Ovitamon agmamba, Husana & Kase & Ng, 2013

Husana, Daniel Edison M., Kase, Tomoki & Ng, Peter K. L., 2013, On A New Species Of Freshwater Crab Of The Genus Ovitamon Ng & Takeda 1992 (Crustacea: Brachyura: Potamidae) From Panay Island, Philippines, Raffles Bulletin of Zoology 61 (2), pp. 651-655 : 651-654

publication ID	https://doi.org/ 10.5281/zenodo.5352644
persistent identifier	https://treatment.plazi.org/id/03BD87FC-FFE4-FFAA-FC03-02B99520E0CB
treatment provided by	Tatiana
scientific name	Ovitamon agmamba
status	sp. nov.

Treatment

Ovitamon agmamba View in CoL , new species

( Figs. 1–4 View Fig View Fig View Fig View Fig )

Material examined. — Holotype: male (50.0 × 38.8 mm) ( NMCR 39075 ) Agmamba creek , Barangay Traciano , Dumarao , Capiz, Panay Island, 11°14.662'N, 122°38.528'E, Philippines, coll. T. Kase, 12 May 2012 GoogleMaps . Paratypes: 1 female (50.7 × 39.4 mm) ( NMCR 39080 ), same data as holotype GoogleMaps ; 1 male (50.4 × 40.1 mm) (NSMT- Cr 22314), 1 female (49.7 × 38.6 mm) (NSMT-Cr 22315), 1 male (41.4 × 32.7 mm), 1 female (46.4 × 37.0 mm) ( ZRC 2013.0273 View Materials ), same data as holotype GoogleMaps .

Comparative material. — Ovitamon tomaculum (Ng & Takeda, 1992) , paratypes: 2 males, 5 females (largest 21.6 × 17.1 mm), two juveniles (NSMT-Cr 11220) Pitogo River, Panay , Philippines, coll. M. Takeda & S. Shokita, 19 Aug.1985 . Ovitamon baloy Manuel- Santos & Ng, 2013, holotype male (19.5 × 14.7 mm) ( NMCR 15007 ), Philippines, Panay island, Antique, Valderama, Mount Baloy , 1340 m asl, coll. M. R. Manuel , Oct.1989 .

Diagnosis. — Carapace ovoid, proportionately rounded, smooth; anteroexternal angle of third maxilliped merus produced; male telson longer than somite 6, proximal lateral margin concave; G1 proportionately stout, tapering to distal end, slender, terminal segment cylinder-shaped, upcurved, surfaces covered with dense, smooth, spiniform, short setae, outer distolateral margin of subterminal segment concave.

Description of holotype male. — Carapace ovoid ( Fig. 1a View Fig ), broader than long; dorsal surface and posterolateral regions smooth; suborbital, sub-branchial and pterygostomial smooth; branchial region swollen, carapace appearing inflated

laterally and longitudinally. Frontal margin gently sinuous; supraorbital margin entire; external orbital angle triangular, outer margin granulated; epibranchial tooth low, blunt, distinctly separated from external orbital angle; anterolateral margin convex, granulated; posterolateral margin distinctly converging posteriorly. Epigastric cristae distinct, low, rugose, vaguely confluent with low but sharp postorbital cristae.

Eyes well developed, well pigmented, fills entire cavity, cornea wider than peduncle in dorsal view. Buccal cavern quadrate. Exopod of third maxilliped with long flagellum, as long as width of merus; ischium squarish with shallow indistinct median sulcus on proximal three-quarters of ventral surface, relatively deeper proximally; anteroexternal angle distal margin of merus produced ( Fig. 1b, c View Fig ). Epistome relatively wide, margins cristate, posterior margin with triangular median lobe with concave margins; lateral lobes low ( Fig. 1b View Fig ).

Chelipeds unequal, outer surface of cheliped smooth, finger subequal in length with palm ( Fig. 2a, b View Fig ), carpus with prominent inner distal spine and sharp basal granule on proximal part. Ambulatory legs relatively slender, long, surfaces smooth, without subdistal spines on dorsal margins of meri; posterior margins of all legs smooth.

Thoracic sternites smooth, setae present on junctions of suture and lateral margins of sternites 2, 3; suture between sternites 2, 3 gently convex; sternites 1, 2 completely fused, with setae on suture, triangular with apex long, sharp. Sterno-abdminal cavity reaching imaginary line joining anterior edges of coxae of chelipeds. Abdominal segment triangular ( Fig. 3a View Fig ); somite 3 widest, narrowing progressively towards telson; lateral margins of somite 6 almost straight; telson longer than somite 6, lateral margins slightly concave proximally.

