Periclimenella agattii, Bharathi & Purushothaman & Akash & Jose & Madhavan & Dhinakaran & Saravanane & Kumar & Lal, 2019

Bharathi, S., Purushothaman, P., Akash, S., Jose, Sheena, Madhavan, Manu, Dhinakaran, A., Saravanane, N., Kumar, T. T. Ajith & Lal, Kuldeep Kumar, 2019, Periclimenella agattii sp. nov., a new Palaemonid shrimp (Crustacea, Decapoda, Palaemonidae) from Lakshadweep Islands, India, Zootaxa 4706 (3), pp. 483-493 : 484-490

Periclimenella agattii sp. nov.

( Figs. 1–4 )

Material examined: Holotype: NBFGR-PALPAGA01, male (CL 1.0 cm), Arabian Sea , off Agatti Islands, Lakshadweep, India, 10°50’41”N, 72°11’23”E, 1–3 feet, December 2018.

Diagnosis. Periclimenella species with rostrum is directed dorsally or straight, rostral dentition 5–7/3–5 with an epigastric tooth. Antennal and hepatic spines are small; antennal spine is situated marginally and hepatic spine appears slightly lower to antennal spine. Orbital angle ovate and cornea globular with small dark accessory pigment present on dorsally at distal end of stalk. Thoracic sternite 4 with an acute median process. The posterio-dorsal margin of 3 rdabdominal somite denticulate finely. First pereiopod slender, fingers with denticulate cutting edges are situated laterally; well-developed second pereopod with carpus bearing two strong teeth distally, third to fifth pereiopods dactylus are simple with curved sharp unguis, propods spinulate disto-ventrally. Telson bearing 3 pairs of dorsolateral spines with 2 pairs of spinules posteriorly.

Description: Body moderately compressed and glabrous ( Fig 1 , 2a,b ). Rostrum is longer than carapace (1.31– 1.5 times in males and 1.08–1.15 times in females) ascending anteriorly, and slightly reaching distal end of antennal scale; rostral teeth formula:5+1/3 for females and 6+1/3 for males with anteriorly directed, 1 stdosral teeth is situated on anterior of post-orbital margin; 1 stventral rostral teeth is in middle of rostrum.

Carapace (fig. 2a,b): Small supra-orbital spine present; antennal and hepatic spines well developed, hepatic spine is situated slightly lower and posterior to antennal spine with haptic groove; pterygostomial angle rounded. Fourth thoracic sternite with minute median tooth, fifth sternite having transverse ridge with median notch.

Abdomen with third somite projecting fine denticulate in posterodorsally; pleura of first to four somites broadly rounded, fifth slightly produced posteriorly and blunt, sixth one with slightly projecting, sharp posterolateral angle, rounded posteroventral angle.

Telson (fig. 2c,d) about 2.8 times as long as anterior width, few long setae on middle of anterior side, lateral margins straight, posterior margin triangle with a projection, about 0.28 anterior width; dorsal surface of telson with two pairs movable and well-developed spines; posterior margin with one pair of lateral spines, intermediate and submedian are spiniform; lateral one similar to dorsal spines; intermediate spiniform setae stouter and at least six times longer than to lateral spines, each about 0.3 telson length; submedian spiniform setae slender, about 0.5 length of intermediate spiniform setae. Uropods ovoid shape with distolateral tooth and long movable spine; just extended beyond distal end of telson.

Eyes: large with globular shaped cornea and small accessory dark pigment spot present on dorsally at distal end of stalk; eyestalk slightly depressed.

Antennular peduncle (fig. 2f): Proximal segment flattened and 2.1 times longer than broad with disto-lateral spine; stylocerite short and distally acute; upper flagellum biramous, fused with 14–16 segments, short free ramus 12–13 segments and about 18 groups of aesthetascs; lower flagellum thin and longer than upper one with 35–37 segments. Antenna with basicerite bearing distolateral tooth; carpocerite reached to distal end of basal antennular segment; scaphocerite elongate, concave laterally with a strong distolateral spine extending well beyond anterior margin of lamina, lamina is 3.9 times longer than the maximum width, flagellum well developed.

