Caridina excavatoides Johnson 1961
Creators: name: Cai, Yixiong
name: Ng, Peter K. L.
name: Choy, Satish
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Atyidae
Caridina
Caridina excavatoides

description: Caridina excavatoides Johnson, 1961   
(Figs. 11, 12)  
 Caridina excavatoides Johnson, 1961: 127, Figs. 3–11 [type locality: Kedah, Malaysia]; Wowor et al., 2004: 343, Figs. 7T, U.   
 Material examined. – Holotype: ovigerous female, cl 4.6 mm, eggs ca. 0.7 × 0.5 mm, ZRC 1979.4.11.14, stream at about 9 miles from Alor Setar, Kedah, on the Pokok Sena Road, Peninsular Malaysia, coll. D. S. Johnson, 7 Dec.1955.   
Paratype: 1 ovigerous female, cl 4.3 mm, ZRC 1979.4.11.15, data same as holotype.  
 Others: Malaysia: 2 females, cl 2.2–3.0 mm, ZRC 2007.0393, Sungai Basar, Kuantan, Malaysia, 5 Sep.1998; 4 males, cl 1.8–2.3 mm, 5 females, cl 2.1–2.8 mm, 2 ovigerous females, cl 2.9–3.2 mm, eggs 0.6 × 0.4 mm, ZRC 2007.0394, Sungai Atong, Pahang near Kuantan, Malaysia, 7 Sep.1998.   
 Comparative material examined. – Sumatra: 3 males, cl 2.4–2.5 mm, 4 females, cl 2.9–3.5 mm, 5 ovigerous females, cl 3.2–3.4 mm, eggs 0.7 × 0.42 mm, ZRC 2007.0395, Sumatra, 250km south of Medan, Sei Rampah, Pastai Berdagai, Kg. Nagur, stagnant pools, pH 6.4, coll. H. H. Tan, 15 Jun.1996.   
 Description. – Rostrum (Figs.11A, 12A) sigmoid, reaching near middle of second segment of antennular peduncle, or to end of third segment. Rostral formula 3–6+10–17/2–4. Suborbital angle acute, distinctly separated from antennal spines; pterygostomian margin rounded.   
Sixth abdominal somite 0.6 times of carapace, 1.8 times as long as fifth somite, slightly shorter than telson. Telson (Figs. 11B, C) 3.1 times as long as wide, distal margin rounded, not terminating in a projection, with 3 pairs of dorsal spinules and one pair of dorsolateral spinules; distal end with 3 or 4 pairs of spines, lateral pair slightly longer than intermediate pairs. Preanal carina (Fig. 11K) low, without spine.  
Eyes well developed, anterior end reaching to 0.7 times length of basal segment of antennular peduncle. Antennular peduncle 0.63–0.77 times as long as carapace; basal segment of antennular peduncle longer than combined length of second and third segments, anterolateral angle reaching to 0.3 times length of second segment, second segment distinctly longer than third segment. Stylocerite reaching to 0.8 times length of basal segment of antennular peduncle. Scaphocerite (Fig. 11J) 3.7 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 elongated, with a number of distinct teeth on inner margin, palp slender. Upper endites of maxilla (Fig. 11D) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Palp of first maxilliped (Fig. 11E) ending in a triangular projection. Second maxilliped (Fig. 11F) typical, arthrobranch well developed. Third maxilliped (Fig. 11G) reaching beyond end of second segment of antennular peduncle, with ultimate segment shorter than penultimate segment.  
Epipods well developed on first 2 pereiopods, reduced in third pereiopod, rudimentary or absent in last 2. First pereiopod (Figs. 11H, 12B) reaching near anterior end of eye; merus 2.5 times as long as broad, slightly shorter than carpus; carpus excavated anteriorly, shorter than chela, 3.5 times as long as high; chela 2.7 times as long as broad; fingers 1.7 times as long as palm. Second pereiopod (Figs. 11I, 12C) reaching to end of second segment of antennular peduncle; merus shorter than carpus, 5.1 times as long as broad; carpus 1.3 times as long as chela, 7.8 times as long as high; chela 4.0 times as long as broad; fingers 1.4 times as long as palm. Third pereiopod (Figs. 12D, E) reaching to end of antennular peduncle, propodus 10 times as long as broad, 3.2 times as long as dactylus; dactylus 4.1 times as long as wide (spines included), terminating in a claw, with 6 accessory spines on flexor margin. Fifth pereiopod (Figs. 12F, G) reaching beyond end of basal segment of antennular peduncle, propodus 11 times as long as broad, 2.7 times as long as dactylus; dactylus slender, 4.2 times as long as wide (spinules included), terminating in a claw, with 50–60 spinules on its flexor margin.  
Endopod of male first pleopod (Fig. 12H) subrectangular, 2.7 times as long as wide, reaching to 1/3 length of endopod, no appendix interna. Appendix masculina (Fig. 12I) of male second pleopod slender, reaching to half length of exopod.  
Uropodal diaeresis (Fig. 11L) with 12 or 13 movable spinules.  
Ovigerous females with eggs sized 0.60–0.78 × 0.40–0.48 mm.  
 Habitat. – Rivers and streams.   
 Remarks. – In the form of the rostrum and the ratio of various segments of the pereiopods, C. excavatoides is most similar to C. propinqua. It can be distinguished from C. propinqua by the absence of a preanal spine, the more slender endopod of the male first pleopod and the relatively larger egg size. Caridina excavatoides also morphologically close to C. tonkinensis Bouvier, 1919. It can be separated from C. tonkinensis by the absence of preanal carina and the palp of first maxilliped, which terminates in a triangular (vs. finger-like projection in C. tonkinensis). The species was previously know only from Peninsular Malaysia; its present record from Sumatra being a new record.   
 Distribution. – Known only from Peninsular Malaysia and Sumatra (present study; Johnson, 1961).
description: Published as part of Cai, Yixiong, Ng, Peter K. L. & Choy, Satish, 2007, Freshwater Shrimps Of The Family Atyidae (Crustacea: Decapoda: Caridea) From Peninsular Malaysia And Singapore, pp. 277-309 in Raffles Bulletin of Zoology 55 (2) on pages 294-297, DOI: 10.5281/zenodo.5333541