A bioinspired synthetic fused protein adhesive from barnacle cement and spider dragline for potential biomedical materials

Biomaterials with excellent biocompatibility, mechanical performance, and self-recovery properties are urgently needed for tissue regeneration. Inspired by barnacle cement and spider silk, we genetically designed and overexpressed a fused protein (cp19k-MaSp1) composed of Megabalanus rosa (cp19k) and Nephila clavata dragline silk protein (MaSp1) in Pichia pastoris. The recombinant cp19k-MaSp1 exhibited enhanced adhesion capability beyond those of the individual proteins in both aqueous and non-aqueous conditions. cp19k-MaSp1 protein fiber scaffolds prepared through electrospinning have adequate hydrophilicity compared to cp19k and MaSp1 protein fiber scaffolds, and offer improved overall porosity compared to MaSp1 protein fiber scaffolds. The cp19k-MaSp1 protein fiber scaffolds showed excellent proteolytically stable properties because of only 9.6 % depletion after incubation in a biodegradation solution for 56 d. The cp19k-MaSp1 protein fiber scaffolds present remarkably high extreme tensile strength (112.7 ± 11.6 MPa) and superior ductility (438.4 ± 43.9 %) compared with cp19k (34.4 ± 8.1 MPa, 115.4 ± 32.7 %) and MaSp1 protein fiber scaffolds (65.8 ± 9.3 MPa, 409.6 ± 23.1 %), also 68.4 % of tensile strength was recovered by incubation in K+ buffer after multiple stretches, which create a favorable cell adhesion, growth, and proliferation environment for human umbilical vein endothelial cells (HUVECs). The improved biocompatibility, extensive adhesion, mechanical strength, and self-recovery properties make the bioinspired synthetic cp19k-MaSp1 a potential candidate for biomedical tissue reconstruction.

Larvae of two parasitic barnacles, Parasacculina pilosella (Van Kampen et Boschma, 1925) (Rhizocephala: Polyascidae) and Sacculina pugettiae Shiino, 1943 (Rhizocephala: Sacculinidae) studied by scanning electron microscopy

The complete larval development of Parasacculina pilosella (Van Kampen et Boschma, 1925) and Sacculina pugettiae Shiino, 1943 including five naupliar stages and one cypris stage is described and illustrated using SEM. P. pilosella and S. pugettiae have a sacculinid type of development. Nauplii possess a naupliar eye, short frontolateral horns with terminal processes, and a ventral process between the furcal rami. Larvae lack a flotation collar, seta 6 on the antennule and a seta on the antennal basis. Cyprids have a nearly straight LO2. Breakage zone and a spinous process are present only in male larvae. Nauplii of the two species differ by the morphology of the furca: in P. pilosella, the furcal rami are longer and not drowned into cuticular sockets. Naupliar antenna of S. pugettiae has a lateral seta on the endopod which is lacking in P. pilosella. Dorsal head shield setae 1 and 2a are present in S. pugettiae nauplii and not found in P. pilosella larvae. In P. pilosella, all dorsal setae have subterminal pores, whereas in S. pugettiae, pores of the setae 2 are shifted proximally. It is possible that the presence/absence of setae 1 and 2a is the distinctive feature of nauplii of the families Sacculinidae and Polyascidae.

PDMS networks meet barnacles: a complex and often toxic relationship

The biological impact of chemical formulations used in various coating applications is essential in guiding the development of new materials that directly contact living organisms. To illustrate this point, an investigation addressing the impact of chemical compositions of polydimethylsiloxane networks on a common platform for foul-release biofouling management coatings was conducted. The acute toxicity of network components to barnacle larvae, the impacts of aqueous extracts of crosslinker, silicones and organometallic catalyst on trypsin enzymatic activity, and the impact of assembled networks on barnacle adhesion was evaluated. The outcomes of the study indicate that all components used in the formulation of the silicone network alter trypsin enzymatic activity and have a range of acute toxicity to barnacle larvae. Also, the adhesion strength of barnacles attached to PDMS networks correlates to the network formulation protocol. This information can be used to assess action mechanisms and risk-benefit analysis of PDMS networks.

Lack of a genetic cline and temporal genetic stability in an introduced barnacle along the Pacific coast of Japan

Background

Large numbers of exotic marine species have been introduced worldwide. Monitoring of introduced species is important to reveal mechanisms underlying their establishment and expansion. Balanus glandula is a common intertidal barnacle native to the northeastern Pacific. However, this species has been introduced to Japan, South America, South Africa, and Europe. While a latitudinal genetic cline is well known in its native range, it is unclear whether such a genetic cline occurs in introduced areas. Twenty years have passed since it was first identified in Japan and its distribution now ranges from temperate to subarctic regions.

Methods

In the present study, we examined genotypes of cytochrome oxidase subunit I (COI) of mitochondrial (mt)-DNA and elongation factor 1a (EF1) across the distribution of B. glandula in Japan at high and mid intertidal zones.

