Meeting Abstract

51.5  Sunday, Jan. 5 11:15  Development of adipose fin innervation and implications for fin evolution. STEWART, TA*; HALE, ME; University of Chicago; University of Chicago tomstewart@uchicago.edu

Adipose fins are found on the dorsal surface of many teleost fishes, between the dorsal and caudal fins. They have evolved repeatedly, at least three times in ray-finned fishes. The developmental programs that generate these structures are, as yet, unknown, and adipose fin function remains poorly understood. To inform these questions, we characterize adipose fin development in the South American armored catfish, Corydoras aeneus (Callichthyidae), describing the innervation of the adipose fin. Nerves were stained with antibody labeling in fish that ranged in age from the early larval stage (10 days post-hatching) through complete development of the adipose fin, approximately four weeks post-hatching. We find that the adipose fin of C. aeneus is heavily innervated. In adults, a primary nerve runs along the proximo-distal axis of the fin, posterior to the adipose fin spine. This nerve extends projections parallel to the antero-posterior axis of the fin, as well as anteriorly through the adipose fin spine. Adipose fin nerves originate from branches of the recurrent ramus of the facial nerve and from spinal projections. Adipose fin innervation is compared to sensory innervation of the larval fin fold and the anal fin, and evolutionary implications of sensory potential in new vertebrate appendages are considered. We hypothesize that adipose fin evolution involved the retention and elaboration of the larval fin fold. Adipose fins represent a new a model for studying the evolution of form and function in novel vertebrate limbs.