Parathelphusa manguao, Freitag & Yeo, 2004

Freitag, Hendrik & Yeo, Darren C. J., 2004, Two New Species Of Parathelphusa H. Milne Edwards, 1853, From The Philippines (Crustacea: Decapoda: Brachyura: Parathelphusidae), Raffles Bulletin of Zoology 52 (1), pp. 227-237 : 232-236

Parathelphusa manguao , new species

( Figs. 5-8 )

Material examined. – Holotype – male (21.9 by 18.2 mm) ( PNM 17283 ), Lake Manguao, Municipality of Taytay, coll. S. Schoppe ( SPCP-ASTD), 21 Nov.2001.

Paratypes – 1 female (26.6 by 22.3 mm) ( SPCP-ASTD) , 1 male (16.6 by 14.3 mm) ( SPCP-ASTD) , 1 female (16.4 by 14.2 mm) ( ZIH) , 1juvenile male (13.8 by 12.3 mm) ( ZIH) , 1 juvenile female (15.6 by 13.5 mm), 1 juvenile male (13.2 by 11.4 mm) ( ZRC2004.0623 ) , 1 juvenile female (15.3 by 13.1 mm) ( PNM 17283 ) , same data as holotype .

Others (designated for ecological studies) – 4 juvenile females (largest 14.3 by 12.5 mm) ( SPCP-ASTD), same data as holotype .

Diagnosis. – Carapace low, dorsal surface gently convex; postorbital cristae strongly developed, sinuous, with lateral part strongly arched in adults; cervical grooves shallow but distinct; epibranchial teeth well developed, sharp, directed forwards. Merus of ambulatory legs with well developed subdistal spine on dorsal margin. Male sixth abdominal segment relatively stout, longer than telson (segment 7). G1 gently but distinctly bent outwards at the middle, slender, with upper half of proximal part subequal in width to distal part; tip truncate, broad, with slight subdistal swelling.

Etymology. – The species is named for the type locality, Lake Manguao, (Municipality of Taytay, northern Palawan). The name is used as a name in apposition.

Colour. – In life, dorsal carapace dark brown, and slightly spotted; legs dark brown with a cross pattern of lighter brown; ventral parts (sternum and abdomen) dirty-white colour; fingers of the chelipeds dark reddish brown, except for the lighter coloured fingertips (S. Schoppe, pers. comm). All preserved type specimens in alcohol with similar coloration, probably due to initial preservation in formalin.

Remarks. – Among the Philippine freshwater crab fauna, P. manguao may be confused with P. palawanensis ( Bott, 1969) , P. saginata Ng & Takeda, 1993 , P. mindoro Ng & Takeda, 1993 , or P. cabayugan , new species, by virtue of its sharp and well-developed epibranchial teeth. The form of the G1 of P. manguao also superficially resembles that of P. rasilis Ng & Takeda, 1993 , and P. ovum Ng, 1994 [Sabah, Borneo]. However, the very slender overall form of the G1 immediately distinguishes P. manguao from all the above species. While the G1 of P. saginata is also relatively slender in appearance when compared with its other congeners, that of P. manguao is still more slender, more strongly bent, and has a truncate tip (versus sharp tip)( Fig. 6 ; cf. Ng & Takeda, 1993: Fig. 4 ). Furthermore, the ambulatory legs of P. manguao possess a well developed subdistal spine on the dorsal margin (versus subdistal spine absent in P. saginata ) ( Figs. 5C, D , 8A, B ; cf. Ng & Takeda, 1993: Fig. 4 ). In addition to these, other small specific differences in the G1 as well as differences in external characters such as the strongly arched lateral part of the postorbital cristae combine to give a diagnostic suite of characters for the species (see Tables 1A, B).

While juvenile specimens also have sharp, well-developed epibranchial teeth ( Fig. 8A ), the condition of the postorbital cristae mentioned above is seen only in adults of P. manguao .

Ecological notes. – The type specimens of P. manguao were caught at the northern littoral of Lake Manguao (10 45’27”N, 119 33’30” E) among stony substrate. Parathelphusa species have also been observed from many other parts of the lake (S. Schoppe, pers. comm.). The authors have not had the opportunity to examine these other specimens; however, bearing in mind the highly restricted distributions of most Philippine Parathelphusa species (present study; Ng & Takeda, 1993), it is likely that they are also P. manguao .

The banks of Lake Manguao are dominated by rock, rarely grit and sand. Physico-chemical data for April 1989 are provided by Davies & Green (1990), and for 21-22 November 2001 from a survey conducted by the SPCP Aquatic Science & Technology Department. Water temperature ranged from 26.4 C to 30.5 C in 1989, and around 26.8 C in 2001. The water was slightly alkaline, with the pH varying from 8.1 to 8.86 (Davies & Green, 1990), and 7.44 to 7.77 at the surface slightly decreasing towards bottom to a minimum of 6.79 (SPCP-ASTD). Dissolved oxygen (DO) was found between 9.5 mg /lª 127% saturation (morning, water surface) and 6.3 mg /lª 79% saturation (early night, water surface) in the Davies & Green (1990) study. Values of the second study were 5.2 mg /l to 8.7 mg /l. From both studies, no substantial variations in DO were reported between surface and bottom layers indicating good vertical circulation. Conductivity was reported to be 43 S/cm (Davies & Green, 1990) and 55 S/ cm to 79 S/cm (SPCP-ASTD).

Figures

Fig. 5. Parathelphusa manguao, new species. Holotype male (21.9 by 18.2 mm) (PNM 17283). A, dorsal view of carapace; B, frontal view of carapace; C, right fourth ambulatory merus; D, right third ambulatory merus; E, right chela; F, abdominal segments 5-7. Scales = 10.0 mm.

Fig. 6. Parathelphusa manguao, new species, left G1. A-D, holotype male (21.9 by 18.2 mm) (PNM 17283); E-H, paratype juvenile male (13.8 by 12.3 mm) (ZIH). A, E, ventral view; B, F, dorsal view; C, G, ventral view of distal part; D, H, dorsal view of distal part. Scales = 1.0 mm.

Fig. 7. Parathelphusa manguao, new species. Holotype male (21.9 by 18.2 mm) (PNM 17283). A, dorsal view; B frontal view; C, ventral view.

Fig. 8. Parathelphusa manguao, new species. A, paratype juvenile male (13.8 by 12.3 mm) (ZIH); B, paratype female (26.6 by 22.3 mm) (SPCP-ASTD).

Fig. 4. Parathelphusa cabayugan, new species, paratype female (26.4 by 21.6 mm) (ZIH).