Abstract

The present study reports two new distributional records of palaemonid shrimp, Palaemonella tenuipes Dana, 1852, and P. rotumana (Borradaile, 1898) from the Lakshadweep region, Arabian Sea. The study provides detailed information on, and insight into, diagnostic characters, distinctiveness, and illustrations of both species. The individuals of P. tenuipes were collected from a depth of about 0.5 m in shallow barren pools on rocky flats near the shore, while a specimen of P. rotumana was collected from a dead coral patch at a depth of 1-2 m. The intraspecific genetic divergences were estimated for both species using COI and 16S sequence data.

Keywords
Arabian Sea; First record; Genetic divergences; Palaemonella; Palaemonid shrimp

INTRODUCTION

In the Lakshadweep Sea, the corals form a reef system that is home to globally significant populations of green and hawksbill turtles, whale sharks, reef sharks, and many marine invertebrates (Ajith Kumar, 2012Ajith Kumar, T.T. 2012. Glimpses of marine biodiversity at Lakshadweep. Uttar Pradesh state biodiversity board, Lucknow, 1-8.). Despite this biodiversity, more knowledge is needed on the diversity of marine invertebrates in the region of the Lakshadweep islands. Continuous biodiversity studies have been carried out in the Lakshadweep intertidal regions since 2018, and have successfully yielded many caridean shrimps such as Lysmata amboinensis (de Man, 1888de Man, J.G. 1888. Bericht über die von Herrn Dr. J. Brock imindischen Archipelges ammelten Decapoden und Stomatopoden. Archivfür Naturgeschichte, 53 (3): 289-600, pls. 11-22a. [in de Man, 1887-1888]), L. hochi Baeza and Anker, 2008Baeza, J.A. and Anker, A. 2008. Lysmata hochi n. sp., a new hermaphroditic shrimp from the Southwestern Caribbean Sea (Caridea: Hippolytidae). Journal of Crustacean Biology, 28: 148-155., L. ternatensis de Man, 1902de Man, J.G. 1902. Die von Herrn Professor Kükenthal im Indiscen Archipel gesammelten Dekapoden und Stomatopoden. Abhandlungen herausgegeben von der Senckenbergischen Naturforschenden Gesellschaft, 25: 466-929., Palaemonella pottsi (Borradaile, 1915Borradaile, L.A. 1915. Notes on Carides. Annals and Magazine of Natural History, series 8, 15: 205-213.), Periclimenella agattii Bharati, Purushothaman, Akash, Jose, Madhavan, Dhinakaran, Saravanane, Ajith Kumar and Kumar Lal, 2019, Pontoniopsis comanthi Borradaile, 1915, Synalpheus carinatus (de Man, 1888de Man, J.G. 1888. Bericht über die von Herrn Dr. J. Brock imindischen Archipelges ammelten Decapoden und Stomatopoden. Archivfür Naturgeschichte, 53 (3): 289-600, pls. 11-22a. [in de Man, 1887-1888]), S. comatularum (Haswell, 1882Haswell, W.A. 1882. Description of some new species of Australian Decapoda. Proceedings of the Linnaean Society of New South Wales, 6(4): 750-763.), S. stimpsonii (de Man, 1888de Man, J.G. 1888. Bericht über die von Herrn Dr. J. Brock imindischen Archipelges ammelten Decapoden und Stomatopoden. Archivfür Naturgeschichte, 53 (3): 289-600, pls. 11-22a. [in de Man, 1887-1888]), Thor hainanensis Xu and Li, 2014Xu, P. and Li, X. 2015. Report on the Hippolytidae Bate (sensu lato) from China seas. Zoological Systematics, 40: 107-165., and Urocaridella arabianensis Akash, Purushothaman, Madhavan, Ravi, Hisham, Sudhakar, Kumar and Kuldeep, 2020 (see Bharathi et al., 2019Bharathi, S.; Purushothaman, P.; Akash, S.; Jose, S.; Madhavan, M.; Dhinakaran, A.; Saravanane, N.; Ajith Kumar, T.T. and Lal, K.K. 2019. Periclimenella agattii sp. nov., a new palaemonid shrimp (Crustacea, Decapoda, Palaemonidae) from Lakshadweep Islands, India. Zootaxa, 4706: 483-493.; Madhavan et al., 2019Madhavan, M.; Purushothaman, P.; Akash, S.; Bharathi, S.; Sheena, J.; Dhinakaran, A.; Charan, R.; Ajith Kumar, T.T. and Lal, K.K. 2019. New record of Thor hainanensis Xu & Li, 2014 and taxonomical remarks on Lysmata ternatensis de Man, 1902 (Decapoda: Thoridae & Lysmatidae) from the Lakshadweep Islands, India. Zootaxa, 4624: 351-364. ; Akash et al., 2020Akash, S.; Purushothaman, P.; Madhavan, M.; Ravi, C.; Hisham, T.J.; Sudhakar, M. and Kuldeep, L.K. 2020. Urocaridella arabianensis n. sp., a new palaemonid shrimp (Crustacea, Decapoda, Palaemonidae) from Lakshadweep Islands, India with taxonomic comparison on the genus Urocaridella Borradaile, 1915. Zootaxa, 4816: 49-66.; Jose et al., 2020Jose, S.; Purushothaman, P.; Madhavan, M.; Akash, S.; Bharathi, S.; Dhinakaran, A.; Ajith Kumar, T.T. and Lal, K.K. 2020. Two new records of hippolytoid shrimps, Lysmata hochi Baeza & Anker, 2008 (Decapoda: Lysmatidae) and Lysmata amboinensis (de Man, 1888) from Lakshadweep Islands, India with taxonomic notes. Zootaxa, 4755: 353-364.; Prakash and Marimuthu, 2020Prakash, S. and Marimuthu, N. 2020. Notes on some crinoid associated decapod crustaceans (Crustacea: Decapoda) of Lakshadweep Archipelago, Central Indian Ocean. Zootaxa, 4766: 86-100.).

