Scandarma lintou, Schubart & Liu & Cuesta, 2003

Schubart, Christoph D., Liu, Hung-Chang & Cuesta, José A., 2003, A New Genus And Species Of Tree-Climbing Crab (Crustacea: Brachyura: Sesarmidae) From Taiwan With Notes On Its Ecology And Larval Morphology, Raffles Bulletin of Zoology 51 (1), pp. 49-59 : 51-58

Scandarma lintou , new species

( Figs. 1-8 )

Material examined. – Holotype - male (17.55 by 16.9 mm) ( TMCD 3276 ), Taiwan, Luidau ( Green Island ), coll. H.-C. Liu et al., 11 Sep.1999.

Paratypes – 1 male (13.8 by 13.6 mm), 2 females (16.2 by 15.7, 16.05 by 14.75 mm) ( TMCD 3277 ) , 1 male (19.20 by 18.7 mm), 1 female (18.55 by 16.7 mm) ( SMF 28099), Taiwan, Pingtung County, Manchow, Kangkou River mouth, (21 59' 26" N, 120 50' 09" E), coll. H.-C. Liu, 2 Sep.1999 ; 2 males (14.8 by 14.3 mm, 13.4 by 12.7 mm), 6 females (17.2 by 15.8 mm, 17.1 by 16.1 mm, 16.8 by 15.5 mm, 16.6 by 15.4 mm, 15.5 by 14.3 mm, 13.9 by 13.0 mm) ( TMCD 3278 ), same locality, coll. H.-C. Liu, 1 Sep.1999 (4 females parental vouchers) ; 1 male (16.8 by 16.5 mm) ( ZRC 2000.1830 ), same locality, coll. C.D. Schubart & H.-C. Liu, 14 Sep.1999 (DNA voucher) ; 1 male (16.2 by 15.75 mm), 2 females (17.25 by 16.5, 18.4 by 17.9 mm) ( ZRC 2001.0026 ) , 1 juvenile male (8.2 by 8.15 mm) ( ZRC 2001.0027 ), same locality, coll. P. K. L. Ng, 8 Nov.2000 ; 1 male (15.6 by 15.0 mm), 1 female (15.8 by 15.0 mm) ( ASIZ 72746 ) , 1 male (14.9 by 14.95 mm), 1 female (16.7 by 15.95 mm) ( ZRC 2002.0164 ), same locality, coll. H.-C. Liu, 20 Jun.2001 ; 3 males (14.05 by 13.80, 13.3 by 12.6, 12.40 by 12.05 mm), 1 female (11.35 by 10.8 mm) ( ASIZ 72744 ), Taiwan, Hualien County, Hualien, Meilun R. mouth, (23 58' 54" N, 121 36' 37" E), coll. H.-C. Liu, 17 Jun.2000; 1 ovigerous female (12.7 by 11.85 mm) ( ASIZ 72745 ), same locality, coll. H.-C. Liu, 21 Sep.2000 (parental voucher) ; 1 male (13.8 by 13.55 mm), 1 female (18.1 by 17.25 mm) ( ZRC 2002.0165 ) , 1 male (18.3 by 18.1 mm) ( ZRC 2002.0169 ) , 1 male (19.25 by 18.85 mm) ( ZRC 2002.0168 ), same locality, coll. H.-C. Liu, 17 Jun.2001 ; 1 male (19.3 by 18.5 mm); 1 female (14.5 by 13.5 mm) ( TMCD 3288 ), same locality, coll. H.-C. Liu, 27 Oct.2001 .

