Caridina trifasciata Yam & Cai 2003

Caridina trifasciata Yam & Cai, 2003

(Colour plate 2A, B)

Caridina trifasciata Yam & Cai, 2003 [type locality: Tsak Yue Wu, New Territories, Hong Kong]

Material examined. 5 ♂ cl 2.3–4.5 mm, 3 ♀ cl 3.2–4.3 mm, 1 ov. ♀ cl 5.0 mm (OUMNH.ZC 2013-07-033); 4 ♂ cl 3.3–4.1 mm, 4 ♀ cl 3.9–4.0 mm (RMNH. CRUS.D.56063), 5 ♀ with blackish life coloration cl 4.1–5.0 mm (OUMNH.ZC 2013-07-034), Hong Kong, stream at Kau Sai Chau Island, 22.35220°N 114.31700°E, coll. W. + M. Klotz 24.03.2010. 1 ♂ cl 3.1 mm, 1 ♀ cl 3.9 mm (OUMNH.ZC 2013-07-035) Hong Kong, Tsak Yue Wu, Sai Kung, 22.397831°N 114.326098°E, coll. W. Klotz 20.3.2011; 5 ♂ cl 3.0–4.0 mm, 1 ♀ cl 4.5 mm (OUMNH.ZC 2013-07-036); 4 ♂ cl 3.2–4.0 mm, 1 ♀ cl 3.5 mm (RMNH. CRUS.D.56064), Hong Kong, High Island, Sai Kung, small rocky hill stream, 22.36106°N 114.33721°E; coll. W. Klotz 20.03.2011; 6 ♂ cl 3.8–4.2 mm, 4 ♀cl 3.5–4.9 mm, 2 ov. ♀ cl 4.8 and 4.9 mm (OUMNH.ZC 2013-07-037), 11 ♂ cl. 2.5–3.6 mm, 1 juv. cl 2.9 mm, 6 ♀ cl 2.8–5.0 mm (RMNH. CRUS.D.56065) China, Guangdong Prov., Henquin Island, Zhuhai, San Die Quan spring, 22.113694°N 113.502778°E, coll. W. Klotz 0 5.04.2009.

Caridina trifasciata was originally described from two streams: Tsak Yue Wu on Sai Kung Peninsula and Yi Leng stream on the Kau Sai Chau Island, Sai Kung, New Territories, Hong Kong. During a field trip in April 2011 C. trifasciata could also be collected from a small stream on High Island, Sai Kung, Hong Kong. In 2009, a few specimens of shrimp with a “bee shrimp pattern” of life coloration (colour plate 2A) were collected from a rocky pool in Sandiequan Scenic Area, Zuhai, Guangdong Province, Southern China. Compared to the description of C. trifasciata given by Yam & Cai, 2009 these specimens differ in some morphometric characters, viz. carpus of first cheliped more slender (length to width ratio 1.5–1.9 median 1.6 vs. 1.4–1.5 in C. trifasciata), merus of first cheliped more slender (length to width ratio 2.2–3.0 median 2.6 vs. 2.0– 2.2 in C. trifasciata), carpus of second cheliped more slender (length to width ratio 5.5–8.4 median 6.7 vs. 5.4–5.9 in C. trifasciata), propodus of 3rd pereiopods more slender (propodus length to width ratio 8.9–15 median 10.4 vs. 9.3–9.5 in C. trifasciata), propodus of 3rd and 5th periopods shorter in comparisation with dactylus (3.2–4.2 median 3.7 and 3.8–4.1 median 4.0 vs. 4.2–4.6 and 4.5–4.8 in C. trifasciata). Compared with C. trifasciata from 3 localities in Hong Kong (this study) most of these morphometric characters are overlapping, just a more slender carpus of first cheliped (length to width ratio 1.5–1.9 median 1.6 vs. 1.3–1.5 median 1.4 in C. trifasciata from Hong Kong) serves to differentiate the specimens from Zuhai from specimens from Hong Kong. Thus, the population from Zuhai is considered as a local variant with different life coloration conspecific with C. trifasciata.