High values of DNA content in the hypotalamic neurons of Lophius piscatorius and Diodon holacanthus (Osteichthyes)

Computerised image analysis on Feulgen-stained preparations indicated that in both Lophius piscatorius and Diodon holacanthus the Feulgen-DNA content of the hypothalamic magnocellular neurons in the preoptic and tuberal compl exes largely exceeded 2C. Subsequent quantitative microfluorometric evaluat ion revealed that the DNA content of these cells was as higher as 68C in L. piscatorius and 84C in D. holacanthus. The presence of high levels of DNA content in neuron nuclei is well known in the case of the giant neurons of Molluscs but, although it has recently been found in the supramedullary neu ron cluster of the same Teleosts used in this study, it must be considered exceptional for the nervous system of Vertebrates.