Shrimps of the genus PalaemonellaDana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28. are commonly distributed in the Indo-West Pacific region and occur in wide bathymetric ranges from intertidal to 544 m depth (Bruce, 1970Bruce, A.J. 1970. Observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda, Pontoniinae). Crustaceana, 19: 273-287.; 2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18., 2002bBruce, A.J. 2002b. Notes on some Indo-Pacific Pontoniinae, XLVI. Palaemonella foresti sp. nov., a new pontoniine shrimp from Western Australia (Decapoda, Palaemonidae), with a review of the Indo-West Pacific species of the genus Palaemonella Dana, 1852. Crustaceana, 75: 277-298.; 2006Bruce, A. J. 2006. Pontoniine shrimps (Decapoda: Palaemonidae) from the island of Socotra, with descriptions of new species of Dactylonia Fransen, 2002 and Periclimenoides Bruce, 1990. Zootaxa, 1137: 1-36.; 2008Bruce, A.J. 2008. A new species of Palaemonella Dana, 1852, (Crustacea: Decapoda; Pontoniinae) from the Red Sea. Zootaxa, 1844: 63-68.; 2010Bruce, A.J. 2010. Palaemonella dijonesae sp. nov. (Crustacea: Decapoda: Pontoniinae) from Western Australia. Zootaxa, 2372: 151-156.; Hayashi, 2001Hayashi, K. 2001. Prawns, shrimps and lobsters from Japan (117). Family Palaemonidae, subfamily Pontoniinae - Genus Palaemonella. Aquabiology, 133: 160-164. [in Japanese]; Li and Bruce, 2006Li, X. and Bruce, A.J. 2006. Further Indo-West Pacific palaemonoid shrimps (Crustacea: Decapoda: Palaemonoidea), principally from the New Caledonian region. Journal of Natural History, 40: 611-738.; Marin, 2008Marin, I.N. 2008. Description of two new species from the genera Palaemonella Dana, 1852 and Vir Holthuis, 1952 (Crustacea: Caridea: Palaemonidae: Pontoniinae). Zoologische Mededelingen, 82: 375-390.; Komai and Yamada, 2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.; Okuno, 2017Okuno, J. 2017. Palaemonella shirakawai, a new species of shrimp (Crustacea: Decapoda: Palaemonidae), associated with burrow dwelling opistognathid fish from the Ryukyu Islands, Japan. Zootaxa, 4299: 521-528.). Currently, the genus consists of 23 valid species worldwide (De Grave and Fransen, 2011De Grave, S. and Fransen, C.H.J.M. 2011. Carideorum Catalogus: the recent species of the Dendrobranchiate, Stenopodidean, Procarididean and Caridean Shrimps (Crustacea: Decapoda). Zoologische Mededelingen 85: 195-589.; Komai and Yamada, 2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.; Okuno, 2017Okuno, J. 2017. Palaemonella shirakawai, a new species of shrimp (Crustacea: Decapoda: Palaemonidae), associated with burrow dwelling opistognathid fish from the Ryukyu Islands, Japan. Zootaxa, 4299: 521-528.), among which three species are reported from Indian waters: Palaemonella rotumana (Borradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391.) and Palaemonella lataKemp, 1922Kemp, S. 1922. Notes on Crustacea Decapoda in the Indian Museum. XV. Pontoniinae. Records of the Indian Museum, 24: 113-288. from Andaman and Nicobar Islands (Radhakrishnan et al., 2012Radhakrishnan, E.V.; Deshmukh, V.D.; Maheswarudu, G.; Josileen, J.; Dineshbabu, A.P.; Philipose, K.K.; Sarada, P.T.; Pillai, S.; Lakshmi, S.K.N.; Chakraborty, R.D.; Dash, G.; Sajeev, C.K.; Thirumilu, P.; Sridhara, B.; Muniyappa, Y.; Sawant, A.D.; Vaidya, N.G.; Johny, R.D.; Verma, J.B.; Baby, P.K.; Unnikrishnan, C.; Ramachandran, N.P.; Vairamani, A.; Palanichamy, A.; Radhakrishnan, M. and Raju, B. 2012. Prawn fauna (Crustacea: Decapoda) of India-An annotated checklist of the Penaeoid, Sergestoid, Stenopodid