Abstract
Simple SummaryThis paper proposes a new methodology for evaluating fish coloration, which allows us to identify differences in the intensity of coloration of specific areas of the body. Changes in fish coloration occur during growth and under the influence of environmental factors. Male fish belonging to the family Nothobranchius are characterized by extremely diverse coloration, depending on the age of the fish, environmental factors, and social hierarchical status. As the lifespan of this genus of fish is very short (12–14 months), studies on age-dependent changes are possible. In this study, we demonstrate correlations between the coloration of particular body zones of male Nothobranchius guentheri and age using new photofixation methods and image processing software. This methodology can be applied to other fish with unique coloration patterns, for example, family Cichlidae and order Cyprinodontiformes.Fish as model objects have found wide applications in biology and fundamental medicine and allow studies of behavioral and physiological responses to various environmental factors. Representatives of the genus Nothobranchius are one of the most convenient objects for such studies. Male fish belonging to the family Nothobranchiidae are characterized by extremely diverse coloration, which constantly changes, depending on the age of the fish, environmental factors, and social hierarchical status. These fish species are characterized by a short life cycle, which allows changes in coloration, an indicator of the ontogenesis stage, to be estimated. Existing methods of fish color assessments do not allow the intensity of coloration of particular body zones to be clearly differentiated. In the present study, we suggest a method of two-factor assessment of specific fish body zones using modified methods of photofixation and image processing software. We describe the protocol of the method and the results of its application to different-aged groups of male Nothobranchius guentheri. The coloration of selected areas (i.e., red spot on the gill cover (RSGC), black border on the caudal fin (BBCF), and white border on the dorsal fin (WBDF)) differed significantly according to the size and age of the fish (p < 0.05). The data obtained suggest that N. guentheri can be a model for studying aging by the intensity of body coloration in males.
Highlights
Fish as model objects have found wide applications in biology and fundamental medicine and allow studies of behavioral and physiological responses to various environmental factors
As shown by our results, the methods proposed in this study are suitable for comparative analysis of the coloration of N. guentheri males, both in individual fish and among groups of fish of different ages and sizes
When the entire sample consisting of individuals of different sizes was assessed, the selected zones reliably distinguished between individuals of different age groups
Summary
Fish as model objects have found wide applications in biology and fundamental medicine and allow studies of behavioral and physiological responses to various environmental factors. Have become widely used as representative teleosts This model organism is not suitable for studying the aging process or changes in coloration with age due to the longer life span. It is difficult to study colorations and their changes at various stages of ontogenesis due to species differences and different rates of maturation [3]. The family Nothobranchiidae comprises a large group of fish, which mainly inhabit shallow ephemeral pools in northern Africa. As a result, they have formed a unique mechanism of reproduction and development, where the individual stages of ontogenesis are very close to each other [4]. Representatives of this family are a convenient object for studying the processes of evolution, development, and aging [6,7,8,9,10]
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