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The sperm of most barnacle species show negligible motility unless exposed to oviducal gland fluid; a secretion associated with oviposition. Artificial activation has previously been induced in Semibalanus balanoides by elevating seawater pH using an ammonia buffer. To date, the information pertaining to barnacle sperm biology is rather limited. This study has investigated the activation of vesicular sperm from three species of acorn barnacles in response to the elevation of seawater pH using alkaline buffers, either sodium hydroxide (NaOH) or ammonium ( ). Elevation of seawater pH was observed to increase activation success, particularly for Balanus amphitrite and Elminius modestus. In all cases, there was a high degree of variability in the data. A median value of 20% sperm activation (mean ± SE = 20.65 ± 4.86%) was determined for E. modestus at pH 9 ( ). The lowest activation success was observed in S. balanoides which displayed maximal median activation of 1.79% at pH 8.4 (NaOH) (mean ± SE = 1.93 ± 0....

In 2004, a study began on a small (25 individuals) population of Nucella lapillus on the south coast of England. Following the global ban of tributyl-tin in the same year, freed from “imposex”, the size of the population increased such that by August 2010 it comprised > 1240 individuals. On the groyne, N. lapillus fed on barnacles (Semibalanus balanoides) up to a mean shell height of 14 mm, i.e. the first year of life. Thereafter, N. lapillus fed principally on Mytilus galloprovincialis by shell drilling. When the numbers of N. lapillus had risen significantly, a relationship with Carcinus maenas was detected, the latter feeding on M. galloprovincialis, by mandibular chipping in summer, but also consuming the remains of N. lapillus meals in winter. Further, the polychaete Eulalia viridis scavenged the remains of N. lapillus meals, both barnacles and mussels. This is the first time such feeding interactions have been identified.

Barnacle cypris larvae respond to many cues when selecting a settlement site. The settlement of over a million larvae on tiles of different textures, orientations and densities of incumbent settlers was measured on the rocky intertidal at Great Cumbrae, Scotland. Half of the tiles were replaced every tide whereas the others simultaneously accumulated settlers. Factor effects varied on each tide, and converged in the accumulating deployment. Increasing incumbent density led to net loss of settlement, which was less probable on the textures on which fastest settlment occurred ('very fine'), and more probable on those on which settlement was slowest ('smooth'). More settlement occurred on down-facing orientations during daylight and vice versa. Cue ranks were non-linear, so a path analysis model quantified the relative influence of each factor. Gregariousness was the most influential cue measured, although unmeasured factors had greater effects, highlighting the complexity of settlement influences in this species.

Although consequences of the settlement preference of larvae have been well documented, the consequence of these settlement choices on subsequent mortality, morphology and fecundity has been little studied. The aim of this study was to determine the relationship between recruit and adult density and to determine the effect of recruitment on adult morphology and egg tissue mass. This study follows 48,718 barnacles (Semibalanus balanoides) from recruitment at the end of the settling season to reproductively mature adults at a field site in the Clyde Sea (UK). Overall survivorship of the recruits to adulthood was 8.5%, although survivorship was up to 42% on low density settlement panels. In low density colonies (< 10 recruits cm-2), recruitment density was related to adult density (P < 0.001), whereas no relationship was found for higher density colonies. A shell morphology index measured at adulthood was related to recruitment density for low density recruited colonies (P < 0.001) but not high density colonies. Using ANCOVA, variations between the colonies in shell and egg tissue mass were not explained by mass of somatic tissue. However, egg mass was explained by recruitment density (P < 0.01). These results show that adult density is not a reliable indicator of the previous population density of the colony. Moreover, there are marked differences in population development between colonies with high and low recruit densities in terms of impact upon shell morphology and egg production. The dynamics that operate between recruits at the end of the settlement season and sexually mature adults to create the patterns elucidated in this paper, and other literature, remain unclear.

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 (λmin = 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 Monte‐Carlo randomisation model showed that larval supply was random or aggregated. The mean exploration time spent on the target was 163 s with a mean distanc...

