The early ontogeny of the southern mouthbrooder,Pseudocrenilabrus philander (Pisces, Cichlidae)

The early development of the southern mouthbrooder, Pseudocrenilabrus philander, is documented from activation until the early stages of the juvenile period. The duration of the embryonic period is about 14 days at 25 degree C. Development is direct and there is accelerated exogenous feeding into the embryonic period. The pattern of development and the timing of ontogenetic events and structure formation are a reflection of both internal and external environmental conditions. During mouthbrooding, oxygen uptake is facilitated by embryonic respiratory plexuses and flapping of the pectoral fins. At the time of first release from the buccal cavity, the embryos are in an advanced state of development. The switch-over from the temporary embryonic respiratory system to the adult branchial system has occurred. The yolksac serves as a supplemental source of nutrition as the embryos develop their external food-gathering abilities. The skeletal and sensory systems are sufficiently developed to allow the young to return to the safety of the female's buccal cavity. Pigmentation may provide disruptive colouration. The rate and pattern of development of another mouthbrooding cichlid. Oreochromis mossambicus, is similar to that of P. philander despite their phylogenetic differences, and may be a consequence of similar life-history styles.