Results

At all sampling sites, native northern genotypes are abundant and I did not detect significant effects of latitude, tide levels, or their interaction on genotypic frequencies. Further, I did not detect any change of genotype composition between data collected during a study in 2004 and samples in the present study collected in 2019. Data from the present study offer an important baseline for future monitoring of this species and supply valuable insights into the mechanisms of establishment and expansion of introduced marine species generally.

Microplastic pollution in fragile coastal ecosystems with special reference to the X-Press Pearl maritime disaster, southeast coast of India

Microplastics (MPs) are a global environmental concern and pose a serious threat to marine ecosystems. This study aimed to determine the abundance and distribution of MPs in beach sediments (12 beaches), marine biota (6 beaches) and the influence of microbes on MPs degradation in eco-sensitive Palk Bay and Gulf of Mannar coast. The mean MP abundance 65.4 ± 39.8 particles/m² in beach sediments; 0.19 ± 1.3 particles/individual fish and 0.22 ± 0.11 particles g^-1 wet weight in barnacles. Polyethylene fragments (33.4%) and fibres (48%) were the most abundant MPs identified in sediments and finfish, respectively. Histopathological examination of fish has revealed health consequences such as respiratory system damage, epithelial degradation and enterocyte vacuolization. In addition, eight bacterial and seventeen fungal strains were isolated from the beached MPs. The results also indicated weathering of MPs due to microbial interactions. Model simulations helped in tracking the fate and transboundary landfall of spilled MPs across the Indian Ocean coastline after the X-Press Pearl disaster. Due to regional circulations induced by the monsoonal wind fields, a potential dispersal of pellets has occurred along the coast of Sri Lanka, but no landfall and ecological damage are predicted along the coast of India.

Anti-barnacle biofouling coatings for the protection of marine vessels: synthesis and progress

Marine biofouling has gnawed both mobile and non-mobile marine structures since time immemorial, leading to the deterioration of designed operational capabilities as well as a loss of valuable economic revenues. Mitigation of biofouling has been the primary focus of researchers and scientists from across the globe to save billions of dollars wasted due to the biological fouling of marine structures. The availability of an appropriate environment along with favorable substrata initiates biofilm formation within a few minutes. The crucial element in establishing a gelatinous biofilm is the excreted metabolites of destructive nature and exopolymeric substances (EPSs). These help in securing as well as signaling numerous foulants to establish themselves on this substrate. The larvae of various benthic invertebrates adhere to these suitable surfaces and transform from juveniles to adult barnacles depending upon the environment. Despite biofouling being characteristically witnessed for a month or lengthier timeframe, the preliminary phases of the fouling process typically transpire on a much lesser timescale. A few natural and synthetic additives had demonstrated excellent non-toxic anti barnacle establishment capability; however, further development into commercial products is still far-fetched. This review collates the specific anti-barnacle coatings, emphasizing natural additives, their sources of extraction, general life cycle analysis, and concluding future perspectives of this niche product.

A comparative investigation of toxicity of three polymer nanoparticles on acorn barnacle (Amphibalanus amphitrite)

Pollution from plastic waste is increasingly prevalent in the environment and beginning to generate significant adverse impact on the health of living organisms. In this study, we investigate the toxicity of polymer nanoparticles exposed to Acorn Barnacle (Amphibalanus amphitrite) nauplii, as an animal model. Highly stable aqueous dispersion of luminescent nanoparticles from three common polymers: polymethylmethacrylate (PMMA), polystyrene (PS), and polyvinylchloride (PVC), were prepared via nanoprecipitation and fully characterised. Exposure studies of these polymer particles to freshly spawned barnacle nauplii were performed within a concentration range from 1 to 25 mg/L under laboratory-controlled conditions. The exposure to PMMA and PS nanoparticles did not show detrimental toxicity and did not cause sufficient mortality to compute a LC₅₀ value. However, PVC nanoparticles were significantly toxic with a mortality rate of up to 99% at 25 mg/L, and the calculated LC₅₀ value for PVC nanoparticles was 7.66 ± 0.03 mg/L, 95% CI. Interestingly, PVC nanoparticle aggregates were observed to adhere to the naupliar carapace and appendages at higher concentrations and could not be easily removed by washings. To explore the possibility of chemical toxicity of polymer nanoparticles, analysis of the polymer powders which was used to prepare the nanoparticles was conducted. The presence of low molecular weight oligomers such as dimers, trimers and tetramers were observed in all polymer samples. The chemical nature and concentration of such compounds are likely responsible for the observed toxicity to the barnacle nauplii. Overall, our study shows that care should be exercised in generalising the findings of exposure studies performed using one type of plastic particles, as the use of different plastic particles may elicit different responses inside a living organism.

