Temperature dependence of egg laying inAplysia brasiliana andA. californica

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Abstract
The temperature dependence of egg laying was examined in winter-caughtAplysia. Cold-waterAplysia californica and warm-waterA. brasiliana were individually housed in the same large aquarium for 16 days at 15°C, and then for 16 days at 20°C. Initially, the majority of theA. californica were not reproductively mature (as determined by injections of atrial gland extracts) whereas all of theA. brasiliana were reproductively mature. When the temperature was increased from 15 to 20°C, both species showed a marked increase in the frequency of egg laying. At both temperatures,A. brasiliana laid eggs more frequently but produced smaller egg masses thanA. californica. We conclude that increased egg laying inA. californica was attibutable both to facilitation of oogenesis in previously reproductively immature animals and to increased activity of the bag cells which release an egg-laying hormone. Increased egg laying inA. brasiliana was attributable primarily to increased bag cell activity.