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Das, Mitali, Pahari, Priti Ranjan, Bhattacharya, Tanmay (2021): A new species of palaemonid prawn Macrobrachium ramae sp.nov. (Malacostraca Decapoda:Palaemonidae) from Rupnarayana River, West Bengal, India with its molecular profiles. Zootaxa 4952 (3): 540-550, DOI: https://doi.org/10.11646/zootaxa.4952.3.6

Macrobrachium ramae sp. nov. (Fig. 1–3) Materials examined. Measurements (in mm), HOLOTYPE (1♂, Fig.1A): total length 44.0, carapace length 10.0, rostrum length 9.0, telson length 9.0. First pereiopod: ischium (i) = 2.6, merus (m) = 4.8, carpus (c)= 5.0, propodus (p) = 3.0, dactylus (d) = 1.5. Second pereiopod: i = 5, m = 5.8, c = 8.0, p = 9.0, d = 5.0. Third pereiopod: i = 3.5, m = 6.0, c = 3.0, p = 5.5, d = 2.0. Fourth pereiopod: i = 4.0, m = 6.2, c = 3.8, p = 7.5, d = 2.0. Fifth pereiopod: i = 4.0, m = 6.5, c = 4.0, p = 7.8, d = 2.8. ALLOTYPE (1♀ Fig.1B): total length 64.0, carapace length 16.0,rostrum length 12.0, telson length 10.0. First pereiopod: ischium (i) 4.0, merus (m) 7.0,carpus (c) 9.0, propodus (p) 4.5. dactylus (d) 2.5. Second pereiopod: i = 8.0, m = 9.0, c = 12.5, p = 13.5, d = 7.0. Third pereiopod: i = 3.8, m = 9.0, c = 3.8, p = 6.8, d = 2.5. Fourth pereiopod: i = 4.0, m = 9.0, c = 4.5, p = 8.5, d = 2.8. Fifth pereiopod: i = 4.0, m = 9.5, c = 4.8, p = 10.0, d = 3.0. PARATYPES: (based on 4 ♂) Total length 38–44, carapace length 9–10, rostrum length 8–14,telson length 6–9.5. First pereiopod: ischium (i) 2.0 –2.5; merus (m) 4.0–4.8, carpus (c) 6,0–7.5, propodus (p) 2.5–3.0; dactylus (d) 1.0–1.5. Second pereiopod: i = 4.5–5.0, m = 4.8–5.8, c = 7.2–8.0, p = 8.5–9.2, d = 4.75–5.0. Third pereiopod: i = 2.8–3.0, m = 5.5–6.0, c = 2.2–2.5, p = 4.5–5.5, d = 1.8–2.0. Fourth pereiopod: i = 3.0–3.5, m =5.0– 6.0, c = 2.5–3.0, p = 6.2–7.0, d = 1.5– 2.0. Fifth pereiopod: i = 3.5–3.8, m = 6.2–6.8, c = 3.75–4.5, p = 7.0–7.8, d = 2.0–2.8. (Based on 4 ♀) Total length 59.0–69.5, carapace length 16.0–18.0, rostrum length 11.5–14.0,telson length 8.5–10.0. First pereiopod: ischium (i) 4.5–4.8, merus (m) 6.8–7.0, carpus (c) 8.5–10.0, propodus (p) 4.25–5.0, dactylus (d)1.5–2.75. Second pereiopod: i = 6.75–8.0, m = 9.0–9.5, c = 12.0–14.0, p = 15.5–17.0, d = 7.5–8.2. Third pereiopod: i = 3.8–4.2, m = 8.0–10.0, c = 3.5–4.5, p = 7.0–8.0, d = 2.5–3.0. Fourth pereiopod: i = 4.0–4.5, m =9.0– 9.25, c = 4.0–4.5, p = 8.0–8.5, d = 2.5–3.0. Fifth pereiopod: i = 3.8–4.5, m = 9.0–10.0, c = 4.5–5.8, p = 9.5–10.0, d = 3.0–3.5. Description. Rostrum broad, overreaching antennal scale, tip directed slightly upwards. Rostral formula 9– 12/3–5 with 2 postorbitals; wide gap between 1 st and 2 nd post orbital tooth, 1 st post orbital and rest of the dorsals closely packed; 1 st ventral is located at half length of rostrum and last one at the level of 9/10 dorsal tooth. Carapace smooth, 6–8 mm in males, 17–19 mm in females; both antennal and hepatic spine present, latter situated below and behind the former (Fig.1C). Abdomen glabrous, pleurae of somites I–III typical, IV and V directed backwards, VI ending in spine. Telson broad, stout. conical with a median projection and two pairs of dorsal spines and two pairs of distal spines;1 st dorsal pair situated at 45–50%, 2 nd pair at 66–70% distance; inner pair of distal spines very long, overreaching tip of telson;3 pairs of plumose setae present between inner pair of spines. Eyes and cornea well developed, broader than eye stalk, slightly pigmented. Length of three segments of antennular peduncle, 5.5(proximal): 2(middle): 3(distal); lateral spine of basal segment not reaching middle segment. Tip of antennal scale round, outer spine subdistal, length 3 times as long as breadth. Mandible three segmented, middle segment shortest,apical one longest with one apical and one subapical row of setae (Fig.3F). Maxillula, maxilla,1 st maxilliped, 2 nd maxilliped typical of Macrobrachium. 