Temporal and mosaic distribution of large ganglion cells in the retina of a daggertooth aulopiform deep–sea fish ( Anotopterus pharao )

Abstract

The daggertooth Anotopterus pharao (Aulopiformes: Anotopteridae) is a large, piscivorous predator that lives within the epipelagic zone at night. In this species, the distribution of retinal ganglion cells has been examined. An isodensity contour map of ganglion cells shows that the cells concentrate in a slightly ventral region of the temporal retina. The region of high ganglion cell density contains 4.07 x 10(3) cells mm(-2), and the resulting visual acuity is 3.5 cycles deg(-1). Outside the area centralis, conspicuously large ganglion cells (LGCs) are observed in the temporal margin of the retina. The LGCs are regularly arrayed, and displaced into the inner plexiform layer. Thick dendrites extend into the outer part (sublamina a) of the inner plexiform layer. In the retinal whole mount, the total number of LGCs is 1590 (90.7 cm specimen), and the mean size of the LGCs is about four times larger than that of the ordinary ganglion cells. The morphological appearance of the LGCs was similar to the off-type alpha cells of the cat retina. The function of these distinctive LGCs is discussed in relation to specific head-up feeding behaviour.

Retinal specialisations in the dogfish <i>Centroscymnus coelolepis</i> from the Mediterranean deep-sea

“…These cells usually constitute a low percentage of the total cell population in the ganglion cell layer, but in deep-sea species their density can increase and/or form regional density variations. Specialised areas of large ganglion cells, defined as "areas giganto cellularis" were found in the tubular eyes of the deep-sea pearleye Scopelarchus michaelsarsi and Scopelarchus analis (Collin et al, 1998) and in the daggertooth deep-sea fish Anotopterus pharao (Uemura et al, 2000). Large ganglion cells were also found in G. melastomus and E. spinax (Bozzano and Collin, 2000).…”

Guanine-type retinal tapetum and ganglion cell topography in the retina of a carangid fish,Kaiwarinus equula

“…All neural elements (ganglion cells and displaced amacrine cells) containing Nissl substance in their cytoplasm, and lying within the retinal ganglion cell layer, were counted (Uemura et al 2000). Therefore, the densities (and retinal resolving powers, see below) calculated represent upper limits, which should be revised downwards when data from retrograde transport studies separate the ganglion cells from displaced amacrine cells (Collin & Partridge 1996).…”

Retinal Sampling and the Visual Field in Fishes

“…pharao may respond to a silhouetted prey item against the bright background of downwelling skylight (the daggertooth adopts a head-up posture within the water column, Uemura et al, 2000). Interestingly, an AGC comprising ON-type cells has also been described in the temporal retina of five species of procellariform sea birds, which feed on prey moving against a dark background (Hayes et al, 1991).…”

“…However, of all the receptor patterns described, the square mosaic comprising four double cones surrounding a central single cone appears to be relatively common and has received particular attention. Although not definitively tested, a number of theories about the function of the square mosaic have been put forward, which include increasing both visual acuity (Engström, 1963a,b;Ahlbert, 1976) and contrast (Marc and Sperling, 1976;Meer, 1994), providing a more uniform spectral sampling (Bowmaker, 1990), allowing more detailed chromatic patterns to be resolved (Lythgoe, 1979), and enhancing the detection of polarized light (Cameron and Easter, 1993;Novales-Flamarique and Hawryshyn, 1998; Chapter 13). Although not mutually exclusive, the square mosaic may also aid in the analysis of movement in all directions in contrast to a row mosaic, which may be suited to the perception of movement in two directions (Engström, 1963a;Anctil, 1969;Bathelt, 1970).…”

“…In the pearleye Scopelarchus michaelsarsi and the daggertooth Anotopterus pharao (Uemura et al, 2000), the aptly named area giganto cellularis (AGC) is comprised of large soma with dendritic terminals stratifying within the outer and inner parts of the IPL, respectively. Due to their size and large dendritic field, these cells are thought to be motion sensitive to objects crossing the binocular visual field.…”