Embryonic Fissures in Teleost Eyes and Their Possible Role in Detection of Polarized Light

Abstract

The persistence of the embryonic (optic) fissure into adulthood and development of the falciform process in the eye varied among three fish species: guppy Poecilia reticulata, Mozambique tilapia Tilapia mossambica, and brown trout Sal mo trutta. The falciform process is a ridge of pigmenied and vascular tissue associated with the embryonic fissure in teleosts. In guppies, the embryonic fissure closed during embryonic development, and no falciform process developed. In Mozambique tilapias, the embryonic fissure persisted into adulthood but was lined only with retinal pigment epithelium and lacked photoreceptive layers; it was associated with a partially formed falciform process. In brown trout, the embryonic fissure remained well defined with both retinal pigment epithelium and photoreceptor layers, and the falciform process was well developed. The temporal zone of the fissure in adult brown trout exhibited active growth and had a ventral area of high cone density. The well-developed fissure in brown trout and the oblique orientation of its ventrotemporal cones relative to incident light may be correlated with the species* ability to locate prey above and in front of its body. This system also may allow brown trout to detect polarized light, which could assist in navigation during migration.

The cone photoreceptor mosaic of the green sunfish,Lepomis cyanellus

“…Figs, la and lc), and never parallel to it, as would be expected if new retina had been added along this contour. In contrast, Ahlbert (1976) and Kunz and Callaghan (1989) have claimed that the edge of the fissure is a proliferative zone, but their evidence (a band of differentiating cells restricted to the temporal side of the fissure) implies an asymmetry opposite to what we have shown. It seems likely that they have described the "dorsal hook" region ( Fig.…”

Novel characteristics of the cultured Lumpfish Cyclopterus lumpus eye during post‐hatch larval and juvenile developmental stages

“…At all stages, the peripheral regions of the retina were prominent and well developed, but, as revealed by serial sectioning, also contained some novel structures which, to our knowledge, were not previously described. Firstly, a very prominent rete mirabile consisting of tightly packed vascular tissue extended from the posterior portion of the globe, where it is expected for teleosts, to project from a region adjacent to what we interpret as a peripheral embryonic fissure (Kunz & Callaghan, ) and what appeared to be a separate retinal lobe. This peripherally located, pigment epithelium circumscribed portion of retina that was physically separated from the main retina, might represents a C. lumpus version of an accessory retina, reminiscent of that described previously in deep sea fish (Partridge et al ., ; Wagner et al ., , ).…”

Retinal vascularisation in the loach Noemacheilus rupicola rupicola: coexistence of falciform process and vitreal vessels

“…In teleostean eyes, there are reports of a total closure of the embryonic fissure in some species and the partial closure of it in others (Hanyu 1959, Kunz & Callaghan 1989. In N. rupicola, there appears to be no trace of a fissure in adult eyes and it might be that the hyaloid artery entered the vitreous cavity before the total obliteration of the fissure during embryonic development.…”

“…hyaloid artery), Walls (1942) suggested that they are mutually exclusive for a given teleostean retina. This has been substantiated in several species (see e.g., Hanyu 1959, 1962, O'Connell 1963, Ali et al 1968, Sivak & Roth 1978, Munk 1984, Kunz et al 1985, Kunz & Callaghan 1989. Franz (1934) andlater Walls (1942) suggested that vitreal vessels may nevertheless occur in association with a falciform process which is restricted to the distal end (close to ora terminalis) of the retina, projecting rather less conspicuously into the vitreous cavity (the so-called low falciform process after Hanyu's classification, see Hanyu 1962).…”