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![Illustrations of (A) the brain and (B) gut of brown trout. The brain was drawn from a photograph and was annotated after Meek & Nieuwenhuis [51]; the gut was drawn and annotated after illustrations in Olsson [50] and Burnstock [52]. The grey shaded parts were not included in the measurements of mass.](profile/Joacim-Naeslund/publication/327955074/figure/fig4/AS:676137122422784@1538215060208/Illustrations-of-A-the-brain-and-B-gut-of-brown-trout-The-brain-was-drawn-from-a.jpg)
Illustrations of (A) the brain and (B) gut of brown trout. The brain was drawn from a photograph and was annotated after Meek & Nieuwenhuis [51]; the gut was drawn and annotated after illustrations in Olsson [50] and Burnstock [52]. The grey shaded parts were not included in the measurements of mass.
Source publication
This study investigated whether compensatory growth causes long-term effects in relative brain-or intestine size in a wild, predominantly anadromous, population of brown trout (Salmo trutta). The subject fish belonged to two treatment groups; one group had undergone starvation and subsequent growth compensation, while the other were unrestricted co...
Contexts in source publication
Context 1
... Inc., Tokyo, Japan) which was mounted vertically on a table-top tripod. Thereafter, the fish were dissected; sex was determined by inspection of the gonads [50], the intestines (without the stomach, see Figure 4) were emptied from food-particles and were put in 95% ethanol, and the heads were cut off behind the gill covers and put in 4% phosphate-buffered paraformaldehyde. In November 2012, the brains were dissected out of the heads, were put in 4% phosphate-buffered formaldehyde, and were stored in a refrigerator (4 • C). ...
Context 2
... nerves were cut off as close to the brain as possible. Epiphysis and hypophysis were removed as these structures were not successfully retained from all of the specimens at the dissection (see Figure 4). The brainstem was cut as illustrated in Figure 4. ...
Context 3
... and hypophysis were removed as these structures were not successfully retained from all of the specimens at the dissection (see Figure 4). The brainstem was cut as illustrated in Figure 4. In January 2014, the brains and intestines were blotted dry using filter paper and thereafter, they were dried for 43 h in 70 • C; after this, dry mass was weighed to the nearest 0.1 mg (AB54-S, Mettler Toledo, Columbus, OH, USA). ...
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Citations
... 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. ...
It has been suggested that a trade‐off between cognitive capacity and developmental costs may drive brain size and morphology across fish species, but this pattern is less well explored at the intraspecific level. Physical habitat complexity has been proposed as a key selection pressure on cognitive capacity that shapes brain morphology of fishes. In this study, we compared brain morphology of brown trout, Salmo trutta, from stream, lake, and hatchery environments, which generally differ in physical complexity ranging from low habitat complexity in the hatchery to high habitat complexity in streams and intermediate complexity in lakes. We found that brain size, and the size of optic tectum and telencephalon differed across the three habitats, both being largest in lake fish with a tendency to be smaller in the stream compared to hatchery fish. Therefore, our findings do not support the hypothesis that in brown trout the volume of brain and its regions important for navigation and decision‐making increases in physically complex habitats. We suggest that the observed differences in brain size might be associated with diet quality and habitat‐specific behavioral adaptations rather than physical habitat complexity. The trade‐off between the information‐processing capacity and the developmental costs is suggested to drive brain morphology across fish species. We compared brain morphology of brown trout from three habitats differing in their physical complexity and quality of available diet. The overall brain size and size of telencephalon differed across the habitats, and the differences appeared to associate with diet quality and habitat‐specific behavioral adaptations rather than physical habitat complexity.
... Brain weight was determined with the aid of a digital electronic pocket scale (EHA901, 0.01 to 100 g, China). Brain segments were named based on nomenclature by previous reports in fish (Muñoz-Cueto et al., 2001;Näslund, 2018). ...
Wildlife anaesthesiology is a dynamic and emerging field. Different species of aquatic and wildlife species are gradually gaining more recognition for their use in research, as pets or as food. This study highlights some gross and histological features of the central nervous system and vertebral column of the African catfish (Clarias gariepinus). Twenty male adult African catfish (Clarias gariepinus) were used for this experiment. Brains and spinal cords were harvested and linear measurements obtained. Routine stains Heamatoxylin and Eosin and Cresyl Violet stain were used for histological preparation. Grossly, the brain was lobulated, appearing like follicles. Relative brain weight was 0.11± 0.02%. Average fork length was 439.40 ± 21.26 mm, and the calculated encephalisation quotient was 0.084 ± 0.013, making the catfish appear to be at a lower level on the intelligence ladder. Histology revealed a telencephalon with indistinct layers, unlike that observed in mammals. The cerebellum was also unique, with the Purkinje cells appearing like spindle-shaped neurons and irregularly distributed in the molecular layer. The stroma of the molecular layer of the cerebellum was seen to form tracts which extend into the granular layer. The number of vertebral bones were consistent in all animals but there was a variation in the number of spinal nerves observed. The distinguishing features of the vertebral bones were highlighted and the presence of a ventral foramen, partly enclosed by the transverse processes was discussed. Results obtained from this study will find application in comparative anatomy, fish anesthesiology and possibly surgical maneuvers involving neurological diseases.
The trade-off between cognitive capacity and developmental costs drive brain size and morphology across fish species, but this pattern is less explored at intraspecific level. Physical habitat complexity has been proposed as a selection pressure on cognitive capacity that shapes brain morphology of fishes, but development of brain is also inherently linked to supply of energy and nutrients, particularly of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). In this study, we compared brain morphology of brown trout Salmo trutta from stream, lake, and hatchery environments, which differ in physical complexity and availably of dietary n-3 LC-PUFA ranging from low habitat complexity and high n-3 LC-PUFA availability in hatchery to high habitat complexity and low n-3 LC-PUFA availability in streams. We found that brain size, and size of optic tectum and telencephalon differed across the three habitats, being largest in lake fish. We suggest that these differences appeared to associate with diet quality and habitat specific behavioural adaptations rather than physical habitat complexity.