3 rd maxilliped overreaching antennular peduncle, reaching nearly basal 1/3 rd of carpus of 1 st pereiopod.(Fig.2.a,b,c,d,e) 1 st pereiopod slender; chela overreaching antennal scale; ischium slightly shorter than propodus,0.61 to 0.66 times as long as merus,0.50 to 0.57 times as long as carpus; dactylus and palm equal (Fig.1D). 2 nd pereiopods exhibit sexual dimorphism. Male chelipeds equal,0.5 to 0.62 times of total body length; carpus longer than merus, ischum, shorter than propodus, podomere longest; dactylus equal or slightly longer than ischium; fingers distinctly longer than inflated palm with sharp ridge along the cutting edge (Fig.1E, 2 Ai,2D). Ratio (in %) of ischium, merus, carpus, propodus, dactylus, palm are 18(i):20.9(m):28.8(c):32.3(p):18(d):14.3(palm). Female chelipeds subequal, 0.59 to 0.63 times of body length (Fig.1F); carpus stout, conical near palm, longer than merus and ischium, shorter than propodus, podomere largest; dactylus equal to merus,0.50 to 0.62 times as long as propodus; palm inflated, equal to or longer than slender fingers,1 minute and 2 blunt denticles at the base of immovable finger and movable finger respectively. Ratio (in %) of ischium, merus, carpus, propodus, dactylus, palm are 16.0(i):22.5(m):29.7(c): [32.1(p)]:16.0(d): 15.4(palm). 3 rd to 5 th pereiopods simple, 5 th one longest. 1 st pleopod typical of Macrobrachium (Fig.1G). 2 nd pleopod in male with appendix masculina bearing 1 short, 2 long stiff distal setae and two lateral rows of 12-14 spinous setae (Fig.2C,2B), 2 nd pleopod in female simple.3 rd to 5 th pleopod simple in both the sexes (Fig.1I). Colouration. Body transluscent; Carapace, rostrum, antennal scale, antennular peduncle, first three abdominal pleurae without pigmentation, ventrolateral margin of 4 th,5 th, 6 th abdominal pleurae and uropod with dark brown pigmentation; 2 nd chelate leg has reddish brown pigmentation in entire carpus,outer margin of palm and fingers, half of merus close to carpus; red pigmentation in antennular flagella and at distal end of propodus; podomere joints of 3 rd,4 th & 5 th pereiopods with yellow bands.(Fig.2E). Discussion. A comparison of morphological characters (Table.2) shows that M. ramae sp. nov. shares several characters with M. gurudeve, M. jayasreei, M. kunjuramani and M. saengphani. However the new species can easily be distinguished from these species by the structure of rostrum, telson, appendix masculina and in presence of bigger proximal antennular peduncle segment as compared to middle and distal segments.A key is given below for distinctive identification of the five species. I dentification key: 1. Carapace shorter than rostrum........................................................................... 2 - Carapace longer than rostrum............................................................................ 3 2. Uropodal exopod with accessory spine; telson slender........................................................ 4 - Uropodal exopod without accessory spine;telson broad............................................... M.gurudeve 3. Uropodal exopod without accessory spine; telson slender.............................................. M.jayasreei - Uropodal exopod with accessory spine; telson broad............................................. M.ramae sp.nov. 4. Antennal spine with carina,males longer than females............................................ M.kunjuramani - Antennal spine without carina,males smaller than females........................................... M.saengphani Different haplotypes of M. ramae sp. nov. generated using both COI and 16S rRNA gene sequences of 3 males and 3 females cluster together in molecular phylogenetic trees, strongly suggests that the specimens belong to same species. Neither 16s rRNA nor COI gene sequences of M. gurudeve, M. jayasreei, M. kunjuramani are available in NCBI, except COI gene sequence of M. Saengphani, which forms a very distant clade from M. ramae sp. nov. (Fig. 4). Neighbor-joining tree of COI gene sequences of different Macrobrachium species shows that, M. ramae sp. nov. forms cluster with M. lamarrei and M. rude remains as separate clade. However, Neighbor-joining tree using 16S rRNA gene sequences shows that M. ramae sp. nov. forms a cluster with M. rude whereas M. lamarrei belongs to a separate clade. It is well established that morphologically M. lamarrei and M. rude are very easily distinguishable species and could be identified easily. M.rude differs hugely from M.ramae sp. nov. in having larger males than females measuring upto 130 mm of total length,2 nd cheliped 1.5 times longer than total body length.Moreover, all the sengments of 2 nd cheliped bear velvety pubescence, hence known as ‘hairy river prawn’. M. lamarrei also differs significantly from M.ramae sp. nov. in having longer rostrum with characteristic edentate gap, non-hairy appendix masculina longer than 2 nd pleopodal endopod and absence of subapical spine in uropodal exopod. If the sequences submitted to NCBI for M. lamarrei and M. rude are accurate in terms of species identification, then the sequences generated during the current study using COI and 16S rRNA genes should show similarity with any one of the species for both the gene fragments. This indicates that the samples for M. lamarrei and M. rude were collected and sequences were submitted without proper confirmation of the taxonomic status of those species, making their identification done rather doubtful. The sequences of M. lamarrei and M. rude retrieved from NCBI were submitted by three different research groups from two different countries. COI gene sequences MT483220 and MT483221, submitted as M. lamarrei were collected from Bhairab river, Bangladesh which is a coastal river carrying estuarine water. 16S rRNA sequences AY858836 and MG283139, submitted as M. rude were collected from Tamil Nadu and Orissa states of India respectively. These sequences rather indicate the presence of M. ramae sp. nov. in those locations and often be misidentified as other species of Macrobrachium and hence providing a hint of distribution of M. ramae sp. nov. spanning from coast of Bangladesh to entire East coast of India. Conclusion. The results of phylogenetic analysis have clearly pointed out that M. ramae sp. nov. is a new species as indicated through detail morphological study conducted during the present study. The results show the importance of both morphological and molecular data for accurate identification of any species and would surely help future taxonomists to figure out species level identification of the genus Macrobrachium in India with more clarity. Etymology. This new species is named in loving memory of the grandmother of the corresponding author (MD), late Rama Sengupta, who was a constant inspiration to her.The species name is a noun in the genitive singular.