Many temperate marine organisms, including the boreo-arctic barnacle Semibalanus balanoides, have well-delineated reproductive seasons. The aim of this study was to examine the consequences of small changes in deployment time of settlement experiments within such a settlement season upon long term demographic parameters. Repeat deployments of settlement tiles were made at 1-week intervals for six weeks during the April 1996 S. balanoides settlement season in the Clyde Sea, UK. The colonies were harvested in November 1996 and density, mortality, fecundity, morphology, and dry weight of eggs, somatic tissue and shell determined. There were non-linear relationships between density (D) and deployment time (W) (D = 1.11 + 1.38W - 0.24W 2 ), and between morphology (M) and deployment time (M = 21.2 + 0.54W - 0.13W 2 ). There were linear relationships between mortality (L) and deployment time (L = 61.49 - 7.99W), body weight (B) and deployment time (B = 0.0050 + 0.0012W), shell (S) dry weight and deployment time (S = 0.17 + 0.02W). Egg dry weight did not vary significantly with deployment time. This study demonstrates how small changes in deployment time of settlement can have substantial consequences on the long-term demographic processes within single species populations. The relationships between deployment, density and other demographic parameters are discussed, as are strategies for dealing with the confounding effects of reproduction.

A major driving force to mechanistic studies of barnacle gregarious settlement is to contribute to an understanding of observed patterns of settlement in nature. In particular, how cyprids perceive adult conspecifics and how they discriminate between conspecific and allospecific barnacles are questions which have taxed researchers for nearly 50 years. The putative, active component of adult barnacles to which the cyprids respond has long been known to be a glycoprotein, referred to here as the settlement-inducing protein complex (SIPC). The present study examines the discriminatory abilities of laboratory-reared Balanus amphitrite and wild Semibalanus balanoides cyprids at settlement. Using a recently developed nitrocellulose membrane-choice settlement assay, laboratory studies revealed that both species settled at a significantly higher rate on regions of membrane on which crude conspecific SIPC had been adsorbed compared to untreated regions. Moreover, when offered a choice between conspecific and allospecific SIPC, a trend to greater settlement on the conspecific regions was observed. The membrane assay was also evaluated in field trials using real-time video footage of cyprid searching behaviour. Of 211 S. balanoides cyprids recorded during exploratory behaviour, only one settled. Exploratory behaviour was, however, clearly associated with regions of the membrane treated with either conspecific or allospecific (B. amphitrite) SIPC compared to untreated regions. These results are generally in accord with previous reports on the discriminatory abilities of barnacle cyprids and suggest that the membrane assay may be usefully applied to field studies of settlement behaviour.

It is now almost 50 years since the gregarious settlement of barnacles and its chemical basis was first described. Although originally noted for Elminius modestus, mechanistic studies of gregariousness have focused on two species, Semibalanus balanoides and Balanus amphitrite. By virtue of its ease of study and its economic importance as a fouling organism, the latter species has assumed increasing importance in recent years. This paper will provide an overview of studies on settlement pheromones and their perception. An adult glycoprotein, arthropodin (now known as settlement-inducing protein complex or SIPC), was once thought to be the sole pheromone involved in the induction of cypris larval settlement. At least two other pheromones are now known to be involved, a waterborne cue originating from the adult and the cypris temporary adhesive. The latter is related, immunologically, to SIPC. In keeping with many other examples of chemical communication, the available evidence suggests that barnacle settlement induction involves receptor-ligand interactions and a signal transduction pathway(s) that translates into attachment and metamorphosis. Similar findings have been reported for some, but not all, marine invertebrate larvae examined thus far and the implications for antifoulant development are discussed.

A highly precise technique for manufacturing tiles with complex naturalistic three‐dimensional surfaces for macrofaunal settlement studies is described. The tiles are cast in filled polyester resin from polyvinylsiloxane impressions of model surfaces. Comparison of settlement of barnacle cypris larvae (Semibalanus balanoides) between one week and one year old tiles showed that there was no toxic effect of the resin on settlement or recruitment. Analysis of the surfaces using a laser profilometer demonstrated that the mean difference between two tiles cast from the same mould was 1.9 μm. The tiles are very strong, stable in both freshwater and seawater, can be made in most colours and can be used to replicate biotic and abiotic substrata. They have been tested in a variety of settlement studies at various sites around the world.