Others – 1 female (13.9 by 13.2 mm) ( TMCD 3279 ), Taiwan, Pingtung County, Manchow, Kangkou R. mouth, (21 59' 26" N, 120 50' 09" E), coll. H.-C. Liu, 1 Dec.1999 ; 1 ovigerous female (18.5 by 16.2 mm), same locality, coll. H.-C. Liu, 5 Oct.1999 ; 1male (14.7 by 14.2 mm); 4 ovigerous females (18.4 by 17.2 mm, 17.8 by 16.4 mm, 15.0 by 13.8 mm, 14.3 by 13.8 mm), 2 females (18.5 by 17.6 mm, 7.9 by 7.1 mm) ( TMCD 3280 ), same locality, coll. H.-C. Liu, 5 Oct.1999 ; 1 male (14.6 by 14.1 mm); 2 females (19.1 by 17.7 mm, 18.0 by 17.0 mm) ( TMCD 3281 ), same locality, coll. H.-C. Liu, 11 Dec.1999 ; 2 females (18.9 by 18.0 mm, 14.4 by 13.8 mm) ( ASIZ 72747 ), Taiwan, Pingtung County, Manchow, Kangkou R., 1 km from mouth, (21 59' 24" N, 120 49' 29" E), coll. H.-C. Liu, 20 Jun.2001 ; 1 female (13.2 by 11.1 mm) ( TMCD 3282 ) Taiwan, Pingtung County, Hengchun, Hsiangchiaowan , (21 55' 32" N, 120 49' 33" E), coll. H.-C. Liu, 5 Oct.1999 ; 2 males (13.9 by 13.5 mm, 9.6 by 8.9 mm), 4 females (13.2 by 12.2 mm, 12.6 by 11.7 mm, 12.5 by 11.5 mm, 10.0 by 9.4 mm) ( TMCD 3283 ) Taiwan, Pingtung County, Checheng, Paoli R. mouth, coll. H.-C. Liu, 7 Oct.1999 ; 10 males (18.7 by 18.1 mm, 13.5 by 13.1 mm, 13.4 by 12.8 mm, 12.0 by 11.4 mm, 10.2 by 9.9 mm, 9.4 by 9.1 mm, 9.1 by 8.7 mm, 9.1 by 8.4 mm, 8.1 by 7.6 mm, 6.6 by 6.1 mm); 6 females (14.1 by 13.3 mm, 10.0 by 9.1 mm, 9.4 by 8.9 mm, 9.1 by 8.5 mm, 8.7 by 8.1 mm, 6.4 by 6.2 mm), ( TMCD 3284 ) Taiwan, Hualien County, Hualien, Meilun R. mouth, (23 58' 54" N, 121 36' 37" E), coll. H.-C. Liu, 17 Jun.2000 ; 1 male (19.0 by 17.9 mm); 2 ovigerous females (15.5 by 14.6 mm, 15.0 by 14.6 mm), 2 females (20.5 by 18.7 mm, 10.7 by 10.0 mm) ( ASIZ 72748 ), same locality, coll. H.-C. Liu, 5 Aug.2000 ; 2 ovigerous females

(13.7 by 11.0 mm, 14.5 by 13.3 mm) ( TMCD 3285), same locality, coll. H.-C. Liu, 15 Nov.2000 (parental vouchers) ; 2 ovigerous females (14.7 by 13.4 mm, 13.3 by 12.6 mm) ( TMCD 3286 ), same locality, coll. H-C Liu, 21 Sep.2000 (parental vouchers) ; 1 ovigerous female (13.2 by 12.2 mm) ( TMCD 3287 ), same locality, coll. H.-C. Liu, 17 Aug.2000 ; 1 male (8.9 by 8.5 mm); 1 female (12.8 by 12.0 mm) ( TMCD 3289 ), same locality, coll. H.-C. Liu, 18 May.2000 .

Diagnosis. – Carapace squarish to gently sinuous, lateral carapace margin relatively narrow at exorbital teeth, continuously widening posterior to blunt anterolateral teeth, broadest at ventral extension. Dorsal surface of male chelar palm with one longitudinal line of granules, outer surface angular with tubercular protuberance at outermost point and conspicuously flattened fingers; dactylus dorsally with longitudinal row of horny tubercles, pollex ventrally with row of spines. Legs long and slender. G1 relatively short and stout; distal chitinous part short and spoon-shaped; G2 short, with thin and long distal segment.

