Ultrastructural differences in the morphology of the optic tectum of the carp (Cyprinus carpio) and rainbow trout (Salmo gairdneri) with special reference to the synapses
Choms, A.; Probst, W.; Rahmann, H.
Journal für Hirnforschung 22(3): 299-306
1981
ISSN/ISBN: 0021-8359 PMID: 7276542 Document Number: 173727
The optic tectum of two years old rainbow trout (Salmo gairdneri) and carp (Cyprinus carpio) had been compared morphologically, especially concerning the ultrastructural appearance of synapses. Differences between these two species were most pronounced in the stratum fibrosum marginale (SM). In addition to differences in the relative thickness of this lamina as compared with the dimension of the whole tectum (carp: 12%; trout: 23%) significant variations concerning the ultrastructural differentiation were conspicuous: for the carp numerous marginal fibers form convergent synapses together with dendritic spines of pyramide cells, whereas the SM of the trout appears to be less differentiated in so far as convergent synaptic contacts in this species are almost absent. The quantitative analysis of synapses in the SM brought highly significant differences between the two species: number of synapses (carp 45, trout 62 per 1000 micrometer 2); length of synaptic contact (carp 0,31, trout 0,24 micrometer); density of synaptic vesicles (carp 122, trout 61 per micrometer 2). The occurrence of highly effective convergent synapses in carp obviously seems to be compensated in trout by means of an increase in the number of synapses and the intensity of the interlacement of fibers.