Esanthelphusa nimoafi, Yeo, 2004

Yeo, Darren C. J., 2004, A New Species Of Esanthelphusa (Crustacea: Brachyura: Parathelphusidae) From Laos, And A Redescription Of Potamon (Parathelphusa) Dugasti Rathbun, 1902, Raffles Bulletin of Zoology 52 (1), pp. 219-226 : 222-225

Esanthelphusa nimoafi , new species

( Figs. 3-5 )

Esanthelphusa sp. – Carlsson, 2004: 15.

Esanthelphasa nimoafi – Carlsson, 2004: 17, 63, 64, Fig. 4 (nomen nudum).

Material examined. – Holotype - male, 34.6 by 27.2 mm ( ZRC 2003.0268 ), That Luang wetlands, outskirts of Vientianne, Laos, coll. A. Kestrup & M. Martensson, 1-15 Nov.2002.

Paratypes – 2 males (32.5 by 23.9 mm, 30.1 by 23.9 mm), 1 female (36.0 by 27.9 mm) ( ZRC 2003.0269 ), same data as holotype ; 2 males (32.5 by 24.5 mm, 26.6 by 20.9 mm), 2 females (34.4 by 25.9 mm, 33.8 by 26.2 mm) ( ZRC 2003.0270 ), That Luang swamp, outside Vientianne, Laos, coll. N. Carlsson, 17 Jan.2003 .

Diagnosis. – Carapace broader than long, high; dorsal surface longitudinally convex; cervical grooves shallow; epigastric cristae slightly anterior to postorbital cristae; postorbital cristae short, not reaching beginning of cervical grooves; antennular fossae subrectangular; external orbital angle acutely triangular, outer margin longer than inner margin, separated from first epibranchial tooth by narrow triangular cleft; anterolateral margin with three well developed, acute epibranchial teeth. Chelipeds unequal, outer surfaces smooth. Ambulatory meri subdistal spine present. Abdominal cavity reaching imaginary line joining anterior edge of cheliped bases. Male telson tongue shaped, with lateral margins gently concave; sixth male abdominal segment constricted, with gently concave lateral margins. G1 distal part relatively long, subequal in length to proximal part, slender, strongly curved and bent outwards, tip acute, strongly hooked, directed downwards to obliquely inward; proximal part expanded. G2 distal segment distinctly shorter than half of basal segment.

Variation. – Slight variation was observed in the G1 structure of E. nimoafi specimens, in that the tip of some male paratype specimens were more acute in appearance and more strongly hooked than in the holotype ( Figs. 5 C-F, I-K). In addition, the basal part outer margin of the expanded proximal part of the G1 was sometimes collapsed to different degrees in various specimens. This is an artefact resulting from preservation, shrinkage and handling that is often seen in Esanthelphusa species (pers. observ.).

Etymology. – The species is named after the collectors, Nils Carlsson, Asa Kestrup and Monica Martensson, with the specific epithet being an arbitrary combination of their initials.

Ecological notes – Esanthelphusa nimoafi is common in both rice fields and wetlands around Vientianne, Laos. They appear to be territorial and quarrelsome, with larger individuals often attacking smaller conspecifics. They normally burrow into the mud, down to a depth of at least 50 cm (Nils Carlsson, pers. comm.).

In a recent study by Carlsson (2004), E. nimoafi was found to be an important predator of the invasive gastropod species, the Golden apple snail ( Pomacea canaliculata ), which is a major pest on rice and other aquatic plants in Southeast Asian wetlands.

Remarks. – Carlsson (2004) first used the name Esanthelphusa nimoafi in a published thesis (with an ISBN number) and although he citied that it was by “Yeo, in press”, the fact is the latter paper was not yet published. The name as cited by Carlsson, however, is not valid under the current ICZN (1999) rules as it was not accompanied by any description, diagnosis or morphological comparisons. The present paper, which provides the necessary diagnosis and morphological comparisons, thus represents the first valid publication of the name.

The strongly convex carapace dorsal surface, weak cervical grooves, postorbital cristae ending well before the beginning of cervical grooves, and relatively short and hooked G1 distal part clearly place the present species in the genus Esanthelphusa Naiyanetr, 1994 .

Esanthelphusa nimoafi , new species, is most likely to be confused with E. dugasti ( Rathbun, 1902) in its well developed and acute epibranchial teeth and overall form of the G1. However, upon comparing directly with the holotype as well as non-types of E. dugasti , it was found that E. nimoafi can easily be distinguished from E. dugasti by the following diagnostic G1 characters: distal part proportionately longer, subequal in length to basal part, and slenderer (versus G1 distal part proportionately shorter, shorter than basal part, and stouter); and tip of G1 acute and more strongly hooked, directed downwards to obliquely inward (versus tip of G1 broadly tapered and less strongly hooked, directed obliquely outward) ( Figs. 2 B-E, 5C-F, I-K). These differences apply to much larger as well as similar-sized E. dugasti specimens (present study).

