The pattern of the lower jaw dentition in farmed Atlantic salmon (Salmo salar): a tool to study mechanisms of tooth replacement?

We investigated the tooth pattern on the lower jaw of adult farmed Atlantic salmon (Salmo salar L.) to elucidate whether this pattern is more regular, with less variations, than that observed in wild Atlantic salmon studied previously. A highly regular and predictable tooth pattern, in combination with the availability of Atlantic salmon in near unlimited numbers, should provide us with an ideal model to test the hypothesis whether field or local control regulates the process of tooth replacement. In 30 animals a tooth was damaged, or partially or nearly completely extracted. The animals were sacrificed after a recovery period varying between 1 and 12 weeks. X-rays were taken prior to and at various time points after manipulation. After sacrifice, dissected jaws were cleared and stained. Surprisingly, farmed Atlantic salmon do not display a regular pattern of tooth replacement and rather resemble the marine life stage of wild Atlantic salmon. While the irregularity of the tooth replacement pattern speaks against general (field) regulation of the replacement process, it impedes its use as a tool with which the nature of this control mechanism can be studied experimentally. Our observations nevertheless provide the first preliminary data on tooth growth and turnover in Atlantic salmon