Common names: sleeper (English), dormilon (Espanol)
Butis koilomatodon (Bleeker, 1849)
Elongate; head and snout rounded, snout short; mouth short, oblique, reaches under front edge of eye; serrated bony ridge over each eye; front nostril a short tube; lower edge of gill opening extends forward to below eye; gill rakers 4-5 upper, 6-8 lower; no downpointing spine on preopercle; pectoral fin 21-22, rays branched; dorsal fin VI + I, 8; anal fin I, 7-8; pelvics I, 5, long, completely separated; segmented tail fin rays 17; lateral scales 25-28; top of head, cheeks and operculum scaled, no enlarged scale between eyes; no lateral line.
Head and body brown , with darker scale edges; several dark bars radiating down from eye; body with a pair of oblique dark bars under each dorsal fin, which extend onto those fins, forming a dark blotch on front half of 1st dorsal; another pair of dark bars on tail base; tail fin base with dark bar; second dorsal and tail fins with rows of pale spots; lower base of pectoral fin with conspicuous dark blotch ; female and juvenile with stronger body bars.
Reaches 10.7 cm
Lives in estuaries, enters freshwater and marine conditions.
Depth range 0-7m?
Natural range is the Indian Ocean and east to the Philippines, Papua and northern Australia. Collected in the locks at the Pacific entrance to the Panama Canal, most likely carried there in ship ballast water. Such transport may also account for its occurrence Nigeria, W Africa and much of the tropical coast of Brazil.