Tmethypocoelis celebensis, Murniati & Asakura & Davie, 2023

Murniati, Dewi Citra, Asakura, Akira & Davie, Peter J. F., 2023, Two new species of Tmethypocoelis Koelbel, 1897 (Decapoda, Brachyura, Dotillidae) from Sulawesi, Indonesia, ZooKeys 1156, pp. 159-190 : 159

Tmethypocoelis celebensis sp. nov.

Figs 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17B, D

Material examined.

Holotype. Indonesia • 1 ♂ (7.4 × 4.3 mm); Moletang River estuary, Kema Tiga, North Minahasa , North Sulawesi; 1°21'59.6"N, 125°04'38.9"E; 12 Sep. 2020; coll. DC. Murniati and D. Nurdiansyah; MZB. Cru. 5574.

Paratypes. Indonesia • 10 ♂ (2.8 × 1.8 - 7.2 × 4.3 mm) , 8 ♀ (4.8 × 3.6 - 5.7 × 3.7 mm); Moletang River estuary, Kema Tiga, North Minahasa , North Sulawesi; 1°21'59.6"N, 125°04'38.9"E; 12 Sep. 2020; coll. DC. Murniati and D. Nurdiansyah; MZB. Cru. 5180 • 10 ♂ (5.4 × 3.2 - 6.5 × 3.7 mm); Iyok Beach, East Bolang Mongondow , North Sulawesi; 0°35'06.0"N, 124°31'58.6"E; 17 Sep. 2020; coll. D. Nurdiansyah; MZB. Cru. 5181 • 11 ♂ (6.3 × 3.8 - 7.9 × 4.8 mm); Tuladenggi Sibatang, Parigi Moutong , Central Sulawesi; 0°24'41.0"N, 121°07'43.9"E; 10 Jun. 2021; coll. DC. Murniati; MZB. Cru. 5575 • 10 ♂ (7.3 × 3.8 - 7.4 × 4.3 mm); Maleyali, Sausu, Parigi Moutong , Central Sulawesi; 1°05'31.0"S, 120°33'39.6"E; 25 Jun. 2021; coll. DC. Murniati, Muslihun, M. Ikram; MZB. Cru. 5576 • 5 ♂ (5.2 × 3.0 - 6.0 × 3.4 mm); Iyok Beach, East Bolang Mongondow , North Sulawesi; 0°35'06.0"N, 124°31'58.6"E; 17 Sep. 2020; coll. D. Nurdiansyah; ZRC 2023.0056 • 4 ♂ (6.6 × 3.8 - 7.2 × 4.1 mm); Maleyali, Sausu, Parigi Moutong , Central Sulawesi; 1°05'31.0"S, 120°33'39.6"E; 25 Jun. 2021; coll. DC. Murniati, Muslihun, M. Ikram; ZRC. 2023.0057 • 5 ♂ (4.7 × 3.0 - 6.0 × 3.7 mm); Iyok Beach, East Bolang Mongondow , North Sulawesi; 0°35'06.0"N, 124°31'58.6"E; 17 Sep. 2020; coll. D. Nurdiansyah; OMNH-Ar.12770-12774 • 4 ♂ (6.6 × 3.8 - 7.8 × 4.4 mm); Maleyali, Sausu, Parigi Moutong , Central Sulawesi; 1°05'31.0"S, 120°33'39.6"E; 25 Jun. 2021; coll. DC. Murniati, Muslihun, M. Ikram; OMNH-Ar. 12766-12769 • 4 ♂ (6.2 × 3.7 - 7.4 × 4.5 mm); Maleyali, Sausu, Parigi Moutong , Central Sulawesi; 1°05'31.0"S, 120°33'39.6"E; 25 Jun. 2021; coll. DC. Murniati, Muslihun, M. Ikram; RMNH.CRUS.D.58047 • 3 ♂ (4.3 × 3.8 - 4.9 × 3.8 mm); Tuladenggi Sibatang, Parigi Moutong , Central Sulawesi; 0°24'41.0"N, 121°07'43.9"E; 10 Jun. 2021; coll. DC. Murniati; QM W29643 .

Comparative material.

