Fish with no apparent sexual dimorphism

Pineconefish have no apparent sexual dimorphism. Pinecone fishes are small and unusual beryciform marine fish of the family Monocentridae. The family contains just four species in two genera, one of which is monotypic. Their distribution is limited to tropical and subtropical waters of the Indo-Pacific. Pinecone fishes are popular subjects of public aquaria, but are both expensive and considered a challenge for the hobbyist to maintain. These fish are aptly named; their rounded, compressed bodies are completely covered (with the exception of the caudal peduncle) with very large, strong platelike scales called scutes which are fortified with prominent ridges.The first dorsal fin is composed of 4-7 strong, disunited spines which vary in length; the second dorsal fin and anal fin are small, spineless and rounded, situated far back of the convex head. The pelvic fin possesses one large erectile spine which can lock into place. The pectoral fins are somewhat elongate and the caudal fin is truncate.Coloration is typically a yellow to orange, the scales dramatically outlined in black. The eyes are relatively large, and the mouth oblique and subterminal. On either side of the lower jaw there is a bioluminescent organ called a photophore: a pale light is produced by symbiotic bacteria within the organ, and the colour of the light varies with ambient light levels—orange by day and blue-green at night.