Astatotilapia burtoni

Astatotilapia burtoni is a species of fish in the family Cichlidae. It is found in Burundi, Rwanda, Tanzania, and Zambia. Its natural habitats are rivers, intermittent rivers, swamps, freshwater lakes, freshwater marshes, intermittent freshwater marshes, and inland deltas. Astatotilapia burtoni has been used as a model organism to study the behaviors and physical systems of cichlids, including their development and embryogenesis. Moreover, the phylogenetic position of this particular species makes it an ideal model system for comparative genomic research. A. burtoni belongs under the haplochromines, which is the lineage of cichlids with the most species, and has been discovered to be a sister group to both the Lake Victoria region superflock (which has about 600 species) and the species flock of Lake Malawi (which has about 1,000 species). The males of the Astatotilapia burtoni come in two phenotypes that are reversible. The males can readily switch between being territorial and non-territorial based on the social environment they are in: dominant, territorial males possess bright coloration, aggressive behavior while defending territory, and an active role in sexually reproducing with the females; on the other hand, subordinate and non-territorial males possess coloration similar that of the females, lack initiative to pursue female counterparts, and are reproductively suppressed due to regressed gonads. The transitions between different social roles cause several changes in the brain and reproductive system, such that the social transformation affects them both behaviorally and physically. To expand on reversibility, if a territorial male is placed with an individual that is significantly larger in size, it will then rapidly socially transform into the non-territorial type. This change can be detected by the behavior and alternate coloration that follows. The change in reproductive competence, however, occurs about three weeks after the formerly territorial male loses its territory to the larger fish. In regards to the other social transition, when a non-territorial male becomes the territorial type, it will almost immediately exhibit aggressive behavior and an eyebar, while the physiological changes will follow in about one week. Several studies have been done in order to pinpoint the biological basis on which this reversal occurs, and they suggest that the stress hormone cortisol may have a direct role in social status, because cortisol may change the biological priorities of the cichlid's system. Under chronic stress, the animal may experience reproductive regression (as shown in the territorial's male shift to the non-territorial type) as a result of the body's efforts to combat the stressor, as opposed to using the metabolic energy for long-term goals like reproduction. Moreover, studies have also shown that the male cichlid's social phenotype directly influences the hormone levels of testosterone and 11-ketotestosterone. Plasma concentrations of these androgens in both the territorial males and non-territorial males were measured and assessed, and it was found that the territorial males have drastically higher plasma concentrations of both hormones. The cichlid males' behavior of shifting between dominant and subordinate states as a result of the social environment can also be related to females in their vicinity, for females may alternate between reproductive states as well, but independently of social conditions. Females use a complex integration of cues in order to make their mate preferences, which may be from genetic factors, learned behaviors, or hormone levels. They can socially transform between a gravid reproductive state, which is egg-bearing, and a non-gravid reproductive state, and it was shown in a study that the mating preferences of the female highly depended on the reproductive state in which the female was in. Gravid female cichlids will prefer to spend time with the dominant male type instead of the subordinate male type, whereas the non-gravid females do not have a preference for either one. This may be explained by the fact that because for spawning to occur, the gravid females must be courted by the dominant males, suggesting that gravid females' preference for dominant males is a behavioral priming mechanism.