The effect of environmental colour on the growth, metabolism, physiology and skin pigmentation of the carnivorous freshwater catfish Lophiosilurus alexandri

Abstract

The growth, physiology and skin pigmentation of pacamã Lophiosilurus alexandri juveniles were evaluated in an experiment using different tank colours (white, yellow, green, blue, brown and black) over an 80 day period. The tank colours did not cause significant differences to final body mass, total length, survival rate, carcass composition (moisture, crude protein, ash, ether extract, calcium, phosphorus, energy), or to plasma protein, triglyceride and cholesterol values. Haematocrit values, however, were highest for fish kept in white tanks (ANOVA P < 0·05), while the greatest haemoglobin levels were recorded for fish kept in blue and brown tanks (P < 0·01). The concentrations of cortisol (P < 0·001) and glucose (P < 0·01) were the most in fish in the black tanks. Tank colour affected skin pigmentation significantly, with fish in white tanks having the highest values of L* (brightness) and the lowest values in blue and black tanks. L*, however, decreased in all treatments throughout the experiment. C* increased significantly over the course of the experiment in fish kept in white tanks. Similar increases of C* were recorded in the other treatments but to a lesser extent. The use of black tanks during the cultivation of L. alexandri caused stress and should be avoided. Cultivation in white and yellow tanks produced individuals with a pale skin colour, while cultivation in blue and black tanks resulted in juveniles with a darker and more pigmented skin.

Accidentally catching of the catfish Lophiosilurus alexandri (Steindachner, 1876) larvae in aquariums with different colors

“…Water limnological variables did not differ among the different aquarium colors, demonstrating that the coloration did not affect the water quality, as found by Pedreira et al (2012) and Costa et al (2017). The water parameters of this study were within the favorable range for cultivation of the species, as well as described by Pedreira et al (2012).…”

“…The color intensity was different between the colorful aquariums, which was expected, but did not influence the L. alexandri larvae survival, similarly observed by Pedreira et al (2012) and for juveniles by Costa et al (2017). The aquarium with different colors did not influence the catfish larvae development, as observed by Costa et al (2017) for juveniles of the same species. Pedreira et al (2012) verified that L. alexandri larvae ingested the same number of prey and efficiently, when submitted to aquariums with different colors.…”

“…The pacamã Lophiosilurus alexandri, Steindachner, 1876 (Siluriformes: Pseudopimelodidae) is an important species of commercial freshwater aquaculture (Pedreira et al, 2012), endemic of the São Francisco Basin, with a great importance for fishing. Such features have encouraged studies of larval rearing (Pedreira et al, 2012;Costa et al, 2017), morphology (Guimarães-Cruz et al, 2009;Mello et al, 2015) and restocking programs.…”

Effects of light and artificial fish shelter (PVC pipe) on some phenotypic traits of stinging catfish (Heteropneustes fossilisBloch, 1794)

“…Colour is a very important phenotypic trait for all the animals. Studies suggest that fish and other vertebrates have the ability to change the body colour patterns under given circumstances (Costa et al, ; Leclercq et al, ; Matsuno, ). In a study, Rajeswari, Rajasree, and Balasubramanian () reported that the low‐light environment (250–500 lux) was most suitable for dark coloration of skin in marine angelfish ( Apolemichthys xanthurus ).…”

“…In red porgy ( Pagrus pagrus ), fish kept in brighter light showed maximal pallor because of concentration of pigment cells in their skin (Rotllant et al, ). Costa et al () did a study with pacamã (Lophiosilurus alexandri ) juveniles and found that the white and yellow tanks produced individuals with pale skin colour, while the blue and black tanks resulted in juveniles with darker and more pigmented skin. They suggested that the dark coloration of fish in black and blue tanks could be due to the increase in melanophore cell numbers as well as the enlargement of the size of these cells (Amiya et al, ; Sugimoto, ).…”