Description of male holotype. – Carapace squarish to gently sinuous, slightly broader (17.55 mm) than long (16.9 mm), and flattened (9.05 mm height); dorsal surface smooth and glabrous; regions distinct, separated by prominent grooves; branchial regions with faint indication of oblique striae ( Figs. 1A, B ). Frontal margin strongly deflexed, two inner frontal lobes broad and distinct, outer lobes less than half as broad as inner lobes; deep fissure between inner lobes extending posteriorly to mesogastric region, flanked by swollen postfrontal regions ( Fig. 1B ). Front relatively narrow (7.7 mm), clearly less than half (0.44) of maximum carapace width, concave, ventral border strongly deflexed and bent outwards ( Fig. 1C ). Posterior border of orbits slightly directed postero-laterally; external orbital tooth low, directed anteriorly, outer margin of tooth curved, posteriorly bending into shallow but prominent notch; anterolateral tooth elevated and blunt, second anterolateral tooth only indicated as slight elevation; carapace margins posterior to second carapace teeth continuously widening ( Fig. 1B ); lateral border of carapace broadest at most ventral extension, where it touches base of walking legs between pereiopods 3 and 4.

Eyes pigmented, cornea wider than eyestalk; suborbital ridge prominent and setose with tufts of long setae at medial end; epistome flat and granulate, upper row of setae delimiting Verwey’s groove absent ( Fig. 1C ). Pterygostomial and epibranchial regions granulate and covered by dense mat of long and geniculate setae, dorsally separated from lateral carapace border by row of long setae grouped into three short anterior rows and one long posterior one. Third maxillipeds with median gape, uncovering mandibles; ischium with shallow median sulcus; meri of third maxilliped longitudinally ovate, touching each other distally; inner margin straight with thickened ledge ( Fig. 1C ); exopod completely covered, slender, with short and thin flagellum that does not extend across width of merus.

Male chelipeds subequal, left chela slightly smaller, probably regenerated; outer surface (mostly carpus and palm) with numerous rounded granules. Ventral margins of merus serrated, dorsal margin convex with distal indentation, no subdistal spines; inner face oval with one longitudinal row of long setae ventrally, scattered setae dorsally. Carpus roughly quadrangular and short, outer surface coarsely granulate, but without distinct teeth or spines. Propodus with ventral border slightly convex; palm inflated and coarsely granulate at inner and outer base; outer surface angular with tubercular protuberance at outermost point (here defined as apex) ( Figs. 2 A-C); granules ventral of apex small and inconspicuous, granules dorsal of apex coarse and round; outer surface distal from apex smooth and gradually flattening towards fingers; inner surface of palm swollen and granulate, with indication of a vertical row of tubercles; dorsal surface of palm with one longitudinal line of granules anterior to upper crest of tubercles ( Figs. 2A, B ); distal part of upper tubercular crest elevated and pointing towards dactylus. Fingers approximately as long as palm, concavely bent towards outside, forming medial gape when closed; cutting edges armed with smaller denticles at base, with one strong subdistal tooth on pollex and one less strong distal tooth on dactylus, tips of fingers sharp and denticulate; outer surface of fingers smooth and conspicuously flattened ( Figs. 2C , 3A, B); dactylus dorsally with few short proximal spiny granules and a longitudinal row of 12-13 round horny tubercles, pointing distally and extending almost to distal tip ( Figs. 1C , 2 A-C); pollex ventrally lined with approximately 12 sharp granules (spines) pointing distally ( Figs. 3A, B), probably used for stridulation.

Pereiopods 2-5 (ambulatory legs) long and slender, pereiopods 4 longest ( Fig. 1A ); tufts of dense and fine setae between bases of pereiopods 2 and 3 and pereiopods 3 and 4. Meri of all walking legs slender, dorsal margin of merus almost smooth, with low and spiniform subdistal tooth; merus and carpus glabrous; outer surface of carpus with two longitudinal ridges. Propodi of pereiopods 3 and 4 clearly more than three times as long as broad; dorsal and ventral margins of propodus and dactylus with numerous short and stiff setae or spines, not obscuring margins, strongest spines ventrally at distal end of propodus. Dactyls long and curved with short and thin spiny tips.

