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1702 Two visual pathways to the telencephalon in a primitive ray-finned fish, the sturgeon acipenser transmontanus (chondrostei: actinopterygII)
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17. Visual system
1701
DISTRIBUTION OF RETINAL GANGLION CELLS AND RETINAL PROJECTIONS IN A PRIMITIVE ACTINOPTERYGIAN, Acipenser transmontanus. MASAMI YOSHIMOTO. NAOYUKI YAMAMOTO. JAMES S. ALBERT. NOBUHIKO SAWAI. AND HIRONOBU ITO. Nippon Medical Schoo 1. Department of Anatom- Y, Laboratory of Comparative Neuromoruholoav. Sendaai l-l-5. Bunkvoku. Tokvo 113. Janan. The distribution pattern of ganglion cells in the retina was examined in N&l-stained retinal whole mounts of adult sturgeons. In Acipenser transmontanus, a high density area was found in the caudal retina, and a dense band of ganglion cells was observed along the horizontal axis between the caudal retina and the nasal retina. The density of ganglion cells in the dorsal retina is lowest. The total number of ganglion cells is estimated to be about 4.3 X lo4 (mean number of ganglion cells is 370/mm2). The existence of a high density area in the caudal retina suggests binocular vision. The retinofugal and tetinopetal projections were studied by applying biocytin to the optic nerve. Retinal projection areas include the thalamus, optic hypothalamus, pmtectal area, optic tectum, nucl. of posterior commissure, and nucl. of accessory optic tract. Furthermore, several labeled fibers and terminals were found in the lateral area of the telencephalon. All retinal projecting areas were bilaterally labeled, although contralateral projections areas were mote heavily labeled. Biocytin-labeled neurons were found in the pretectal area bilaterally. Retinal projections in the primitive actinopterygian Acipenser transmontanus axe similar to those of other vertebrates, including other actinopterygians and chondrichthyans (sharks), in terms of the targets and extent of bilateral projections.
1702
Two VISUAL PATHWAYS To THE TBLENCEPHALON IN A PRIMITIVE RAY-FINNED FISH, THE STURGEON ACIPENSER TRANwONTANUS (CHONDROSTEI: ACTINOFTERYGII). J.S. ALBERT. M. YOSHIMOTO,
N. YAMAMOTO. N. SAWAl. AND H. ITO. NiDDon Medical School. Deuartment of Anatomv. Laboratorv of Comuarative NeuromomholoPv. SendaPi l-l-5, Bunkvo-ku. Tokvo 113 Comparative studies on the visual system of vertebrates reveal a common plan. With the notable exception of teleost fishes, all species so far examined possess two visual pathways; the geniculate and extrageniculate systems. Whereas in cartilaginous fishes (sharks), retinal and tectal projections converge on a single thalamic nucleus, in amniotes (reptiles, birds, and mammals) there are two distinct visual thalamic nuclei. Amphibians possess an intermediate condition. The condition in ray-finned fishes (Actinopterygii) is ambiguous. In percomorph teleosts there is a well developed extrageniculate system but no obvious geniculate system. This study reports on connections of the visual system in a non-teleost ray-finned fish. Several tract tracing methods (e.g., HRP, biocytin, DiI) were employed in conjunction with normal techniques for identifying neural structures (e.g., Nissl, Golgi). The visual system of Acipenser is determined to closely resemble that of sharks, in that fibers from both visual pathways converge in a single dorsal thalamic area.
17. Visual system
1701
DISTRIBUTION OF RETINAL GANGLION CELLS AND RETINAL PROJECTIONS IN A PRIMITIVE ACTINOPTERYGIAN, Acipenser transmontanus. MASAMI YOSHIMOTO. NAOYUKI YAMAMOTO. JAMES S. ALBERT. NOBUHIKO SAWAI. AND HIRONOBU ITO. Nippon Medical Schoo 1. Department of Anatom- Y, Laboratory of Comparative Neuromoruholoav. Sendaai l-l-5. Bunkvoku. Tokvo 113. Janan. The distribution pattern of ganglion cells in the retina was examined in N&l-stained retinal whole mounts of adult sturgeons. In Acipenser transmontanus, a high density area was found in the caudal retina, and a dense band of ganglion cells was observed along the horizontal axis between the caudal retina and the nasal retina. The density of ganglion cells in the dorsal retina is lowest. The total number of ganglion cells is estimated to be about 4.3 X lo4 (mean number of ganglion cells is 370/mm2). The existence of a high density area in the caudal retina suggests binocular vision. The retinofugal and tetinopetal projections were studied by applying biocytin to the optic nerve. Retinal projection areas include the thalamus, optic hypothalamus, pmtectal area, optic tectum, nucl. of posterior commissure, and nucl. of accessory optic tract. Furthermore, several labeled fibers and terminals were found in the lateral area of the telencephalon. All retinal projecting areas were bilaterally labeled, although contralateral projections areas were mote heavily labeled. Biocytin-labeled neurons were found in the pretectal area bilaterally. Retinal projections in the primitive actinopterygian Acipenser transmontanus axe similar to those of other vertebrates, including other actinopterygians and chondrichthyans (sharks), in terms of the targets and extent of bilateral projections.
1702
Two VISUAL PATHWAYS To THE TBLENCEPHALON IN A PRIMITIVE RAY-FINNED FISH, THE STURGEON ACIPENSER TRANwONTANUS (CHONDROSTEI: ACTINOFTERYGII). J.S. ALBERT. M. YOSHIMOTO,
N. YAMAMOTO. N. SAWAl. AND H. ITO. NiDDon Medical School. Deuartment of Anatomv. Laboratorv of Comuarative NeuromomholoPv. SendaPi l-l-5, Bunkvo-ku. Tokvo 113 Comparative studies on the visual system of vertebrates reveal a common plan. With the notable exception of teleost fishes, all species so far examined possess two visual pathways; the geniculate and extrageniculate systems. Whereas in cartilaginous fishes (sharks), retinal and tectal projections converge on a single thalamic nucleus, in amniotes (reptiles, birds, and mammals) there are two distinct visual thalamic nuclei. Amphibians possess an intermediate condition. The condition in ray-finned fishes (Actinopterygii) is ambiguous. In percomorph teleosts there is a well developed extrageniculate system but no obvious geniculate system. This study reports on connections of the visual system in a non-teleost ray-finned fish. Several tract tracing methods (e.g., HRP, biocytin, DiI) were employed in conjunction with normal techniques for identifying neural structures (e.g., Nissl, Golgi). The visual system of Acipenser is determined to closely resemble that of sharks, in that fibers from both visual pathways converge in a single dorsal thalamic area.