Caridina laoagensis Blanco, 1939

Cai, Y., 2006, Atyid shrimps (Crustacea: Decapoda: Caridea) of the Ryukyu Islands, southern Japan, with descriptions of two new species, Journal of Natural History 40 (38 - 40), pp. 2123-2172 : 2141-2144

Caridina laoagensis Blanco, 1939

( Figures 5 and 6A–E )

Caridina laoagensis Blanco, 1939, p 390 , pl 2 [type locality: not indicated; presumably Laoag River, Laoag, Province of Ilocos Norte, Luzon, Philippines (after Chace 1997)]. Caridina laoagensis: Chace 1997, p 12 , fig. 5a–t; Cai and Anker 2004, p 237, fig. 3; Cai and Shokita 2006, p 246 .

Caridina weberi: Shokita 2003, p 250 , figs. 18I, 19D, 20N.

Material examined

One male, cl 4.9 mm, URB, Aritsu River, Kume-jima Island, Ryukyu Islands, coll. A. Kawakami, 8 December 1995; 1 male, cl 3.5 mm, 124 ° 14.809E 24 ° 22.769N, Gaburumata River, Ishigaki Island, Ryukyu Islands, coll. Y. Cai and T. Naruse , 13 June 2000 ; 1 male, cl 4.3 mm, ZRC 2004.0578 , 123 ° 52.809E 24 ° 16.649N, shallow freshwater stream of Aira River, Iriomote Island, Ryukyu Islands, coll. Y. Cai, N. K. Ng and T. Naruse , 14 June 2000 . 1 male, cl 3.8 mm, URB, Omija River , Iriomote Island , Ryukyu Islands, 1 August, 1998, coll. T. Naruse ; 1 male, cl 8.1 mm, 1 ovigerous female, cl 7.8, RUB, a small stream near Haemida beach, Iriomote, Ryukyu Islands , coll T. Naruse, 28 July 1999 .

Description

Rostrum straight ( Figure 5A ), reaching to base of second segment of antennular peduncle, dorsal margin nearly horizontal, elevated slightly above dorsal margin of carapace, rostral formula 0+9–17/1–6, dorsal teeth evenly spaced, all on rostrum considerably anterior to orbital margin. Antennal spine fused with inferior orbital angle; pterygostomian margin rounded.

Sixth abdominal somite 0.40 times length of carapace, 1.3 times as long as fifth somite, shorter than telson. Telson ( Figure 5C ) 2.5 times as long as wide, terminating in a projection, with five pairs of dorsal spinules and one pair of dorsolateral spinules; distal end with two pairs of spines and three to four pairs of plumose setae, lateral pair of spines distinctly longer than sublateral pair, intermediate pairs of setae distinctly longer than later spines, distal margin broadly rounded. Preanal carina high, without spine ( Figure 5B ).

Eyes well developed, anterior end reaching to 0.7 times length of basal segment of antennular peduncle. Antennular peduncle 0.52 times as long as carapace; basal segment of antennular peduncle longer than sum of second and third segment lengths, anterolateral angle reaching 0.20 times length of the second segment, second segment distinctly longer than third segment. Stylocerite ( Figure 5D ) reaching 0.8 length of basal segment of antennular peduncle. Scaphocerite 2.6 times as long as wide.

Incisor process of mandible ending in irregular teeth, molar process truncated. Lower lacinia of maxillula broadly rounded, subtriangular, upper lacinia elongate, with a number of distinct teeth on inner margin, palp slender. Upper endites of maxilla subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Palp of first maxilliped ending in a finger-like projection. Second maxilliped typical, arthrobranch well developed. Third maxilliped reaching to end of antennular peduncle, with ultimate segment shorter than penultimate segment.

Epipods well developed on first four pereiopods. First pereiopod ( Figure 5E ) reaching to distal end of basal segment of antennular peduncle; merus 2.1 times as long as broad, as long as, or slightly longer than carpus; carpus excavated anteriorly, shorter than chela, 1.3 times as long as high; chela 2.4 times as long as broad; fingers subequal to length of palm. Second pereiopod ( Figure 5F ) reaching to end of second segment of antennular peduncle; merus slightly shorter than carpus, 4.3 times as long as broad; carpus slightly longer than chela, 4.3 times as long as high; chela 2.9 times as long as broad; fingers 1.6 times as long as palm. Third pereiopod ( Figure 5G, H ) reaching to end of scaphocerite, propodus 8.3 times as long as broad, 3.7 times as long as dactylus; dactylus 2.2 times as long as wide (spines included), terminating in one stout claw, with five accessory spines on flexor margin. Fifth pereiopod ( Figure 5I, J ) reaching to end of antennular peduncle, propodus 9.2 times as long as broad, 3.3 times as long as dactylus, dactylus 3.1 times as long as wide (spinules included), terminating in one elongated claw, with 28–42 spinules on flexor margin.

Endopod of male first pleopod sub-triangular, reaching to one-thirds length of exopod, appendix interna reaching beyond distal end of endopod by most of its length. Appendix masculina of male second pleopod reaching to two-thirds length of exopod.

Uropodal diaeresis ( Figure 5K ) with 16–18 movable spinules.

Eggs 0.40–0.42× 0.20–0.25 mm in diameter.

Habitat

Rivers and streams which discharge to the sea.

Remarks

Chace (1997) recently redescribed this species on the basis of specimens from Philippines. He ( Chace 1997, p 13) also commented that it ‘‘…is possible that C. laoagensis will eventually fall into synonymy with the variable C. weberi from Indonesia,…’’ According to an on-going revision by one of the authors (YC), most of the subspecies of C. weberi , are in fact, distinct species. Among all the allied species, C. laoagensis is most similar to C. weberi De Man, 1908a by the form of the rostrum, which is straight, pointed and crested at the base of the rostrum; the spines and setae on the distal margin of the telson (the longer setae arranged between two pairs of strong spines, of which, the sublateral pair shorter than the lateral pair vs. the longer setae arranged between one pair of strong spines).

Caridina laoagesis appears to be rare in Ryukyu Islands. It has previously been reported from Tabaru River of Yonaguni Island, Nagura and Miyara Rivers of Ishigaki Island, and Shigema, Yona and Manna Rivers of Okinawa Island by Shokita (1979, p 2003) as Caridina weberi .

Distribution

Philippines, Japan

Figures

Figure 5. Caridina laoagensis. A, cephalothorax and cephalic appendages, lateral view; B, preanal carina; C, distal portion of telson; D, scaphocerite; E, first pereiopod; F, second pereiopod; G, third pereiopod; H, dactylus of third pereiopod; I, fifth pereiopod; J, dactylus of fifth pereiopod; K, diaeresis. Scale: A, B, D51 mm; E–G, I50.5 mm; C, H, J, K50.2 mm (male, cl 3.5 mm, ZRC).

Figure 6. Caridina laoagensis. A, third maxilliped; B, male first pleopod; C, endopod of male first pleopod; D, male second pleopod; E, appendix masculina and appendix interna of male second pleopod; Caridina rubella. F, cephalothorax and cephalic appendages, lateral view; G, first pereiopod; H, second pereiopod; I, third pereiopod; J, dactylus of third pereiopod. Scale: F51 mm; A, B, D, G–I50.5 mm; C, E, J50.2 mm (A–E, male, cl 3.5 mm, ZRC; F–J, female, cl 3.9 mm, URB).