Tmethypocoelis liki, Murniati & Asakura & Nugroho & Hernawan & Dharmawan, 2022

Murniati, Dewi Citra, Asakura, Akira, Nugroho, Dharma Arif, Hernawan, Udhi Eko & Dharmawan, Wayan Eka, 2022, On a collection of thoracotreme crabs (Crustacea: Brachyura: Ocypodidae, Macrophthalmidae, Dotillidae) from two offshore islands of Papua, eastern Indonesia, with descriptions of two new species, Raffles Bulletin of Zoology 70, pp. 461-491 : 481-489

Tmethypocoelis liki , new species

( Figs. 15–21 )

Material examined. Holotype: male (6.2 × 3.5 mm) ( MZB. Cru.5011), Liki Village, Sarmi District, Sarmi Municipality , Liki Island , Papua Province, 01º37′25.29″S, 138º44′26.54″E, 21 Nov. 2018, DC Murniati.

Paratypes: 15 males (5.3 × 3.1 mm – 5.8 × 3.2 mm), 3 females (3.5 × 2.1 mm – 3.9 × 2.5 mm) ( MZB. Cru. 5012), Liki Village, Sarmi District , Sarmi Municipality , Liki Island , Papua Province, 01º37′25.29″S, 138º44′26.54″E, 21 Nov. 2018, DC Murniati ; 5 males (4.0 × 2.4 – 4.8 × 2.8 mm) ( ZRC 2022.0914 ), Liki Village, Sarmi District, Sarmi Municipality , Liki Island , Papua Province, 01º37′25.29″S, 138º44′26.54″E, 21 Nov. 2018, DC Murniati ; 5 males (3.7 × 2.4 – 4.9 × 2.8 mm) ( OMNH Ar-12646), Liki Village, Sarmi District, Sarmi Municipality , Liki Island , Papua Province, 01º37′25.29″S, 138º44′26.54″E, 21 Nov. 2018, DC Murniati ; 5 males (5.1 × 2.9 – 5.3 × 3.0 mm) ( RMNH. CRUS.D.58042), Liki Village, Sarmi District, Sarmi Municipality , Liki Island , Papua Province, 01º37′25.29″S, 138º44′26.54″E, 21 Nov. 2018, DC Murniati .

Diagnosis. Carapace pentagonal, broad, 1.7 times as broad as long. Front gently narrowed anteriorly; lateral border of carapace distinctly curved, with single row of tubercles and stiff short setae. External orbital angle triangular, posteriorly followed by broad U-shaped sinus. Chelipeds stout, long, subequal. Palm bulky, inner surface coarsely granular on upper half, outer surface distinctly granular over distal-upper half. Fingers not gaping at base; fixed finger short, triangular. Dactylus with outer surface bearing one median ridge of granules; cutting margin with blunt and wide serration; upper margin with median row of granules culminating in one prominent tooth. Male pleon 1.8 times as long as wide. G1 long, slender, curved; apex forming two lobes; apical setae consisting one long and five short setae. Vulva D-shaped, mesial margin of operculum with triangular projection.

