Melitid amphipods from the Gulf of Thailand, with a description of Dulichiella pattaniensis, a new species

Abstract Two species of melitid amphipod were collected from the Gulf of Thailand. Dulichiella pattaniensis is new to science, and Melitalati latiflagella Ren & Andres, 2012 has not been previously reported from Thai Waters. Dulichiella pattaniensis is characterized by male gnathopod 2 distolateral crown with 4 spines; pleonite/urosomite formula 7-7-7-5-6-2; pereopod 5-7 dactylus with 2 accessory spines. This combination of characters has not been recorded previously in the Dulichiella. The characters of the specimens are described and illustrated. All specimens are deposited in the Princess Maha Chakri Sirindhorn Natural History Museum, Prince of Songkla University, Thailand.


Introduction
Melitid amphipods most commonly occur in coastal and freshwater areas. Thailand has a variety of aqueous habitats including coral reefs, seagrass beds, and mangrove forests, but only one melitid amphipod, Rotomelita longipropoda Wongkamhaeng et al., 2013 was described. In this study, we describe a new melitid species Dulichiella pattaniensis sp. n., and our observations of Melita latiflagella Ren & Andress, 2012, which has not been previously reported in Thai Waters. Figures and descriptions of both species are provided.

Materials and methods
Amphipods were collected from some settlement plates in an artificial reef in Ban Pak Bang Ta Wa, Pattani Bay and from sediment of Lower Songkhla Lake ( Figure 1). The sites were visited at low tide and amphipods were collected using a 20×20 cm Ekman grab from the subtidal zone. The amphipod specimens were sorted out and fixed in formalin for 1 week and then stored in 70% alcohol. In the laboratory, the specimens were transferred from alcohol into glycerol for study. Drawing was accomplished using a drawing tube attached to an Olympus CH30 light microscope. The pencil drawings were scanned and digitally inked using a WACOM bamboo CTH-970 graphics board following the method described in Coleman (2003). The following abbreviations are used: A, antenna; G, gnathopod; HD, head; LL, lower lip; MD, mandible; MX, maxilla; MP, maxilliped; P, pereopod; Pl, pleopod; T, telson; U, uropod; UR, urosome; UL, upper lip; r, right; l, left; ♂, male; ♀, female. Specimens of different species were deposited into the Prince of Songkla University Zoological Collection (PSUZC). Diagnosis. (Lowry and Springthorpe 2007) Head anteroventral corner with several long, slender setae. Antenna 1 longer than antenna 2. Maxilla 1 inner plate long, narrow, tapering distally, with 2 well developed apical plumose setae. Maxilla 2 inner plate with oblique setal row. Gnathopod 2 male, asymmetrical, significantly unequal in size; palm in larger slightly obtuse; those of female equal in size. Pereopods 5-7 distal articles strongly to weakly setose; dactylar ungues with accessory spines. Pereopods 6 and 7 in males with bunches of long slender setae. Pereopod 7 basis in female fully expanded. Pleonites dorsally serrate. Uropod 3 inner ramus scale-like; outer ramus 4 to 5× longer than wide, 2-articulate. Telson deeply cleft, lobes tapering distally to an acute point.
Etymology. This species is named after the type locality.
Remarks. Dulichiella pattaniensis sp. n., with pleonite/urosome formular of 7-7-7-5-6-2 has only D. cotesi, D. oahu, D. pacifica and D. tulear that share this characters. This new species can be distinguished from D. cotesi, D. oahu and D. tulear by having male gnathopod 2 (large) with 4 spines on distolateral crown while those three species have 3 spines. D. pattaniensis differs from D. pacifica in the following: the male large gnathopod 2 has a fourth spine on its distolateral crown that is not well developed vs. its well-developed fourth set of spines. The male gnathopod 1 has carpus longer than its propodus vs. a carpus subequal to its propodus. Pereopods 3-4 have a dactyli with 2 accessory spines vs. 3-4 dactyli with 1 accessory spine.
Remarks. Ren and Andres (2012) described the China Sea residing Melita latiflagellaas having an antenna 2 that is long and extended. The specimens from this study are similar to those of Ren's, but smaller in size with a total length of 3 mm as opposed to 5 mm.
Distribution. China Sea and Songkhla Lake (current study).