Macrobrachium placidulum ( de Man, 1892 )

Mazancourt, Valentin De, Marquet, Gerard, Wowor, Daisy & Keith, Philippe, 2024, Macrobrachium ngankeeae, a new species of freshwater shrimp (Crustacea: Decapoda: Palaemonidae) from Papua Barat Province, Indonesia, Zootaxa 5476 (1), pp. 253-266 : 261-262

Macrobrachium placidulum ( de Man, 1892)

Palaemon (Macrobrachium) placidulus de Man, 1892: 489 , pl. 28, fig. 48.

Macrobrachium placidulum . — Holthuis, 1950: 253, fig. 51c; Chace & Bruce, 1993: 35, fig. 14; Chen et al. 2009: 234, tab. 2; Eguia et al. 2009: 36; Keith et al. 2010: 76; Keith et al. 2013: 112; Saeki et al. 2018: 42, fig. 5E–F, 7.

Type material. Syntypes: 2 males (cl 11.1–11.4 mm), 2 ovigerous females (cl 9.2 mm), RMNH D 2582 , Nusa Tenggara Timur Province , Flores Island, Sikka Regency, Sg. Wukur, coll. M. Weber , 1888–1889; 1 male (cl 8.9 mm), 1 ovigerous female (cl 10.2 mm), ZMA De 102.569, Nusa Tenggara Timur Province, Flores Island, Ende Regency, Sg. Nanga Ba, coll. M. Weber , 1888–1889; 1 male (cl 13.3 mm), 3 females (cl 9.0– 11.4 mm), ZMA De 102.565, Sulawesi Selatan Province, Salayar Island, Sg. Bangkalan, coll. M. Weber , 1888–1889.

