Macrobrachium panhai Chaowvieng & Siriwut, 2024

Chaowvieng, Apisara, Sutcharit, Chirasak, Chanabun, Ratmanee, Srisonchai, Ruttapon, Jeratthitikul, Ekgachai & Siriwut, Warut, 2024, Molecular phylogeny and taxonomic position of Macrobrachium lanchesteri (De Man, 1911), with descriptions of two new species from Thailand (Decapoda, Caridea, Palaemonidae), ZooKeys 1190, pp. 163-193 : 163

Macrobrachium panhai Chaowvieng & Siriwut sp. nov.

Figs 3E , 5

Material examined.

Holotype: Kanchanaburi • Ovigerous ♀ from Sri Nakarin Dam, Tha Kradan, Si Sawat; 14°24'12.1"N, 99°07'24.7"E; CUMZ MP00302. Paratypes: 7 ♀♀, 8 ovigerous, 6 ♂♂ from the same locality of holotype; MUMNH MP00303 .

Additional material.

Chiang Mai • 6 ♀♀, 6 ovigerous, Nong Han, San Sai; 18°53'44.9"N, 99°01'05.7"E; MUMNH MP00304. • 1 ♀, Ping, Ki Lek, Mae Taeng; 19°04'37.0"N, 98°56'59.8"E; MUMNH MP00305. Nan • 1 ♀, Ban Na Bua , Nong Daeng, Mae Charim; 18°45'12.8"N, 101°00'39.7"E; MUMNH MP00306. Uttaradit • 1 ♂, Klong Tron, Ban Bueng Pra Kot, Thong Sang Khan; 17°35'39.1"N, 100°29'10.3"E; MUMNH MP00307. • 3 ♀♀, Klong Tron, Nam Khai, Nam Pat; 17°36'15.3"N, 100°32'15.3"E; MUMNH MP00308. Buengkan • 1 ♀, Klong Hi, Sang, Seka; 17°54'17.9"N, 103°57'12.0"E; MUMNH MP00351. Nong Khai • 2 ♀♀, Nam Suai, Song Hong, Mueang Nong Khai; 17°45'01.1"N, 102°51'00.5"E; MUMNH MP00309. Ubon Ratchathani • 1 ♀, 1 ovigerous, 2 ♂♂, Mekong River , Khong Chiam; 15°19'10.3"N, 105°29'53.2"E; MUMNH MP00310 . • 1 ♀, 1 ovigerous, Sae Hua Maew Waterfall, Nong Saeng Yai, Khong Chiam; 15°20'12.2"N, 105°24'02.6"E; MUMNH MP00311. Phitsanulok • 6 ♀♀, 1 ♂, Ban Bo, Wang Nok Aen, Wang Thong; 16°51'13.6"N, 100°36'43.2"E; MUMNH MP00312. Phetchabun • 1 ♀, Ang Kep Nam Nam Khuen Nam Lang, Wang Hin, Wang Pong; 16°25'19.8"N, 100°48'48.2"E; MUMNH MP00313. Nakhon Nayok • 2 ovigerous, Ban Na, Pa Kha, Ban Na; 14°17'11.2"N, 101°04'13.7"E; MUMNH MP00314. Suphan Buri • 10 ♀♀, 8 ovigerous, 4 ♂♂, Ban Chara Mai, Ban Kong, U Thong; 14°34'51.0"N, 99°52'04.7"E; MUMNH MP00315. Sa Kaeo • 1 ovigerous, Huai Yang, Ta Phraya; 14°00'46.5"N, 102°38'37.0"E; MUMNH MP00316. Chachoengsao • 2 ♀♀, 3 ovigerous, Nong Prue Mai Kaeo, Wang Yen, Plaeng Yao; 13°33'31.5"N, 101°17'44.0"E; MUMNH MP00317. Rayong • 12 ovigerous, Khao Chuk, Kong Din, Klaeng; 12°51'32.0"N, 101°46'12.0"E; MUMNH MP00318. • 7 ♀♀, 11 ovigerous, 12 ♂♂, Koh Phasuk, Makham, Makham, Chanthaburi; MUMNH MP00319. Trat • 1 ♀, 2 ovigerous, Huai Raeng, Dan Chumphon, Bo Rai; 12°23'48.4"N, 102°39'15.1"E; MUMNH MP00320. • 1 ♀, 2 ovigerous, Ang Kep Nam Dan Chumphon, Dan Chumphon, Bo Rai; 12°27'45.4"N, 102°38'24.6"E; MUMNH MP00321. Phetburi • 1 ♂, Klong Prachan, Yang Nam Klat Tai, Nong Ya Plong; 13°06'33.27"N, 99°43'22.75"E; MUMNH MP00322.