Thoracic sternites mostly glabrous and smooth; sternite 3 anteriorly pointed and posteriorly lined by fine setae, abdominal cavity reaches beyond midpoint of sternite 4. Abdomen roughly triangular; telson slightly longer than broad and about the length of segment 6, tip rounded ( Fig. 3C). Segment 6 with lateral margins convex, much broader than long; lateral margins of segment 5 straight, that of segment 4 gently concave, and that of segment 3 markedly convex. Segments 1 and 2 narrow and evenly broad. G1 relatively short (5.8 mm) and stout; distal part gently turning outwards; distal chitinous part short and spoon-shaped ( Fig. 4 ), lined by long setae. G2 short, with thin and long distal segment reaching up to half length of G1.

Paratypes. – In most specimens the chelae are homochelous, the paratype male SMF 28099 has a larger right chela with two strong subdistal teeth on the cutting edge of pollex. In smaller specimens, the fingers appear proportionally short and do not gape. The chelae of females are much weaker, with no gape and proportionately more slender and pointed. Female gonopores are elevated, arched, and pointing anteriorly. Otherwise, the female specimens agree with the male in all non-sexual characters.

Colour in life. – The carapace colour of S. lintou is mostly yellowish brown and darkly mottled; four small light spots are grouped symmetrically around the mesogastric region; branchial regions sometimes dark; the lateral carapace border is lined by a bright yellow line posterior to (sometimes imaginary) position of second anterolateral teeth. The bases of the chelae are dorsally light brown, turning into orange towards ventral. The fingers are white ( Fig. 5 ).

Size. – The maximum carapace width (cw) of Scandarma lintou is 22.1 mm in males (n=264) and 21.8 mm in females (n=350). The smallest ovigerous female obtained measured 11.4 mm cw (n=135), but, according to abdomen morphology, the smallest size of mature female was 10.3 mm cw. Males have relatively larger chelae than females.

Etymology. – The name “lintou” corresponds to the Chinese name for the screw pine Pandanus odoratissimus . In southwestern Taiwan and Green Island this plant constitutes the favourite habitat of this crab. The name is used as a noun in apposition.

Ecology. – Scandarma lintou is a semi-terrestrial (adults

terrestrial) crab, usually found less than 300 m away from the sea. Along the Kangkou River, the crabs were encountered in a distance of one kilometre from the sea. In southern Taiwan and Green Island, the presence of this species is always associated with three environmental factors: 1) the close proximity of a stream or freshwater pools, 2) protection from strong winds, and 3) the presence of the screw pine or pandang Pandanus odoratissimus ( Pandanales : Pandanaceae ). At these localities, Scandarma lintou was found hiding in the leaf axils of P. odoratissimus at daytime, while active on the leaf surfaces of the same plant or other nearby plants at night. In eastern Taiwan, however, where P. odoratissimus is not present, Scandarma lintou finds refuge under man-made concrete blocks on the forest floor or in crevices of vertical concrete walls. Also in this case, the habitat is close to fresh water and protected from strong winds.

Scandarma lintou is a nocturnal and mostly arboreal animal. At night, it can be found climbing on leave surfaces, twigs, trunks, vines, grasses and sometimes also on the ground. It moves up trees as high as five metres. When climbing on trees, the crabs are constantly picking small food items from the surface of the plants with both of their chelae. Food items that were observed to be ingested included flowers, fruits, bark and some small invertebrates living on trees. Water availability seems to be the more important factor limiting the activity as compared to temperature: the crabs increased activity when rainfall dampened their habitat.