and Caridean prawns. Marine Biological Association of India, 54: 50-72.; Samuel et al., 2016Samuel, V.K.D.; Sreeraj, C.R.; Krishnan, P.; Parthiban, C.; Sekar, V.; Chamundeeswari, K.; Immanuel, T.; Shesdev, P.; Purvaja, R. and Ramesh, R. 2016. An updated checklist of shrimps on the Indian coast. Journal of Threatened Taxa, 8: 8977-8988.), and Palaemonella pottsi (Borradaile, 1915Borradaile, L.A. 1915. Notes on Carides. Annals and Magazine of Natural History, series 8, 15: 205-213.) from the Lakshadweep islands (Prakash and Marimuthu, 2020Prakash, S. and Marimuthu, N. 2020. Notes on some crinoid associated decapod crustaceans (Crustacea: Decapoda) of Lakshadweep Archipelago, Central Indian Ocean. Zootaxa, 4766: 86-100.). Similar to other members of the family Palaemonidae Rafinesque, 1815Rafinesque, C.S. 1815. Analyse de la nature ou tableau de l’univers et des corps organisés. Self published, Palermo, 224p., they have a subcylindrical body, a well-developed rostrum with ventral and dorsal teeth, a fourth thoracic sternite with spiniform median process, and a simple dactylus on the third to fifth pereiopods. However, the morphological characters of this genus are very close to the genus CuapetesClark, 1919Clark, A.H. 1919. Some necessary changes in crustacean nomenclature. Proceedings of the Biological Society of Washington, 32: 199., and specifically differ by the presence of a mandibular palp and slender dactylus on the third to fifth pereiopods in Palaemonella (Chace and Bruce, 1993Chace Jr, F.A. and Bruce, A.J. 1993. The caridean shrimps (Crustacea: Decapoda) of the Albatross Philippine expedition 1907-1910, part 6: superfamily Palaemonoidea. Smithsonian Contributions to Zoology, 543: 1-152.). The species of the genus Palaemonella are mostly free-living, while some species are symbionts such as: Palaemonella aliska Marin, 2008 associated with alpheid shrimps; P. pottsi associated with the crinoids Stephanometra tenuipinna (Hartlaub, 1890Hartlaub, C. 1890. Beitrag zur Kenntniss der Comatuliden-Fauna des indischen Archipels. Nachrichten von der Königlichen Gesellschaft der Wissenschaften und der Georgs-August-Universität zu Göttingen, 5: 168-187.) (Bruce, 1970Bruce, A.J. 1970. Observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda, Pontoniinae). Crustaceana, 19: 273-287.), and Phanogenia gracilis (Hartlaub, 1893Hartlaub, C. 1893. Beitrag zur Kenntnis der Comatulidenfauna des Indischen Archipels. Nova Acta Kaiserlichen Leopold.-Carol. Deutschen Akademie der Naturforschungen, 58: 1-120.) (Prakash and Marimuthu, 2020Prakash, S. and Marimuthu, N. 2020. Notes on some crinoid associated decapod crustaceans (Crustacea: Decapoda) of Lakshadweep Archipelago, Central Indian Ocean. Zootaxa, 4766: 86-100.); and P. rotumana (Borradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391.), which is known as a facultative symbiont of scleractinian corals, but also occurs in dead coral boulders (Kemp, 1922Kemp, S. 1922. Notes on Crustacea Decapoda in the Indian Museum. XV. Pontoniinae. Records of the Indian Museum, 24: 113-288.; Bruce, 1970Bruce, A.J. 1970. Observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda, Pontoniinae). Crustaceana, 19: 273-287.; 1975Bruce, A.J. 1975. Further observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda: Pontoniinae). Crustaceana, 29: 169-185.; Marin, 2008Marin, I.N. 2008. Description of two new species from the genera Palaemonella Dana, 1852 and Vir Holthuis, 1952 (Crustacea: Caridea: Palaemonidae: Pontoniinae). Zoologische Mededelingen, 82: 375-390.).

