Insulamon, NG & TAKEDA, 1992

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 : 44-48

Insulamon magnum new species

( Figs. 6 A–C, 7A–H, 13A–E)

Type locality. – Lake Manguao catchment, Taytay Municipality, Palawan Island, Philippines.

Type material. – Holotype: male (53.0 by 41.8 mm) (NMCR-39014), Palawan, Taytay, Lake Manguao, Alipuran Stream , riffle, gravel, boulders, CPOM, 45 m asl, c. 10°45'04"N, 119°31'06"E (11c), coll. H. Freitag, 22 Aug.2008.

Paratypes: 1 male (26.9 by 22.0 mm) ( PCSD), Palawan, Taytay, Lake Manguao, Alipuran stream, residual pool, leaves, boulders, c. 50 m asl, c. 10°45'02"N, 119°30'44"E (11b), coll. H. Freitag, 20 Nov.2008 ; 1 male (43.6 by 33.9 mm) ( ZRC 2010.0336 ), Palawan, Taytay, Poblacion, Culanga Stream , private farm Reyes , rocks, leaves, secondary forest, c. 10 m asl, 10°47'48"N, 119°30'46"E (78), coll. H. Freitag, 17 May 2007 ; 1 male (30.9 by 24.7 mm) ( WPU), same locality as previous specimen, coll. G. Albunda, 17 May 2007 ; 1 ov. female (44.0 by 34.2 mm) ( ZRC 2010.0337 ), Palawan, Taytay, Abongan, Ibangley , Abongan River tributary, highway km 178, shallow, sand, CPOM, 10°37'36"N, 119°23'07"E (108), coll. H. Freitag, 28 Sep.2007 ; 1 juv. male (21.5 by 17.3 mm) ( ZRC 2010.0338 ), Palawan, Taytay, Abongan, Ibangley , Abongan River tributary, Kaylubong Stream , highway km 179.1, gravel, sand, CPOM, c. 10°37’35’’N 119°23’44’’E (109), coll. H. Freitag, 28 Sep. 2007 ; 1 male (32.1 by 25.1 mm) (SMF-38296), Palawan, Taytay, Cataban, Cataban River , highway km 230, medium lowland river, farmland, FPOM, gravel, slightly polluted, 10°59'15"N, 119°24'12"E (115), coll. H. Freitag, 16 Oct.2007 ; 3 males (17.6 by 13.9 mm, 19.4 by 15.4 mm, 23.3 by 17.4 mm), 1 female (25.5 by 20.2 mm) (SMTD-Crustac-S105), Palawan, Roxas, Abaroan, Candelaria , Road to Port Barton , slash and burn farmland, small temporary creek, sand, boulders, CPOM, 10°20'14"N, 119°16'29"E (127c), coll. H. Freitag, 16 Nov.1995 ; 1 male (37.3 by 29.2 mm) (SMTD-Crustac-S106), Palawan, El Nido, Pasadeña, Nagkalit- Kalit Falls , small mountain river, degraded primary forest, rocks, gravel, wood litter, c. 11°15'N, 119°26"E (112), coll. H. Freitag, 14 Oct.1994 ; 1 male (33.4 by 26.0 mm) (NHMW-25176), same data as previous specimen ; 1 male (31.1 by 25.0 mm), 1 female (26.3 by 21.0 mm) (ZMUC-CRU-10086), Palawan, El Nido, Villa Libertad, small creek near dump site, secondary forest, rocks, sand, CPOM, fall & pool, c. 50 m asl, c. 11°12'N, 119°26'E (113b), coll. H. Freitag, 15 Oct.1994 ; 1 male (33.6 by 26.2 mm), 1 ov. female (38.0 by 29.5 mm) (NMCR-39015), PHIL.: Palawan, El Nido, Pasadeña, Sitio Kalanpinay, downstream Bulalacao Falls , degraded primary forest, rocks, gravel; c. 100 m asl, 11°13'18"N, 119°27'52"E (114a), coll. H. Freitag, 15 Oct.1994 ; 1 female (34.7 by 27.2 mm) (SMF-38297), Palawan, El Nido, Pasadeña, Sitio Kalanpinay, Bulalacao River , degraded primary forest, boulders, gravel, CPOM, c. 80 m asl, 11°13'18"N, 119°27'28"E (114b), coll. H. Freitag, 15 Oct.1994 .

