Labuanium papuomalesiacum ( Nobili, 1899 )

Ng, Peter K. L. & Davie, Peter J. F., 2011, Labuanium vitatum (Crustacea: Decapoda: Brachyura: Sesarmidae), a new Indo-West Pacific species of arboreal crab, Zootaxa 2889, pp. 35-48 : 36-37

Labuanium papuomalesiacum ( Nobili, 1899)

( Figs. 2 B, 3B, 4B, 5C, 6B, 9, 10H-K)

Sesarma (Episesarma) rotundata papuo -malesiaca Nobili, 1899: 268 (type locality New Guinea); Nobili 1900: 510 (part). Sesarma (Sesarma) rotundata — Tesch 1917: 193 (in part); Sendler 1923: 33.

Material examined. Ovigerous female (25.5 × 24.9 mm) ( ZRC), Kri I., Raja Ampat, northwestern Irian Jaya, Indonesia, coll. H. H. Tan, December 2010; 4 males (38.0 × 37.4 mm, 32.5 × 32.1 mm, 33.0 × 32.4 mm, 18.5 × 18.7 mm), 2 females (31.9 × 31.9 mm, 31.2 × 29.0 mm, 21.0 × 21.0 mm) ( SMF 1971.18.5.53), Yap, Caroline Is., coll. E. Wolff; 3 males (28.8 × 29.0 mm, 26.3 × 26.1 mm, 24.6 × 24.5 mm), 1 female (30.5 × 30.3 mm) ( SMF 1972.18.5.53), Bertrand I., Papua-New Guinea, coll. E. Wolff; 1 male (40.9 × 38.8 mm) ( USNM 1150441), Teurai Bay, Vanikoro I., St. Cruz Group, Solomon Islands, coll. 6 May 1933.

Diagnosis. Carapace width and length subequal; antero-dorsal surfaces finely granular, posterior surfaces almost smooth ( Figs. 2 B, 9A, B); posterolateral regions with fine granular oblique striae ( Figs. 2 B, 9A, B); postfrontal cristae distinct, sharp, medially separated by prominent cleft ( Figs. 2 B, 3B, 9A, B); merus of third maxilliped in adult male longitudinally ovate, length 1.5–1.6 times width (Fig. 4B); inner margin of cheliped carpus with prominent triangular tooth, margins not lined with prominent granules ( Figs. 2 B, 5C, 9A, B); outer surface of chela with numerous small, closely arranged rounded granules ( Figs. 9 C, D); dorsal margin of male chela with a nonpectinate ridge on outer edge of about 39–42 small granules, with 2 shorter, less distinct oblique rows of granules posterior to it, ridges distinct even in large males ( Figs. 2 B, 5C); dorsal surface of cheliped dactylus with row of 10–12 granules ( Figs. 2 B, 5C); outer surface of ambulatory meri gently rugose, dorsal margin finely granulated ( Figs. 2 B, 9A, B); male abdominal somite 6 broader than long, distal part of lateral margins convex, proximal part gently sinuous or convex ( Fig. 6 B); telson as long as somite 6, subtriangular in shape with rounded tip ( Fig. 6 B); G1 relatively long; distal part bent about 60° from vertical, distal chitinous part relatively long, tip more rounded ( Fig. 10 H–K).

Remarks. Labuanium rotundatum sensu lato, is characterised by the presence of large, rounded, and well spaced granules on the outer surface of the chela ( Ng & Liu 2003: fig. 7A). Ng & Liu (2003) reidentified old records of “ L. rotundatum ” from China, Japan and Taiwan, as a new species, L. scandens , characterised by the outer surface of the chela possessing numerous small and closely spaced granules ( Figs. 7 A, 9C, D; Ng & Liu 2003: fig. 3A).

Sesarma (Episesarma) rotundata papuomalesiaca Nobili, 1899 , has long been synonymised under L. rotundatum (see Tesch 1917), but a re-examination of material from New Guinea and nearby areas shows that it is actually much closer to L. scandens . Nobili’s (1899) taxon was described from two males and one female from Andai and Geelvink Bay (= present day Cenderawasih Bay) in New Guinea (present day Indonesian West Papua or Irian Jaya). Nobili (1899) also mentioned a male specimen from Nias I., and noted that like the New Guinean material, it was different from L. rotundata but would be treated elsewhere. Although he did not explicitly refer the Nias material to his new taxon, he nevertheless treated it as such. Only later ( Nobili 1900) did he formally refer this Nias specimen to his new subspecies. However, in the context of his 1899 paper, all his New Guinean and Nias material should be regarded as syntypes. To stabilize the taxonomy of this species as well as L. vitatum new species, we here select the male described and measured by Nobili (1899: 269) which measures 35.0 by 33.0 mm from Geelvink Bay as the lectotype of Sesarma (Episesarma) rotundata papuomalesiaca Nobili, 1899 . All other syntype specimens mentioned above are thus now paralectotypes.

