Two new species of Grandidierella (Amphipoda, Corophiida, Aoridea) from Singapore

1,2 Tropical Marine Science Institute (TMSI), National University of Singapore, 18 Kent Ridge Road, 119227, Singapore. 3 Marine Ecosystem Research Centre (EKOMAR), Faculty of Science and Technology, Universiti Kebangsaan Malaysia 43600 Bangi, Selangor, Malaysia. 4 Department of Earth Sciences and Environment, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia.


Introduction
In recent years, there have been efforts aimed at cataloguing the biodiversity of the fauna in Singapore. One such effort comes with the initiative of the Comprehensive Marine Biodiversity Survey (CMBS) carried out over a fi ve-year period (2010)(2011)(2012)(2013)(2014)(2015) jointly by the National Park's Board and the National University of Singapore's Tropical Marine Science Institute (NUS -TMSI). In relation to neighbouring countries, information on Singapore's marine biodiversity is still lacking and many regions and habitats remain insuffi ciently studied. To date, only 27 species of amphipods have been recorded from the coast of Singapore (Stebbing 1887;Mayer 1903;Lowry 2000;Azman & Alip 2015;White 2015). As one of the busiest entrepôt countries in the world, Singapore's waters are known to be a complex zone where ecological and human interaction have a dramatic impact on the marine biodiversity. The survey expanded the scope of habitats sampled to include a range of shallow and deep benthic habitats comprising hard and soft benthic types around Singapore in order to establish a reliable baseline to guide future coastal development, conservation, and rehabilitation, as well as to build local capacity and widen the appreciation of the marine biodiversity. It is therefore of high priority to improve descriptions of numerous taxonomic groups and to expand our knowledge of their geographical distributions. In the present contribution, we describe two new species of Grandidierella Coutière, 1904. These species represent the fi rst Singapore records of the genus.

Material and methods
Grandidierella pawaiensis sp. nov. was collected in August 2012 from the northern part of Pulau Pawai ( Fig. 1) at GPS point 01º11.336ʹ N, 103º43.372ʹ E by random sampling at a tidal height of 1.1 m-1.4 m above Chart Datum (CD). Grandidierella sungeicina sp. nov. was collected from the Sungei Cina river mouth, in a mudfl at environment at GPS point 01º26.969ʹ N, 103º43.696ʹ E in January 2011, via transect sampling within a rectangle of 50 m by 10 m, at a tidal height of 0.9 m-1.3 m above CD, parallel to the waterline.
Sediments from both locations were washed in situ through a 2 mm mesh before specimens were brought back to the laboratory for sorting and identifi cation using an Olympus SZX10 light stereo microscope. Grandidierella pawaiensis sp. nov. was fi rst fi xed in 2% buffered formalin before being stored in 75% denatured ethanol while G. sungeicina sp. nov. was preserved directly in 75% denatured ethanol. Specimens were transferred from 75% ethanol into increasing concentrations of glycerol before being dissected. Individual appendages were then mounted on a glass slide in glycerol.
Illustrations were done using a camera lucida system mounted on an Olympus BX50 light compound microscope before being digitally 'inked' following Coleman (2003). The terminology for cuticle projections (spines and setae) follows Watling (1989). Type material is deposited at the Lee Kong Chien Natural History Museum, National University Singapore (LKCHM NUS), Singapore.