Tmethypocoelis liki Murniati, Asakura, Nugroho, Hernawan & Dharmawan, 2022: Indonesia • paratypes 5 ♂ (5.3 × 3.1 mm - 5.5 × 3.2 mm); Liki Village, Sarmi District, Sarmi Municipality , Liki Island , Papua Province; 01°37'25.29"S, 138°44'26.54"E; 21 Nov. 2018; coll. DC. Murniati; MZB.Cru.5012 .

Diagnosis.

Carapace pentagonal, ca. 1.6-1.7 × as wide as long (Fig. 10A ). Branchial region sloping, protobranchial, mesobranchial and metabranchial regions well-defined. Sub-branchial region bulging, bearing regular setae and tubercles. Posterior margin slightly concave, ca. 0.64 distance between exorbital angles. Exorbital angle triangular, acute, directed forward (Fig. 12A ). Second anterolateral tooth less acute, slightly shorter. Male pleon ca. 2.0 × longer than wide (Fig. 12E ). Male chelipeds long. Palm bulky, ca. 1.3 × longer than wide (Fig. 13M, N ). Fingers shorter than palm. Pollex short, triangular, cutting margin slightly oblique, without large differentiated tooth or lobe (Fig. 13M ); cutting margin of dactylus with large teeth over proximal half, small teeth on distal half, without median lobe, upper margin with row of fine tubercles; one triangular, upturned tooth subdistally (Fig. 13M-O ). G1 long, recurved, very slender; sub-proximal portion bulging (Fig. 15A, B ); apical portion forming two lobes, with three short setae on outer margin, two or three long setae apically, four or five short setae on inner margin (Fig. 15C, D ).

Description.

Carapace (Figs 10A , 12A ) pentagonal; weakly convex laterally and longitudinally; ca. 1.6-1.7 × wider than long. Dorsal surface smooth, regions semi-defined; epigastric lobe poorly defined. Cervical grooves, well-marked; cardiac region slightly depressed. Branchial regions sloping, protobranchial, mesobranchial and metabranchial regions well-defined. Carapace widest between exorbital angles. Sub-branchial region bulging, bearing regular setae and tubercles. Intestinal and branchial regions well-defined. Posterior margin weakly concave, ca. 0.6 × distance between exorbital angles; fine ridge parallel with posterior margin forming broad rim. Lateral margin recurved with row of tubercles and short stout setae. Frontal margin rounded, moderately convergent, basal width ca. 0.19 × distance between exorbital angles, ca. 0.13 × at anterior margin; anterior margin with small central blunt prominence (Fig. 11A ). Exorbital angle triangular, acute, directed forwardly; anterior margin with microscopic tubercles, lateral margin slightly tubercular; posteriorly followed by broad U-shaped sinus. Epibranchial tooth less acute, slightly shorter. Posterolateral facet well-defined by a crest originating anteriorly from base of exorbital angle (Fig. 12A ). Supra-orbital borders sinuous, sloping backward, microscopically tubercular. Infra-orbital border with medial notch; pterygostome with inwardly directed oblique channel. Inner part of infra-orbital border with two granular ridges separated by shallow channel; upper ridge with row of setae; granules on lower ridge larger than that of upper ridge, without setation. Outer part of infra-orbital border granular, concave, ending in broad notch below exorbital angle (Fig. 12B ).

Eyestalks (Figs 10 , 11A , 12C ) reaching exorbital angle, medial and distal diameters similar size; ocular style as long as cornea, tipped with setae; medial slope gives twisted appearance; cornea bulging.

Third maxillipeds (Fig. 12D ) slightly vaulted, not completely covering buccal cavern. Ischium subquadrate, outer surface covered with spaced long setae, with one oblique row of long setae near upper margin, upper margin concave, upper-mesial angle with narrow, rounded lobe; lower-mesial angle curved; inner and lower margins with dense setae; lateral margin without setation (Fig. 12D ). Merus slightly larger than ischium, ca. 1.3 × longer; outer surface with regularly scattered short setae; lateral margin convex, narrower distally, covered with short setae; mesial margin straight with long setae (Fig. 12D ). Carpus trihedral, subequal in length to propodus and dactylus together; mesial margin and distal portion with dense long setae (Fig. 12D ). Propodus shorter than dactylus; margins entire, with long dense setae (Fig. 12D ). Dactylus slender, with long dense setae laterally (Fig. 12D ).