Scandarma lintou has a seasonal breeding, taking place from June to January. Ovigerous crabs have small eggs which hatch out into pelagic, free-swimming larvae. As the hatching approaches, ovigerous females migrate to the estuaries and release larvae into brackish water. The timing of larval release does not seem to follow lunar or semilunar periodicity. Releasing behavior could be observed throughout the month during the breeding season. The timing of larval release also does not correlate with tidal peaks. Female Scandarma lintou most abundantly released larvae in the evening hours (between 1900 and 2000 hours). It was noticed that both sexes lose their appendages by autotomy easily during handling.

Description of zoea I.

Dimensions: rdl: 0.78 0.03 mm; cl: 0.44 0.02 mm; cw: 0.36 0.02 mm.

Carapace ( Fig. 6A ). Globose, smooth and without tubercles. Dorsal spine present, short and curved. Rostral spine present, straight and equal in length to dorsal spine. Lateral spines absent. A pair of setae on posterodorsal and anterodorsal regions. Posterior and ventral margin without setae. Eyes sessile.

Antennule ( Fig. 6B ). Uniramous; endopod absent. Exopod unsegmented with 4 terminal aesthetascs (3 long, 1 shorter and thin) and 1 terminal seta.

Antenna ( Fig. 6C ). Well developed protopod almost reaching the tip of the rostral spine and bearing two unequal rows of well-developed spines. Endopod absent; exopod elongated, more than 2/3 of the protopod length, with 2 terminal setae (1 long reaching to the tip of protopod, 1 shorter) and 5 small terminal spines.

Mandible. Endopod palp absent.

Maxillule ( Fig. 7A ). Coxal endite with 6 plumose setae. Basial endite with 5 setae (2 cuspidate and 3 plumodenticulate). Endopod 2-segmented with 1 seta on the proximal segment and 1 subterminal and 4 terminal plumodenticulate setae on the distal segment. Exopod seta absent; epipod seta absent.

Maxilla ( Fig. 7B ). Coxal endite bilobed with 5+2 (plus a marginal spine) plumodenticulate setae. Basial endite bilobed with 5+4 plumodenticulate setae. Endopod unsegmented, bilobed with 2+3 long plumodenticulate setae on the inner and outer lobe respectively. Scaphognathite with 4 plumose marginal setae and a long setose posterior process.

First Maxilliped ( Fig. 7C ). Coxa with 1 seta. Basis with 10 medial setae arranged 2,2,3,3, and a mat of long dorsobasal microtrichiae. Endopod 5-segmented with 2,2,1,2,5 (1 subterminal + 4 terminal) setae. Exopod 2-segmented, distal segment with 4 long terminal plumose natatory setae.

Second Maxilliped ( Fig. 7D ). Coxa without setae. Basis with 4 medial setae arranged 1,1,1,1. Endopod 3-segmented with 0,1,6 (3 subterminal + 3 terminal) setae. Exopod 2- segmented, distal segment with 4 long terminal plumose natatory setae.

Third Maxilliped. Absent.

Pereiopods. Absent.

Abdomen ( Figs. 8A, B ). Five abdominal somites. Somites 2 and 3 with pair of dorsolateral processes. Somites 3-5 with small posterolateral processes of subtriangular shape. Somites 2-5 with a pair of posterodorsal setae. Pleopods absent.

Telson ( Fig. 8C ). Telson bifurcated with 3 pairs of serrulate setae on posterior margin; mid-internal side of inner pair without spines. Dorsal part of each furcal branch with two rows of spines.

Remarks. - Scandarma lintou has been previously mentioned as undescribed crab with two colour photographs in the Taiwanese natural history crab book “The information of crabs’ watching in Taiwan ” ( Lee, 2001: 135). During the publication process of the present study, an undescribed crab species, which is strikingly similar in its morphology as well as habitat preferences to S. lintou was discovered in Sarawak by Peter K. L. Ng (pers. comm., 2002). This crab species probably will have to be considered congeneric with S. lintou .

