Meeting Abstract
3.7 Jan. 4 Retinal Photoreceptor Arrays in Larval Tarpon (Megalops atlanticus) and Speckled Worm Eel (Myrophis punctatus) TAYLOR, S.M.; GRACE, M.S.*; Florida Institute of Technology, Melbourne, current: St. Matthew’s University, British West Indies; Florida Institute of Technology, Melbourne mgrace@fit.edu
The teleost subdivision Elopomorpha includes tarpon (Megalops atlanticus), ladyfish (Elops saurus), bonefish (Albula vulpes) and an array of eels. Adult elopomorphs are remarkably diverse among species in morphology, ecology and behavior. However, their leptocephalus larvae are very similar- clear, ribbon-like fish with tiny heads, fang-like teeth, and unusual modes of nutrient acquisition. In a comprehensive study of elopomorph visual development, we characterized photoreceptor arrays in tarpon and speckled worm eel (Myrophis punctatus). Retinas labeled with rod opsin- or cone opsin-specific antisera showed that M. atlanticus anti-cone immunoreactivity (IR) was confined to the central/mid-temporal (forward-looking) retina while anti-rod IR occurred throughout the retina. In M. punctatus (and 12 other eel species), anti-cone IR was confined to the ventral retina, and anti-rod IR occurred throughout the retina. However, cone opsin-like IR co-localized with rod opsin-IR in eels, suggesting that either rod and cone opsins are coexpressed (at least briefly) in single cells, or the cone opsin antiserum cross-labels a non-cone opsin epitope. High-resolution transmission electron microscopy allowed clear distinction of rods and cones. In M. atlanticus, both rods and cones were observed, while in M. punctatus, all photoreceptors appeared morphologically rod-like. These results show that larval tarpon and eel retinas are highly rod-dominated. These rod-dominated larval retinas are in stark contrast to the cone-dominated retinas of most larval teleosts. This unusual and shared developmental pattern provides strong evidence for monophyly of the Elopomorpha despite contradictory conclusions from recent molecular data.
