Cell Types and Connectivity Patterns in Mosaic Retinas by Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner (auth.)

By Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner (auth.)

In many elements of vertebrate and invertebrate significant frightened structures, teams of nerve or receptor cells are available which are prepared and hooked up in keeping with an exact, functionally outlined development (Braitenberg, 1973; Santini, 1975; Strausfeld, 1976; Chan-Palay, 1977). In those circumstances, teams of telephone our bodies or synapses seem as primarily comparable configurations, which, notwithstanding, are assorted intimately from one another. Such summary styles of connectivity are of a statistical nature and don't permit, in a given instance, for the prediction of the localization or connections of a selected mobile. "Wiring diagrams", accordingly, will be got simply from a large number of person observations. by contrast, in numerous sensory organs, concrete styles ensue that con­ sist of a customary, mosaic-like, and geometric association of comparable mobilephone forms. The fidelity of the sort of mosaic permits predictions approximately yes devices of the trend at the foundation of just a couple of exemplary observations. regular examples are present in the visible method: within the compound eye of bugs, every one ommatidium features a convinced variety of visible cells which are grouped round the optical axis in a hexogonal array (Kirsch­ feld, 1967); within the vertebrate retina, mosaics of geometrically prepared cones are came upon most often in reduce vertebrates; they're universal between teleosts. a few experiences have handled their phylogenetic value and their sensible function as variation to express environments or modes of feeding.

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Therefore, species with row patterns should be schooling fishes, because such animals ought to be capable, above all, of discerning movements in horizontal directions. Square mosaics, on the other hand, should be expected in predators, since these do not show any directional preference. , predators with a square pattern (see Ahlbert, 1975). However, the different behavioral patterns of Nannacara anomala during ontogeny do not permit a generalization of this model: During the first 3-4 weeks, the free-swimming alevins form a close school and are guarded by the mother (Kuenzer, 1968).

Functionally, they may be characterized by their contacts with the different cone types: One type has synapses only with certain combinations of chromatic cone types whereas others are in contact selectively with cones of identical spectral sensitivities (Scholes, 1975). In some exceptional cases, connections to rod terminals have been observed in the latter type of bipolar celL Compared to these types, the sizes of the dendritic fields of the intermediate as well as of the small bipolar cell of Nannacara are markedly smaller.

18a and b. Ribbon in a double cone pedicle of Nannacara. a. Cross section of a synaptic ribbon (sr) exhibiting the trilaminar substructure. The synaptic ribbon is anchored in the synaptic ridge (srd) by the arciform density (ad). Numerous round and oval synaptic vesicles (sv) line the lateral border of the synaptic ribbon at a distance of about 30 nm. Facing the vitread edge of the synaptic ridge is a cross-sectioned bipolar dendrite (bi). Laterally, the synaptic ridge is flanked by two pro- 50 surrounded by a halo of clear synaptic vesicles.

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