Palaemonella rotumana ( Borradaile, 1898 )

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 : 7-9

Palaemonella rotumana ( Borradaile, 1898)

( Figs. 4, 5)

Periclimenes rotumanus Borradaile, 1898: 383 .

Palaemonella vestigialis Kemp, 1922: 123–126 , figs. 1, 2, pl. 3.

Palaemonella rotumana — Bruce, 1970: 276–279, pl. 1e–f. — Ďuriš, 2017: 7.

Material examined. NBFGR /PALPROT.01 (1 male, CL: 2.4 mm, ID no: NBFGR: DBTLD65 ), 1 male (CL: 2.5 mm, ID no: NBFGR: DBTLD65 A), Arabian Sea , off Agatti Islands, Lakshadweep, India, (10°49’50”N 72°10’10”E), 1–2 m depth, temperature 28.1 oC, salinity 35 ppt, March 2020 .

Diagnosis. Rostrum straight, reaching distal end of third antennular peduncle, distal end pointing slightly upward, dorsally armed with 6 teeth, and 2 teeth ventrally ( Fig.4A). Carapace smooth, glabrous, without supraorbital spine; an epigastric tooth found far behind orbital margin; inferior orbital angle well formed; antennal spine well developed, extended far from distal end of inferior orbital angle ( Fig. 4B); hepatic spine small, sharp; pterygostomial region rounded. Eyes well developed, with thick eyestalk, shorter than cornea. Abdominal tergites smooth, rounded dorsally. Mandible with 2-segmented palp. Third maxilliped extending beyond distal end of the rostrum. First pereiopod thin, overreaching distal end of antennal scaphocerite by length of carpus ( Fig. 4C). Fifth pereiopods slender, with dactylus slightly curved inferiorly. Telson bearing 2 well-developed pairs of movable dorsolateral spines; 3 pairs of posterodistal spines, lateral one similar to dorsolateral spine, intermediate spine slender, about 0.3 times as long as telson length, sub-median pair shorter, barely extended past middle of intermediate spine ( Fig. 4D).

Ecological information. The present specimens were collected from dead coral and rocky areas, southwest side of Agatti Island, Lakshadweep, India, at depths of 1–2 m.

Geographical distribution. Palaemonella rotumana is widely distributed throughout the Indo-West Pacific region ( Fig. 5): from the Red Sea to Mozambique, eastwards to Hawaiian Islands with wider bathymetric ranges from 10–126 m ( Bruce, 1974; 1979; 2002a; 2002b; Ďuriš, 2017). The type locality of this palaemonid shrimp is the coast of Rotuma Island, in the Fijian Islands of the central Pacific region ( Bruce, 1970). Presently, the distribution of this species is noted in Agatti Island, Lakshadweep, Arabian Sea, in Indian waters at a depth of 1– 2 m.

Remarks. The present material closely agrees with the morphological keys of Bruce (2002a), and Komai and Yamada (2015). However, the second to fourth pereiopods are missing from the present Indian material with only the fifth pereiopod present. Generally, the preserved specimen of P. rotumana closely resembles P. pottsi in the morphology of the carapace, rostrum orientation, abdominal, and telson structures. Recently, Prakash and Marimuthu (2020) have reported P. pottsi from Amini Island of Lakshadweep at a depth of 10 m, associated with crinoids ( Phanogenia gracilis ). However, both species can be clearly distinguished by the configuration of the dactylus, and propodus of the third to fifth pereiopods ( Bruce, 1970; 2002a; De Grave, 2000). In the present material of P. rotumana , the ventral margin of the dactylus of the fifth pereiopods are smoothly concave, and the distal propodal spines are slender, and overreaching the middle of the dactylus length. In P. pottsi , the ventral margin of the dactylus of the third to fifth pereiopods are sinuous and the distal propodal spines are small ( Bruce, 2002a; Komai and Yamada, 2015). Palaemonella rotumana are commonly reported from shallow waters to 126 m depth, but the present Indian material was observed at 1–2m depth in Agatti Island, which is the shallowest recorded depth for this species. Similarly, Li et al. (2004) had noted a depth record of 1–2 m at Lingshui County, China.