Grows to 3 in (75 mm) in length. Hermaphrodites. Cylindrical in shape, with tapering of the head and caudal peduncle and a high scale count. Dorsal and anal fins are set far back (typical for all Rivulus species), with the dorsal fin origin set back farther than the anal fin origin. A characteristic splotchy brown pattern, with an irregular dark mark just behind the operculum (humeral blotch) and a rivulus spot (ocellus) on the caudal peduncle. Primary and secondary males have the same body shape, an orange or pink overlay (more often orange) on the body and fins, mottling, and a dark humeral blotch. The rivu-lus spot sometimes is absent, unpaired fins at times are clear and at times have dark edges. The proportion of primary males in Belize is high (25%), whereas elsewhere the proportion is very low for both primary and secondary males.
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