Influence of temperature on the microstructure of statoliths of the thumbstall squid Lolliguncula brevis

A laboratory study investigating the influence of temperature on the micros tructure of statoliths of Lolliguncula brevis is described. Groups of squid were subjected to various temperature regimes for periods in excess of 30 d. Statoliths extracted from 20 squid were examined using a confocal micros cope in laser scanning mode. The pelts of the statoliths deposited during t he course of the experiments were identified using either putative daily in crement counts or from checks produced in response to capture and handling. These checks appear to consist of a series of prominent increments rather than reflecting a period of interrupted statolith growth. Increments deposi ted during the experiment generally displayed reduced contrast and clarity in comparison to the "wild parts of the statolith, presumably in response t o the constant conditions imposed in the laboratory. Average statolith grow th rates observed over the course of the experiment showed a strong positiv e relationship to ambient temperature. A significant sex effect was apparen t, with statoliths of female squid generally growing Faster than those of m ales. Observed statolith growth rates at 15 degrees C were generally below 1 mu m d(-1), suggesting that the widths of daily increments produced under these conditions may approach the resolution limits of a light microscope. The implications for studies using increment numbers to estimate age are d iscussed.