Description. Carapace pentagonal, broad; convex longitudinally, slightly convex transversely; 1.7 times as broad as long, greatest width across external orbital angles ( Fig. 15B , 16A ). Dorsal surface almost smooth, sparsely tubercular; regions defined by shallow grooves, epigastric lobe just visible ( Fig. 16A ). Cervical groove dividing gastric and cardiac regions, well-marked; cardiac regions with slight central depression. Branchial region sloping, with small, well-spaced, low tubercles, each bearing single seta. Sub-branchial region bulging, bearing regular setae, separated from branchial region by sinuous lateral border fringed with short setae. Front gently narrowed anteriorly, basal and distal widths 0.22 and 0.12 times as wide as external orbital width, respectively; distolateral angles rounded ( Fig. 16A ); anterior margin with small central blunt prominence. External orbital angle triangular, anterior and lateral margins slightly convex, with microscopic tubercles, one small ridge extending from mid-lateral margin, parallel to anterior margin, as long as anterior margin, posteriorly followed by broad U-shaped sinus ( Fig. 16A, B ). Second anterolateral tooth posterior to U-shaped sinus, concave posteriorly, distance between second anterolateral teeth less than between external orbital angles. Lateral margin of carapace distinctly curved, with single row of tubercles and stiff short setae ( Fig. 16A ). Anterolateral margin convex; posterolateral margin concave, adjoin with posterior margin without sharp angle. Posterior margin slightly concave, c.0.53 distance between external orbital angles; fine ridge parallel with posterior margin forming broad rim ( Fig. 16A ). Supraorbital margin sinuous, diverging backward, microscopically tuberculate ( Fig. 16C ). Infraorbital margin with medial notch, below which, on pterygostome, oblique channel running inwardly; inner portion of infraorbital margin consisting of two granular ridges separated by shallow channel; outer portion of infraorbital border granular, concave, ending in broad notch below external orbital angle ( Fig. 16C ).

Epistome forming three lobes posteriorly, distinctly convex laterally and medially, margins without tuberculation ( Fig. 16E ).

Eyestalks long, widening distally, distal end of cornea reaching slightly beyond external orbital angles, distally with short projection, projection 0.3 times as long as cornea, tip with several short setae; cornea bulging; medial thickening gives twisted appearance ( Figs. 15A , 16D ).

Third maxillipeds distinctly vaulted, almost completely covering buccal cavern. Ischium subquadrate, antero-mesial angle narrowly triangular; mesial and lateral margins with dense short setae; outer surface smooth, with one oblique row of setae. Merus trapezoidal, subequal in size to ischium, about 1.1 times as long as ischium laterally; outer surface covered sparsely by regular short setae, without granules; mesial margin slightly convex, with long feathered setae; lateral margin convex, converged distally, covered with short setae; anterior margin slightly concave, without setae. Carpus trihedral, distal portion with dense long setae, lateral margin with sparse short setae, mesial margin with dense long setae. Propodus, shorter than dactylus, lateral margins with sparse short setae. Dactylus slender, two times as long as propodus, margins serrated, with long stiff setae apically ( Fig. 16F ).

Male chelipeds (P1) stout, long, subequal ( Fig. 15B ). Merus with cross-section triangular ( Fig. 17A–F ); higher than external orbital angle when held against external orbital angle; outer margin with two irregular rows of sharp tubercles ( Fig. 17A ); lower margin with one row of tubercles ( Fig. 17B ); upper margin covered by scattered granules, granulation on distal portion continuous to outer surface, distal margin with one row of tubercles ( Fig. 17C ); oval tympani on outer and upper surfaces ( Fig. 17E–F ), tympanum on outer surface smaller than that of upper surface, microscopic granules present outside tympanum ( Fig. 17F ); lower surface smooth, without tympanum ( Fig. 17D ). Carpus shorter than merus; elongate, 2.15 times as long as wide; all margins tubercular ( Fig. 17J–L ); upper surface flattened, with triangular shape ( Fig. 17G ); lower surface smooth ( Fig. 17H ); outer surface peak with microscopic granules (17I). Palm bulky, 1.4–1.5 times as long as high (excluding fixed finger); inner surface coarsely granular on upper half, granulation extending to sharply cut upper margin ( Fig. 17M ); outer surface distinctly granular over distal-upper half, distinct groove extending below granular rows forming clear granular string near upper margin, half-lower part smooth ( Fig. 17N ); upper margin with granules ( Fig. 17O ); lower margin tubercular ( Fig. 17P ). Fingers without gaping proximally; curved inwards, expanded distally to form spooned tip; cutting margins evenly serrated; inner margins at tip of both fingers with short row of stout setae ( Fig. 17M, N ). Fixed finger short, triangular shape, 0.34 times as long as palm; inner surface with granules near cutting margin; outer surface with granules near cutting margin; cutting margin slightly convex over entire length, but without one large differentiated tooth or lobe; lower margin granular only along middle to base ( Fig. 17P ). Dactylus with outer surface bearing one median ridge of granules extended nearly whole length, scattered granules between ridge and cutting margin, flat depression with microscopic granules between granular ridge and upper margin, dense granulation on proximal portion near upper margin ( Fig. 17N ); inner surface granular near cutting margin and near upper margin, median portion smooth ( Fig. 17M ); cutting margin with blunt and wide serrates; upper margin with median row of granules culminating into one prominent tooth ( Fig. 17M–O ).