While Nobili’s (1899: 268, 269) description is relatively short, he nevertheless comments: “Le mani sono abbondantemente fornite all’esterno di granuli rotondi, che si riscontrano pure, ma minori di numero e di dimensioni dalla parte interna. Il suo margine superiore è definito da una ben distinctcrest denticolata, decorrente dalla porzione terminale superiore dell’articolazione del carpo, all’articolazione del dito mobile. Dietro e fra essa e la faccia interna trovansi due piccole crestine varaiamente disposte secondo gli esemplari e le mani, ma sempre ad angolo colla cresta stessa. La prima anzi vi si congiunge al termine del bordo superiore della mano. Questo carattere non trovo accennato nella descrizione di De Man, e quindi data la precisione scrupolosa di questo illustre carcinologo, credo manchi nella forma tipica. Il dito mobile presenta sul dorso un numero variabile di tubercoli sporgenti e più o meno acuti, mai però appuntiti. In un maschio della Baja del Geelvink essi sono 8 sulla mano destra e 7 sulla sinistra; nell’altro maschio della stessa località sono in numero di 6, e alcuni minori, irregulari, alla base, e 8 sulla sinistra; nel maschio di Nias sono 13 sulla destra e 14 sulla sinistra; nelle femmina di Andai, come frequentemente accade nel g. Sesarma , sono cancellati ..... Riassumendo, credetti oportuno creare una nuova sottospecie per gli esemplari esaminati, che si distinguono dalla formatipo per: 1.º smarginatura del fronte; 2.º maggior larghezza (massima) propozionale e conseguentemente figura più curva dei lati del carapace; 3.º differenza di numero di tubercoli sul dito mobile (carattere incerto)” [Outer surface of chelae abundantly covered with granules, also found on the inner surface but fewer in number and smaller. Upper edge of the chela defined by a distinct denticulated crest, extending from the terminal portion of the upper joint of the carpus to the articulation of the dactylus. Behind and between it and the inner ridges are two small crests that can vary between specimens and chelae, but are always at the same angle with the longitudinal crest. The first joins at the end of the upper edge of the hand. This character is not mentioned in De Man’s description, and given the normal accuracy of this illustrious carcinologist, I think must be lacking in the typical form { L. rotundatum }. The dactylus has a variable number of prominent and more or less acute tubercles, but which are never sharp. In a male from Geelvink Bay, there are 8 tubercles on the right dactylus and 7 on the left, while another male from the same locality has 6 on the right, with some being smaller and irregular at the base of the finger, and 8 on the left; the male from Nias has 13 on the right and 14 on the left; they are absent in the female as frequently happens in the genus Sesarma . … In summary, I thought it opportune to create a new subspecies for the specimens examined, which are distinguished by: 1, form of the frontal margin; 2, greater maximum width and therefore the sides of the carapace proportionately more curved; 3, differences in the number of tubercles on the upper surface of the dactylus (status uncertain)].

The relatively broader carapace proportions, slightly more curved lateral margins and the presence of numerous granules on the chela agree well with the present material from New Guinea and the Caroline Is. as well as L. scandens . We were unable to examine the type material of this species (supposedly in the Museo Civico in Genoa, Italy) but the present material leaves no doubt that Sesarma (Episesarma) rotundata papuomalesiaca Nobili, 1899 , is a distinct species from L. rotundatum as defined by Ng & Liu (2003).

Labuanium papuomalesiacum is close to L. scandens , but they are easily separated by the G1 morphology. The G1 of L. scandens is proportionately more slender, and the distal pectinated process is relatively longer and more distinctly bent (almost 90° from vertical) than L. papuomalesiacum (almost 60° from vertical) ( Ng & Liu 2003: fig. 4 versus Fig. 10 H–K). When similar size specimens are compared, the adult male abdomen (notably somite 6) and telson of L. scandens are also relatively more slender ( Fig. 6 C) when compared with L. papuomalesiacum ( Fig. 6 B).

Nobili’s (1899, 1900) paralectotype material from Nias, which he also referred to L. papuomalesiacum , is here reidentified as L. vitatum new species.

Figures

FIGURE 2. Overall views of Labuanium species. A, L. vitatum new species, holotype male (34.8 × 34.9 mm) (WAM C 13977), Christmas I.; B, L. papuomalesiacum (Nobili, 1899), male (38.0 × 37.4 mm) (SMF 1971.18.5.53), Caroline Is.; C, L. scandens Ng & Liu, 2003, holotype male (42.3 × 41.2 mm) (TMCD 3290), Taiwan.

FIGURE 6. Thoracic sternal views and abdomens of Labuanium species. A, L. vitatum new species, holotype male (34.8 × 34.9 mm) (WAM C 13977), Christmas I.; B, L. papuomalesiacum (Nobili, 1899), male (38.0 × 37.4 mm) (SMF 1971.18.5.53), Caroline Is.; C, L. scandens Ng & Liu, 2003, holotype male (42.3 × 41.2 mm) (TMCD 3290), Taiwan.

FIGURE 7. Labuanium vitatum new species, holotype male (34.8 × 34.9 mm) (WAM C 13977), Christmas I .. A, outer view of left chela; B, fourth right ambulatory leg; C, third right ambulatory leg.

FIGURE 9. Labuanium papuomalesiacum (Nobili, 1899). A, ovigerous female (25.5 × 24.9 mm) (ZRC), Kri I., Irian Jaya; B, male (28.8 × 29.0 mm) (SMF 1972.18.5.53), Bertrand I., New Guinea; C, male (38.0 × 37.4 mm) (SMF 1971.18.5.53), Caroline Is. A, B, overall views; C, outer view of left chela; D, outer view of right chela.

FIGURE 10. Denuded gonopods of Labuanium species. A – E, L. vitatum new species, holotype male (34.8 × 34.9 mm) (WAM C 13977), Christmas I.; F, G, L. vitatum new species, male (22.3 × 21.8 mm) (RMNH 1202), Java; H – K, L. papuomalesiacum (Nobili, 1899), male (38.0 × 37.4 mm) (SMF 1971.18.5.53), Caroline Is. A, B, C, D, F, G, left G 1; H, I, J, K, right G 1, E, left G 2. Scales: A, B, E, F, G, H, I = 1.0 mm; C, D, J, K = 0.5 mm.