Specialization in the diencephalon of advanced teleosts

Abstract

Cytoarchitectonic studies of the pretectum and diencephalon of five teleosts (Gaidropsarus mediterraneus, Syngnathus acus, Gasterosteus aculeatus, Pleuronectes platessa, and Coris julis) have shown the hypothalamus to be the most highly developed region in all five. The nucleus praeopticus magnocellularis is well developed in Coris and the euryhalines Gasterosteus and Pleuronectes; in Coris and Pleuronectes the nucleus lateralis tuberis is also prominent. Except in Gaidropsarus, however, the most striking area in the hypothalamus is the glomerulosus complex, with its voluminous nucleus glomerulosus. In Coris and Pleuronectes a glomerular offshoot of this nucleus in the dorsal thalamus is evidence of its being homologous with the nucleus anterior thalami of primitive teleosts. The nucleus diffusus is also very large in all except Gaidropsarus. In Coris and Syngnathus the saccus vasculosus exhibits a peduncle, and in Pleuronectes it invades the hypophysis. The descriptive analysis is complemented by measuring the relative size and cell density of the cell groups studied. A comparison among the five species studied shows that nuclei probably related to the olfactory system are more developed in Gaidropsarus and Pleuronectes, whereas the supposed visual nuclei are prominent in Coris, Gasterosteus, and Syngnathus but poorly developed in Gaidropsarus. In general, the findings of the present study, together with published results concerning Lizza (Gómez-Segade and Anadón, Trab. Inst. Cajal Invest. Biol. 72:187-214, 1981), show that Coris has the most complex diencephalon among these species. Moreover, Gaidropsarus presents an organization very different from that of the other five species and probably represents a parallel evolutionary lineage.

Evolutionary Plasticity of Habenular Asymmetry with a Conserved Efferent Connectivity Pattern

“…Variability in habenular cytoarchitecture was evident when testing the ability to distinguish the borders that separate dHb from vHb, which was unambiguous in both species of Cypriniformes (D. rerio and E. bicolor), partially clear in F. gardneri and P. scalare, and rather obscure in the remaining species. These findings are consistent with previous cytoarchitectonic reports in teleosts, most of which show the Hb at a very low resolution [10], [16], [17], [18], [19], [20], [21], [22], [23], [24], and contrast with the ease to distinguish the mammalian homolog of the teleost dHb and vHb, known as medial and lateral habenular nuclei, respectively [25], [26], [27]. Inter-species variability also extended to several aspects of the distribution of left and right habenular volumes.…”

The Brain of the Archerfish Toxotes chatareus: A Nissl-Based Neuroanatomical Atlas and Catecholaminergic/Cholinergic Systems

“…Ventral to midline (tuberal) hypothalamus, the lobular structure of the saccus vasculosus (SV) ( Figures 3J–N ) is easily recognizable (whereas the pituitary was lost in our preparations). The SV is a photoperiodic sensor which acts on seasonal gonadal changes in teleosts (Nakane et al, 2013) and is associated with a small nucleus in the posterior tuberculum, the NSV ( Figure 3L ), as previously shown in other species (Gómez-Segade and Anadón, 1988; Yáňez et al, 1997). …”

Calretinin expression in specific neuronal systems in the brain of an advanced teleost, the grey mullet (Chelon labrosus)

“…2F, 5B). The latter cells correspond to the anterior glomerular (posterior thalamic) nucleus, a dorsorostral extension of the nucleus glomerulosus reported in many acanthopterygians (Franz, 1912;Gómez-Segade and Anadón, 1988). Precise discrimination between these nuclei was, however, not possible, because intermediate cells were found scattered between them.…”

“…These cells send processes both to the diffuse nucleus of the lateral hypothalamic lobes ventrolaterally and to the mesencephalic tegmentum dorsally. This population, which crosses the boundary between the posterior tubercle and the mesencephalic tegmentum, corresponds with the lateral thalamic (tegmental) nucleus (Braford and Northcutt, 1983;Gómez-Segade and Anadón, 1988).…”