The adult ecophenotype of an animal is the result of interactive events which occur during its early ontogeny through a series of sequential steps of increasing morphological complexity. At the step boundaries, there are qualitative and quantitative changes in the structures present which will allow the developing animal to successfully cope with new trophic features of its internal and external environment. There is some controversy as to whether the shifts that occur at these step boundaries are gradual or saltatory. Environmental parameters, early life-history plasticity and genetic instructions are the interactive events which produce the ecophenotype. The early ontogeny of Oreochromis mossambicus was followed from the time of egg activation until juvenilization. The eggs, embryos and larvae were artificially incubated at 25±0.5ºC. The descriptive text and the figures are composites derived from drawings, photomicrographs and observational notes of live and preserved individuals. It was found that the early ontogeny of O. mossambicus consists of an embryonic period of approximately 11 days and a truncated larval period of about 4-5 days. The embryonic period can be further divided into a cleavage, an embryonic and a free-embryonic phase. Comparisons of the early development of three other mouthbrooding and one substrate-spawning cichlid done by other researchers, revealed that the early ontogeny of O. mossambicus closely resembles that of Sarotherodon melanotheron (also a mouthbrooding species). Embryo length and yolksac area changed gradually in the cleavage and embryonic phases, showed little or no change in the free-embryonic phase, and changed rapidly in the larval period. Heart rate increased gradually in the embryonic phase and peaked just before the shift into the free-embryonic phase. Gradual decrease in heart rate occurred in the free-embryonic phase followed by a second peak at the boundary between the embryonic and larval periods. In the larval period, heart rate levelled off. Although distinctive boundaries were not clearly evident at all steps, it was concluded that there are three definite ontogenetic steps which occur at the boundaries between the embryonic phase, the free-embryonic phase and the larval period. These thresholds occur at a point where shifts in the trophic features of the external environment are expected. Regression analysis revealed that two regimes exist for changes in embryo length and yolksac area and that a breakpoint occurs just prior to the boundary between the embryonic and larval periods. It appears that ontogeny is saltatory at points where a change in the trophic features of the environment requires a new set of interactions to occur between the environment and the ecomorphological and eco-ethological features of the animal.

Four species were selected within the littoral of Tshegera Island, and include H. astatodon, H. olivaceus, H. crebridens and H. paucidens. These species, identified on basis of the SMRS, express their individuality most strongly with respect to dentition, breeding colours, normal habitat and preferred breeding territory. All four species are maternal mouthbrooders. This reproductive strategy is characterized by complete division of labour and polygamy. Breeding males compete for optimal territories and ready to spawn females. They are characterized by fast growth, large size and overall low condition factor. Females invest in few but large yolked ova and go through a fasting period while incubating the eggs. Females are generally characterized by slower growth, smaller size and higher condition factor when compared to males. In females the energy turnover during gonadal development and subsequent mouthbrooding is high, but the energy expenditure low. Mean fecundity varies between 25 and 36 eggs per brood and mean egg size between 2.6 and 2.7 rnrn. The right ovary, although small, is functional. Breeding of variable intensity goes on throughout the year. The main dry season corresponds to synchronized breeding. During the other months of the year species breed asynchronously. Both types of breeding are related to food availability for adults and offspring. The major breeding peak which starts in July coincides to improved body condition in both sexes. In similarity with the East African flocks, the Lake Kivu haplochromines display subdivision within the major trophic groups and invasion of the major lacustrine habitats. They are nevertheless morphologically and ecologically generalized. They tend to be plesiomorphic with low diversification within each trophic group, have a lake wide distribution (eurytopic) and incline to be altricial within their specialized reproductive guild. The evolutionary status of the Lake Kivu haplochromines may be explained by survival of members of an ancestral fauna in an isolated bay during the Recent volcanic events which destroyed life in the Main Basin. The Lake Kivu flock, therefore, is a relict and is believed not to have evolved within the confines of the present-day lake.