Larvae of Belonepterygion fasciolatum (Plesiopidae: Acanthoclininae)

Abstract

Larvae of Belonepterygion fasciolatum (in the plesiopid subfamily Acanthoclininae) are described based on two postflexion, pelagic specimens from Espirito Santo, Vanuatu (5.7 mm SL) and Magnetic Island, Great Barrier Reef, Australia (6.3 mm SL), as well as two settled individuals (9.4 and 11.9 mm SL) from One Tree Island, Great Barrier Reef, Australia. Distinct morphological characteristics of acanthoclinins form early in development (c. 6 mm SL), including weak head spination limited to a single opercular spine, a large oblique mouth and three unbranched lateral lines. Dorsal and anal fins have many more spines than soft rays, dorsal and anal fin spines have thickened fleshy pads distally, the body is relatively slender with a deep, short caudal peduncle. Pigmentation consists of melanophores more-or-less evenly distributed across the trunk and head as well as a pale brown background (not obvious melanophores, the colour of skin and muscle) on the body that intensifies with growth. These are the first tropical acanthoclinin larvae to be reported. For reasons that are unclear, larvae of tropical and warm-temperate acanthoclinin species are rare in collections, but cool-temperate acanthoclinin larvae can be abundant.