Male pleon (Fig. 12E ) ca. 2.0 × longer than wide. Pl1 trapezoidal, ca. 8.0 × wider than long; ca. 1.3 × wider than pl2. Pl2 very narrow, ca. 10 × wider than long. Pl3 ca. 3 × wider than long. Pl4 ca. 3.2 × wider than long, lateral margins convergent distally, distolateral angle pointed. Pl5 ca. 1.5 × wider than long (at widest point), markedly constricted at base. Pl6 ca. 1.5 × wider than long; widest sub-distally; subequal in length to pl5. Male telson rounded, ca. 1.4 × wider than long (Fig. 12E ).

Female pleon (Fig. 12F ) conspicuously broad. Pl1 shortest; pl2 distinctly longer, as wide as pl1; pl3 trapezoidal, longer than pl2; pl4 rectangular, slightly longer than pl3, lateral margins convex; pl5 longer than pl4; pl6 distinctly longest. Female telson (Fig. 12F ) triangular.

Male chelipeds stout, long, equal. Merus triangular in cross-section; standing higher than exorbital angle (Fig. 11B ); lower margin with two rows of granules extending whole length of margin (Fig. 13A ); upper margin narrowing proximally, with irregular rows of granules on distal half (Fig. 13K ); outer margin with one row of granules extending whole length (Fig. 13L ); upper surface flattened, ovate smooth tympanum, scattered long setae around tympanum, more setation distally, microscopically tuberculate (Fig. 13I ); lower surface flattened, nearly smooth, with scattered granules, lacking tympanum (Fig. 13J ); outer surface convex, tympanum smaller than that of upper surface, evenly distributed granules and setae (Fig. 13B ). Carpus shorter than merus, elongate, ca. 1.4 × longer than wide; upper and lower margins tubercular (Fig. 13C, D ); outer surface rectangular, scattered microscopic granules near upper and lower margins, median portion without microscopic tubercles (Fig. 13E ); lower surface smooth, with one longitudinal row of granules, one patch of tubercles on proximal part (Fig. 13F ). Palm bulky, ca. 1.3 × longer than wide; inner surface granular over upper half, with granules extending over upper margin and curved to sharply cut upper margin of outer surface, distally with one row of regular granules reaching pollex, smaller granules near lower margin, median portion smooth (Fig. 13M ); outer surface distinctly granular over upper half reaching to base of pollex, lower half smooth (Fig. 13N ); upper margin with one row of granules, distinct groove extending below granular rows forming clear granular string (Fig. 13G ); lower margin with granulation extending to lower part of inner surface (Fig. 13H ). Fingers shorter than palm, lacking obvious basal gape, curved inwards, spooned-tip; cutting margins evenly serrated; inner margin at tip of both fingers with short row of stout setae. Pollex short, triangular, cutting margin slightly oblique, without large differentiated tooth or lobe, ca. 0.5 × as long as palm; inner surface nearly smooth, one row of granules over proximal half (Fig. 13M ); outer surface granular parallel to cutting margin, granules with similar size (Fig. 13N ); lower margin granulated only along proximo-medially (Fig. 13H ). Cutting margin of dactylus with teeth, larger teeth over proximal half, smaller teeth over distal half, without median lobe; inner surface with one row of granules parallel to upper margin, granulation extending from proximal to distal, one patch of granules proximally (Fig. 13M ); band of granules on outer surface near cutting margin and junction to palm, one tubercular ridge extending medially parallel to upper margin (Fig. 13N ); upper margin with row of tubercles terminating with triangular upturned tooth subdistally (Fig. 13O ).

Female chelipeds small dotillid type (Figs 10B , 14 ). Not conspicuously different from T. simplex sp. nov. (see description for T. simplex sp. nov.).

Pereiopods (Fig. 15 ) slender, elongate, P2-P5 similar; smooth ovate tympanum on anterior and posterior surfaces of meri. Tympani on posterior surfaces becoming progressively smaller from P2-P5. Dactyli nearly straight, pointed, shorter than propodi.

P2 (Fig. 15A, B ) shorter than P3; merus ca. 2.7 × longer than wide; anterior surface bearing scattered granules outside tympanum, granules denser near lower margin, sparse setae near lower margin; posterior surface sparsely granulate, denser distal to tympanum; upper margin convex, sparse long setae, distally tubercular; lower margin smooth, sparse setae. Carpus shorter than propodus, surfaces smooth; margins without granules, sparse setae. Propodus with anterior and posterior surfaces with few small granules only; margins with sparse long setae.

