Adhesion in lepadomorph barnacles
The larvae of Pollicipes pollicipes were succesfully reared in the laboratory and their morphological characteristics described and compared to the previously described P. polymerus. Attempts to induce apparently healthy cyprids to settle in quantity, using methodology commonly employed for balanomorph barnacles, were unsuccessful indicating the lack of some major settlement cue(s). The scalpellids P. pollicipes and Capitulum mitella were shown able to voluntarily relocate, with measured speeds of up to 50 gm d'', but the lepadid Lepas anatifera cannot do so. The scalpellids used different mechanisms for relocation although both involved growth and sloughing of basal integument. A stimulus for directed travel was not found but gravity and unidirectional flow were rejected. The cement of lepadomorphs was shown to dissolve very slowly in sterile seawater. Cement in flowing seawater tanks, or in the presence of bacterial isolates collected from the cement, or in the presence of protease concentrated from bacterial cultures, did not dissolve at faster rates, to that of sterile cement, than could be explained by the sample sizes. The proteinaceous cement of P. pollicipes was delivered as a liquid in nl quantities over a period of 5-20 minutes before curing which took around 2 hours. Cement masses cured in seawater were found to be zoned due to a variable volume of space within, whilst cement delivered and cured in air or nitrogen was homogeneous. It was determined that the more porous inner zone of cement masses was inhibited from curing fully as a result of an inability to displace water. The partially cured zone could be induced to cure fully, by heating to dryness from a minimal volume of water. The presence of water was determined to be essential for curing. Differential degrees of curing of cement masses allowed for various physical and histochemical treatments which support both the rejection of disulphide bonding and phenol tanning and the growing evidence of hydrophobic complexing as central to the solidification mechanism of barnacle cement.