Mandible (fig. 2g) without palp, molar process stout and provided with 2 strong obtuse teeth, incisor process short with truncate tip armed with 3 broad teeth. Maxillula with bilobed palp, upper lobe without setae and lower lobe with small hook-shaped setae. Maxilla with simple palp, basal endite bilobed, exopod with caridean lobe well developed, flagellum broad, densely setose distally. The first maxilliped with basial and coxal endites short, broad, flattened and medially fringed with sparse short simple setae. 2nd maxilliped with large epipod and long exopod fringed with setose distally, fourth and fifth fringed with long setae distally. Third maxilliped (fig. 2l) slender, coxa with rounded lateral plate, without epipod; having slender exopod barely extended distal end of antepenultimate article; endopod slender, and reaching to distal end of carpocerite; antepenultimate article somewhat twisted with 4 distolateral spines and long setose, ultimate article tapering with minute terminal spinule and numerous setae.

First pereiopod (fig 3a,b) slender and extending beyond the distal end of scaphocerite; ischium is 0.4 times length of merus, merus is slightly shorter than carpus, 7 times as long as wide, carpus double the length of chela, 7.5 times as long as distal width, chela with palm slightly compressed, with numerous groups of setae on ventral (13–14) and dorsal (5–6) side; fingers about 1.45 length of palm, concave, slightly gaping, with small terminal tooth; cutting edges of fingers denticulate laterally.

Major second pereiopod ( Fig. 3c ) robust, elongate and extending beyond antennular flagellum. Chela slender; Palm smooth, subcylindrical, tapering slightly to distal end and about 3.6–4.0 times longer than depth; fingers slen- der, 0.76 times long as palm with numerous long setae; Dactylus about 0.4 of palm length, slender, about 3.8 times longer than proximal depth, inner basally a tooth and lateromedially a blade like plate are present, distally concave with acute terminal end; Fixed finger with 2–3 large teeth basally, tapering to distally and concave terminal with acute end; Carpus very short, tapering proximally, about 1.7 times longer than distal width with 2 strong teeth on distal margin, palm:carpus ratio for Ovig female is 3.3 and for adult male is 4.1–4.3; merus with straight dorsal and ventral margins, about 0.4 of palm length, 3.5 times longer than width with strong distal tooth; Ischium slender, about 0.61 of palm length, 5.1 times longer than distal width, tapering slightly proximally, unarmed.

Minor second pereiopod ( Fig 3e ) is similar but noticeably more slender than major second pereiopod; chela more slender; palm smooth, about 4.4 times as long as depth; fingers are about 0.7 lengths of palm; Dactylus is about 3.9 times longer than proximal depth with inner basally a strong tooth and lateromedially a blade like plate are present, distally concave with acute terminal end; Fixed finger with 2 large teeth basally, tapering to distally and concave terminal with acute end; Carpus short with two distal teeth, about 0.3 length of palm; merus about 3.5 times as long as depth almost equal length to merus length of major pereopod with a distal tooth; Ischium is about 0.37 of palm length, 4.6 times longer than distal width.

Ambulatory pereiopods (fig. 3f–h) are long and slender; third pereiopod is extending near to distal end of scaphocerite, dactylus short, simple, curved and terminally sharped end with long setae, about 0.18 length of propodus; propodus about 13.5 times as long as depth, ventral margin With 7–8 ventral spiniform setae including a distal pair; compressed carpus, dorso-distally extended projection, about 4 times longer than depth, unarmed; merus about 0.9 of carpus length and about 7.5 times as long as depth, unarmed; ischium about 0.4 of merus length, 3.3 times length of distal width.

Endopod (fig. 3i) of 1 st peleopod leaf-like, basao-laterally concave and dorsally ovoid shape with long plumose setae; Second pleopod with appendix masculine (fig. 3j) is shorter than appendix interna, furnished with slender spiniform setae on distally; appendix masculina tapering distally with furnished long setae.

Living Coloration: Carapace very transparent; pereopods and peleopods are transparent light greenish; merus, carpus, propodus are semi-transparent or transparent light greenish with few black dots; dactylus is semi-transparent and covered with small brown or black dots; pleon is semi-transparent and 2 nd to 4 th pleura with small white dot is marking on each side, which presents distally. Telson and uropods are transparent and light brownish in distally.

