Temperature sensitivity of skeletal ontogeny in Oreochromis mossambicus

Sensitivity of skeletal ontogenesis to temperature was assessed in Mozambican tilapia Oreochromis mossambicus and Culture temperature manipulations (22, 27 and 32degrees C) were used to establish if age or length gave the most suitable metric For standardization. Oreochromis mossambicus larval growth was composed of two growth stanzas: an initial period of rapid growth, followed by a slower growth phase. Irrespective of culture temperature chondrogenesis occurred during the first rapid growth phase and ossification was initiated during the second slower growth phase. The sequence of events and rate at which ossification Occurred was much more sensitive to temperature than chondrogenesis. Cumulative counts provide a useful developmental index for skeletal ontogenesis; overall, age (effective days-degrees) gave the best estimation of developmental status during chondrogenesis and the initiation of ossification, although standard length (as log(10)L(S)) was a better metric for completion of ossification. The timing of development of functionally important structures, such as Meckel's cartilage, the branchial arches, the centra and the cleithrum important for breathing, feeding and swimming, was well conserved at all temperatures and may be a good index of teleost developmental stages. (C) 2004 The Fisheries Society of the British Isles.