Diagnosis. — Carapace ( Figs. 6A, B ) c. 1.23–1.29 times as broad as wide, moderately high; branchial region only

slightly inflated laterally; cervical grooves rather deep; frontal margin slightly sinuously curved; suborbital margin obliquely connecting to external orbital angle; epigastric cristae projected over postorbital cristae; mesogastric cristae rather low; branchial, progastric, mesogastric, cardiac and intestinal regions slightly convex; medio-posterior carapace margin distinctly convex in dorsal view.

Male abdominal somites ( Fig. 6C ) broad; telson c. 1.25 (juveniles) to 1.55 (holotype) times as broad as long; sixth abdominal somite c. 1.65 (juveniles) to 1.95 (holotype) times as broad as long; telson and sixth abdominal somite subequal in length in adult males as well as in females ( Fig. 6D ).

Mandible with deep and narrow incision opposite of palp incertation; terminal segment of palp rather short and broad, evenly tapering towards apex.

Second maxilliped ( Fig. 7B ) exopod subcylindrical, moderately chitinous, lateral margin not indented; propodus slightly longer than broad; outer distal margin of carpus slightly protruding.

Third maxilliped ( Fig. 7A ) with dactylus about 1/3 longer than carpus; propodus slightly shorter than carpus; merus about 2/3 as long as broad, margins slightly curved, outer distal edge slightly rounded, inner distal groove (for carpus) shallower; exopodit with distinctly protruding subdistal projection at inner dorsal side.

Larger cheliped in adult males rather broad; dactylus almost half as broad as chela length, comparably stout and short.

G1 ( Fig. 7 D–H) rather stout; distal part of terminal segment at least as long as its dilated proximal base, narrow, elongate, with subclavate to hamulose tip, twisted at its proximal area, entirely slightly dorso-laterad directed; dilated proximal base of terminal segment broader than distal subterminal segment; collar distinctly cuneatly protruding dorso-mediad; ventral collar region distinctly notched. G2 ( Fig. 7C ) flagellum c. 0.55 times as long as basal segment; enlarged proximal portion of basal segment subtrapezoidal, rather slender.

Remarks. — Juvenile male specimens of the species have a straighter and slenderer G1 and G2, and the typical species characters (protruding collar region; subbasally dilated proximal part of terminal segment; distal part of terminal segment proximally twisted and distally subclavate to hamulose) are less distinct ( Fig. 7G, H ).

Insulamon magnum, new species, differs most remarkably from other species of the genus, not only by the unique gonopod characters (distal part of terminal segment long, twisted to ventrad, not distinctly attenuate, with subclavate to hamulose tip; collar distinctly, cuneatly protruding dorsolaterad), but also by the more distinct antero-lateral dentation (versus rather granulose antero-lateral margin in all other species of the genus) and the more squarish carapace (only 1.23–1.29 times as broad as long, versus at least 1.29 times as broad as long in the other species from Palawan) and the relatively broader and shorter telson than in all other species of the genus (about as long as sixth abdominal somite versus longer than sixth abdominal somite, 1.25–1.55 times as broad as long versus not more than 1.25 times as broad as long in males). The third maxilliped exopod displays a more protruding subdistal projection at the inner dorsal side, than in all other species of the genus and the G2 basal segment is more slender than in I. unicorn and I. palawanense , new species.

The immature stage of the G 1 in males of intermediate size (26.9 by 22.0 mm; Figs. 7 G–H) as well as the size of the holotype (53.0 by 41.8 mm) suggest that this is the biggest species in the genus. It was found sympatric with I. johannchristiani , new species.

Etymology. — Magnum (Latin), big. The species is named for its large size, as it is indicated by the examined material that the species grows bigger than its congeners.

Distribution. — Northern Palawan Island

Figures

Fig. 6. Insulamon magnum, new species. Holotype male from Lake Manguao catchment: A, dorsal view; B, frontal view; C, ventral view. D, ov. female (44.0 by 34.2 mm) from Abongan (108), ventral view.

Fig. 7. Insulamon magnum, new species. Paratype male (33.6 by 26.2 mm) from Pasadeña (114a): A, left third maxilliped; B, left second maxilliped; C, left G2 ventral view; D, left G1 ventral view; E, left G1, dorsal view, F, tip of left G1, ventral view (SEM picture). Paratype male (26.9 by 22.0 mm) from Manguao (11b) tip of left G1: G, ventral view; H, dorsal. Scale bars = 1 mm.