Intrasexual and intersexual dimorphisms of the red salmon prosencephalon

Abstract

Intrasexual as well as intersexual dimorphisms were found in the prosencephalon and mesencephalon of adult Oncorhynchus nerka (red/sockeye salmon). These dimorphisms are concerned with the position of the preoptic nucleus, nucleus lateralis tuberis, habenula, third ventricle, tectal ventricles, preoptic recess, recessus lateralis, horizontal commissure, posterior commissure, and toral commissure. The intrasexual dimorphism was characterized by either a rostral ("r"-pattern) or a caudal ("c"-pattern) position of the preoptic region as well as varying locations of other structures within the prosencephalon. As compared to "c"-pattern fish, the preoptic nucleus and nucleus lateralis tuberis were located more rostral, and the habenula was positioned further caudal, in "r"-type animals. The intersexual dimorphism was also characterized by different positions of the structures listed above. With the exception of the preoptic nucleus, all of these were located further rostral in "r"-pattern females than in type "r" males. In "c"-pattern females, they were positioned further caudal than in type "c" males. The number of neurons in the parvocellular and in the magnocellular portion of the preoptic region differed in the two genders with respect to "r"- as well as "c"-pattern fish. Males had more neurons than females in both the magno- and the parvocellular subdivisions of the preoptic region. In "r"- and "c"-pattern fish, the average size of magnocellular preoptic neurons was larger in females than in males. The observed intersexual variations may reflect gender-specific differences in the control of the pituitary. Functional correlates of intrasexual dimorphism are obscure.

Galanin-like immunoreactivity in the brain and pituitary of the "four-eyed" fish, Anableps anableps

“…Intrasexual and intersexual dimorphisms have been demonstrated in the NPO of red salmon (Jadhao et al 2001). Earlier studies on goldfish did not report any sexual dimorphism (Olivereau and Olivereau 1991a), whereas a more recent study has revealed GAL-ir perikarya within and lateral to the NPO only in males (Prasada Rao et al 1996).…”

Neuroanatomical relationships between FMRFamide-immunoreactive components of the nervus terminalis and the topology of olfactory bulbs in teleost fish

“…When the same cell appeared in more than one micrograph, we measured the largest cell section by using the Leica Application Suite. Because the cell shape often seemed not to be round in the sections, we calculated the mean between the long and the short axes (see Jadhao et al 2001).…”

A comparative cluster analysis of nicotinamide adenine dinucleotide phosphate (NADPH)‐diaphorase histochemistry in the brains of amphibians

“…However, these observations are not surprising, because the brain could respond to environmental variations through rapid adaptive mechanisms, whereby different types of brain organization could be observed in closely related species within a subgroup of vertebrates, with respect to different life histories (Northcutt, ; Kolm et al, ), or even in the same species. In this regard, one of the most common differences in brain anatomy concerns sexual dimorphism (Morris et al, ); in some cases, up to four different types of preoptic nucleus morphologies have been described in the same species (Jadhao et al, ). Of course this strong adaptive brain plasticity can make brain comparisons difficult for evolutionary purposes, because some adaptations can originate in a species as a response to a contingent environmental request, and thus do not reflect the real evolutionary history.…”