During the recent survey conducted off Agatti Island, Lakshadweep, some specimens of Palaemonella were collected with Cuapetes sp. and Periclimenella agattii from the intertidal regions of 0.5-2 m depth. Careful examination of the Palaemonella specimens revealed the presence of Palaemonella tenuipesDana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28., and P. rotumana, representing new distributional records for the Lakshadweep waters. A detailed study on morphology and molecular characters were carried out on these two species.

MATERIAL AND METHODS

The specimens were collected from the intertidal regions of Agatti Island, Lakshadweep, India, by handpicking and snorkeling during March 2020. The specimens were examined under a stereo zoom microscope (Nikon SMZ1270) and identified according to Kemp (1922Kemp, S. 1922. Notes on Crustacea Decapoda in the Indian Museum. XV. Pontoniinae. Records of the Indian Museum, 24: 113-288.), Bruce (2002aBruce, A.J. 2002b. Notes on some Indo-Pacific Pontoniinae, XLVI. Palaemonella foresti sp. nov., a new pontoniine shrimp from Western Australia (Decapoda, Palaemonidae), with a review of the Indo-West Pacific species of the genus Palaemonella Dana, 1852. Crustaceana, 75: 277-298.), and Komai and Yamada (2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.). The examined specimens are deposited in the National Fish Museum and Repository of ICAR-National Bureau of Fish Genetic Resources (NBFGR), Lucknow, India. The standard measurement used was carapace length (CL: measured from posterior margin of orbital angle to posterior margin of the carapace). The illustrative line images were drawn using the GNU Image Manipulation Program (Version 2.10.12) and all other images were edited with Adobe Photoshop CS2.

