摘要:

The distribution of immunoreactive gonadotropin-releasing hormone (GnRHir) in relation to endocrine and behavioral pathways is not well established for lizards. To more completely understand the GnRHir distribution and its possible function in a lizard, we investigated the brain of Anolis carolinensis, a species whose visual courtship displays, mating postures and gonadal cycles are well known. Using antisera that recognize multiple GnRH forms, we observed no GnRHir cells or fibers in the forebrain. In the midbrain, however, GnRHir cells occurred along the medial border of the medial longitudinal fasciculus. These cells appeared to project GnRHir fibers to nuclei of cranial nerve III and IV. In the hindbrain, positive fibers were observed in the area of the vestibular nuclei and dorsal funiculus. These hindbrain fibers were followed to their terminals in the cerebellum. The GnRHir midbrain distribution suggests an association of GnRH with eye movements, whereas the hindbrain distribution suggests a GnRH-vestibular association. The lack of GnRHir in the forebrain of Anolis could reflect the minimal role of the vomeronasal system in mediating reproduction in this species. Thus, our study cannot verify hypothalamic GnRH control of the pituitary in A. carolinensis, but it does indicate GnRH control of oculomotor and vestibular nuclei, which might play a role in Anolis reproductive behaviors.

ISSN:0006-8977    

DOI:10.1159/000113327

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The morphology of the pit organs and canal neuromasts of the actinopterygian Polypterus and the lungfishes Lepidosiren, Neoceratodus and Protopterus are described using light microscopy, scanning electron microscopy and transmission electron microscopy. Pit organs resemble canal neuromasts in their hair cell polarization, but they differ in size, shape, hair cell density and in the length of the kinocilia. Pit line neuromasts in Lepidosiren, Polypterus and Protopterus are arranged in dense lines, with numerous neuromasts between pores in the canal, and are an order of magnitude smaller than canal neuromasts in Polypterus. We suggest that the evolutionary transformation of canal neuromasts into superficial neuromasts occurred through the evolutionary reduction of the lateral line canals, either as the result of selection for changes in neuromast function, or as the result of non-adaptive reduction of dermal bone around the lateral line canals and their neuromasts. Protopterus (a lepidosirenid lungfish) is apparently unique among bony fishes in that it has multiple neuromasts between adjacent pores in lateral line canals on the head. An analysis of the distribution of this character among major gnathostome clades indicates that multiple canal neuromasts between pore positions is a primitive gnathostome character. Latimeria, Neoceratodus and actinopterygian fishes are characterized by an alternative character state, the presence of one canal neuromast between adjacent pores.

ISSN:0006-8977    

DOI:10.1159/000113328

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The distribution of reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-D) was mapped histochemically in the forebrain of Rana pipiens, the leopard frog. Intense staining was observed which was strikingly restricted to certain nuclear groups and fiber tracts. The densest concentrations of NADPH-D stained cell bodies and fibers were observed in the granule layer of the accessory olfactory bulb and in the ventral aspect of the lateral pallium. Intense staining has also been reported in the presumed mammalian homologues of these regions. Less densely packed clusters of intensely stained neurons were found in the striatum, the anterior entopeduncular nucleus, the olfactory tubercle and the pars lateralis of the amygdala, whereas the preoptic region and the medial septum exhibited dense accumulations of lightly stained cells. Several fiber systems or terminal fields could be detected, including a ring of heavy staining which enclosed the striatum and an apparent terminal field in the lateral part of the medial pallium. A prominent compact tract, which may be homologous to a component of the stria terminalis of mammals, could be also followed from the ventral portion of the lateral pallium to the infundibular hypothalamus.

ISSN:0006-8977    

DOI:10.1159/000113329

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The species assemblages of cichlids in the three largest African Great Lakes are among the richest concentrations of vertebrate species on earth. The faunas are broadly similar in terms of trophic diversity, species richness, rates of endemism, and taxonomic composition, yet they are historically independent of each other. Hence, they offer a true and unique evolutionary experiment to test hypotheses concerning the mutual dependencies of ecology and brain morphology. We examined the brains of 189 species of cichlids from the three large lakes: Victoria, Tanganyika, and Malawi. A first paper demonstrated that patterns of evolutionary change in cichlid brain morphology are similar across taxonomic boundaries as well as across the three lakes [van Staaden et al., 1995 ZACS 98: 165–178]. Here we report a close relationship between the relative sizes of various brain structures and variables related to the utilization of habitat and prey. Causality is difficult to assign in this context, nonetheless, prey size and agility, turbidity levels, depth, and substrate complexity are all highly predictive of variation in brain structure. Areas associated with primary sensory functions such as vision and taste relate significantly to differences in feeding habits. Turbidity and depth are closely associated with differences in eye size, and large eyes are associated with species that pick plankton from the water column. Piscivorous taxa and others that utilize motile prey are characterized by a well developed optic tectum and a large cerebellum compared to species that prey on molluscs or plants. Structures relating to taste are well developed in species feeding on benthos over muddy or sandy substrates. The data militated against the existence of compensatory changes in brain structure. Thus enhanced development of a particular function is generally not accompanied by a parallel reduction of structures related to other modalities. Although genetic and environmental influences during ontogeny of the brain cannot be isolated, this study provides a rich source of hypotheses concerning the way the nervous system functions under various environmental conditions and how it has responded to natural selectio

ISSN:0006-8977    

DOI:10.1159/000113330

出版商:S. Karger AG    

年代:1997

数据来源: Karger