Anatomy and Ultrastructure of the Cyprid Temporary Adhesive System in Two Species of Acorn Barnacle

Joshua J Raine,Nick Aldred,Anthony S Clare

doi:10.3390/jmse8120968

Joshua J Raine, Nick Aldred + Show 1 more

Open Access

https://doi.org/10.3390/jmse8120968

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Abstract

Acorn barnacles are sessile as adults and select their settlement site as a cypris larva. Cyprids are well adapted to exploring surfaces in dynamic environments, using a temporary adhesive secreted from the antennules to adhere during this process. The temporary adhesive and the secretory structures are poorly characterized. This study used serial block-face scanning electron microscopy and three-dimensional modelling to elucidate the anatomy related to temporary adhesion. The temporary adhesive glands of two acorn barnacle species, Balanus amphitrite and Megabalanus coccopoma, were located in the proximal region of the first antennular segment, contrary to previous descriptions that placed them in the more distal second segment. The temporary adhesive systems of these acorn barnacles are therefore similar to that described for the stalked barnacle, Octolasmis angulata, although not identical. Knowledge of the true location of the temporary adhesive glands will underpin future studies of the production, composition and secretion of the adhesive.

Highlights

Barnacle cypris larvae use a proteinaceous adhesive secreted from their paired antennules to temporarily attach to the substratum, allowing them to effectively explore dynamic environments [1,2]
This adhesive is secreted via pores on the third antennular segment and contains the settlement-inducing protein complex (SIPC), or an analogue [3]
Neither the temporary adhesive nor the structures related to its synthesis and secretion have been fully characterised in acorn barnacles

Summary

Introduction

Barnacle cypris larvae use a proteinaceous adhesive secreted from their paired antennules to temporarily attach to the substratum, allowing them to effectively explore dynamic environments [1,2]. The image series allowed for three-dimensional reconstruction and modelling of the cyprid anatomy in the Microscopy Image Browser (MIB) [13] Using these techniques, this study explored the temporary adhesive system of two acorn barnacle species, Balanus amphitrite (= Amphibalanus amphitrite) and Megabalanus coccopoma, in order to provide a basis for future investigations into the composition and secretion of the adhesive material

Organism Acquisition

Sample Preparation

Serial Block Face-Scanning Electron Microscopy

Balanus amphitrite