The Cytoarchitecture of the Telencephalon of Betta Splendens Regan 1910 (Perciformes: Anabantoidei) with a Stereological Approach to the Supracommissural and Postcommissural Nuclei

Abstract

Teleostean fish brains are useful models to study cellular and functional specializations along the phylogenesis. The Betta splendens Regan 1910 (Siamese fighting fish; Perciformes:Anabantoidei) is known for its aggressive display, courtship behavior, nest building, and offspring care. Here, we present novel and detailed data about the cytoarchitecture of the olfactory bulb and the telencephalic hemispheres of this fish. The hematoxylin-eosin and Nissl techniques served to identify brain nuclei (n = 19 males and n = 21 females) and for the stereological evaluation of the numerical density of cells and the proportion of neurons and glial cells in the ventral telencephalon supracommissural (Vs) and postcommissural (Vp) nuclei of adult males and females. These nuclei are putative homologs of the sexually dimorphic medial amygdala in mammals. The olfactory bulb of Betta splendens consists of 5 concentrically arranged layers plus ganglion cells of the terminal nerves. The dorsal telencephalon consists of 16 different cell groups. The ventral telencephalon has 8 nuclei, plus the lateral septal organ and the nuclei of the preoptic area forming an anatomical continuum. The rostrocaudal extent of the Vs and Vp is not different between sexes. In both nuclei, the proportion of neurons to glial cells is approximately 2:1 and the density of neurons and glial cells is not different between sexes. These morphological findings can subserve future research on the brain function of the Betta splendens and the search for neural sex differences in other central areas of this same species, in other teleost species, or yet in other related vertebrate group. Anat Rec, 00:000-000, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:88-110, 2018. © 2017 Wiley Periodicals, Inc.

Coordination and persistence of aggressive visual communication in Siamese fighting fish

“…Fish were euthanized by submerging ice water until immobile, followed by rapid decapitation. Brain regions were identified based on NeuroTrace labeling by reference to a published betta neuroanatomy atlas 57,58 . pS6+ neurons in each region were counted manually using the Cell Counter feature in FIJI2 59 .…”

“…(E) Diagram of extent of lesion along anteroposterior axis. (F) Select sections from series aligned to published atlas 57 . Arrows point to the brain region removed by the lesion.…”

Quantifying the Neural and Behavioral Correlates of Repeated Social Competition in the Fighting Fish Betta splendens

“…Tissue was imaged using a Zeiss Axio Image Microscope with Apotome.2 set to 10× magnification. To select appropriate sections, we referred to a telencephalic atlas published by Magalhães Horn and Rasia-Filho (2018) [34]. Tissue was imaged between −180 µm and 0 µm, with at least one hemisphere completely visible in the image and six consecutive sections imaged when possible.…”

“…But, to our knowledge, the current study is the first to investigate brain regions within the Social Decision-Making Network in Betta splendens. In fact, only recently has a brain atlas of the Betta splendens telencephalon (the forebrain, the area where the SDMN regions are located) been published [34]. The tools to conduct this work are certainly available in Betta: researchers have characterized the electrophysical responses of the Betta optic tectum, a region used for visual processing in teleosts when observing an opponent [35], and a more recent transcriptomic analysis [36] on whole-brain Betta tissue uncovered neural signals (upregulated immediate early genes) produced when Bettas are synchronizing their competition behavior with their opponent.…”