G1 tapering to distal end ( Figs. 3d, e View Fig , 4a, b, d, e View Fig ), sinuous, slender, membranous collar separating terminal and subterminal segments dorsally, slightly swollen proximally at dorsomesial corner. Terminal segment cylindrical, upcurved, 0.38 times length of subterminal segment. Surfaces of subterminal segment covered with dense, smooth, spiniform, short setae, longitudinal groove running from base to distal end of ventral surface, lined with long setae along margins. Distal segment of G2 ( Figs. 3f View Fig , 4c, f View Fig ) long, 0.57 times length of basal segment.

Paratype female. — The female agrees in all aspects to the male holotype in non-sexual characters. The subcircular abdomen covers almost the entire thoracic sternum ( Fig. 3b View Fig ).

Etymology. — The new species is named after the type locality of this species. The name is used as a noun in apposition.

Habitat. — Ovitamon agmamba , new species, was collected from small creek in low mountain area. This new species was found hiding under rocks and crevices during daytime.

Remarks. — Three species of potamids are known from Panay-Guimaras region on Panay Island: Ovitamon cumingii Miers, 1884 (from Guimaras Island, ca. 10°35'N, 122°36'E), O. tomaculum Ng & Takeda, 1992 (from Pitogo River, ca. 10°34.78'N, 122°3.82'E, in southern Panay), and O. baloy Manuel-Santos & Ng, 2013 (Mount Baloy, western Panay, ca. 11°8.800'N, 122°15.183'E). The new species, O. agmamba (from northeastern Panay, 11°14.662'N, 122°38.528'E), is the fourth to be described from this region. This is also the largest known Ovitamon species and can easily be distinguished from all congeners by several very distinct characters.

Compared to O. cumingii , which is only known from dried specimens from Guimaras Island (G1 structure not known) (see Ng & Takeda, 1993), the overall appearance of the carapace of O. agmamba , new species, is more rounded, the lateral margins are more convex and inflated while the branchial regions are relatively smooth ( Fig. 1a View Fig ) (vs squarish carapace, lateral margins are less convex and the branchial regions have weak but distinct striae or granules in O. cumingii , cf. Ng & Takeda, 1993: fig. 1A, B). These differences cannot be accounted for by size related aspects as the type male of O. cumingii is relatively large at 38.0 by 28.9 mm (Ng & Takeda, 1993: 112), and comparable in size to one of the small paratype males (ZRC 2013.0273, 41.4 × 32.7 mm) of O. agmamba examined here.

The dorsal surface of the carapace of O. agmamba is similar in appearance to O. tomaculum and the adult material of the latter could easily be mistaken as a juvenile form of the new species if they are compared side by side. Other than the much larger adult size of O. agmamba (which reaches carapace widths of 40–50 mm vs only 20 mm for O. tomaculum ), other differences include the lateral margins of the male telson being concave in the proximal part ( Fig. 3a View Fig ) (vs almost straight in O. tomaculum , cf. Ng & Takeda, 1992: 156), the middle angle of the distal margin of the third maxilliped merus is relatively more produced ( Fig. 1b View Fig ) (vs less produced in O. tomaculum , cf. Ng & Takeda, 1992: fig. 3D), the outer distolateral margin of the subterminal segment of the G1 is more concave ( Figs. 3d, e View Fig , 4a, b, d, e View Fig ) (vs slightly sinuous in O. tomaculum , cf. Ng & Takeda, 1992: fig. 3E–F, J–K, G–H), and the terminal segment of the G1 is proportionately more slender ( Figs. 3d, e View Fig , 4a, b, d, e View Fig ) (vs stouter in O. tomaculum , cf. Ng & Takeda, 1992: fig. 3E–F, J–K, G–H).

Adult specimens of O. agmamba are twice as large as O. baloy and the identities of the two species cannot be confused, even though they are from nearby localities. The carapaces of the two species are quite different from each other: the anterolateral margin of O. agmamba is distinctly serrated due to the presence of granules ( Figs. 1a–b View Fig , 3c View Fig ) (vs absent in O. baloy , cf. Manuel-Santos, 2013: fig. 1A, B). The G1s of the two species are also quite different, with that of O. agmamba relatively more slender ( Figs. 3d, e View Fig ; 4a, b, d, e View Fig ) (vs stouter in O. baloy , cf. Manuel-Santos, 2013: fig. 3A–B)

With regard to the general shape of the G1, that of O. agmamba is most similar to O. arcanum Ng & Takeda, 1992 , described from Marinduque Island. The G1 of O. agmamba , however, is relatively more slender towards the distal end and the terminal segment is more upright distally ( Figs. 3d, e View Fig , 4a, b, d, e View Fig ) (vs evenly cylindrical with more prominently bent terminal segment in O. arcanum , cf. Ng & Takeda, 1992: fig. 1D–G). The shape of the male telson is also different, with the lateral margins of O. agmamba distinctly concave ( Fig. 3a View Fig ) (vs straight in O. arcanum , cf. Ng & Takeda, 1992: fig. 1C).