Urothoe tinggiensis, Azman, B. A. R. & Melvin, C. W. H., 2011

Azman, B. A. R. & Melvin, C. W. H., 2011, Two new species of Urothoe (Crustacea, Amphipoda, Gammaridea) from the East Johor Islands Archipelago, Malaysia, ZooKeys 87, pp. 43-62 : 48-50

Urothoe tinggiensis sp. n. Figs 3A3E

Type material.

Holotype, female, 2.0 mm, UKMMZ-1399, muddy-sand substrate of Pulau Tinggi, 2°16'51.70"N, 104°7'15.96"E, airlift suction sampler, 9 m, B.A.R. Azman, C.W.H. Melvin, J.H.C. Lim, 19 July 2007, UKM I.D. 8632. Paratype: 4 females UKMMZ-1401, same station data.

Type locality.

Pulau Tinggi, Johor, Malaysia, South China Sea

Etymology.

Named after the type locality, Pulau Tinggi in East Johor, Malaysia.

Description:

Based on holotype female, 2.0 mm, UKMMZ-1399.

Head

lateroventral cephalic lobes rounded and very pronounced, rostrum absent. Eyes minute, circular. Antenna 1 peduncular articles 1 - 2 provided with setae along the ventral margin; accessory flagellum triarticulate; main flagellum distinctly shorter than peduncle, about as long as peduncle article 3, 5 articulate. Antenna 2 subequal to antenna 1; flagellum biarticulae; first article with several robust setae and long setae all over; second article with several robust setae and long setae. Upper lip semicircular. Lower lip inner plate large, shoulders broad, mandibular process prominently winged outward. Maxilla 1 inner plate with pinnate seta apically; outer plate with two setae, one pinnate and a seta; palp densely filled with robust setae apically. Maxilla 2 inner and outer plates furnished with pinnate and simple setae. Mandible molar rounded and well-developed; incisor smooth; palp strong; first article shorter than second article; second and third article subequal in length; third article with several robust setae distally. Maxilliped inner plate elongate with about 2 blunt robust setae; outer plate suboval with several spines and setae; palp 4-articulate, second article wide and densely setose on inner margin, third article subtrianglular with several long setae, fourth article subtriangular and small.

Pereon

Gnathopod 1 coxa narrow, subrectangular; basis elongate with several long setae along the posterior margin; carpus broad furnished with several setae at posterior margin, about as broad as long; propodus wide with several long setae situated anterodistally; dactylus normal. Gnathopod 2 coxa narrow, subrectangular; basis elongate with several long setae along the posterior margin; carpus suboval in shape; propodus wide provided with several long setae at anterodistal angle; dactylus falcate, slightly extending palm when closed.

Pereopod 3 - 4

homopodous, coxa subquadrate; basis elongate provided with few long setae; carpus twice as long as merus; propodus narrow; dactylus nodulate. Pereopod 5 coxa small, bilobate; basis semicircular, few plumose setae along posterior margin; ischium wider than long; merus wider than long, provided with two transverse rows of robust setae and a row of plumose setae; carpus twice as long as wide, 4 transverse rows of robust setae, one traverse row of plumose setae; propodus longer than wide, provided with 3 traverse rows of robust setae; dactylus large, with 3-4 robust setae along anterior margin. Pereopod 6 coxa subquadrate; basis wide, oval shape, several plumose setae along posterior margin; merus longer than wide; carpus longer than wide, robust setae along anterior margin; propodus shorter than merus, robust setae along anterior margin; dactylus nodulate. Pereopod 7 coxa subtriangular; basis oval shape; merus longer than wide, few robust setae; carpus longer than wide, robust setae along anterior margin and posterior margin; propodus longer than wide provided with several robust setae; dactylus nodulate.

Pleon

Pleopods 1-3 peduncle shortened and slightly expanded distally; outer ramus longer than inner ramus; rami multiarticulate. Uropod 1 peduncle with several robust setae lining at the medial margin and distally; rami subequal in length. Uropod 2 peduncle provided with 2 robust setae and a robust seta distally; rami subequal in length. Uropod 3 well developed; both rami with long plumose setae; outer ramus 2 biarticulate; inner ramus shorter than outer ramus. Telson about 5/6 cleft; both lobes with 2 setae apically and a seta medially.

Remarks.

According to the proposed classification of the ‘falcata’ group by Barnard (1962), members of this group possess dissimilar gnathopods; gnathopod 1 simple, elongated and slender propodus, bearing no palm; gnathopod 2 has a suboval or slightly expanding propodus with a distinct, rounded palm. With these characters our species is clearly attributed to the ‘falcata’ group. However, there are perceivable d ifferences that can be ruled out between the new species and all the members of the group. As such, the setose dactylus of pereopod 5 in Urothoe tinggiensis is readily distinguished from the non-spinose dactylus of pereopod 5 in Urothoe pinnata and Urothoe tumorosa . Differing from Urothoe platydactyla in the expanding and elliptical shape of the pereopod 5 dactylus. Both the pereopod 6 and 7 are somewhat different from Urothoe platypoda ; the merus and carpus in Urothoe tinggiensis is considerably linear and elongated while the merus and carpus of both pereopod 6 and 7 in Urothoe platypoda are lobed posteriorly. The enormously produced coxa 4 in Urothoe coxalis is contrastingly distinctive from the normal subquadrate coxa 4 of Urothoe tinggiensis . The new species appears to have close affinities to Urothoe orientalis due to the wide carpus of pereopod 5 but clearly distinguished from the latter in the shape of propodus of gnathopod 1 and the absence of robust setae on the outer ramus of uropods 1 and 2. Urothoe tinggiensis is also distinguished from Urothoe oniscoides by the presence of eyes. The new species has some remarkable similarities with Urothoe cuspis Imbach, 1969 from Bay of Nhatrang, Vietnam, but seem to be different from the latter in the acuminate cuspidate coxa 2.

Distribution.

Malaysia. Johor: Pulau Tinggi.