Genetic analyses

To find out the genetic divergences and phylogenetic relationships, the total genomic DNA was isolated from 95 % alcohol preserved tissue samples (pleopods and pereiopods) with a DNeasy Blood and Tissue Kit (Qiagen, UK). Partial sequences of the mitochondrial genes cytochrome c oxidase I (COI) and 16S rRNA (16S) were amplified through polymerase chain reaction with the universal primers: COI, Forward (5′-TAAACTTCAGGGTGACCAAAAAATCA-3′) and Reverse (5′-GGTCAACAAATCATAAAGATATTGG-3′) (Folmer et al., 1994Folmer, O.; Black, M.; Hoeh, W.; Lutz, R. and Vrijenhoek, R. 1994. DNA primers for amplification of mitochondrial cytochrome c oxidase subunit I from diverse metazoan invertebrates. Molecular Marine Biology and Biotechnology, 3: 294-299.) and 16S, AR (5'-CGCCTGTTTATCAAAAACAT-3' and BR (5'-CCGGTCTGAACTCAGATCACGT-3') (Palumbi et al., 1991Palumbi, S.; Martin, A.; Romano, S.; McMillan, W.O.; Stice, L. and Grabowski, G. 1991. The simple fools guide to PCR Version 2.0. Honolulu, HI, Department of Zoology and Kewalo Marine Laboratory, University of Hawaii. ), respectively. The 25 µl PCR reaction mixture contained 60 ng of total DNA, 0.5 units of Taq DNA polymerase, 0.3 mM of each primer, 2.0 mM of MgCl_2, 200 mM of dNTPs, and 1X reaction buffer. PCR amplifications were conducted with ProFlex™ 3 x 32-well thermocycler (Applied Biosystems, USA). The annealing temperature for both the gene regions was 50 °C. The PCR, sequencing process and data analysis were carried out following the methods of Akash et al. (2020Akash, S.; Purushothaman, P.; Madhavan, M.; Ravi, C.; Hisham, T.J.; Sudhakar, M. and Kuldeep, L.K. 2020. Urocaridella arabianensis n. sp., a new palaemonid shrimp (Crustacea, Decapoda, Palaemonidae) from Lakshadweep Islands, India with taxonomic comparison on the genus Urocaridella Borradaile, 1915. Zootaxa, 4816: 49-66.).

The sequence quality was screened with an ABI Sequence Scanner v1.0. The sequence editing and aligning process were performed with Clustal W multiple alignment program at Bioedit tool v. 5.0.9 (Thompson et al., 1994Thompson, J.D.; Higgins, D.G. and Gibson, T.J. 1994. CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic acids research, 22: 4673-4680.). The edited sequences were submitted to the public NCBI database (https://www.ncbi.nlm.nih.gov/). Available COI and 16S sequences of the genus Palaemonella were retrieved from GenBank and BOLD system (Tab. 1). The pairwise genetic divergences were performed in MEGA 10.0.5 (Kumar et al., 2018Kumar, S.; Stecher, G.; Li, M. and Tamura, K. 2018. MEGA X: Molecular evolutionary genetics analysis across computing platforms. Molecular Biology and Evolution, 35 : 1547-1549.). Consequently, the phylogenetic trees for both genes were constructed using the Maximum Likelihood (ML) method with 1000 bootstraps in MEGA 10.0.5 (Kumar et al., 2018Kumar, S.; Stecher, G.; Li, M. and Tamura, K. 2018. MEGA X: Molecular evolutionary genetics analysis across computing platforms. Molecular Biology and Evolution, 35 : 1547-1549.).

TAXONOMY

Family Palaemonidae Rafinesque, 1815Rafinesque, C.S. 1815. Analyse de la nature ou tableau de l’univers et des corps organisés. Self published, Palermo, 224p.

Genus Palaemonella Dana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28.

Palaemonella tenuipes Dana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28.

(Figs. 1-3)

Figure 1.
Preserved specimen of Palaemonella tenuipesDana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28. (ID no: NBFGR: DBTLD206, female, CL 2.5 mm) from Lakshadweep Islands, India.

Figure 2.
Palaemonella tenuipesDana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28. (female, CL 2.5 mm) from Lakshadweep Islands, India. A, dorsal view of antennal scaphocerite; B, lateral view of the mandible, closer; C, lateral view of the first pereiopod; D, dorsal view of first pereiopod chela, closer; E, lateral view of the second pereiopod; F, dorsal view of second pereiopod chela, closer; G, lateral view of the third pereiopod; H, dorsal view of the posterior part of telson.

Figure 3.
Biogeographical distribution of Palaemonella tenuipesDana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28. worldwide.

Palaemonella tenuipesDana, 1852Dana, J.D. 1852. Conspectus crustaceorum quae in orbis terrarum circumnavigatione, Carolo Wilkes e Classe Reipublicae Foederatae Duce, lexit et descripsit. Proceedings of the Academy of Natural Sciences of Philadelphia, 6: 10-28.: 25. - Bruce, 2002aBruce, A.J. 2002b. Notes on some Indo-Pacific Pontoniinae, XLVI. Palaemonella foresti sp. nov., a new pontoniine shrimp from Western Australia (Decapoda, Palaemonidae), with a review of the Indo-West Pacific species of the genus Palaemonella Dana, 1852. Crustaceana, 75: 277-298.: 288. - Komai and Yamada, 2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.: 360.