Esanthelphusa nimoafi further differs from E. dugasti by the lateral margins of the sixth abdominal segment being gently and less strongly concave, with distal margin about 1.8 to 1.9 times as broad as narrowest part (versus sixth abdominal segment lateral margins abruptly and more strongly concave, with distal margin broadest about 1.9 to 2.1 times as broad as narrowest part) ( Figs. 1C , 5G ). This character, however, is less reliable when the comparing E. nimoafi against small, similar-sized E. dugasti specimens. Esanthelphusa nimoafi does appear to be a generally smaller species than E. dugasti , as all individuals encountered were no larger than those in the present type series (carapace width up to 36 mm) (Nils Carlsson, pers. comm.). Esanthelphusa dugasti , on the other hand, attains sizes of up to carapace width 50 mm or more (present study).

The only other Esanthelphusa species with superficially similar G1 shapes to E. nimoafi are E. phetchaburi (Ng & Naiyanetr, 1993) and E. chiangmai (Ng & Naiyanetr, 1993) . Esanthelphusa nimoafi , however, possesses well developed and acute epibranchial teeth (versus epibranchial teeth very low, weak and broad in E. phetchaburi and E. chiangmai ) ( Figs. 3 , 5A ; cf. Ng & Naiyanetr, 1993: Figs. 31, 32). The G1 of E. nimoafi also differs from both E. phetchaburi and E. chiangmai in the outwardly bent portion of the distal part being proportionately longer (versus proportionately shorter) ( Figs. 5 C-F, I-K; cf. Ng & Naiyanetr, 1993: Figs. 66, 67).

Distribution. – The present specimens of Esanthelphusa nimoafi were collected from Thet Luang swamp, outside Vientianne, Laos.

Comparative Material. – Esanthelphusa phetchaburi (Ng & Naiyanetr, 1993) – Holotype - male (33.5 by 26.1 mm) ( ZRC 1991.1886 ), 2-3 km from Phetchaburi town (99 56’N 13 06’E), Muang Phetchaburi District, Phetchaburi Province, Thailand, coll. P. K. L. Ng, Dec.1984 . Paratype - 1 female (18.4 by 14.6 mm) ( ZRC 1991.1887 ), same data as holotype. Others - 2 males 1 female ( ZRC), Khok Samrong District, Lop Buri Province, southern Thailand, coll. Vinai, 21 Oct.1979 ; 1 male 2 females (male 44.0 by 33.0 mm) ( CUMZ), same data as above ; 4 males, 1 female ( ZRC), Muang Prachuap Khiri Khan District, Prachuap Khiri Khan Province, Thailand, coll. Varoonphorn, 8 Oct.1979 . Esanthelphusa chiangmai (Ng & Naiyanetr, 1993) – Holotype - male (44.0 by 33.3 mm) ( RMNH D 42347 ), Buagcrok village , near Sonkampaeng, Muang Chiang Mai District, Chiang Mai Province, northern Thailand, coll. P. K. L. Ng, 29 Dec.1991 . Paratypes - 2 males, 5 females ( ZRC) , 1 male (43.8 by 33.1 mm), 1 female (32.7 by 25.2 mm) ( RMNH D 42028 ), Buagcrok village , near Sonkampaeng, Muang Chiangmai District, Chiangmai Province, Thailand, coll. P.K.L. Ng, 28-29 Dec.1991 ; 8 males, 28 females ( ZRC), Sanpathong District, Chiangmai Province, Thailand, coll. P.K.L. Ng, 28-29 Dec.1991 ; 10 males, 3 females ( ZRC), Handong District, Chiangmai Province, Thailand, coll. P.K.L. Ng, 28-29 Dec.1991 ; 12 males, 5 females ( ZRC), Handong District ; 12 males, 8 females ( ZRC), Mae Sa Village , Muang Chiangmai District, Chiangmai Province, Thailand, coll. P.K.L. Ng, 28-29 Dec.1991 . Others - 3 males ( ZRC), Muang Lamphun District, Lamphun Province, Thailand, coll. P. Naiyanetr, 20 Aug.1974 ; 2 males, 1 females ( ZRC), Muang Uttaradit District, Uttaradit Province, Thailand, coll. P. Naiyanetr, 13 Aug.1974 .

Figures

Fig. 3. Esanthelphusa nimoafi, new species, holotype male (34.6 by 27.2 mm) (ZRC 2003.0268). Dorsal view.

Fig. 5. Esanthelphusa nimoafi, new species. A-H, holotype male (34.6 by 27.2 mm) (ZRC 2003.0268); I, paratype male (30.1 by 23.9 mm) (ZRC 2003.0269); J, K, paratype male (32.5 by 23.9 mm) (ZRC 32.5 by 23.9 mm). A, anterior carapace; B, left third maxilliped; C-F, I- K, right G1, C, I, J: dorsal view, D, K: ventral view, E: dorsal view of distal part, F, ventral view of distal part; G, abdominal segments 5-7; H, right G2. Scales = 5.0 mm in A, B, G; 1.0 mm in C, D, H-K; 0.5 mm in E, F.

Fig. 2. Esanthelphusa dugasti (Rathbun, 1902), holotype male (46.0 by 36.7 mm) (MNHN-B 5113). A, left third maxilliped; B-E, right G1, B: dorsal view, C: ventral view, D: dorsal view of distal part, E: ventral view of distal part; F, right G2. Scales = 2.0 mm in A; 1.0 mm in B, C, F; 0.5 mm in D, E.

Fig. 1. Esanthelphusa dugasti (Rathbun, 1902), holotype male (46.0 by 36.7 mm) (MNHN-B 5113). A, dorsal view; B, frontal view; C. ventral view.