Third, in larvae of Cryptosula pallassiana, a rise in temperature decreases the photopositive phase, but the amount of illumination has no effect on the rate of change in sign of the response to light (Ryland, 1962).
Larvae are strongly photopositive on release and with time either change to photoneutral or alternate between photopositive and photonegative.
In controls without applied 5HT, the percentage of larvae remaining photopositive decreased from a mean of 88% to 70% over the 140-min period.
In controls lacking exogenous DA, the percentage of larvae remaining photopositive decreased from a mean of 83% to 41% over 240 min.
We report that 5HT and its immediate metabolic precursor, 5-hydroxytryptophan (5HTP), rapidly caused photopositive larvae of B.
Bath-application of [10.sup.-5] Mor [10.sup.-6] M 5HT rapidly induced negative phototaxis in newly released photopositive larvae of B.
The sharp initial decrease in the percentage of photopositive larvae seen after treatment with [10.sup.-7] M quinpirole, contrasted with enhancement of phototaxis at higher concentrations, may reflect interactions with more than one class of DA receptor; no pharmacological profiles of bryozoan DA receptors are available.