Diagnosis.

Rostrum straight proximally and slightly upward distally. Rostrum length reaching beyond end of antennular peduncle and exceeding the scaphocerite. Rostral formula: 8-12/3-6 teeth including two or three distal teeth with small gap separate from rest. Carapace smooth. Epistome bilobed. First pereiopods reaching end of scaphocerite. Second pereiopods thin and long, similar in form and equals in length, exceeding scaphocerite. Fingers covered with scattered setae, slightly shorter than palm. Translucent razor edge present anteriorly between fingers and no teeth on inner side of cutting edges. Carpus cylindrical shape and articulation margin expanded. Carpus 1.5 × longer than chela. Merus subcylindrical. Carpus 1.5 × longer than merus. Third pereiopods thin and long, reaching end of scaphocerite. Dactylus curved distally with short setae. Propodus 2 × longer than dactylus. Propodus with three or four pairs of spines and fine setae present scarcely on articulation margin. Propodus 2 × longer than carpus. Sixth to eighth thoracic sternites smooth. First and second pleonal sternites with small median process or smooth. Third and fourth pleonal sternites smooth. Fifth pleonal sternite with triangular ridge. Uropodal diaeresis with inner movable spine slightly longer than outer angle.

Composite description

(holotype in parentheses). Rostrum (Fig. 5B ). Straight or proximal convex and slightly distal upward. Rostrum length exceeding end of antennular peduncle and slightly exceeding scaphocerite (rl 7.32 mm). Dorsal margin with 8-12 (10) teeth including two or three (3) teeth distally with small gap from rest. Postorbital margin with one or two (1) teeth, reaching one-third of carapace length. First dorsal tooth positioned slightly behind hepatic spine. Ventral margin with 3-6 (4) teeth, starting from middle to distal margin. Short setae present between rostral teeth.

Cephalon (Fig. 5B ). Eye well developed. Ocular beak without laterally expanded tip. Cornea longer and broader than stalk. Postantennular carapace margin rounded. Cornea osculum longer than stalk. Antennular peduncle longer than wide, with fine setae. Basal segment short, second segment shorter than third segment. Stylocerite projection sharp, reaching beyond basal segment. Antennal spine sharp, situated below orbital margin. Hepatic spine slightly larger than antennal spine, positioned posteriorly and lower than antennal spine. Scaphocerite with straight margin, distolateral tooth sharp and not reaching end of lamella. Epistome bilobed (Fig. 5C ). Branchiostegal suture beginning at carapace margin to behind hepatic spine. Carapace surface smooth (cl 5.76 mm).

First pereiopods. Thin and long, reaching end of scaphocerite. Fingers as long as palm, tips with fine setae. Series of setae present on anterior inner part of palm. Carpus slightly longer than merus. Distal articulation of carpus with series of fine setae. Ischium shorter than merus. Scattered setae present on all segments.

Second pereiopods (Fig. 5D ). Thin and long, similar in form and exceeding scaphocerite. Fingers subcylindrical covered with scattered setae. Palm 1.1-1.5 × longer than fingers (Fin 1.06: Pal 1.39 mm). Fingers with translucent razor edges present anteriorly and cutting edge between fingers smooth. Tip of fingers crossed and covered by fine setae (Fig. 5E ). Carpus cylindrical shape and articulation margin expanded. Carpus 1.2-2 × longer than chela (Che 2.45: Car 4.22 mm). Merus subcylindrical. Carpus 1.2-1.7 × longer than merus (Mer 2.85: Car 4.22 mm). Ischium as long as merus. Scattered short setae present on all segments.

Third pereiopods (Fig. 5F ). Thin and slender, reaching end of scaphocerite. Dactylus short and curved distally. Propodus 2 × longer than dactylus. Propodus with three or four pairs of spines along inferior-lateral margin and fine setae at distal articulation, 2 × longer than carpus. Ischium shorter than carpus. Scattered short setae present on all segments.