Ambulatory legs (P2–P5) slender, elongate. P2 shorter than P3. Merus 2.9 times as long as wide; tympani on anterior and posterior surfaces; anterior surface without granules; posterior surface with scattered granules near upper margin; upper margin narrowed, convex in cross section, with spaced tubercles, tuberculation not forming ridge, sparse setae distributed irregularly; surface of lower margin wider than that of upper margin, smooth, nearly without setae. Carpus shorter than propodus, surfaces smooth; upper margin with sparse tubercles proximally, sparse setae distributed irregularly; lower margin smooth. Propodus shorter than merus, with anterior surface smooth; posterior surface with oval tympanum, tympanum smaller than that of merus; upper margin smooth, with sparse setae; lower margin smooth, without setation ( Figs. 18A, E , 19A, E ).

P3 longest. Merus 3.8 times as long as wide; oval tympani present on both surfaces; anterior surface without granules; posterior surface with sparse granules near tympanum; upper and lower margins convex, narrowed medially by two tympani on two surfaces; upper margin with scattered tubercles and setae; lower margin smooth. Carpus shorter than propodus; anterior and posterior surfaces smooth; surface of upper margin narrow, with sparse setae; surface of lower margin wide, smooth. Propodus shorter than merus; anterior surface smooth; posterior surface with one shallow groove, without granules; upper and lower margins with sparse setae ( Figs. 18B, F , 19B, F ).

P4 shorter than P2. Merus 3.6 times as long as wide; tympani present on anterior and posterior surfaces, without granules on both surfaces; upper and lower margins convex, narrowed medially by tympani on anterior and posterior surfaces; upper margin with one row of spaced microscopic tubercles, one row of spaced short setae parallel to tuberculation; surface of lower margin smooth, with sparse setae. Carpus shorter than propodus; anterior and posterior surfaces smooth; surface of upper margin narrow, lower margin wide, both margins with sparse setae, without tuberculation. Propodus shorter than merus, anterior and posterior surfaces smooth; posterior surface with one shallow groove; upper and lower margins narrow, without tuberculation, with sparse setae ( Figs. 18C, G , 19C, G ).

P5 shortest. Merus 3.2 times as long as wide; tympani present on both surfaces, tympanum on anterior surface larger than that on posterior surface; upper and lower margins without tubercles, with sparse short setae. Carpus shorter than merus; upper and lower margins smooth; surface of upper margin narrow, with sparse short setae; lower margin wide, with sparse short setae. Propodus slightly as long as carpus; anterior and posterior surfaces smooth; surfaces of upper and lower margins narrowed, with sparse short setae. Dactylus with all surfaces and margins smooth ( Figs. 18D, H , 19D, H ).

Tympani on anterior surfaces of all meri larger than tympani on posterior surfaces, smaller from P2 to P5. Dactyli of P2–P5 proximally straight, slightly curved distally, pointed, slightly shorter than propodi; anterior and posterior surfaces with one ridge extending slightly whole length; surfaces without granules, with sparse setae.

Male pleon 1.8 times as long as wide. First somite trapezoid, 13 times as wide as long; anterior margin 0.86 times as long as posterior margin; 1.3 times wider than second somite. Second somite distinctly curved downward, 10 times as wide as long. Third somite 3.4 times as wide as long, anterior margin slightly concave, posterior edge convex.

