for lectotype, NMB 6.IV.a; 1 ♀, cl 5.5mm and 1 ♂, cl 3.4mm, same data as for lectotype, NMB 6.IV.b.

Caridina weberi, 1892 .

Syntypes: 2 ♂, cl 4.4 – 4.5 mm and 1 ♀ ovig, cl 6.1 mm, Kotting , Flores Island, Indonesia, M. Weber coll., MNHN-IU-2015-1755.

Description

Cephalothorax. Rostrum ( Figure 6 (h)) always bent down, short, 0.3 – 0.5 of cl, reaching to base of second segment of antennular peduncle, armed dorsally with 0 – 5 teeth, occupying distal fourth of border, none situated on carapace posterior to orbital margin, ventral margin with 1 – 6 teeth. Rostral formula (0) 0 – 5/1 – 6. Suborbital angle indistinguishably fused with antennular tooth. Pterygostomian margin rounded.

Eyes well developed, anterior end reaching to 0.77 length of antennular peduncle basal segment. Antennular peduncle 0.44 times as long as carapace. Anterolateral angle of basal antennular segment reaching 0.20 length of second antennular segment, second antennular segment distinctly longer than third. Stylocerite reaching to end of antennular peduncle basal segment. Scaphocerite reaching just slightly beyond tip of antennular peduncle, about 3.1 times longer than wide.

Mouthparts. Left mandible, right mandible, first maxilla, second maxilla, first maxilliped, second maxilliped and third maxilliped typical of genus.

Pereiopods. Epipods on first four pereiopods.

Pereiopod 1 ( Figure 6 (a)): chela about 1.5 – 2.5 times as long as wide, movable finger 1.5 – 4.4 times as long as wide, 0.5 – 1.4 times length of palm, carpus 1.2 – 1.7 times as long as wide. Tips of both fingers with prominent claws ( Figure 6 (b)).

Pereiopod 2 ( Figure 6 (c)): more slender and long than the first pereiopod with chela 2.0 – 2.7 times as long as wide: movable finger 3.2 – 4.7 times as long as wide, 1.3 – 1.9 times length of palm, carpus slender 4.2 – 5.2 times as long as wide.

Pereiopod 3 ( Figure 6 (d, g)): stout, dactylus 2.7 – 3.9 times as long as wide including terminal spine with 6 – 8 spines including terminal spine, propodus 9.0 – 12.8 times as long as wide, 3.9 – 4.9 times as long as dactylus.

Pereiopod 5 ( Figure 6 (e, f)): dactylus 3.1 – 4.9 as long as wide, ending in two large claws with 30 – 45 spiniform setae on flexor margin, propodus 11.7 – 19.0 times as long as wide, with numerous spines on ventral margin, 4.5 – 5.4 times as long as dactylus.

Abdomen. Third abdominal somite with moderarely convex dorsal profile. Sixth abdominal somite about 0.4 times carapace length, 1.2 times as long as fifth somite, shorter than telson. Telson ( Figure 6 (k)): 2.9 times as long as wide, with five or six pairs of dorsal spines and one pair of dorsolateral spines, posterior margin with small median process, rounded with 5 – 13 intermediate plumose setae much longer than lateral spines.

First male pleopod ( Figure 6 (m)): Endopod extending to 0.42 times length of exopod, rectangular, with a short appendix interna near distal end of endopod.

Second male pleopod ( Figure 6 (n)): Appendix masculina reaching 0.83 times length of endopod, appendix interna reaching about 0.34 times appendix masculina length.

Preanal carina ( Figure 6 (i)): High, unarmed.

Uropodal diaeresis ( Figure 6 (k)): with 15 – 20 spinules.

Eggs ( Figure 6 (j)): Size 0.44 – 0.49 × 0.26 – 0.29 mm.

Habitat

This new species prefers fresh and well-oxygenated running waters from the lower course to the middle course.

Colour pattern ( Figure 7 (dı e))

The live general colour of the body is yellowish to greenish and slightly translucent. Numerous red spots are visible all over the body.

Distribution ( Figure 8 )

This species is known only from Austral Islands (Rurutu and Rapa islands) so far and seems to be endemic.

