No abstract

Measurements were made of the strength of temporary attachment of the cypris larvae of Balanus balanoides using a sensitive micro-balance. The strength of adhesion on arthropodin treated slate panels exceeded that on clean panels and the measured forces increased as the season progressed. The observed maximum cyprid attachment strength reached 3·8 × 105 N m−2, considerably less than the bond strength of a commercial epoxy adhesive (107 N m−2) but of the same order as the force required to remove limpets (Patella) from a slate substrate. The results are discussed in the context of substrate recognition by barnacle cyprids and the possible mechanisms of adhesion involved.

It is conclusively shown that cyprids of the barnacle Balanus balanoides (L.) use a secretion released onto the antennulary discs for temporary attachment. This secretion does not stain with conventional histochemical techniques but was shown to be proteinaceous by staining blue in Bio-Rad protein-dye reagent normally used in protein assay. The discovery of this proteinaceous secretion adds further evidence to suggest that cyprids use a form of Stèfan adhesion for temporary attachment during exploration prior to settlement.IntroductionAlthough recent advances have been made in the measurement of cyprid temporary adhesion (Yule & Crisp, 1983), the question of the precise mechanism has remained speculative. Earlier suggestions that the attachment organs of the antennules operated by suction (see Saroyan, Lindner & Dooley, 1969) were challenged on morphological grounds by Nott & Foster (1969) and finally disproved by the force measurements of Yule & Crisp (1983).Nott (1969) and Nott & Foster (1969) were able to show numerous unicellular glands opening out, individually, onto the surface of the antennulary disc arranged in two concentric rings, one near the margin, and the other around the central sense organ. It was considered that these glands could produce a tacky secretion used for temporary adhesion. Yule & Nott (unpublished, reported in Yule & Crisp, 1983) failed to find any traces of such a tacky secretion on glass surfaces after cyprids had walked across them. To establish the presence or absence of a fluid secretion on the antennulary disc is fundamental to the further understanding of the type of temporary adhesion employed by cyprids.

Liocarcinus depurator is the most abundant brachyuran by--catch from commercial trawl fisheries along the Spanish Mediterranean coast. Individuals of this species were collected from bottom trawl surveys covering the entire Iberian Mediterranean coast (from Gibraltar to Cape Creus), throughout the species' depth distribution. Geometric morphometric techniques were used to determine any differences in shape between male and female crabs. Differences in shape not observed with traditional morphometric techniques were detected. Females were found to have a larger base of the abdomen which is discussed in the context of reproductive success.

In a recent paper we reported on the discovery of an adhesive antennular secretion used by exploring cyprids of Balanus balanoides (L.) and hinted at its possible implication in settlement behaviour (Walker & Yule, 1984). This secretion is thought to be modified integumentary protein. Since the integumentary protein of adult B. balanoides is widely accepted as a powerful stimulus to settlement (Knight-Jones, 1953; Crisp & Meadows, 1962, 1963; Larman, Gabbott & East, 1982), we devised settlement experiments in May 1984 to investigate whether cyprid antennular secretion acts in a similar manner. The outcome of these experiments with B. balanoides cyprids is presented here.