The larvae of Scandarma lintou did not differ among the three Taiwanese localities from which they had been obtained. The larval morphology presents the typical combination of features that characterize all sesarmid larvae. However, two remarkable characters allow to distinguish this genus and species from other related ones. The antenna presents a well developed exopod, with a length of more than 2/3 of the protopod and a long terminal seta reaching to the tip of the protopod. Among all known sesarmid zoea, only the first zoeal stage of Selatium brockii presents a somewhat similar antenna (see Vijayakumar & Kannupandi, 1987). Also the presence of a mat of long microtrichiae on the dorsobasal part of the basis of the first maxilliped had not been noticed previously in any other sesarmid larvae. The larval characters clearly show that this species belongs to Sesarmidae , but confirm that it cannot be placed in any of the presently recognized sesarmid genera.

In 2002, the second author returned to the locality in southern Taiwan, where Scandarma lintou was initially discovered and originally abundant: the Kangkou River mouth in Pingtung County. He found that most of the vegetation had been cut down including the Pandanus screw pines. Together with the vegetation, most of the tree-climbing crab fauna had disappeared. Considering that Scandarma lintou has so far only been found near freshwater in the vicinity of the coast and that the screw pines are the most preferred shelter and feeding ground of this species, this loss of estuarine vegetation constitutes a severe threat for this crab species, which is apparently restricted to the island of Taiwan. The authors therefore recommend that the vegetation around estuaries along the southern and eastern coast of Taiwan must be protected to ensure the survival of this newly discovered and beautiful Taiwanese species.

The present description of the genus Scandarma is one more component to the revision of the systematics of several sesarmid genera currently carried out by P. K. L. Ng and the first author of the present study. According to Serène & Soh’s (1970) classification, Scandarma lintou would be closest to Pseudosesarma or Sesarmops . However, the here described species, and possibly a new one from Sarawak (P. K. L. Ng, pers. comm., 2002), can be distinguished by several key characters (see genus diagnosis). Furthermore, morphological and molecular work on several sesarmid genera, has shown that Pseudosesarma as well as Sesarmops are polyphyletic and need to be re-defined (some of its members are closely related to Chiromantes sensu lato). A major reclassification of sesarmid species will be necessary to account for these recent findings. The DNA-sequence of the mitochondrial 16S rRNA gene of Scandarma lintou (unpublished) as well as its adult and larval morphology (see above), do not allow to place this species close to any currently recognized species of Pseudosesarma or Sesarmops . Consequently, and for the purpose of taxonomic clarity, a monotypic genus Scandarma is herewith created in the hope that its affinities to other sesarmid genera will be further clarified in the future.

Figures

Fig. 1. Scandarma lintou, new species. Holotype male (17.55 by 16.9 mm) (TMCD 3276), Taiwan. A, overall view; B, dorsal carapace; C, frontal view.

Fig. 2. Scandarma lintou, new species. Holotype male (17.55 by 16.9 mm) (TMCD 3276), Taiwan.Right chela; A, outer dorsal view with flattened fingers; B, inner dorsal view with curved fingers; C, dorso-frontal view with dactylar tubercles.

Fig. 4. Scandarma lintou, new species. Holotype male (17.55 by 16.9 mm) (TMCD 3276), Taiwan. Male right gonopod (setae removed), A, ventral view, B, dorsal view.

Fig. 5. Scandarma lintou, new species. Life colours.

Fig. 6. Scandarma lintou, new species. Zoea 1, Taiwan. A, carapace, lateral view; B, antennule; C, antenna, including detail of terminal end of exopod. Scale bars: A, 0.1 mm, B,C, 0.05 mm.

Fig. 7. Scandarma lintou, new species. Zoea 1, Taiwan. A, maxillule; B; maxilla; C, first maxilliped; D, second maxilliped. Scale bars: A, B, 0.05 mm; C, D, 0.1 mm.

Fig. 8. Scandarma lintou, new species. Zoea 1, Taiwan. A, abdomen, dorsal view; B, abdomen, lateral view; C, telson detail. Scale bars: A, B, 0.1 mm; C, 0.05 mm.