Three Dimensional Tracking of Exploratory Behavior of Barnacle Cyprids Using Stereoscopy

Abstract

Surface exploration is a key step in the colonization of surfaces by sessile marine biofoulers. As many biofouling organisms can delay settlement until a suitable surface is encountered, colonization can comprise surface exploration and intermittent swimming. As such, the process is best followed in three dimensions. Here we present a low-cost transportable stereoscopic system consisting of two consumer camcorders. We apply this novel apparatus to behavioral analysis of barnacle larvae (≈800 μm length) during surface exploration and extract and analyze the three-dimensional patterns of movement. The resolution of the system and the accuracy of position determination are characterized. As a first practical result, three-dimensional swimming trajectories of the cypris larva of the barnacle Semibalanus balanoides are recorded in the vicinity of a glass surface and close to PEG2000-OH and C11NMe3+Cl− terminated self-assembled monolayers. Although less frequently used in biofouling experiments due to its short reproductive season, the selected model species [Marechal and Hellio (2011), Int Biodeterior Biodegrad, 65(1):92–101] has been used following a number of recent investigations on the settlement behavior on chemically different surfaces [Aldred et al. (2011), ACS Appl Mater Interfaces, 3(6):2085–2091]. Experiments were scheduled to match the availability of cyprids off the north east coast of England so that natural material could be used. In order to demonstrate the biological applicability of the system, analysis of parameters such as swimming direction, swimming velocity and swimming angle are performed.Electronic supplementary materialThe online version of this article (doi:10.1007/s13758-012-0050-x) contains supplementary material, which is available to authorized users.

Classification of the pre-settlement behaviour of barnacle cyprids

“…Surface interaction at similar velocities has been reported previously for highly hydrated surfaces ( polyethylene glycol) [26], hydrophilic surfaces and also for zwitterionic hydrated surfaces [10].…”

“…The stereoscopy set-up consisted of two synchronized consumer camcorders as described recently [26]. The cameras imaged the surface of interest from the top at a relative angle to each other of ca 808 and a distance to the water surface of ca 40 cm.…”

“…Therefore, the two-dimensional coordinates were recorded in both camera perspectives and merged into three-dimensional coordinates for each object of interest. To apply the epipolar transformation and to allow the extraction of quantitative information from the data points, both cameras were calibrated using a calibration procedure as described in Maleschlijski et al [26]. Here, the zvalues represented the distance to the surface, whereas the xand y-values denoted the position in the surface plane.…”

Surface Sensing and Settlement Strategies of Marine Biofouling Organisms

“…Recent work showed that 3D tracking of cyprids provides more detailed information, since it allows a clear distinction between sinking and swimming phases (Fig. 11) [102]. The data reveals that positively charged surfaces seem to cause longer periods of close surface inspection of cyprids of the barnacle Semibalanus balanoides than glass or PEG.…”

“…11 3D Trajectories of swimming and exploring cyprids of the barnacle Semibalanus balanoides close to a glass surface (reproduced from Ref. [102] (Fig. 5a, Ó Springer 2012) with kind permission from Springer Science and Business Media) electrostatic interactions between the footprint material and the negatively charged surfaces occur.…”