Shallow water marine gammaridean amphipods of Pulau Tioman, Malaysia, with the description of a new species

Abstract Eleven taxa including one new species of gammaridean amphipods are reported from the waters of Pulau Tioman. The presence of Tethygeneia sunda sp. n. represents the first record of the genus from the South China Sea. Additional material of Ampelisca brevicornis (Costa, 1853); Cymadusa vadosa Imbach, 1967; Paradexamine setigera Hirayama, 1984; Ericthonius pugnax (Dana, 1853); Leucothoe furina (Savigny, 1816); Microlysias xenokeras (Stebbing, 1918); Monoculodes muwoni Jo, 1990 are identified from the South China Sea, supporting previous records by Lowry (2000), Huang (1994), Imbach (1967), Margulis (1968) and Nagata (1959). Three additional species, Gitanopsis pusilla K.H. Barnard, 1916, Liljeborgia japonica Nagata, 1965b and Latigammaropsis atlantica (Stebbing, 1888), whilst previously reported from the neighbouring waters, comprise new records for the South China Sea.


introduction
According to Lim et al. (2010), taxonomic knowledge on the gammaridean amphipods from the waters of Peninsular Malaysia has been poorly studied in the past. Whilst there have been several revisions of species or even genera around Malaysia, most of the studies have been of a sporadic nature, with miscellaneous small papers on various taxa (e. g Muller 1993;Morino 1996, 2006;Othman and Azman 2007;Tomikawa et al. 2007;Melvin 2011, andOthman 2012). All these indicate the regional gammaridean taxa are largely poorly known but likely to be diverse and potential diversity of species still waiting for our investigation.
Particular efforts in conducting more regional based studies should be emphasized to further advance the biodiversity knowledge of these numerically abundant and taxonomically diverse taxa. Hence, the result of this work should in addition to documenting the amphipod fauna, provide new insights into the diversity and distribution patterns of the South China Sea amphipods.
Located 2°35' north of the equator and in the South China Sea, Pulau Tioman (pulau = island) is an island of approximately 100 km 2 in area, lying 20 km off the southeastern coast of the Malay Peninsular. Apart from its beautiful beaches and marine ecosystems, the marine areas around Pulau Tioman and eight other nearby islands (Pulau Tulai, Pulau Sepoi, Pulau Chebeh, Pulau Tokong Bahara, Pulau Sembilang, Pulau Sri Bulat, Pulau Labas and Pulau Gut) have also been gazzeted as marine parks and marine reserves under the Fisheries Act (1985). The establishment of the marine parks and marine reserves is to conserve, protect marine fauna and flora such as fishes, coral reefs and aquatic floras from being destroyed by fishing and other human activities.
In the framework of research on taxonomic revision and ecology of selected families of gammaridean amphipods conducted at Pulau Tioman, several qualitative benthic samples from different habitats and substrate types have been analysed. In some of these samples, specimens of gammaridean amphipods were found, one of which belongs to new species herein described, and for those species already known, the morphology of populations from Pulau Tioman are compared with other populations described in the literature. Due to the high importance of Pulau Tioman to maintain inventories for scientific marine studies in the Marine Protected Areas of Malaysia, we consider it important to include these species in this report, together with the description of the new taxa.
Remarks. Ampelisca brevicornis is known to be a cosmopolitan species and has been collected from the soft substrata and water column from the littoral zone to the continental shelf from the waters of the world except for boreal areas (Rabindranath 1975;Lincoln 1979;Hirayama 1983). A. brevicornis was first recorded from the Mediterranean Sea (Costa 1853) by the name Araneops brevicornis; it occurs in waters of variable temperatures from north east Atlantic (Schellenberg 1925), south and west Norway (Sars 1895), Atlantic coast of Europe (Lincoln 1979), north Africa (Kaim-Malka 1969;Reid 1951), Indian Ocean (Rabindranath 1975), Japan (Nagata 1965a;Hirayama 1991), Indonesian archipelago (Pirlot 1936) as well as the neighbouring waters of Vietnam (Imbach 1967). Although several morphological variations in antennae, pleonal epimera and urosome are reported between European (Schellenberg 1925) and African specimens (Reid 1951), the present specimens agree in detail with descriptions by Imbach (1967) and Nagata (1959). Imbach (1967) discussed some of the variations concerning this particular species and refuted the idea of naming the existing ecophenotypes reported by Schellenberg (1925), Reid (1951), Dahl (1945) and Pirlot (1936) as a subspecies due to their insignificant distinctions.
Taking into consideration that A. brevicornis is one of the most popular inhabitants on a littoral sea bottom and widely distributed on the sea floor of the east coast (South China Sea) and the west coast (Straits of Malacca) of Peninsular Malaysia, and numerous specimens have been meticulously examined, misidentification can be confidently ruled out. The specimens at hand show only minor disparities from Imbach's by having a broader propodus of pereopod 7, so it is clearly satisfactory to identify the specimens as A. brevicornis.
Remarks. The Malaysian specimens differ from those described from the waters of Japan only by the lack of the accessory setae of the mandible. At present, this seems inadequate for subspecific distinction due to the enormous resemblance of other char- acters shared between them. Even though Hirayama (1984) mentioned the closely related P. micronesica, it also lacks the accessory setae of the mandible. Furthermore, the Pulau Tioman specimens show several differences from P. micronesica by having; 1) slenderer basis of pereopod 7; 2) several robust setae on dorsal surface of telson; 3) shorter carpus of male gnathopod 2.

