Influence of temperature on the microstructure of statoliths of the thumbstall squid Lolliguncula brevis |
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Authors: | M D Durholtz M R Lipinski |
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Institution: | (1) Department of Zoology, University of Cape Town, Rondebosch, 7700, Cape Town, South Africa, ZA;(2) Marine and Coastal Management, Roggebaai 8012, Cape Town, South Africa, ZA |
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Abstract: | A laboratory study investigating the influence of temperature on the microstructure 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 microscope in laser scanning mode. The parts of the statoliths deposited during
the course of the experiments were identified using either putative daily increment 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 deposited during the experiment generally displayed reduced contrast and clarity
in comparison to the “wild” parts of the statolith, presumably in response to the constant conditions imposed in the laboratory.
Average statolith growth rates observed over the course of the experiment showed a strong positive relationship to ambient
temperature. A significant sex effect was apparent, with statoliths of female squid generally growing faster than those of
males. Observed statolith growth rates at 15 °C were generally below 1 μm 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 discussed.
Received: 23 July 1999 / Accepted: 17 February 2000 |
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