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Joaquin De Juan, Bassima Boughlala, Alba Isabel De Juan, Noemi Martínez-Ruiz, Maria Angeles Esteban; Do they have spinules the cone pedicles of sturgeon retina?. Invest. Ophthalmol. Vis. Sci. 2016;57(12):569.
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© ARVO (1962-2015); The Authors (2016-present)
In teleost retinas, the cone pedicles are invaginated by finger-like protrusions (spinules) from lateral processes of cone horizontal cell dendrites. Spinules are dynamic structures that appear during light adaptation and disappear during darkness adaptation.Teleost is the only vertebrate group that present these structures. Data suggest that spinules may be the sites of feedback transmission from HCs to the pedicles of cones.Actinopterygians (ray-finned fishes) are the largest and most diverse vertebrate group and are formed by teleosts, holostean and chondrosteans. However, teleosts are the most successful vertebrates and constitute them alone more than the 50% of vertebrate species (over 30,000 living species).Given the phylogenetic proximity between teleostean and chondrosteans, our aim is to verify whether sturgeons (chondrosteans) has spinules.
The experiments were performed on the sturgeon species of Acipenser ruthenus. The animals were kept in an aquarium under a 12h:12h light-dark cycles. Previously to the sacrifice, fishes were adapted during two hours in light or during two hours of darkness. Retinas were removed and processed for transmission electron microscopy studies and thin vertical sections were obtained. The number of spinules (Sp) and synaptic ribbons (SRN), per cone pedicle, were calculated.
The sturgeon Acipenser ruthenus has a dual typical vertebrate retina with cone and rod photoreceptors. The cone photoreceptors have large ellipsoids and an oil droplet. Cone pedicles have abundant and long finger-like invaginations from horizontal cells in a similar way to teleosts spinules. In contrast with teleosts, the spinule-like of Acipenser ruthenus lack of electrodense material in its ends and have a deeper invagination into the pedicle. Synaptic ribbons have similar characteristics to other vertebrate retinas. Finally, Sp and SRN are more numerous in light-adapted retinas than in darkness-adapted ones.
Spinules are a typical feature of teleost cone pedicle, not observed in any other vertebrate retina. However in this work we have found the existence of spinule-like invaginations in cone pedicles of Acipenser ruthenus. These invaginations suggest being a precursor of teleosts spinules. Both, spinule-like and synaptic ribbons are more abundant in the retinas adapted to light than in darkness-adapted ones.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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