Meeting Abstract

P2.102  Saturday, Jan. 5  Brood Parasitism and Variation in Early Growth Rates of African Rift Lake Cichlids ROSCOW, R. F.*; CRUZ, A.; Univ. of Colorado, Boulder robroscow@snet.net

The cichlid fishes of the Rift lakes of equatorial east Africa represent a model of rapid speciation due to geographic and other reproductive isolating mechanisms. A paramount trait among these species is the common strategy of mouthbrooding, the practice of incubating eggs within the mouth. Within Lake Tanganyika, a catfish species, Synodontis multipunctatus, has evolved to take advantage of mouthbrooding in cichlids. By mixing their eggs with the eggs of a cichlid host, S. multipunctatus tricks the cichlid into caring for the parasitic young to the detriment of the cichlid larvae. This study investigates traits associated with ontogeny (timing of individual development), specifically early growth rates and whether the presence of S. multipunctatus affects growth and development of host cichlid larvae compared to species not exposed to parasitism. Four fish species from the Rift lakes, representing all three lakes, were observed in aquaria during the initial three weeks of life, to establish notochord (embryonic spinal structure) growth rates and early ontogeny. The data collected for each of the four species showed that of the spread of growth attained by individuals for each day observed, the Ctenochromis horei from Lake Tanganyika showed the greatest spread around the mean, as well as the greatest mean standard length attained for each day. Observation of the actual growth profiles for all of the species clutches showed C. horei displayed the most variability in growth rate, due to the large variability in notochord growth observed day to day. Overall, the data supports the hypothesis of C. horei experiencing selection different from the observed cichlids of Lake Malawi and Victoria due to the presence of the brood parasitic S. multipunctatus.