Morphological and molecular identification of rare longhorn butterflyfish larvae (Chaetodontidae)

Among previously unidentified chaetodontid larvae, one form is distinguished by a long, straight, or curved horn above each eye. Because of its remarkable morphology, this chaetodontid larva has been mentioned in earlier publications, but assignment to a species has been difficult. We have cleared and double stained 2 specimens of this long-horned larva to document the anatomy and its possible bearing on its identification. Based on anatomical data, such as 5 instead of 6 infraorbitals and the reduction in size of the endopterygoid and the ectopterygoid, we have identified our cleared and double-stained specimens as members of the Chaetodon subgenus Citharoedus. Additionally, we have obtained barcode sequences from ethanol-fixed specimens that identified both specimens as mailed butterflyfish (Chaetodon reticulatus), one of the 3 species of the Citharoedus subgenus. An intriguing aspect of these larvae remains the enigma of how the horns are apparently lost, and we continue to pursue this avenue of research.

Nobody really metamorphoses. Cinderella is always Cinderella, just in a nicer dress. The Ugly Duckling was always a swan, just a smaller version. And I bet the tadpole and the caterpillar still feel the same, even when they’re jumping and flying, swimming and floating. 
Just like I am now. 
–– Holly Smale, British writer