P3 (Fig. 15C, D ) longest; merus ca. 2.7 × longer than wide; anterior surface scarcely granular; posterior surface sparsely granulate, denser near upper margin; upper and lower margins convex; upper margin tubercular distally, sparse long setae; lower margin smooth, sparse setae. Carpus shorter than propodus, surfaces nearly smooth, sparse setae distally; margins without tubercles, sparse setae. Propodus with anterior and posterior surfaces smooth; margins with sparse long setae.

P4 (Fig. 15E, F ) nearly as long as P2; merus ca. 2.6 × longer than wide; anterior surface scarcely granular; posterior surface with evenly distributed granules; upper and lower margins convex; upper margin tubercular distally, spaced long setae extending whole length; lower margin smooth, sparse setae. Carpus shorter than propodus, surfaces smooth; margins smooth, sparse setae. Propodus with anterior and posterior surfaces smooth; margins with sparse long setae.

P5 (Fig. 15G, H ) shortest; merus ca. 2.8 × longer than wide; anterior surface without granules; posterior surface granulate, granules denser near upper margin; upper and lower margins convex; upper margin sparsely tubercular, with sparse long setae, short setae proximally; lower margin smooth, with sparse setae. Carpus shorter than propodus, surfaces smooth; margins smooth, with sparse setae. Propodus with anterior and posterior surfaces smooth; margins with sparse long setae.

Reproductive organs. G1 long, recurved, very slender; sub-proximal portion bulging (Fig. 16A, B ); apical portion forming two lobes, with three short setae on outer margin, two or three long setae apically, four or five short setae on mesial margin (Fig. 16C, D ). Vulva (Fig. 16E ) rounded, projecting.

Gastric mill. Median tooth plate simple, without defined ridges. Urocardiac ossicle relatively narrower throughout length. Propyloric ossicle semi-circular, relatively narrow and protruding; posterior margin curved; anterior margin with one pointed lobe medially; lateral margins quadrate with anterior lobes discrete, prominent, and rounded (Fig. 17B ). Lateral zygocardiac tooth plate with eight slender teeth, three anterior teeth large (Fig. 17D ).

Habitat.

Tmethypocoelis celebensis sp. nov. inhabits sandy substrata in estuarine areas (Fig. 18 ).

Etymology.

The species name is derived from the type locality. Celebes is the former name of Sulawesi Island, one of the great islands in Indonesia.

Remarks.

The two new species described here differ from each other and from the other known species by numerous characters compared below. In general, the species of Tmethypocoelis are all extremely similar in general morphology with only small differences in male cheliped shape and dentition (Table 1 ), differences in the apical setal ornamentation of the male first gonopod, and sometimes differences in the proportions of the somites of the male pleon.

A comparison of male first gonopod setation patterns of described species suggests that the possession of two or three of markedly elongated apical setae (Figs 8C-E , 16C, D ; Davie 1990: fig. 2), common to both Tmethypocoelis simplex sp. nov. and T. celebensis sp. nov., is so far shared with T. liki from Papua and T. koelbeli from the Northern Territory, NW Australia. Therefore, these four species may be more closely related to each other than they are to T. ceratophora , T. choreutes , and T. odontodactylus , which all share a coronet of shorter more evenly sized stout setae on the tip of the G1. A more thorough analysis of relationships within the genus will be undertaken as part of a larger revision of the genus, and with the help of DNA sequencing data.

Both Tmethypocoelis simplex sp. nov. and T. celebensis sp. nov. differ significantly from T. koelbeli in the shape of the male pleon, with that of T. koelbeli being relatively narrower, and in particular Pl5 being more constricted proximally (Table 2 ). The pleons of T. simplex sp. nov. and T. celebensis sp. nov. are similar, however, both Pl6 and the telson are slightly proportionately wider in T. celebensis sp. nov.