Abbreviations
The following abbreviations are used:
UPPER LIP (Fig. 4UL). Broader than long, margin covered in short fi ne setae, distal margin prepubescent.
MAXILLA 2 (Fig. 4MX2). Inner lobe subequal in length to outer lobe; inner lobe medial and lateral margins slightly convex, deep face covered in short setae, medial margin possessing long plumose setae; outer lobe lateral and medial margins straight, slightly distally expanded, lateral margin with short setae, distal end rounded with mixture of long slender and plumose setae. MAXILLIPED (Fig. 4MXP). Inner lobe distally truncate, extending slightly beyond article 1 of palp, lateral margin with fi ne setae, medioproximal margin with long robust setae, mediodistal margin with 8-10 slender setae and 4 apically oblique processes; outer lobe almost reaching end of article 2 of palp, apically rounded with long robust setae, lateral margin convex and with fi ne setae, medial margin straight with robust setae and submarginal slender setae; palp 4-articulate, article 2 medial margin with long slender setae, article 3 distal margin covered in long slender setae with 1-2 serrate setae, article 4 subtriangular ending in a stout spine. GNATHOPOD 1 (Fig. 3G1). Enlarged, more robust than 2, carpochelate; coxa small, anterodistally unproduced; basis posteriorly expanded, ventrodistal corner with slender setae; ischium subquadrate, ventrodistal corner with slender setae; merus not anterodistally produced, sparsely setaceous along distal margin; carpus enlarged, twice as long as propodus; dorsal margin convex, ventral margin straight, entire margin with slender setae, proximoventral corner with apically acute process, inner midface possessing apically acute process, anteroventral corner with 2 processes forming a broad excavate sinus; propodus posterodistal margin slightly expanded, fringed with slender setae; dactylus less than half length of propodus with notch ⅔ of the way up ventral margin.

Remarks
Grandidierella pawaiensis sp. nov. is closely similar to G. bispinosa. However, the new species possesses a mixture of features that differ from the specimens collected from the Bismarck Archipelago (Schellenberg 1938), the Moluccas (Ledoyer 1979) and Fiji (Myers 1981). Differences between specimens are mainly seen on gnathopods 1 and 2. For gnathopod 1, the dorsal margin of the carpus is more dorsally rounded, similar to the specimens collected from the Moluccas and Fiji. There is also the absence of 2 denticles on the ventromedial margin of the carpus as seen in Myers' specimen. The anterior margin of gnathopod 2 is distinctly more crenulate in the present material. HEAD. Longer than deep, longer than pereonites 1 and 2 combined, anteroventral margin moderately excavate. Eyes present and well developed, set just posterior to margin of lateral lobe. Epimeral plate 3 longer than 1 or 2. ANTENNA 1 (Fig. 12A1). Longer than 2; weakly setiferous; peduncular articles 1-3 with ratio of 5:7:2; peduncular article 1 with robust setae on ventral margin; peduncular article 2 slender; peduncular article 3 shorter than 1 or 2; accessory fl agellum present, minute, uniarticulate, apically rounded; fl agellum consisting of 17 articles, each article distally fringed with fi ne setae.
LOWER LIP (Fig. 13LL). Inner lobe smaller than outer lobe with short setae on distal margin; outer lobe longer than broad, distal margin rounded and with fi ne setae, distomedial margin with a pair of short blunt processes. MANDIBLES (Fig. 13MD). Well developed, subtriangular; left incisor with 5 teeth, right with 4; lacinia mobilis with 4 teeth on both right and left sides; left mandible armed with 6 accessory blades, right mandible with 9 accessory blades; molar process well developed, rounded; palp well developed, triarticulate; article 1 with fi ne setae on proximolateral corner and long setae on distal margin, article 2 slender with long setae throughout entire length, article 3 spatulate with long setae throughout entire length, subapical setae plumose, apical setae serrate.
MAXILLA 2 (Fig. 13MX2). Both lobes apically rounded; inner lobe shorter than outer lobe, lateral margin convex, medial margin with row of long slender setae; outer lobe lateral margin with short setae, apical setae serrate, subapical setae slender. MAXILLIPED (Fig. 13MXP). Inner lobe reaching distal end of article 1 of palp, distal end truncate with plumose setae along entire margin, medioproximal margin with long plumose setae, distolateral corner with fi ne setae; outer lobe almost reaching distal end of palp article 2, medial margin straight with long slender and robust setae, lateral margin convex with long fi ne setae on proximal half and short setae on distal half of margin; palp 4-articlulate, article 2 medial margin with long slender setae, article 3 spatulate, distal end with long slender and serrate setae, article 4 subtriangular, apically truncate ending in a stout spine. GNATHOPOD 1 (Fig. 12G1). Larger than gnathopod 2, carpochelate; distal articles highly setiferous; coxa small, subquadrate; basis proximoposterior margin notched, posterior margin expanded and slightly convex, distoposterior margin with slender setae, anterior margin straight; ischium subquadrate, distoposterior margin with slender setae; merus subtriangular, distoposterior margin with row of slender setae; carpus enlarged, at least twice as long as propodus, dorsal margin convex, ventral margin straight with a row of short plumose setae and submarginal short setae, palm with processes forming a broad excavate sinus; propodus ventral margin produced, with long slender setae, dorsal margin with long plumose setae; dactylus falcate; subequal in length to propodus.