Remarks

Our specimens look like those described by Edmondson (1935): Rostrum always bent down, short, 0.3 – 0.5 of cl, reaching to base of second segment of antennular peduncle (vs rostrum slender, slightly turned down, reaching to the middle of the second segment of the antennular peduncle for Edmondson (1935)), rostrum armed with 0 – 5 teeth on dorsal margin, occupying the distal fourth of the border, ventral margin with 1 – 6 teeth. (vs rostral teeth small and few, stronger above than below, those above occupying the distal fourth of the border, the first (basal) tooth below being posterior to the first one of the upper border for Edmondson (1935)), P1 finger 0.5 – 1.4 times length of palm (vs dactylus as long as upper border of palm for Edmondson (1935)), P3 dactylus with 6 – 8 spines on flexor margin in addition to the terminal spine (vs border dactylus provided with a stout tooth just proximal of the tip, and four other small spines for Edmondson (1935)), P5 dactylus ending in two large claws with 30 – 45 spiniform setae on flexor margin (vs dactylus of fifth leg bearing numerous short hairs and a strong supplementary tooth near the tip for Edmondson (1935)), posterior margin of the telson with a little median process, rounded with 5 – 13 intermediate plumose setae much longer than lateral spines (vs telson with 6 pairs of small spines on upper border, its posterior margin bearing a small median tooth for Edmondson (1935)), and uropodal diaeresis with 15 – 20 spinules (vs uropodal spinelets 20 in number for Edmondson (1935)).

This species differs from C. parvirostris by its bent rostrum with fewer dorsal teeth (0 – 5) (vs bent rostrum with 8 – 10 dorsal teeth in C. parvirostris ) and its P2 carpus shorter 4.2 – 5.2 times as long as wide (vs 6.0 – 7.4 in C. parvirostris ) and so is P2 chela 2.0 – 2.7 times as long as wide (vs 2.6 – 3.0 in C. parvirostris ).

This species differs from C. futunensis n. sp. by its bent rostrum with fewer dorsal teeth (0 – 5) (vs bent rostrum with 5 – 10 in C. futunensis n. sp.) and its P5 dactylus ending in two large claws (vs one large claw in C. futunensis n. sp.).

C. rapaensis was reported by Shokita (2003) from Ryukyu Islands, but according to Cai and Shokita (2006), these specimens actually belong to C. prashadi Tiwari & Pilai, 1971 described from the Andaman Islands. Indeed, even if the rostrum formula is similar (0) 0 – 5/1 – 6 (vs (0)1 – 6/ 3 – 6 in C. prashadi ), C. rapaensis can be distinguished easily from C. prashadi by its prominent claws on the tips of both P1 fingers (vs no prominent claws in C. prashadi ) and by its P5 dactylus ending in two large claws (vs one claw in C. prashadi ) with 30 – 45 spiniform setae on flexor margin (vs 29 in C. prashadi ).

C. rapaensis looks like C. weberi var. keiensis from Kei Islands ( Indonesia) by its bent and short rostrum, its P1 chela bearing prominent claws and its P5 dactylus being biunguiculate. However, they can be distinguished by the number of dorsal teeth on the rostrum 0 – 5 (vs 2 – 13 in C. weberi var. keiensis ). Furthermore, considering the distance between Kei Islands and Polynesia and that C. weberi var. keiensis has never been collected in between, we consider it to be a distinct species.

Figures

Figure 5. Caridina tupaia n. sp. Holotype (MNHN-IU-2018-260; DNA: CA2058), (a). first pereiopod; (b). second pereiopod; (c). third pereiopod; (d). fifth pereiopod; e. dactylus of fifth pereiopod; (f). dactylus of third pereiopod; (g). cephalothorax; h. preanal carina; (j). uropodal diaeresis; (k). telson. Paratype (MNHN-IU-2018-268), (i). eggs. Paratype (MNHN-IU-2018-261; DNA: CA1048), (l). first pleopod; m. second pleopod.

Figure 6. Caridina rapaensis. (MNHN-IU-2016-11771; DNA: CA2115), (a). first pereiopod; (b). first pereiopod, detail of the fingertips; (c). second pereiopod; (d). third pereiopod; e. fifth pereiopod; f. dactylus of fifth pereiopod; (g). dactylus of third pereiopod; (h). cephalothorax; (i). preanal carina; (k). uropodal diaeresis; (l). telson. (MNHN-IU-2015-1921: ♀ ovig, 4.0 mm), (j). eggs. (MNHN-IU-2015- 1921: ♂, cl 2.9 mm), m. first pleopod; n. second pleopod.

Figure 7. Live colouration of the species: (a, b). C. tupaia n. sp. (c). C. marquesensis n. sp. (d, e). C. rapaensis. (f). C. futunensis n. sp. (g). Habitat of C. futunensis n. sp. in Futuna. Credits: (a, b, c): G. Marquet; (d, e): E. Vigneux; (f): V. de Mazancourt; (g): A. Dutartre.

Figure 8. Distribution map of the four species studied with oceanic currents of Southern Polynesia (from Martinez et al. 2009) represented: SEC. South Equatorial Current. SECC. South Equatorial Countercurrent. MCC. Marquesas Countercurrent. STCC. South Tropical Countercurrent. GYRE. South Pacific Gyre.