Liljeborgiidae Stebbing, 1899
Liljeborgia japonica Nagata, 1965b http://species-id.net/wiki/Liljeborgia_japonica Remarks. The Pulau Tioman material accords well with the description and figures of Nagata (1965b). This is the first record of the species outside Japan.

Lysianassidae Dana, 1849
Microlysias xenokeras (Stebbing, 1918) http://species-id.net/wiki/Microlysias_xenokeras   Remarks. Griffiths (1975) re-examined this species after discovering an erroneous identification in his earlier publication (see Griffiths 1973a) was based on Barnard's (1937) M. indica. Specimens from Durban Bay, described by Stebbing were the same as Griffiths's M. xenokeras. M. xenokeras is the only species in the genus known thus far, and has only been recorded in from the waters of South Africa and Mozambique. It has quite distinctive characters: 1) antenna 1 short and stout, 2) gnathopod 2 minutely chelate, 3) uropod 3 outer ramus 2-articulate, 4) telson with short robust setae dorsally and apically.
Remarks. The Pulau Tioman specimens closely resemble Jo's (1990) figures described from the Korean peninsula; since then it has not been recorded anywhere else. The short and rather stout rostrum, propodus length of gnathopod 2, parallel sided telson and poorly produced posterodistal corner of coxal plate 4 are several characters unique to this species. However, the identification is not fully satisfactory in the following respects: the long carpal lobes of gnathopods and the double spine rows of the inner ramus of uropod 2. Otherwise, all specimens agree with M. muwoni.

Remarks. Recently Myers
The Pulau Tioman specimens undoubtedly represent the tropical members (afraatlantica group) by having an article 2 on the outer ramus of uropod 3 and the inner plate of maxilla 1 has at least 3, often 5+ setae lining the medial margin (Barnard 1970). The presence of the lageniform eye links the specimens at hand with, L. afra, L. athenae Myers, 2009, L. atlantica, L. photisimilis (Ruffo, 1969) and L. hestia Myers, 2009. Although the Pulau Tioman specimens are more closely related to L. gemina, with the accessory flagellum with 4 articles, inner plate of maxilla 1 with 5+ setae lining the medial margin and occurence of nobs on the urosomal margin. L. gemina still does not agree with the specimens at hand in having oval eyes and the telson lacking medial setae.
Description. Male: 4.5 mm. Head, rostrum large, long, curved down, apically blunt, lateral cephalic lobe broad, shallow, quadriform, defined below by weak but sharp incision; antero-ventral margin bulbous, rounded. Eye large, occupying more than half of head area.
Antenna 1 only about 70 percent as long as antenna 2; flagellum with about 21-articulate, ornamented with aesthetascs ventrally; accessory flagellum absent. Antenna 2 about half as long as body; gland cone of peduncular article 2 broad, extending beyond of peduncle article 3; flagellum long and thin with about 28 articles.
Mandible, molar triturative, each with ragged seta; lacinia mobilis serrate and clearly distinct; palp with article 2 about twice as broad as article 3, latter slightly falcate. Lower lip lacking inner lobes, mandibular lobes subtruncate and apically fringed with small setae. Maxilliped inner plate with apicolateral spine separated from 2 medioapical spines by gap and hollow; outer plate with facial setules in 1 row and a few scattered; palp article 2 broad. Maxilla 1, palp article 2 stout armed with several short teeth apically. Maxilla 2, outer plate broader than inner plate, both with plumose setae along margin.
Uropod 1 peduncle spinose on lateral margin, almost 2 times as long as outer ramus, one medium sized robust seta at distal part; outer ramus about 0.7 times as long as inner ramus, apex bifid, armed with several apical spines, one elongate. Uropod 2 extending beyond telson; peduncle subequal in length to inner ramus, spinose, and with one long robust seta at distal end; outer ramus almost 0.6 times as long as inner ramus with several apical robust setae; inner ramus apically bifid with several robust setae along margin. Uropod 3 peduncle short; rami foliaceous, subequal in length, marginally spinose and setose. Telson flat, broad, cleft more than halfway, apices slightly rounded, broad, smooth, lateral margins of lobes with 2 pairs of partial sets of fine short setae.
warm temperate waters of both hemispheres. The key character that clearly differentiates the genus from the other known eusiriids is the long and linguiform rostrum. Although this linguiform nature of the rostrum is also observed in some genera within the family (e.g. Pontogenia, Gondogeneia), Tethygeneia relatively exhibits a stronger form of prolonged rostrum. Since 1991, Barnard and Karaman listed 10 species of Tethygeneia that are mostly described from the warm-temperate waters of Australia. T. sunda sp. n. falls undoubtedly into the genus according to J.L. Barnard's eusiriid revisional framework (1972). It resembles T. intermedia (Gurjanova) in lacking a carpal lobe on gnathopod 2, but is rather closely related to T. rostrata (Gurjanova) and T. longleyi (Shoemaker) in the other characters. Differing from T. rostrata in the more slender articles of carpus and propodus of gnathopod 2, in the slightly more produced article 3 of antenna 1, and the more spinose rami of uropod 3. Tethygeneia longleyi shares the same form of head, gnathopods and uropods as in T. sunda sp. n. However some noteworthy differences are observed in the mouthparts, especially the mandible. The length and structure of article 2 of the mandible palp clearly distinguish T. longleyi from T. sunda sp. n. Etymology. The specific designation is derived from the name of the Sunda shelf, which was part of the south-east Asian continent during the Pleistocene.
Higher Education of Malaysia and a UKM research grant (DIP-2012-020). Thanks are also due to the Marine Park Section, Department of Fisheries, Malaysia.