Palaemonella tridentataBorradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391.: 1007, pl. 64, figs. 8a-c

Palaemonella elegansBorradaile, 1915Borradaile, L.A. 1915. Notes on Carides. Annals and Magazine of Natural History, series 8, 15: 205-213.: 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, 81A, NBFGR:DBTLD206, 206A, 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 about 0.8 times 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 half-length 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, 2002bBruce, A.J. 2002b. Notes on some Indo-Pacific Pontoniinae, XLVI. Palaemonella foresti sp. nov., a new pontoniine shrimp from Western Australia (Decapoda, Palaemonidae), with a review of the Indo-West Pacific species of the genus Palaemonella Dana, 1852. Crustaceana, 75: 277-298.). 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 (2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18.), and Komai and Yamada (2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.). 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 6.7 times 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 is 3.6 times longer than the maximum width.

Palaemonella rotumana ( Borradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391. )

(Figs. 4, 5)

Figure 4.
Palaemonella rotumana (Borradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391.) (male, CL 2.5 mm) from the Lakshadweep Islands. A, lateral view of carapace; B, closer view of antennal spine; C, lateral view of the first pereiopod; D, dorsal view of telson.

Figure 5.
Biogeographical distribution of Palaemonella rotumana (Borradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391.) worldwide.

Periclimenes rotumanusBorradaile, 1898Borradaile, L.A. 1898. A revision of the Pontoniidae. Annals and Magazine of Natural History, 2: 376-391.: 383.

Palaemonella vestigialisKemp, 1922Kemp, S. 1922. Notes on Crustacea Decapoda in the Indian Museum. XV. Pontoniinae. Records of the Indian Museum, 24: 113-288.: 123-126, figs. 1, 2, pl. 3.

Palaemonella rotumana - Bruce, 1970Bruce, A.J. 1970. Observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda, Pontoniinae). Crustaceana, 19: 273-287.: 276-279, pl. 1e-f. - Ďuriš, 2017Ďuriš, Z. 2017. Palaemonid shrimps (Crustacea: Decapoda) of Saudi Arabia from the ‘Red Sea biodiversity survey’ 2011-2013, with 11 new records for the Red Sea. Marine Biodiversity, 47: 1147-1161.: 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:DBTLD65A), 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, 1974Bruce, A.J. 1974. A report on a small collection of pontoniinid shrimps from the Island of Farquhar. Crustaceana, 27: 189-203.; 1979Bruce, A.J. 1979. Records of some pontoniine shrimps from the South China Sea. Cahiers de l’Indo-Pacifique, 1: 215-248.; 2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18.; 2002bBruce, A.J. 2002b. Notes on some Indo-Pacific Pontoniinae, XLVI. Palaemonella foresti sp. nov., a new pontoniine shrimp from Western Australia (Decapoda, Palaemonidae), with a review of the Indo-West Pacific species of the genus Palaemonella Dana, 1852. Crustaceana, 75: 277-298.; Ďuriš, 2017Ďuriš, Z. 2017. Palaemonid shrimps (Crustacea: Decapoda) of Saudi Arabia from the ‘Red Sea biodiversity survey’ 2011-2013, with 11 new records for the Red Sea. Marine Biodiversity, 47: 1147-1161.). The type locality of this palaemonid shrimp is the coast of Rotuma Island, in the Fijian Islands of the central Pacific region (Bruce, 1970Bruce, A.J. 1970. Observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda, Pontoniinae). Crustaceana, 19: 273-287.). 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 (2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18.), and Komai and Yamada (2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.). 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 (2020Prakash, S. and Marimuthu, N. 2020. Notes on some crinoid associated decapod crustaceans (Crustacea: Decapoda) of Lakshadweep Archipelago, Central Indian Ocean. Zootaxa, 4766: 86-100.) 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, 1970Bruce, A.J. 1970. Observations on the Indo-West Pacific species of the genus Palaemonella Dana, 1852 (Decapoda, Pontoniinae). Crustaceana, 19: 273-287.; 2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18.; De Grave, 2000De Grave, S. 2000. Caridean shrimps (Crustacea, Decapoda) from Hansa Bay, Papua New Guinea: Palaemonidae and Gnathophyllidae. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Biologie, 70: 119-148.). 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, 2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18.; Komai and Yamada, 2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.). Palaemonella rotumana are commonly reported from shallow waters to 126 m depth, but the present Indian material was observed at 1-2 m depth in Agatti Island, which is the shallowest recorded depth for this species. Similarly, Li et al. (2004Li, X.; Bruce, A.J. and Manning, R.B. 2004. Some palaemonid shrimps (Crustacea: Decapoda) from northern South China Sea, with descriptions of two new species. The Raffles Bulletin of Zoology, 52: 513-553.) had noted a depth record of 1-2 m at Lingshui County, China.

