Ecology and Evolutionary Biology
Dr. Alexander Cruz
This study aimed to characterize the reproductive biology of a little-studied, aquaria-raised mouthbrooding cichlid, Melanochromis johanni, endemic to Lake Malaŵi in the East African Rift Valley. Due to threats on lake conservation that are affecting genetic and biological diversity (Odada et al. 2003), it is important for this species, among many others, to be described as thoroughly as possible. The goals of this study were to characterize the reproductive biology of M. johanni, including behavioral aspects of dominance, territoriality, visual communication, courtship, breeding, and early-development. The questions tested are: does M. johanni form a linear hierarchy in a large group, and does the hierarchy remain stable and linear through time? Does territoriality in aquaria imply shared dominance between territorial holders, and to what spatial extent can that shared dominance occur? How does M. johanni use pigments to communicate visually? What is the courtship sequence of this species, and how often does it result in breeding? Does the female’s fecundity have a relationship with her size, and what are the stages of early development? Behavior was recorded using a camcorder and assessed in several aquaria. M. johanni was found to form a linear hierarchy, and only the alpha and beta males (the two most dominant positions in the hierarchy) maintained stable positions over time. Also, I found territoriality between males to imply shared dominance in larger aquaria. However, differing spatial extents of neighboring males were tolerated. The courtship sequence was identified and quantified using a flow diagram. Fecundity was positively correlated with female size, and the stages of early development were carefully documented, including the passage through cleavage, embryonic, and eleutheroembryonic (post-hatching) phases as outlined by Balon (1985).
Mannon, Makenzie, "Behavioral and Early Developmental Biology of a Mouthbrooding Malawian Cichlid, Melanochromis johanni" (2013). Undergraduate Honors Theses. 433.