Fourth somite 2.8 times as wide as long; lateral margins concave, anterolateral angle rounded, posterolateral angle pointed; anterior margin convex; posterior margin nearly straight. Fifth somite 1.3 times as wide as long (at widest point), markedly constricted subproximally; proximal margin distinctly concave. Sixth somite 1.2 times as wide as long; anterior margin slightly concave, posterior margin slightly convex; lateral margins slightly wider subdistally; total length slightly as long as fifth somite, with slightly concave, parallel sides. Telson rounded; 1.3 times as wide as long; mid-posterior margin convex ( Fig. 16G ).

G1 long, very slender, curved; subproximal portion weakly bulging; apex forming two lobes; apical setae consisting one long setae and five short setae ( Fig. 20A–E ).

Female chelipeds equal, small. Palm with outer surface smooth; upper and lower margins with microscopic tubercles ( Fig. 16H ); inner surface smooth. Fingers longer than palm. Fixed finger straight; cutting margin serrated; lower margin entire; tip with spoon shaped, with setae at tip; inner surface smooth. Dactylus with one furrow on outer surface; cutting margin slightly serrated; upper margin smooth and with setae; tip with spoon shaped and setae; inner surface smooth.

Female pleon rounded, nearly as long as wide ( Fig. 16I ). First somite distinctly curved, 13.6 times as wide as long; wider than second somite. Second somite 8.2 times as wide as long. Third somite 6.7 times as wide as long; anterior margin slightly concave; posterior margin nearly straight; lateral margins wider anteriorly. Fourth somite 6.4 times as wide as long; lateral margins concave; anterior margin convex; posterior margin nearly straight. Fifth somite 4.2 times as wide as long (at widest point), narrower and longer than fourth somite. Sixth somite 3.9 times as wide as long; narrower than fifth somite, anterior margin concave, posterior margin slightly convex; lateral margins wider posteriorly. Telson triangular; 1.7 times as wide as long; mid-posterior margin convex.

Vulva D-shaped, mesial margin of operculum with triangular projection ( Fig. 16J ).

Etymology. The specific epithet of the new species is derived from the name of the type locality, Liki Island. The name is used as a noun in apposition.

Remarks. There were four species of Tmethypocoelis worldwide, all of which are distributed in the Indo-West Pacific, T. ceratophora ( Koelbel, 1897) (type locality: Hong Kong), T. choreutes Davie & Kosuge, 1995 (type locality: Okinawa, Ryukyu Islands), T. koelbeli Davie, 1990 (type locality: Northern Territory, Australia), and T. odontodactylus Davie, 1990 (type locality: South of Madang, Papua New Guinea). The key characters to distinguish those species are on the male cheliped and G1. In T. ceratophora , the upper margin of the dactylus has a subdistal tooth formed by a crest without distinct median granules, while in T. choreutes the upper margin of the dactylus has a subdistal tooth formed by a crest with clear median granules ( Davie & Kosuge, 1995: fig. 1A–F). In T. odontodactylus , the upper margin of the dactylus of the cheliped is granular, which culminates subdistally as a strong upturned tooth ( Davie, 1995, fig. 3C). On the other hand, the upper margin of the same portion in T. koelbeli is straight, extending three quarters of the length of the dactylus, which terminates in an overhanging ‘shelf’ ( Davie, 1990). Tmethypocoelis liki , new species, has a small tooth formed by one big granule on the subdistal portion of the dactylus upper margin. This tooth is the last granule on a granular ridge which runs from the proximal to the subdistal portion of the dactylus upper margin ( Fig. 17M–N ). The morphology of the projected tooth varied within the samples. Some specimens had a low tooth, whereas the others had a high tooth. There is no correlation between the tooth size and carapace size.