Eye: cornea with semi-transparent or ash in colour, eyes-stalk is semi-transparent with transverse deep brown bands.

Distribution and ecology: Present specimens are observed only from the type locality of intertidal regions in Agatti Island (10°50’41”N, 72°11’23”E) at the depth of 1–3 feet. These species are living inside the holes of coral boulders and rock, and it was noticed that, not associated with other organisms. It is indicated that the species has to be a free-living browser. Basically, it shows slow movement while coming out from the rock. However,when it is threatened by a predator, it will scattered by the fast and jump movement, which make difficulties and confusion to the predators. The estimated egg size is 0.50–0.55 mm.

Etymology: The species name is derived from the current distributional location of the new species (Agatti Island).

Paratypes: 10 females (CL 0.5–1.2 cm), 7 males (CL 0.5–1.1 cm) Arabian Sea , off Agatti Island, Lakshadweep, India, 10°50’41”N, 72°11’23”E, 1–3 feet, December 2018 .

Remarks: The present material provides data on the morphological variability of Periclimenella agattii sp. nov. There are some remarkable differences between sexes, rostrum in male is slightly longer and reaching the end of the antennal scale, while it is near to the end of the antennal scale in female (fig. 1). Even, male dorsal teeth of rostrum (6+1) are higher than female (5+1). The male has antennal upper flagellum fused with 14–15 segments, short free ramus 12 segments and lower flagellum contains 35–36 segments. While, the female has 16 segments in upper flagellum with 13 segments of short free ramus and 37 in the lower flagellum. The pleopodal basipodites are thick and without setae in males but slender in females with numerous long plumose setae.

Periclimenella agattii sp. nov. is morphologically very close to Periclimenella spinifera ( De Man, 1902) , 3 ventral teeth in rostrum, supraorbital spine and orbital angle, first pereopods with subspatulate fingers and concave with denticulate cutting edges are situated laterally; palm bearing rows of brush-like setae. Second pereiopod chelae unequal and dissimilar; fingers of major second pereiopod bearing teeth in the inner side of base and dactylus contains lateromedially a blade like a plate. Telson bearing 3 pair of dorsolateral spines.

Periclimenella agattii sp. nov. may be readily distinguished from P. spinifera by the presence of variation in rostral length and dentations ( Table 1 ), strong hepatic spine with groove, upper antennal flagellum biramous, having 14–16 segments, with 12–13 segments in short free ramus; lower antennal flagellum thin and bearing 35–37 segments and longer than upper one. Middle of inner boarder of first antennular peduncle without spine. The basal segment of 3 rd maxilliped contains 4 lateral minute spines. 1 st pereopod of chela compressed with 13–14 group of setae on ventrally and 5–6 in dorsally. Chela of minor second pereiopod dentate appearance similar to chela of major pereopod. Ratio of palm and carpus length of 2 nd pereopod in ovig female 3.3 and in adult male 4.1. 7–8 ventral spines (including distal pair) in 3 rd pereopods. P. spinifera is widely distributed in Indo-West Pacific localities, originally from Seychelles ( Bruce, 1971; 1976), Reunion ( Bruce, 1983a), Maldive Islands ( Bruce, 1974), Burma ( Sastry, 1981), Singapore ( Johnson, 1963), South China Sea ( Bruce, 1979), Moluccas ( Bruce, 1983b), Ryukyu Islands ( Nomura et al., 1988), Mariana and Marshall Islands ( Holthuis, 1953; Devaney and Bruce, 1987), Northern Territory, Australia ( Bruce, 1983c; 1987b), Great Barrier Reef, Australia ( Patton, 1966; Bruce, 1981a; 1983d; 1987b), Fiji ( Bruce,1981 b). Currently, the distribution of P. agattii sp. nov. is observed only in Agatti Island and also further studies are required to know the distributional range of the species in Indian waters.