The aim of this work was to analyse the stratigraphic recruitment pattern of S. balanoides on smooth and textured surfaces, determine the effect of varying tile area on recruitment density and relate the results to larval behaviour, and identify other factors affecting within‐tile variation in recruitment, including panel size and frame design. A set of polyester tiles was manufactured in four textures, viz. smooth, fine, medium and coarse. In addition, a set of smooth polyester tiles of 5 different sizes was also made. Both sets of tiles were deployed intertidally in the Clyde Sea, UK. The smooth tiles of the textured array showed a significant systematic decline in the number of recruits from top to bottom in 1 cm vertical strata. For the tiles of varying size, recruit density ranked 20 × 20 cm tiles > 10 × 10 cm > 5 × 5 cm >2 × 2 cm > 1 × 1cm. A consistent strati‐graphic pattern was found on the 20 × 20 cm tiles. It is suggested that on substrata lacking significant surface texture, a positive phototax...

Previous work on the effect of surface roughness on barnacle settlement has used natural surfaces differing in aspects other than surface roughness, or simplistic manufactured surfaces. A new technique is presented which permits accurate, controlled and repeatable manufacturing of tiles with a range of complex naturalistic surfaces created from natural components. Use of this technique permits an experimental approach to be used to investigate the effects of a range of complex surfaces on barnacle settlement. Moulds with smooth (S), fine (F) ( M > C > S. Settlement pattern, de...

Maritrema arenaria is a microphallid trematode found in the intestines of marine wading birds. The metacercarial stage occurs in barnacles, Semibalanus balanoides. To date the cercarial stage had not been identified. Large numbers of M. arenaria metacercariae were found in barnacles at one site on the north shore of Belfast Lough, N. Ireland (Irish Grid Reference D355,810) where a previously unidentified cercaria, Cercaria littorinae saxatilis V, was also abundant. Experiments were carried out to establish if C. littorinae saxatilis V developed into the metacercariae of M. arenaria. The experiments demonstrated that C. littorinae saxatilis V entered the cirri of feeding barnacles and later accumulated in the haemocoel close to the barnacle's gut. There the cercariae formed cysts which increased in size until they attained the structure of M. arenaria metacercariae. The study has clearly demonstrated that the cercariae of M. arenaria are those previously known as C. littorinae saxatilis V.

The effect of the heavy metals copper and cadmium on the behaviour of the sessile barnacles Semibalanus balanoides and Balanus crenatus over periods of 24 hours to 15 days has been studied using a photoelectric system to monitor cirral activity. In unstressed barnacles the amount of cirral movement remained fairly constant for several days although there was a marked decrease in the level of activity in animals kept in the laboratory for extended periods of time. In contrast to the response exhibited by bivalve molluscs, exposure to copper or cadmium did not elicit a rapid closure response in the barnacle. However, sublethal (80 ppb Cu, 100 ppb Cd) as well as lethal (500 ppb Cu, 500 and 1000 ppb Cd) levels resulted in a significant (P

Small-scale changes in a mid-tide level patchy fucoid/barnacle community were investigated for 7 years on a moderately exposed shore in the Isle of Man. A fixed area was repeatedly sampled non-destructively to assess the abundance and spatial pattern of the major species present. Considerable natural change was recorded on this unpolluted shore, especially in seaweed cover and number of limpets. Concurrent manipulative field experiments were run to clarify the role of biological interactions in generating and maintaining the observed fluctuations and patchiness. Local reductions in Patella vulgata grazing induced development of Fucus vesiculosus clumps. Such clumps dislodged up to 80% of settling Semibalanus balanoides cyprids, but encouraged aggregation and recruitment of Patella, Actinia equina and Nucella lapillus. Dense barnacles inhibited Patella grazing and growth. A simple model of the generation and maintenance of patchiness is presented.