Abstract:
A cheap and effective method of obtaining bryozoan larvae of a known age is described.  The influence of three different lighting regimes on patterns of larval release in Flustrellidra hispida were investigated in the laboratory.  Evidence of endogenous rhythms as controlling factors was inconclusive. The main and possibly only cue for larval release in F. hispida was found to be light following a period of darkness;  the effect of this cue was exaggerated when the dark period was lengthened beyond that typical of the field period.

Settlement success and the rate of settlement of Alcyonidium hirsutum larvae onto artificial substrata increased as water temperature increased (8°C, 13°C and 18°C).  The source site of larvae, however, did not affect either settlement success or the rate of settlement.  For F. hispida larvae, settlement success increased with water temperature (13°C and 18°C) but the rate of settlement did not.  In contrast, settlement success was not affected by levels of water turbulence but the rate of settlement was; the rate of settlement was higher in turbulent conditions.

The phasing of larval release and the duration to settlement of A. hirsutum and F. hispida larvae is discussed in the context of (i) two conceptual models described by Cancino et al. (1994), and (ii) the potential for larval dispersal.
 

Larval Release in Flustrellidra hispida

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