Effects of different levels of temperature on some phenotypes of stripped dwarf catfish (Mystus vittatus)

Abstract

In an era of rapid climate change, there is a crying need to understand how organisms will cope with faster and less predictable variation in environmental conditions. Several studies show that temperature is one of the most important climate change variables for all aquatic organisms, especially for fish, because it can directly affect different life history traits. Therefore, the present study was carried out under laboratory condition to explore the expression of some phenotypic traits by manipulating water temperatures using a popular freshwater fish species, the stripped dwarf catfish (Mystus vittatus). The study assigned almost same-sized juvenile fish haphazardly to one of three experimental temperatures (i.e. ambient: 26-28°C, low: 20-22°C, high: 30-32°C), and each of these temperature treatments was further divided into two replications. Each replication contained 15 good-looking and healthy juveniles up to one month of the experimental period. Thus, the experimental design was able to explore the effects of temperature manipulation on the expression of some selected phenotypic traits (e.g. body length and size, colour patterns, egg and sperm numbers, etc.). After one month of experiment, the study revealed that temperature manipulations had significant effects on some of the phenotypic traits in M. vittatus. Fish reared in low temperature showed significantly higher body weight than the hot and ambient treatment group. The study also revealed that high treatment group had significantly brighter/darker coloured fish than the low and ambient treatment group, while the ambient treatment group had significantly higher number of normal/natural coloured fish than high and low treatment group. Moreover, the study showed that the low treatment group fish possessed significantly higher number of eggs as well as sperm than the high and ambient treatment group. However, no significant effect of temperature manipulation was found on standard length, tail length, head length and body area. These results further underscore the sensitivity of some phenotypic traits of M. vittatus under different levels of temperatures and highlight the important role of environmental temperature.