Exploratory behaviour of barnacle larvae in field conditions

Abstract

The aim of this work was to develop techniques for the real time filming of Semibalanus balanoides cyprid larvae in the field in order to describe the exploratory behaviour of S. balanoides cyprids under natural field conditions. The underwater camera system consisted of a high resolution, remotely controlled colour camera attached to a cradle which could be deployed from a pier. A light utilising a battery of far-red light-emitting diodes (λ min = 615 nm) was used for filming at night. Transparent acrylic treated with barnacle settlement factor and smooth green polyester tiles were used as targets. From the films the tracks of the exploring cyprids were digitised from the 30 min trials. During five, 30 min trials a total of 1014 cyprids explored the surface. The numbers of cyprids exploring the surface varied from 49 to 522 cyprids per trial, and a MonteCarlo randomisation model showed that larval supply was random or aggregated. The mean exploration time spent on the target was 163 s with a mean distance travelled on the target of 8.5 cm. Exploratory track length was related to water current velocity by a negative curvilinear regression (R 2 = 0.92, F = 45.65, p < 0.05). There were significant differences in exploratory behaviour between day and night for total distance travelled (p < 0.001), straight line distance (p < 0.001) and velocity (p < 0.001) and the mean heading angle of the exploratory track (p < 0.01). The results are discussed in relation to settlement patterns and the screening of antifouling surfaces.

Rejection of unsuitable substrata as a potential driver of aggregated settlement in the barnacle Balanus improvisus

“…5). Walters (1992), Lemire & Bourget (1996) and Walters et al (1999) Hills et al (2000) and Matsumura et al (2000) observed a much lower proportion of settlement for Semibalanus balanoides cyprids in short-term fieldbased behavioural studies (<1% settled during 30 min recording intervals). The high propensity for settlement on smooth substrata explains the dominant role of B. improvisus as a fouling organism on boat hulls in the Baltic, Kattegatt and Skagerrak Seas.…”

“…Hills et al 1998, Walters et al 1999, Berntsson et al 2000a), but may not correspond to natural conditions in the field where larvae are subjected to several stimuli simultaneously (e.g. Hills et al 2000). As advocated by Zimmer & Butman (2000), studies of larval responses should be performed in the presence of major stimuli experienced in the field to avoid serious artefacts.…”

Evidence for different pharmacological targets for imidazoline compounds inhibiting settlement of the barnacleBalanus improvisus

“…However, the endogenous neurotransmitters, neurohormones, neuromodulators and intracellular signal pathways involved in the regulation of barnacle larval settlement is as yet not fully revealed (Clare and Matsamura, 2000). Several studies describe intriguing behavioural mechanisms (Crisp, '61;Berntsson et al, 2000;Hills et al, The results are presented as an increase in the mean percentage settlement by the addition of methoxy-idazoxan as compared with the dishes where larvae were subjected to the inhibitor alone and no methoxy-idazoxan was added.The concentration refers to both the concentration of the inhibitor and methoxy-idazoxan. In those cases where the settlement in the dishes with the inhibitor was zero, this value was set to 1.…”

Settlement and Behaviour of Marine Fouling Organisms

“…[49] Larvae significantly altered their surface exploratory behaviour between day and night, in terms of gross and net distance travelled, speed and heading angle.…”