Fourth and fifth pereiopods. Long and slender, exceeding scaphocerite. Propodus of fourth pereiopods with 3-6 (4) pairs of spines distributed along its length, 2.5 × longer than dactylus. Propodus as long as merus. Ischium shorter than merus. Propodus with fine setae at distal articulation. Scattered short setae present on all segments. Propodus of fifth pereiopods with 4-8 pairs of spines distributed along its length and fine setae at distal articulation. Propodus 2.5 × longer than carpus. Propodus as long as merus. Scattered short setae present on all segments.

Thoracic sternum. Fourth and fifth thoracic sternites with moderately transverse plate without median process, and seventh thoracic sternite smooth. Eighth thoracic sternite usually smooth.

Pleon. Smooth. All pleonal sternites with transverse ridges. First and second pleonal sternites with or without small median processes. Third and fourth pleonal sternites smooth. Fifth pleonal sternite with triangular ridge. Preanal carina present, obtuse ridge developed without spine or setae. Ventral margin of pleural tergum with small setae.

Telson (Fig. 5G ). Tapered posteriorly, protruding point on middle margin with lateral spines and few fine setae. Inner spines longer than outer spines. Dorsal surface with two pairs of small spines, similar in size.

Uropods (Fig. 5G ). Uropodal diaeresis with inner movable spine, as long as or slightly longer than outer angle. Exopods longer than endopods.

Etymology.

The specific name panhai is dedicated to Prof. Dr. Somsak Panha, a taxonomist from Faculty of Science, Chulalongkorn University, Thailand well known for his remarkable contributions and endorsement to the study of invertebrate fauna in Thailand.

Distribution.

This species is distributed in the Chao Phraya and Mekong River Basins, Thailand.

Remarks.

Macrobrachium panhai sp. nov. differs from M. lanchesteri s. str. due to having the rostral formula with 8-12/3-6 teeth (vs 6-10/1-6 teeth in M. lanchesteri ). Movable spine at uropodal diaeresis is slightly longer than outer angle (vs movable spine is shorter in M. lanchesteri ). Third propodus has 3-6 pairs of spines (vs 4-8 pairs of spines in M. lanchesteri ). The teeth between fingers of second pereiopods are absent (vs 1 or 2 teeth on fixed and movable finger in M. lanchesteri ). The ratio between rostrum and carapace length is 0.89-1.53 (vs 0.78-1.14 in M. lanchesteri ) and the ratio between chela and carpus is 1.2-2.08 (vs 1.15-1.72 in M. lanchesteri ). M. panhai sp. nov. occasionally co-exists with M. lanchesteri in the Chao Phraya and Mekong River Basins.

This new species also differs from M. peguense sensu Tiwari (1952) by processes of rostral formula 8-12/3-6 teeth (vs 6-9/2-4 teeth in M. peguense ). Second pereiopods had palms shorter than half of carpus (vs palm slightly more than half of carpus in M. peguense ). Propodus of third pereiopods are 2 × longer than dactylus (vs 3 in M. peguense ). Dorsal surface of telson is without depression (vs longitudinal depression in M. peguense ). Movable spine at uropodal diaeresis is slightly longer than outer angle (vs movable spine is shorter in M. peguense ). Cai and Ng (2002) also mentioned that the egg size can be used to distinguish M. peguense and M. lanchesteri group (1.15-1.5 × 1.6-2.1 mm and 0.6-0.7 × 0.8-1 mm, respectively). Currently, the distribution range of M. peguense was found only from Myanmar.

Figures

Figure 3. Living habit of specimens of three Macrobrachium species A, B M. lanchesteri from Bang Khiat, Singhanakhon, Songkhla, Thailand C, D M. rostrolevatus sp. nov. from Bueng Khong Long, Bueng Kan, Thailand E M. panhai sp. nov. from Sri Nakarin Dam, Tha Kradan, Si Sawat, Kanchanaburi, Thailand. Scale bars: 1 cm.

Figure 5. Morphological characteristics of Macrobrachium panhai sp. nov. (A, F ovigerous female paratype MUMNH MP 00303 B-E, G-H ovigerous female holotype CUMZ MP 00302) A lateral view B carapace C epistome D second pereiopod E teeth between fingers F third pereiopod G uropod and H movable spine at uropodal diaeresis. Scale bars: 1 mm.