Abstract:
Previously, encrusting epialgal bryozoans, which are easily cloned and cultured under laboratory conditions, have proved to be extremely valuable experimental material for the study of genotype × environment (G×E) interactions. The suitability of the dominant epialgal species Flustrellidra hispida for such studies was assessed.

As large colonies facilitated the cloning procedure of G×E interaction studies a suitable diet enabling the rapid growth of F. hispida was required.  A 1:1 mix of the microalgae Rhinomonas reticulata and Tetraselmis chuii proved to be superior over monospecific diets of either species.  The monospecific R. reticulata diet, although inferior to the 1:1 mix, was suitable as colonies still grew at a fast rate.  Colonies fed the monospecific T. chuii diet exhibited retarded growth which barely exceeded that of colonies fed a 'settled seawater' diet.  Subsequent transferral of colonies from the 2 poor diets to a monospecific R. reticulata diet resulted in rapid growth.

The possible factors controlling spine development in F. hispida were examined.  Evidence for G×E interactions was recorded as both source site (genotype) and water turbulence were significant factors affecting spinosity in this species.  Under conditions of high turbulence increases in colony area were significantly higher for spinose 'Rhoscolyn' colonies than for lightly-spined 'Menai Bridge' larvae.

F. hispida colonies were grown in the laboratory under different levels of sediment loading, representative of field conditions.  Growth and spinosity were not significantly affected by the sediment loads investigated.  No mortality, lophophore damage or zooidal damage was observed (cf. Best & Thorpe, 1996).
 

Low Turbulence Bottle

High Turbulence Bottle