Genetic analyses

Partial sequences of mitochondrial genes COI and 16S sequences were generated for two individuals of P. tenuipes (COI: MW380740, MW380741, and 16S: MW350006, MW350007) and one individual of P. rotumana (COI: MW351713 and 16S: MW349979), which have subsequently been submitted to GenBank. The pairwise genetic divergences were estimated using the Kimura 2-parameter model with a gamma distribution for both genes against available sequences from Genbank (Tabs. 2, 3). The intraspecific genetic divergence of P. rotumana is 0.08 - 2.7 % for COI and 0.07 % (KU064830; Horká et al., 2016Horká, I.; De Grave, S.; Fransen, C.H.; Petrusek, A. and Ďuriš, Z. 2016. Multiple host switching events shape the evolution of symbiotic palaemonid shrimps (Crustacea: Decapoda). Scientific Reports, 6: 1-13.) for 16S data, except for sequences of JX025197, which showed greater genetic divergence (> 5 %) with present Indian material (Kou et al., 2013Kou, Q.; Li, X.; Chan, T.Y.; Chu, K.H.; Huang, H. and Gan, Z. 2013. Phylogenetic relationships among genera of the Periclimenes complex (Crustacea: Decapoda: Pontoniinae) based on mitochondrial and nuclear DNA. Molecular Phylogenetics and Evolution, 68: 14-22.). It is recommended that these specimens be reexamined in the future (see Tab. 2). For P. tenuipes, the intraspecific genetic divergence ranged from 0.0 - 0.08 %. However, the COI sequences MH339412, MH339413 from Saudi Arabia, and JQ180253 from French Polynesia are not incorporated in the present study, as these sequences show greater genetic variation compared to the total divergence. This might indicate a possible case of misidentification. Further, the phylogenetic tree constructed from Maximum Likelihood (ML) analysis with the available data of P. rotumana, P. tenuipes, and P. pottsi for both gene sequences (Fig. 6) clearly demonstrates that P. rotumana forms a monophyletic clade, which is more closely related to P. pottsi than it is to P. tenuipes. The present molecular findings confirm the morphological identification of these species (Bruce 2002aBruce, A.J. 2002a. A new species of Palaemonella (Crustacea: Decapoda: Pontoniinae) from East Africa. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 18: 15-18.; Komai and Yamada, 2015Komai, T. and Yamada, Y. 2015. A new species of the palaemonid shrimp genus Palaemonella Dana, 1852 (Crustacea: Decapoda: Caridea) from Okinawa Island, Ryukyu Islands, Japan. Zootaxa, 3964: 352-362.). The present reports also strengthen the knowledge of the caridean fauna of Lakshadweep waters.

Figure 6.
Phylogenetic tree constructed by the Maximum likelihood (ML) analysis Hasegawa-Kishino-Yano model using the available data of COI (A) and 16S (B) genes.

ACKNOWLEDGMENTS

The authors thank the Director, ICAR-National Bureau of Fish Genetic Resources for the facilities and encouragement. The Department of Biotechnology (DBT) is acknowledged for financial support. Gratitude is also extended to the Centre for Marine Living Resources and Ecology (CMLRE) and the Department of Fisheries, Lakshadweep administration for the local logistical support. We also sincerely thank the anonymous reviewers for detailed comments and suggestions, which allowed substantial improvements to our manuscript.

REFERENCES

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