Tmethypocoelis ceratophora has 7–8 apical setae on the G1 (Davie & Kosuge: 1995, fig. 2A–B; Shih et al., 2015: fig. 62A–D), while T. choreutes has 12 apical setae ( Davie & Kosuge, 1995: fig. 2C–D). In T. odontodactylus , the apical portion of the G1 is unilobed with one row of regular setae, with a simple pattern of setation ( Davie, 1990: fig. 3E–G). In T. koelbeli , the apical portion of the G1 is symmetrically bilobed, with five short and two long setae ( Davie, 1990: fig. 2). In contrast, the apical portion of the G1 of T. liki , new species, is asymmetrically bilobed and armed with five short setae and one long seta ( Fig. 20 ).

Habitat. This species inhabits mangrove areas with a sandy substrate, mixed with very small gravel. Around its habitat, there are some long and narrow trenches which are inundated by water remaining from the previous high tide ( Fig. 15C, D ).

Behavior. Male waving display of the new species is distinctly different from those of T. ceratophora and T. choreutes ( Davie & Kosuge, 1995) . The display of five males was recorded with a digital camera. The waving ( Fig. 21 ) is started with both chelipeds positioned in front of the buccal cavern, the finger tips directed downward; they are then swung forward with the inner surface of the chela facing downward (1). The chela are then raised and directed outward, with fingertips also directed outward (2), then raised and directed centrally (3). The maximum height of the fingertips reaches beyond the projecting eyestalks. When reaching maximum height, the cheliped is in a nearly straight position with the fingertips pointing forward slightly (not pointing upward), meanwhile the P2 is raised (4). The chelipeds are then centrally gathered at a similar height to the maximum height, then refolded promptly (5) and returned to the initial position.

Figures

Fig. 15. Tmethypocoelis liki, new species. A, paratype, MZB.Cru.5012, male, 5.3 × 3.1 mm, in situ with life colouration. B, holotype, MZB.Cru.5011, male, 6.2 × 3.5 mm, dorsal habitus, preserved colouration; Papua, Liki Island. C–D, habitat of Tmethypocoelis liki, new species (photograph C by Sumaryanto Bronto).

Fig. 16. Tmethypocoelis liki, new species. Holotype, MZB.Cru.5011, male, 6.2 × 3.5 mm; Papua, Liki Island. A, carapace; B, external orbital angle; C, orbit area; D, eyestalk; E, epistome; F, outer surface of left third maxilliped; G, male pleon. Paratype, MZB.Cru.5012, female, 3.5 mm × 2.1 mm; Papua, Liki Island. H, outer surface of left chela; I, pleon; J, left vulva.

Fig. 17. Tmethypocoelis liki, new species. Holotype, MZB.Cru.5011, male, 6.2 × 3.5 mm; Papua, Liki Island. Merus of the left cheliped: A, outer margin; B, lower margin; C, upper margin; D, lower surface; E, upper surface; F, outer surface. Carpus of the left cheliped: G, upper surface; H, lower surface; I, outer surface; J, upper margin; K, lower margin; L, outer margin. Left palm: M, inner surface; N, outer surface; O, upper margin; P, lower margin.

Fig. 18. Tmethypocoelis liki, new species. Holotype, MZB.Cru.5011, male, 6.2 × 3.5 mm; Papua, Liki Island. Left pereopods: A–D, anterior surfaces; E–H, posterior surfaces; A, E, P2; B, F, P3; C, G, P4; D, H, P5.

Fig. 19. Tmethypocoelis liki, new species. Holotype, MZB.Cru.5011, male, 6.2 × 3.5 mm; Papua, Liki Island. Left pereopods: A–D, upper margin; E–H, lower margin; A, E, P2; B, F, P3; C, G, P4; D, H, P5.

Fig. 20. Tmethypocoelis liki, new species. Paratypes: A–C, MZB.Cru.5012, male, 5.0 × 3.0 mm; D–E, MZB.Cru.5012, male, 5.1 × 3.2 mm; Papua, Liki Island. Left G1: A, D, whole morphology; apical portion: B, E, lateral; C, mesial.

Fig. 21. Successive motion of waving display by male Tmethypocoelis liki, new species. Refer to text for details.