Insulamon porculum, Freitag, 2012

Freitag, Hendrik, 2012, Revision Of The Genus Insulamon Ng & Takeda, 1992 (Crustacea: Decapoda: Potamidae) With Description Of Four New Species, Raffles Bulletin of Zoology 60 (1), pp. 37-55 : 49-51

Insulamon porculum new species

( Figs. 10 A–D, 11A–H)

Type locality. — Barangay [= municipal district] Tinitian, Roxas Municipality, Palawan Island, Philippines

Type material. — Holotype: male (33.1 by 25.1 mm) (NMCR- 39018), Palawan, Roxas, Tinitian , small temporary tributary, highway km 83.9, c. 600 m asl, boulders, sand, FPOM, CPOM, pool, 10°02'15"N, 119°08'15"E, coll. H. Freitag, 22 Aug.1994.

Paratypes: 1 male (23.5 by 17.7 mm) ( ZRC 2010.0343 ), Palawan, Puerto Princesa, Concepcion, Taranaban River , c. 6 km upstream highway, mountain river, riffle, boulders, woodlitter, c. 150 m asl, 10°02'30"N, 119°00'45"E (16b), coll. H. Freitag, 20 Jan.1995 .

Other material. — 1 female (32.5 by 25.1 mm) ( PCSD), Palawan, Roxas, Tinitian , small creek, highway km 83.9, c. 200 m from coast, boulders, CPOM, FPOM, sand, c. 50 m asl, 10°01'44"N, 119°08'01"E (110a), coll. H. Freitag, 11 Oct.1994 .

Diagnosis. — Carapace ( Fig. 10A, B ) c. 1.32–1.35 times as broad as wide, moderately high; cervical grooves shallow; suborbital margin finely beaded, distinctly arcuate, convex towards ventral, not oblique; epigastric cristae archly aligned with postorbital cristae; mesogastric cristae conspicuous; progastric, mesogastric, cardiac and intestinal regions slightly convex; branchial region convex; medio-posterior carapace margin more or less straight in dorsal view.

Male abdominal somites ( Fig. 10C ) moderately broad, telson c. 1.14 times as broad as long (holotype), sixth abdominal somite c. 2.0 times as broad as long (holotype); telson in the holotype male 1.3 times as long as sixth abdominal somite, in the female specimen 1.2 times as long as sixth abdominal somite ( Fig. 10D ).

Mandible with rather shallow and broad incision opposite of palp incertation; terminal segment of palp long, most narrow medially, not evenly tapering.

Second maxilliped ( Fig. 11B ) exopod rather flat, partly membranous, lateral margin somewhat contorted, not indented; propodus distinctly longer than broad, outer distal margin of carpus protrudingly dilated. Third maxilliped ( Fig. 11A ) with dactylus slightly longer than carpus; propodus about 1/3 shorter than carpus; merus more than 2/3 as long as broad, margins slightly curved, outer distal edge broadly rounded.

Larger chela in the holotype male rather elongate, with dactylus distinctly less than half as broad as entire chela long.

G1 ( Fig. 11 D–H) moderately stout, distinctly curved mediad; distal part of terminal segment short, very distinctly curved, pigtail-like curly at its base; tip pointing more or less in the direction of the G1 longitudinal axis; proximal portion of terminal segment rather slender, elongate, not inflated subproximally, appearing evenly tapered; collar comparably inconspicuous, not protruding. G2 with flagellum c. 0.45 times as long as basal segment; enlarged proximal portion of basal segment subrectangular.

Remarks. — The species most resembles externally I.

palawanense by the carapace proportions and shape of striae, grooves and granulations, but varies in the epigastric cristae that are less distinctly separated from postorbital cristae in I. porculum , new species, than in other representatives of the genus (except for I. unicorn ).

It can, however, easily be distinguished by the unique G1 characters (distal part of terminal segment short, pigtail-like curly; tip straight; collar less pronounced). Furthermore, the base of the G1 terminal segment is very slender and conically elongate, not inflated as in all other Palawan species. This might be interpreted as an anatomical barrier inhibiting interbreeding, especially with I. palawanense , new species, which was found to be sympatric in that area and even syntopic in the same streams, but displays a distinctly inflated base of the terminal segment, particularly in central Palawan (see remarks for I. palawanense ).

Etymology. — Porculus (Latin), piglet. The species is named for its curly, pigtail-like distal part of the terminal G1 segment.

Distribution. — Central Palawan Island, north of Honda Bay / Ulugan Bay demarcation

Figures

Fig.10. Insulamon porculum, new species. Holotype male:A, dorsal view; B, frontal view; C, ventral view. D, female (32.5 by 25.1 mm) from Tinitian (110a), ventral view.

Fig. 11. Insulamon porculum, new species. Holotype male: A, left third maxilliped; B, left second maxilliped; C, right G2, ventral view, flipped; D, left G1 (with G2 flagellum) ventral view; E, left G1dorsal view; F, tip of left G1 ventral view (SEM picture). Paratype male (23.5 by 17.7 mm) from Taranaban (16b), tip of G1: G, ventral view; H, dorsal view. Scale bars = 1 mm.