Remarks
Grandidierella sungeicina sp. nov. is rather similar to illustrations made by Asari & Myers (1982) and Ledoyer (1979) of G. gilesi. However, there is much morphological variation of the gnathopod 1 propodus. Both Asari & Myers (1982) and Ledoyer (1979) showed no processes on the ventrodistal corner of the gnathopod 1 propodus, Chilton (1921) showed an apically acute process mid-margin while Myers (1981) had a blunt process. Grandidierella sungeicina sp. nov. on the other hand has an apically acute process. The new species also differs from G. gilesi wherein the merus of gnathopod 2 is distally truncate, instead of rounded, the ventral margin of the carpus is more convex and the inner face of propodus possesses a transverse row of long plumose setae instead of being oblique. Pereopod 6-7 coxae on the ventral margin do not possess plumose setae.

Discussion
The genus Grandidierella has a worldwide distribution with about fi ve valid species have been reported from the South China Sea -G. gilesi: Thailand (Bussarawich et al. 1984); G. halophilus: Thailand (type locality); G. melakaensis: Malaysia (type locality); G. phetraensis: Thailand (type locality); European Journal of Taxonomy 683: 1-28 (2020) G. vietnamica: Vietnam (type locality). As of now, only two species of Grandidierella are known from the waters of Singapore. Both Grandidierella pawaiensis sp. nov. and G. sungeicina sp. nov. are described and illustrated in detail based on specimens collected from Pulau Pawai and Sungei Cina respectively. The characteristics of G. pawaiensis sp. nov. agree well with those of G. bispinosa in Ledoyer (1979) and Myers (1981) in: 1) fl agellum of antenna 1 with a minimum of 11 articles; 2) carpus of gnathopod 1 large, with a single mediodistal tooth on inner face; 3) anterior margin of basis of gnathopod 2 crenulated; 4) strong interramal process of uropod 1 and; 5) uropod 3 with both one terminal and marginal seta each. However, it can easily be separated from both Ledoyer's (1979) and Myers' (1985) specimens by the following characters (characters of Ledoyer's and Myer's in parentheses): proximal margin of dactylus of gnathopod 1 male with excavation (without excavation and with fi ne setae along palm); peduncle of uropod 3 setulose anterodistally (not setulose). Grandidierella sungeicina sp. nov. on the other hand shares the diagnostic characters of G. gilesi, mainly in the structure of gnathopod 2. Based on the descriptions of G. gilesi by Asari & Myers (1982) and Ledoyer (1979), however, G. sungeicina sp. nov. can be distinguished from these specimens by different morphologies of the gnathopod 1, carpus of gnathopod 2 with a more convex ventral margin, and the lack of plumose setae on the ventral margin of coxae 6-7.
Taking into account the two species described in this paper, the genus Grandidierella now comprises 46 species. A further examination of the shallow and deep benthic habitats of the Singapore coasts, could reveal more undescribed gammaridean amphipods. The fi nding of these two new species of Grandidierella in South East Asia considerably extends the distributional range of the genus. Species of the genus are now known from European-North American (Munari et al. 2016), African and East Asian waters, which suggests that the genus basically could be present anywhere in the world.