Adhesion in Barnacles

There are two types of adhesion occurring in these crustaceans: (i) temporary adhesion, which occurs in larval barnacles; and (ii) permanent adult adhesion. The antennular attachment organ holds the larva on the substrate while it explores, prior to permanent settlement. The bond allows the larva to remain attached against moving sea waves, but still provides some movements.

The so-called ‘antennulary sucker’ cannot produce suction; rather, attachment is due to the presence of secretion on the attachment disc. The secretion is produced from the numerous (about 20) glands located in the second antennal segment. These gland cells open individually, in two concentric rings on the surface of the attachment disc [105]. Additionally, the attachment discs demonstrate high deformability, allowing them to adapt to the substrate profile.

There are two cell types responsible for permanent adhesion: (i) the a-type cell, which gives a positive reaction to histochemical tests for proteins, phenols and polyphenoloxidase; and (ii) the b-type cell, which gives a positive reaction only for proteins. In the larva, two cement glands are located just posterior to the compound eyes. From each of these glands a collecting duct leads into the single cement duct, which passes down an antennule and opens out at several points on the attachment disc surface. Although the cement is in a fluid state when secreted, its tanning begins immediately and the liquid cement fills in the microscopic depressions of the surface. The tanning process is gradual, during which the attachment force, when plotted versus time from settlement, shows an asymptotic increase. This natural adhesive apparently meets the criteria for good bonding agents for use in medicine, although further investigations are required in this respect [106].

Вы можете оставить комментарий, или ссылку на Ваш сайт.

Оставить комментарий