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Abstract
Junctions between photoreceptors of carp and catfish were examined to determine the potential pathways for interaction in the distal retina. In the carp, each cone emits many basal processes which course horizontally for up to 15 µm in the outer plexiform layer. These make both en passant and terminal contacts, which resemble gap functions, with both the pedicles and basal processes of neighboring cones. Another possible route for communication between carp cones is suggested by the shallow penetration of a basal process of one cone into the invagination of another. Carp rods emit short basal processes which contact the spherules and basal processes of neighboring rods. These junctions form punctate regions of close apposition. Light microscopic observations indicate the presence of rod-cone contacts in carp retina, but their fine structure has not been elucidated. In the catfish retina, numerous, typical gap junctions are found between adjacent receptor bases, their short basal processes, and between perinuclear regions of neighboring receptors. Due to the similar electron microscopic appearance of rod and cone bases in this retina, the receptor type participating in a given junction could not be identified with certainty.