Eirmotus furvus, Kottelat, 2008

Kottelat, Tan Heok Hui Maurice, 2008, Revision Of The Cyprinid Fish Genus Eirmotus, With Description Of Three New Species From Sumatra And Borneo, Raffles Bulletin of Zoology 56 (2), pp. 423-433 : 428-430

Eirmotus furvus , new species

( Figs. 5 , 7c )

Material examined. – MZB 10971 , holotype , 25.8 mm SL, Sumatra, Jambi: Berbak Nature Reserve, Sungai Air Hitam Dalam (1°17'54.8"S 104°08'30.4"E); aquarium fish collectors, 16–17 Jun.1995 ; ZRC 39152 , 15 paratypes , CMK 11906 , 5 paratypes , MZB 10972 , 2 paratypes , USNM, 3 paratypes , 17.1–27.3 mm SL, same locality as holotype ; ZRC 50993 , 17 paratypes , CMK 11138 , 17 paratypes ; 18.6–34.4 mm SL, Sumatra, Jambi, Danau Rasau , a black water lake draining to Batang Hari, opposite Kampung Rantau Panjang; M. Kottelat & H. H. Tan, 1 Jun.1994 .

Non-type material: ZRC 50994 , 10 ex., 18.3–22.1 mm SL, Sumatra, Jambi: from aquarium trade; P. K. L. Ng et al., Jun.1995 ; ZRC 50995 , 4 ex., 9.0– 11.9 mm SL, Sumatra, Jambi: stream adjacent to swamp forest and rubber plantation, km 32 into turnoff (westwards) to Pematang Lumut before turnoff to Kuala Tungkal (1°06'06.4"S 103°24'02.1"E); H. H. Tan & S. H. Tan, 22 Nov.1996 .

Diagnosis. – Eirmotus furvus is distinguished from all other species of Eirmotus by its wider, very conspicuous and contrasted black bars on the body (width of bar 5 equal to 1½ to 2 lateral row scales, vs. ½ to 1½ in the other species). It is further distinguished by the following combination of characters: bar 1 (on snout) conspicuous; simple dorsal-fin rays black on their entire length, black pigmentation sometimes extending onto interradial membrane before first branched ray; a distinct black mark at posterior tip of dorsal fin, appearing as part of 6 ( Fig. 7c ); pectoral fin with black upper margin; simple anal-fin rays black on their entire length in adults; all fins dusky with scattered chromatophores on all rays; serrae along posterior edge of last simple dorsal-fin ray 17–21; a small and distinct black mark immediately anterior to anus, visible in lateral view ( Fig. 7c ); mouth terminal, lower jaw wide, anteriorly rounded.

Description. – See Fig. 5 for general body shape and Table 1 for meristics and morphometrics. Size up to 34.4 mm SL. Dorsal with 3 simple and 8½ branched rays; origin above lateral row scale 5–6. Anal fin with 3 simple and 5½ branched rays; origin under lateral row scale 10–11. Pelvic fin with 1 simple and 8 branched rays, origin under lateral row scale 4–5. Lateral row scales 19–20; predorsal scales 7–8; transverse scales ½7½ between dorsal-fin and anal-fin origins, ½3½ on caudal peduncle.

Mouth terminal, upper lip not entirely visible in ventral view; lower jaw relatively wide, rounded anteriorly. No marked angle at articulation of lower jaw.

Colouration. – Preserved: Body reddish-brown; markings bold, dark brown to intense black. All bars reaching ventral midline. Bar 1 conspicuous. A large conspicuous spot on ventral midline immediately in front of anus, about halfway between bars 5 and 6. Axial streak distinct between bars 5 and 8, sometimes on whole flank. Usually no spots between bars in middle of flank.

Fins dusky with scattered chromatophores. Dorsal fin with simple rays black on their entire length, black pigments sometimes extending onto interradial membrane before first branched ray; distinct black mark situated at posterior tip of dorsal fin, appearing as part of bar 6. Anterior rays of anal fin black at basis in smaller individuals, along entire simple rays in larger ones, continuing bar 6. Base of pelvic-fin rays black. Pectoral fin with black upper margin. In life, body reddish-brown, marks black.

Distribution. – Eirmotus furvus is known from the coastal peat swamp forests, near Rantau Panjang, Sabak and Bernam, along the coast east of Jambi (Sumatra). We have seen photographs of material collected by aquarists, possibly in peat swamp forests in the area of Kumai (Borneo: Kalimantan Tengah) that may belong to this species.

Life history notes. – Eirmotus furvus is the only species of Eirmotus found in the black waters of peat swamp forests. We have observed it only deep inside the forested area, in the less disturbed sections.

Etymology. – From the Latin furvus , meaning dark black, dusky; alluding to the dusky overall appearance of the fish. An adjective.

Comparative notes. – See under E. octozona and E. isthmus for characters distinguishing them from E. furvus . Eirmotus furvus is distinguished from E. insignis by: simple dorsal-fin rays black along their entire length (vs. pigmentation restricted to anterior two rays and proximal quarter of third ray); chromatophores on dorsal fin scattered on entire branched rays (vs. concentrated at about 2/3 of their length, sometimes extending on the adjacent membranes); a black upper margin on pectoral (vs. missing); simple anal-fin rays black on their entire length in adults (vs. only at base); bars broader (width of bar 5 equal to 1½–2 lateral row scales, vs. 1–1½); longer body (BL 69.0–73.6 % SL, vs. 66.3–68.4); smaller predorsal length (66.2–73.7 % BL, vs. 76.4–78.8); smaller prepelvic length (43.7–45.7 % SL, vs. 45.5–47.2; 60.1–66.3 % BL, vs. 67.3–70.1); shorter head (length 29.7– 32.8 % SL, vs. 32.3–33.5; 40.3–46.9 % BL, vs. 47.4–50.0); narrower head (width 12.5–13.9 % SL, vs. 13.8–14.8); and greater interorbital width (27–30 % HL, vs. 22–25).

Figures

Fig. 5. Eirmotus furvus, MZB 10971, holotype, 25.8 mm SL, Sumatra: Berbak.

Fig. 7. Flank of Eirmotus species, showing dorsal fin and pre-anus patterns in: a, E. octozona, ZRC 8385, 35.6 mm SL; b, E. isthmus, ZRC 50992, 32.0 mm SL; c, E. furvus, ZRC 39152, 27.3 mm SL; and d, E. insignis, ZRC 38786, 23.2 mm SL.