Palaemonella tenuipes Dana, 1852

Lal, Sheena Jose Purushothaman Paramasivam Rejani Chandran S. Bharathi A. Dhinakaran Thipramalai Thangappan Ajith Kumar Kuldeep K., 2018, Two new distributional records of Palaemonella Dana, 1852 shrimps (Decapoda: Caridea: Palaemonidae) from Lakshadweep Islands, India, Nauplius (e 2021049) 29, pp. 1-18 : 3-7

Palaemonella tenuipes Dana, 1852

( Figs. 1–3)

Palaemonella tenuipes Dana, 1852: 25 . — Bruce, 2002a: 288. — Komai and Yamada, 2015: 360.

Palaemonella tridentata Borradaile, 1898: 1007 , pl. 64, figs. 8a–c

Palaemonella elegans Borradaile, 1915: 210 .

Material examined. NBFGR /PALPTEN.01 (1 ovigerous female, CL: 2.5 mm, ID no: NBFGR: DBTLD20 ) Arabian Sea , off Agatti Islands , Lakshadweep, India (10°83’4”N 72°18’ 25”E); 5 females (CL: 2.5–2.7 mm, ID no: NBFGR: DBTLD81 , 81 A, NBFGR: DBTLD206 , 206 A, 206B), Arabian Sea, off Agatti Islands, Lakshadweep, India (10°83’5”N 72°18’33”E), 0.5–1 m depth, temperature 28.1 o C, salinity 35 ppt, March 2020 .

Diagnosis. Body glabrous, small; rostrum usually straight, slightly extended beyond distal end of third antennular peduncle, distal end directed slightly upward, dorsally armed with 7 strong teeth including 1 epigastric tooth; epigastric tooth situated on carapace behind orbital angle; rostrum ventrally armed with 2 teeth, situated at level of fourth and fifth dorsal teeth. Carapace smooth, without supraorbital spine; hepatic spine appears directed slightly upward; inferior orbital angle extended like triangle; antennal spine well developed, reaching near to the middle of eyestalk; pterygostomial region rounded.Antennal scaphocerite broad, with distolateral tooth overreaching level of distal margin of lamella ( Fig. 2A). Abdominal tergites smooth, third one extending over fourth tergite dorsoposteriorly; posteroventral angle of fourth and fifth pleura extended like triangular lobe, sixth pleura with posteroventral, posterolateral teeth. Telson about 1.5 times as long as sixth abdominal segment length, bearing 2 pairs of dorsolateral spines, and 3 pairs of posterior telson spines ( Fig. 2H), lateral spine similar to dorsolateral spines, intermediate spine slender, long, submedian pair extended to middle of intermediate one. Mandible with small 2-segmented palp ( Fig. 2B). Third maxilliped reaching almost to distal end of third antennular peduncle; exopod slightly thick, reaching distal end of antepenultimate segment; penultimate segment about0.8times as long as antepenultimate, 1.3 times longer than ultimate segment. First pereiopod thin, overreaching distal end of antennal scaphocerite by length of carpus and chela; merus equal to carpus; carpus about 2.0 times as long as palm, 1.3 times as long as chela ( Fig. 2C), few long sensory setae present distoventrally; fingers about 0.95 times as long as palm, inner margin smooth, distally armed with tooth ( Fig. 2D). Second pereiopod slightly asymmetrical, extending beyond distal end of scaphocerite by halflength of carpus; merus bearing strong distoventral tooth, about 1.06 times as long as carpus; carpus about 3.5 times as long as distal width, 0.7 times palm length, with sub-terminal spine distally; palm about 3.8 times as long as maximum width, 1.75 times longer than fingers; fingers with two small teeth in proximal region ( Figs. 2E, F). Pereiopods III– V slender and extending beyond the distal end of scaphocerite; merus about 1.7–1.8 times as long as carpus; carpus about 0.5 times propodal length; propodus long, with 3–4 spines, and long distal pair ventrally, about 3.6–4.0 times as long as dactylus; dactylus simple, curved slightly, with few long setae present dorsally and ventrally, about 4.5–5.0 times proximal width ( Fig. 2G).

Ecological information. The specimens were found in shallow barren pools on rocky flats near the shore of Agatti Island, Lakshadweep, at the depth of 0.5–1 m.

Coloration in life. Carapace, abdomen, and appendages are transparent. All of the pereiopods and pleopods are transparent. The second pereiopod fingers have a muddy brownish band; each joint with a muddy-brownish band. Eyes are translucent with a dark brownish cornea with a small dark spot dorsally. Matured eggs are muddy greenish.

Geographical distribution. Palaemonella tenuipes widely occurs in shallow water depths and is extensively distributed throughout the Indo-West Pacific region ( Fig. 3). Scattered records extend from the Red Sea to the Line Islands, through Madagascar, Seychelle Islands, Maldive Islands, Chagos Islands, Malaya to the Ryukyu Islands, Marshall Islands, Fijian Islands, Society Islands, Wake Island, and Johnson Atoll ( Bruce, 2002b). However, this species has not previously been reported from the Lakshadweep region, and Indian waters.Agatti Island is a new record among these regions.

Remarks. The six specimens examined were collected from 0.5–1 m depth. One specimen lost both the second pereiopods, but other specimens were in good condition with mature eggs. Accordingly, we could positively characterize it as P. tenuipes by the presence of a moderately slender dactylus on ambulatory pereiopods about 4.4–5.6 times as long as basal width, the second pereiopod of the merus with a strong distoventral spine, carpus with a sub-terminal distal spine, and absence of a supraorbital spine. The present Indian materials agreed well with the illustrated keys of Bruce (2002a), and Komai and Yamada (2015). The present report of P. tenuipes from India represents the shallowest depth recorded from the Indian Ocean and it is the first report from Lakshadweep, Indian waters.

Palaemonella tenuipes is morphologically very close to P. rotumana and P. pottsi , which were previously collected from the Lakshadweep Islands. Palaemonella tenuipes differs from P. rotumana (Indian material) by the length of the carpus (more than 6.7times the distal width, and 2.0 times as long as palm) compared to P. rotumana (carpus is 6.1 times as long as distal width, and 2.2 times palm length). Palaemonella tenuipes is distinguished from P. pottsi by the presence of the transparent body and a muddy brownish band on the fingers of the second pereiopods, the presence of a carpal sub-terminal spine, and scaphocerite length 3.8 times as long as maximum width; P. pottsi has a transparent body with a dark black band on the fingers of second pereiopods, and the scaphocerite is3.6 times longer than the maximum width.