Spectral absorbance, structure, and population density of photoreceptors in the retina of the lake sturgeon (Acipenser fulvescens)

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Abstract:

Lake sturgeon (Acipenser fulvescens Rafinesque, 1817) photoreceptors were studied with scanning electron microscopy and microspectrophotometry. The retina contains both rods and cones, with cones estimated composing about 30% of the photoreceptor population. Only large single cones were identified and they are similar to those found in other species of the order Acipenseriformes. The rods are large, with long, broad outer segments, and are similar to the dominant rod found in other sturgeons and the North American paddlefish (Polyodon spathula (Walbaum, 1792)). Mean (SD) rod packing density at 22624± 3509 rods/mm2 is low compared with those of other animals that function primarily in dim light. The visual pigment of the rods has a mean (SD) peak absorbance (max) at 541± 2nm. Three different cone populations were identified: a long wavelength sensitive cone containing a visual pigment with max at 619± 3nm; middle wavelength sensitive cone with max at 538± 1nm; and short wavelength sensitive cone with max at 448± 1nm. All the visual pigments are based on the vitamin A2 chromophore.

Nous avons examiné les photorécepteurs de l’esturgeon jaune (Acipenser fulvescens Rafinesque, 1817) au microscope électronique à balayage et par microspectrophotométrie. La rétine comprend des bâtonnets et des cônes; selon notre estimation, les cônes représentent environ 30% de la population de photorécepteurs. Nous n’avons identifié que des cônes grands et isolés qui sont semblables à ceux trouvés chez les autres espèces de l’ordre des acipensériformes. Les bâtonnets sont grands avec un segment externe large; ils ressemblent aux bâtonnets dominants trouvés chez les autres esturgeons et chez le spatulaire (Polyodon spathula (Walbaum, 1792)). La densité moyenne (ET) d’entassement des bâtonnets de 22624± 3509 bâtonnets/mm2 est faible par comparaison à celle observée chez d’autres animaux qui vivent principalement en lumière réduite. Le pigment visuel des bâtonnets a une absorbance maximale (max) moyenne (ET) à 541± 2 nm. On peut reconnaître trois populations différentes de cônes: des cônes sensibles aux grandes longueurs d’onde contenant un pigment visuel avec un max à 619± 3 nm, des cônes sensibles aux longueurs d’onde moyennes avec un max à 538± 1nm et des cônes sensibles aux longueurs d’onde courtes avec un max à 448± 1nm. Tous les pigments visuels sont basés sur le chromophore de la vitamine A2.

Document Type: Research Article

Publication date: April 1, 2007

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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