Tmethypocoelis simplex sp. nov. differs from T. celebensis sp. nov., T. koelbeli , and T. liki in the form and number of the apical setae of the G1. The G1 of T. simplex sp. nov. typically has two or three very long setae apically (Fig. 8C-E ), and subapically there are three shorter stout setae on the outer margin increasing in length distally, and four short, downwardly reflexed setae on inner lobe. The G1 of T. celebensis sp. nov. has two or three very long recurved setae apically (Fig. 16B-D ), and subapically there are also three stout setae on the outer margin, though the proximal seta is much smaller and less prominent than on T. simplex sp. nov., and also four or five short, downwardly reflexed setae on the inner lobe. The G1 of T. koelbeli similarly has two long apical setae but lacks a row of outer subapical setae and has a row of five short distally pointed setae on the inner lobe ( Davie 1990: fig. 2). The G1 of T. liki has one long and five short apical setae ( Murniati et al. 2022: fig. 20C).

Figures

Figure 5. Tmethypocoelis simplex sp. nov. Holotype, male (7.7 x 4.4 mm) (MZB. Cru. 5573), Towale River, Central Banawa District, Donggala, Central Sulawesi. Left cheliped A merus lower margin B merus outer surface. Carpus C outer surface D inner surface E upper surface F lower surface. Chela G upper margin H lower margin. Merus I upper surface J lower surface K upper margin L outer margin. Chela M inner surface N outer surface O dactylus upper margin.

Figure 8. Reproductive organs of Tmethypocoelis simplex sp. nov. Paratype, males (A-D 4.1 x 2.6 mm E 6.9 x 4.0 mm) (MZB. Cru. 5183), Tosale, Banawa District, Donggala, Central Sulawesi, left G 1 A dorsal view B apical (dorsal view) C, D apical (ventral view) E mesial view. Paratype female (5.8 x 3.6 mm) (MZB. Cru. 5182), Towale river, Central Banawa District, Donggala, Central Sulawesi F vulva.

Figure 10. Habitus dorsal of Tmethypocoelis celebensis sp. nov. Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi A holotype, male (7.2 x 4.4 mm) (MZB. Cru. 5574) B paratype, female (5.5 x 3.5 mm) (MZB. Cru. 5180).

Figure 11. Tmethypocoelis celebensis sp. nov. Holotype, male (7.2 x 4.4 mm) (MZB. Cru. 5574), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi A front area B left merus held against external orbital angle.

Figure 12. Tmethypocoelis celebensis sp. nov. Holotype, male (7.2 x 4.4 mm) (MZB. Cru. 5574), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi A exorbital angle B orbit area C eyestalk D third maxilliped E pleon. Paratype, female (5.5 x 3.5 mm) (MZB. Cru. 5180), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi F pleon.

Figure 13. Tmethypocoelis celebensis sp. nov. Holotype, male (7.2 x 4.4 mm) (MZB. Cru. 5574), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi. Left cheliped. Merus A lower margin B outer surface. Carpus C upper margin D lower margin E outer surface F inner surface. Chela G upper margin H lower margin. Merus I upper surface J lower surface K upper margin L outer margin. Chela M inner surface N outer surface O dactylus upper margin.

Figure 14. Tmethypocoelis celebensis sp. nov. Paratype, female (5.5 x 3.5 mm) (MZB. Cru. 5180), Moletang river (estuary), Kema Tiga, North Minahasa, North Sulawesi. Left chela A inner surface B outer surface.

Figure 15. Left pereiopods of Tmethypocoelis celebensis sp. nov. Holotype, male (7.2 x 4.4 mm) (MZB. Cru. 5574), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi A, B P 2 C, D P 3 E, F P 4 G, H P 5. Right side, anterior surfaces; left side, posterior surfaces.

Figure 16. Reproductive organs of Tmethypocoelis celebensis b paratype, male (7.3 x 4.4 mm) (MZB. Cru. 5180), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi, left G 1 A mesial view B dorsal view C, D apical portion C dorsal view D ventral view. Paratype, female (5.5 x 3.5 mm) (MZB. Cru. 5180), Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi E vulva.

Figure 17. Teeth of gastric mill (posterior portion on upper part). Tmethypocoelis simplex sp. nov., paratype, male (6.9 x 4.0 mm) (MZB. Cru. 5183) (A, C). Tmethypocoelis celebensis sp. nov., paratype, male (7.3 x 4.4 mm) (MZB. Cru. 5180) (B, D). A, B median tooth C, D lateral tooth.

Figure 18. Habitat of Tmethypocoelis celebensis sp. nov. at Moletang River (estuary), Kema Tiga, North Minahasa, North Sulawesi.