Ontogeny of the brain of Microglanis garavelloi Shibatta and Benine 2005 (Teleostei: Siluriformes: Pseudopimelodidae)

Abstract

The gross brain morphology and the peripheral olfactory organ of Microglanis garavelloi are described throughout development, and the relationship of these organs to the general behaviour of the species is discussed. During the development, the main brain subdivisions undergo a series of morphological changes keeping a relatively constant volume increase. However, we observed different growth rates in the brains of males and females when these were compared. During the maturation process, a series of hormonal events result in the development of some secondary sexual traits in the brain of male specimens, like faster growth rate of brain areas linked to motor control, olfactory and visual responses. The number of olfactory‐organ lamellae increases continuously in both males and females, during their maturation period. These results suggest that changes may be caused by cognitive demands that this species is exposed to throughout its lifespan. The gross morphological arrangement of the central nervous system indicates shared patterns with other members of the family Pseudopimelodidae.

Gross morphology of the brain and some sense organs of subterranean pencil catfishes of the genus ItuglanisCosta and Bockmann, 1993 (Siluriformes, Trichomycteridae), with a discussion on sensory compensation versus preadaptation in subterranean fishes

“…Another potential source of intraspecific variability is the fact that some parts of the brain, as well as some sense organs (e.g., the eyes) exhibit allometric growth during ontogeny (e.g., Abrahão et al, 2021;Kotrschal et al, 1998). In fact, we observed variability in the size of different regions of the brain among specimens of the same species, more accentuated in those with more different sizes (e.g., the length of the olfactory tract in the two specimens of I. mambai analysed;…”

“…The dissected dorsal region of the head of one specimen of I. ramiroi is illustrated in Figure 3 The rostral most region of the brain is formed by the olfactory bulb, which is not separated from the telencephalon as in most catfishes (Abrahão et al, 2021;Kapoor & Finger, 2003), but is adjacent and united to it by a short and wide olfactory tract (tractus olfactorius). The length of the olfactory tract seems to increase ontogenetically in some fishes (e.g., Abrahão et al, 2021). Indeed, we noticed some intraspecific variation in the length of the olfactory tract in some of the species analysed of the eyes both inter-and intraspecifically, including specimens with asymmetrical eyes (e.g., Figure 3).…”

Differences in brain morphology of brown trout across stream, lake, and hatchery environments

“…Other factors that have been shown to influence brain size and morphology in fishes and were not explicitly considered in our comparative study include predation pressure (Burns & Rodd, 2008 ; Gonda et al, 2012 ; Kotrschal et al, 2017 ), sex (Kolm et al, 2009 ; Näslund, 2018 ), and ontogeny (Abrahao et al, 2021 ; Lisney et al, 2007 ; Lisney & Collin, 2006 ). Potential predators, such as eel and large trout, were present in all sampled wild populations (see methods section), and thus were unlikely to explain differences between the lake and stream habitats.…”

Differences in brain morphology of brown trout across stream, lake, and hatchery environment

“…Other factors that have been shown to influence brain size and morphology in fishes and were not explicitly considered in our comparative study are predation pressure , sex (Kolm et al , 2009; Näslud 2018), and ontogeny (Abrahao et al 2021). Potential predators, that is eel and large trout, were present in all sampled wild populations (see method section), and thus were unlikely to explain differences between the lake and stream habitat.…”