Further, Periclimenella agattii sp. nov. and P. spinifera are differed from P. petitthouarsii by presences of the supraorbital spines which are constant characters to distinguish it. P. petitthouarsii was distributed in the Gulf of Aden, Tanzania, Kenya, Comoro Islands, and north-east of Madagascar ( Bruce, 1977).

Genus Periclimenella is close related to genera Cuapetes and Exoclimenella by having the same character of the presence of the median process on the fourth thoracic sternite ( Kou et al., 2013). We have generated two COI sequences for the present species (Accession no: MN163278 , MN163279 ) and the genetic divergence was estimated with P. spinifera available from Genbank. It shows the 16.5% COI sequences variation. Additionally, two 16S gene sequences ( MN164640 , MN164641 ) are also generated for this species. The sum of 476 bp for 16S and 604 bp for COI positions of final data set are used phylogenetic analysis. Itshows that both genes data of the present species forms a robust monophyletic clade with topotypic P. spinifera specimen ( Fig 5 and 6 ). The interspecific genetic divergences of 16S are 6.6 ( KU064848 ), 12.6% ( JX025194 ). Specimen of JX025194 was showed greater genetic distance with P. spinifera itself which might be the reason that specimen was misidentified. In general, greater than 3% of COI sequence divergences have been generally considered as indicating a different species in crustaceans groups (e.g., Hebert et al., 2003; Cha n et al., 2009; Radulovici et al., 2009; Purushothaman et al., 2019). The obtained results of both COI and 16S genes data are showed greater variation with P. spinifera and overall the results are strongly supporting to the morphological discovery of new species from the Lakshadweep Islands.

Figures

FIGURE 1. Picture representation of Periclimenella agattii sp. nov. from Agatti Island, India; (A, Female, B, Male; Scale bar—1 cm)

FIGURE 2. Periclimenella agattii sp. nov., a—Lateral view of carapace (Male), b—Lateral view of carapace (female); c— Dorsal view of telson; d—close view of posterior end of telson; e—antennal Scale, f—Antennular peduncle, g—Mandible, h—Maxillula, I-Maxilla, j—Maxilliped 1, k—Maxilliped 2, l—Maxilliped 3.

FIGURE 3. Periclimenella agattii sp. nov. from Lakshadweep, India, a—Pereopod 1, b—close view of 1st pereopod chela; c—2nd major pereopod, d—close view of 2ndpereopod chela; e—2nd minor pereopod, f—3rd Pereopod, g—4th Pereopod, h—5th Pereopod, i—1stPeleopod, j—Appendix masculina, k—Uropod. Scale—1 mm.

FIGURE 4. Picture representations of Periclimenella agattii sp. nov. in live.

FIGURE 5. ML phylogenetic tree from partial sequences (604 bp) of COI gene for Periclimenella agattii sp. nov. with P. spinifera available sequences from GenBank.

FIGURE 6. ML phylogenetic tree from partial sequences (476 bp) of 16S gene for Periclimenella agattii sp. nov. with P. spinifera available sequences from GenBank.

Tables

TABLE 1. Morphological differences between Periclimenella agattii sp. nov. and Periclimenella spinifera (De Man, 1902) as described by Ďuriš & Bruce (1995).

Morphological Characters	Periclimenella agattii sp. nov.	Periclimenella spinifera
		( Ďuriš & Bruce, 1995)
Rostrum longer than CL	Females: 1.08–1.15 times	Female: 1.36–1.47 times
Antennular flagellum	Upper biramous, having 14–16 segments,	Upper biramous, having 10–12 segments,
	short free ramus with 12–13 segments.	short free ramus with 2–3 segments.
1st Antennular penducle	Lower one, thin with 35–37 segments Middle of Inner boarder without spine	Lower one, thin with 30 segments Middle of Inner boarder with minute spine
3rd maxilliped	Basal segment contains 4 lateral minute	Basal segment contains 3 lateral minute
Second pereopod: palm:	spines Adult male: 4.1	spines Adult male: 2.5–2.6
carpus ratio 3rd pereopod -propodus	With 7–8 ventral spines (including distal	With 9–10 ventral spines (including distal
Carapace	pair) Hepatic spine with groove	pair) Hepatic spine without groove