Other material examined. INDONESIA: 1 ovigerous female (cl 7.5 mm), MZB Cru 5354, Papua Barat Province, Kaimana Regency, Buruway District , Ds. Karawawi , Sg. Kunafa station 2, 04°03.532’S 133°06.103’E, 30 m asl, coll. P. Keith, P. Gaucher, G. Ségura, 14 October 2010 ; 1 ovigerous female (cl 9.8 mm; MNHN-IU-2016- 11889), 1 ovigerous female (cl 9.4 mm; MZB Cru 5355), 1 ovigerous female (cl 9.3 mm; MNHN-IU-2016-11891), 1 male (cl 7.4 mm; MZB Cru 5356), Papua Barat Province, Kaimana Regency , Kaimana District , Ds. Jarati , Sg. Kumbawa , 04°09.943’S 133°09.292’E, 77 m asl, coll. P. Keith, P. Gaucher, G. Ségura, 15 October 2010 ; 1 male (cl 8.7 mm), 1 female (cl 8.5 mm), 1 ovigerous female (cl 9.0 mm), MNHN-IU-2019-413, Papua Barat Province, Kaimana Regency, Kaimana District, Ds. Jarati, Sg. Kumbawa , 04°09.943’S 133°09.292’E, 77 m asl, coll. P. Keith, P. Gaucher, G. Ségura, 15 October 2010 ; 2 ovigerous females (cl 8.9–9.9 mm; MNHN-IU-2019-411), 1 female and 2 ovigerous females (cl 8.9, 8.9, 9.9 mm; MZB Cru 5357), Papua Barat Province, Kaimana Regency, Teluk Etna District , Ds. Kayu Merah , Sg. Kayu Merah, 3°53.291’S 134°28.654’E, coll. P. Keith, P. Gaucher, G. Ségura, 22 October 2010 . PALAU: Babelthuap: 1 ovigerous female (cl 9.1 mm), MNHN-IU-2018-2378, Tireloch R., 7°36.527’N 134°36.958’E, 5 m asl, coll. P. Keith, G. Marquet, L. Taillebois, M. Castelin, P. Gerbeaux, 28 February 2011 . PAPUA NEW GUINEA: New Britain: 3 males (cl 10.9–11.3 mm), 1 female (cl 7.8 mm), 3 ovigerous females (cl 7.8–10.mm), MNHN-IU-2016-11904, Crusher R., 05°38.603’S 150°10.957’E, coll. P. Keith, R. Causse, C. Lord, 31 October 2018 ; 1 male (cl 7.3 mm), MNHN-IU-2016-11902, Garu road, 5°27.278’S 149°58.415’E, coll. P. Keith, R. Causse, C. Lord, 26 October 2018 ; 1 juvenile (cl 4.8 mm), MNHN-IU-2017-9323, Gavuvu R., 05°28.733’S 150°23.557’E, coll. P. Keith, R. Causse, C. Lord, 27 October 2018 . SAMOA: Upolu: 3 ovigerous females (cl 7.6–9.3 mm, MNHN-IU-2016-10635 (formerly MNHN-Na-17505), Namoi R., 13°57.023’S 171°30.994’W, coll. P. Gerbeaux, P. Keith, G. Marquet, 23 July 2008 . SOLOMON ISLANDS: Choiseul: 1 male (cl 11.9 mm), MNHN-IU-2016-11900, Gu’ma R., 07°02.328’S 156°49.571’E, 70 m asl, coll. P. Keith, P. Gerbeaux, G. Marquet, 17 October 2014 ; 1 male (cl 13.0 mm), MNHN-IU-2016-11857 ( CA2523 ), Tutuku R., coll. P. Keith, R. Causse, C. Lord, 19 October 2019 ; Kolombangara: 1 ovigerous female (cl 8.9 mm), MNHN-IU-2016-11936, Poitete R., 07°52.413’S 157°07.982’E, coll. P. Keith, C. Lord, G. Marquet, 15 November 2015 . Ranongga: 1 male (cl 9.6 mm; MNHNIU-2017-9443), 1 male (cl 8.4 mm; MNHN-IU-2016-11858; CA2601 ), Poro R., 08°03.082’S 156°35.711’E, coll. P. Keith, C. Lord, 24 October 2016 . VANUATU: Malekula : 1 male (cl 14.3 mm; MNHN-IU-2016-11897), 1 male (cl 12.9 mm; MNHN-IU-2016-11898), 1 male (cl 18.2 mm; MNHN-IU- 2016-11899), Brenwé R., 16°07.593’S 167°16.779’E, coll. P. Keith, P. Feutry, C. Lord & L. Taillebois, 20 November 2008 ; Pentecost: 2 males (cl 9.6–11.1 mm), MNHN-IU-2017-9362, Bayomo R., coll. P. Keith, P. Feutry, C. Lord & L. Taillebois, 26 October 2010 ; Santo: 1 male (cl 11.3 mm), MNHN-IU-2017-9410, Mamara R., coll. M. Pouilly, 8 November 2006 .

Diagnosis. Medium-sized species with subcylindrical body form. Rostrum short, tip slightly extend beyond end second article of antennular peduncle but never reach end of third article of antennular peduncle; slender; dorsal carina convex, with total 10–12 teeth, 4–6 teeth completely postorbital; ventral carina convex with 2 or 3 teeth. Carapace glabrous. Ocular beak absent or very poorly developed. Third maxilliped with exopod longer than ischiomerus. Second pereiopods robust, dissimilar in shape, unequal in size; distal part of dactylus and pollex of major second pereiopod with double row of tubercles each, fingers shorter than palm, carpus long conical, carpus shorter than chela, carpus longer than merus; cutting edges of minor second pereiopod gaping, densely covered with long stiff setae concealing surface; all articles covered with modified squamiform and mamilliform setae. Third, fourth and fifth pereiopods with modified squamiform setae and few scattered short stiff setae. T4 without median process. Pre-anal carina well developed. Uropods glabrous, exopod with mobile mesial spine longer than distolateral tooth. Developed eggs small, maximum size 0.6 × 0.5 mm, ovoid, numerous.

Distribution. Commonly found in the Indo-West Pacific from south coast of Java to eastern Indonesia, the Philippines, Taiwan and subtropics Japan to Palau, Vanuatu, New Caledonia, Futuna, Fiji and Samoa.