Regional variations in the outer retina of atherinomorpha (Beloniformes, Atheriniformes, Cyprinodontiformes: Teleostei): Photoreceptors, cone patterns, and cone densities

Abstract

The outer retinae of adults of 13 atherinomorph species, representing nine different families, were examined by both light and electron microscopy. The retinae were investigated with respect to photoreceptor types, cone densities, and cone patterns. All data were composed to eye maps. This procedure allows an interspecific comparison of the regional differences within the outer retina among these shallow-water fish. Furthermore, for a more detailed pattern analysis nitro-blue tetrazolium chloride- (NBT)-stainings in the retina of Melanotaenia maccullochi are presented. Apart from rods, eight morphologically different cone types could be identified: short, intermediate, and long single cones, double cones (equal and unequal), triple cones (triangular and linear), and in Ameca splendens one quadruple cone. Dimensions and occurrence of photoreceptors vary among the respective species and within the retinal regions. In the light-adapted state, the cones are arranged in highly ordered mosaics. Five different cone tessellation types were found: row patterns, twisted row patterns, square patterns, pentagonal patterns, and, exclusively in Belone belone, a hexagonal pattern. In Melanotaenia maccullochi the different spectral photoreceptor classes correspond well with the distribution of morphological photoreceptor classes within the mosaic. Double cone density maxima together with a highly ordered cone arrangement usually occur in the nasal and/or ventral to ventrotemporal retina. In most of the species that were examined these high-density regions are presumed to process visual stimuli from the assumed main directions of vision, which mainly depend on feeding behavior and predator pressure. Our findings are discussed with respect to the variable behavioral and visual ecology and phylogeny of the respective species.

Spatiotemporal features of neurogenesis in the retina of medaka, Oryzias latipes

“…Consistent with studies in other species, the two members of the medaka double cone pair are separated from each other by an array of several membranes. Supernumerary membranes most likely belong to subsurface cisternae, which have been previously reported to exist on both sides of the interface between double and triple cones (Berger, 1967; Reckel and Melzer, 2003). Smaller structures of this type were also reported in other neurons of the retina and elsewhere in the nervous system (Fisher and Goldman, 1975).…”

“…Although many exceptions are known, most teleost cone mosaics consist of 3 elements: the double cone, and two types of the single cone. This is true for the zebrafish (Larison and Bremiller, 1990), trout (Bowmaker and Kunz, 1987), perch (Loew and Wahl, 1991), salmon (Cheng et al, 2006), guppy (Kunz et al, 1983), and many species of the series antherimorpha (Reckel and Melzer, 2003), which includes medaka. These three elements can be organized in many ways, including row arrangement, twisted row arrangement, square pattern, and less frequently pentagonal and hexagonal patterns.…”

“…These three elements can be organized in many ways, including row arrangement, twisted row arrangement, square pattern, and less frequently pentagonal and hexagonal patterns. The variety of arrangements is further confounded by the presence of less typical cone morphologies, such as miniature cones, triple, and even quadruple cones (Reckel and Melzer, 2003). The organization of cones is frequently inconsistent across the retina, and in many species square mosaic may exist in the center of the retina while row mosaic is present in its periphery (Cameron and Easter, 1993; Reckel and Melzer, 2003).…”

Topographic mapping of retinal neurons in the european anchovy by nuclear staining and immunohistochemistry

“…Moreover, global cell topographies provide evidence about regional adaptations to differences in quality and behavioral relevance of light from different sectors in visual space (see, e.g., Collin,1999). This effect concerns pigment epithelium and tapetum (Braekevelt et al,1989; Somiya et al,2000), the occurrence of different photoreceptor types (Reckel et al,2001; Reckel and Melzer,2003; Heß,2009), horizontal and radial photoreceptor patterns (Engström,1963; Locket,1985), photoreceptor density (Collin and Pettigrew,1988a,b), and organization of the inner retina (bipolar cells: Euler and Wässle,1995; horizontal cells: Wässle et al,2000; amacrine and ganglion cells: Zhang et al,2004).…”

Modifications of the falciform process in the eye of beloniformes (Teleostei: Atherinomorpha): Evolution of a curtain‐like septum in the eye

“…Additionally, no lens muscle was found and specific characteristics were observed in the outer retinal morphology (see Reckel and Melzer, 2003).…”