Species: Hiatirhaphis cascajalensis, Cascajal Mosquitofish

Hiatirhaphis cascajalensis (Meek & Hildebrand, 1913)

Cascajal Mosquitofish

Head and body moderately robust, moderately compressed at rear; head depressed; front nostril not tubular; covering of eye not continuous with skin of head; mouth small, at front, slightly oblique, lower jaw slightly projecting, top jaw protractile; jaw teeth consist of an outer row of large backward curved teeth, and several rows of small pointed teeth; 12 gill rakers; 1 dorsal fin with short base, 7, at rear of body; anal fin 9, origin distinctly before dorsal fin origin; pelvic origin well behind pectoral base, near anal fin, tips of pelvics of males not swollen; pectorals high on flank, male with 5th ray not scalloped; 3rd anal ray unbranched; anal fin modified in male to form an elongate sex organ, tip of that organ curved slightly upwards, without club-like spines at tip, without a fleshy palp; tail base relatively narrow; tail fin rounded; scales smooth and relatively large, 26 in lateral series, 13 before dorsal fin.

Pale brown above, lighter below; operculum silvery, with a bluish tint; iris pale blue-green; dorsal and tail fins translucent; pelvic fins yellowish; anal fin of female and sex organ of male yellowish, with a large black blotch at the base; tip of dorsal fin black; a broad curved dark bar (often indistinct) at base of tail fin.

Reaches 7.5 cm.

Mainly in freshwater, but also occurs in brackish water.

Depth range: 0-2 m.

Costa Rica to Panama.