Flatfoot in Africa, the cirripede Chthamalus in the west Indian Ocean

Barnacles of the genus Chthamalus are commonly encountered rocky intertidal shores. The phylogeography of the different species in the Western Indian Ocean is unclear. Using morphological characteristics as well as the molecular markers mitochondrial cytochrome oxygenase subunit I (COI) and the nuclear sodium-potassium ATPase (NaKA), we identified four clades representing four species in the Western Indian Ocean and its adjacent seas. Among these species, a newly identified species, Chthamalus barilani, which was found in Madagascar, Zanzibar and Tanzania. Chthamalus from the coasts of Tanzania and Zanzibar is identified morphologically as C. malayensis, and clusters with C. malayensis from the Western Pacific and the Indo Malayan regions. C. malayensis is regarded as a group of four genetically differentiated clades representing four cryptic species. The newly identified African clade is genetically different from these clades and the pairwise distances between them justify the conclusion that it is an additional cryptic species of C. malayensis. This type of genetic analyses offers an advantage over morphological characterization and allowed us to reveal that another species, C. barnesi, which is known from the Red Sea, is also distributed in the Arabian Sea and the Persian Gulf. We could also confirm the presence of the South African species C. dentatus in the Mozambique channel. This represents the Northeastern limit of C. dentatus, which is usually distributed along the coast of southern Africa up to the Islands of Cape Verde in West Africa. Altogether, based on a combination of morphology and genetics, we distinct between four clusters of Chthamalus, and designate their distribution in the West Indian Ocean. These distinctions do not agree with the traditional four groups reported previously based merely on morphological data. Furthermore, these findings underline the importance of a combining morphological and genetics tools for constructing barnacle taxonomy.

Artificial Light at Night (ALAN) negatively affects the settlement success of two prominent intertidal barnacles in the southeast Pacific

Many coastal processes are regulated by day/night cycles and are expected to be altered by Artificial Light at Night (ALAN). The goal of this study was to assess the influence of ALAN on the settlement rates of intertidal barnacles. A newly designed settlement plate equipped with a small central LED light source was used to quantify settlement rates in presence/absence of ALAN conditions. "ALAN plates" as well as regular settlement plates were deployed in the mid rocky intertidal zone. Both ALAN and control plates collected early and late settlers of the barnacles Notochthamalus scabrosus and Jehlius cirratus. Early settlers (pre-metamorphosis cyprids) were not affected by ALAN. By contrast, the density of late settlers (post-metamorphosis spats) was significantly lower in ALAN than in control plates for both species, suggesting detrimental ALAN impacts on the settlement process. The new ALAN plates represent an attractive and alternative methodology to study ALAN effects.

Characterizing the cirri and gut microbiomes of the intertidal barnacle Semibalanus balanoides

BACKGROUND

Natural populations inhabiting the rocky intertidal experience multiple ecological stressors and provide an opportunity to investigate how environmental differences influence microbiomes over small geographical scales. However, very few microbiome studies focus on animals that inhabit the intertidal. In this study, we investigate the microbiome of the intertidal barnacle Semibalanus balanoides. We first describe the microbiome of two body tissues: the feeding appendages, or cirri, and the gut. Next, we examine whether there are differences between the microbiome of each body tissue of barnacles collected from the thermally extreme microhabitats of the rocky shores' upper and lower tidal zones.

RESULTS

Overall, the microbiome of S. balanoides consisted of 18 phyla from 408 genera. Our results showed that although cirri and gut microbiomes shared a portion of their amplicon sequence variants (ASVs), the microbiome of each body tissue was distinct. Over 80% of the ASVs found in the cirri were also found in the gut, and 44% of the ASVs found in the gut were also found in the cirri. Notably, the gut microbiome was not a subset of the cirri microbiome. Additionally, we identified that the cirri microbiome was responsive to microhabitat differences.

CONCLUSION

Results from this study indicate that S. balanoides maintains distinct microbiomes in its cirri and gut tissues, and that the gut microbiome is more stable than the cirri microbiome between the extremes of the intertidal.

Evaluation of barnacle (Crustacea: Cirripedia) colonisation on different fabrics to support the estimation of the time spent in water by human remains

The estimation of the time since death (minimum Post Mortem Interval, minPMI) is an essential aspect of forensic investigations. This is particularly complex when a human body is found submerged, floating or beached in a marine environment. When a cadaver is found in a terrestrial environment the minPMI estimation is generally based on the presence of carrion insects. However, when a cadaver is found in an aquatic environment, a correct crime scene reconstruction is more complex and requires the consideration of the time the remains spent submerged underwater (minimum Post Mortem Submersion Interval, minPMSI) and/or floating (Floating Interval, FI). In marine crime scene scenarios, the use of barnacles (Crustacea: Cirripedia) has recently received some attention, due to their permanent settlement on human remains and their accompanying clothing. Previous research considered barnacle growth on human shoes, but the present research is the first to focus on the colonisation of barnacles on clothing materials (fabrics). Polystyrene floats were covered by either cotton, velvet, satin or neoprene and submerged underwater over a period of six months off the coast of Perth, Western Australia. The aims of this research were 1) the identification of marine species colonising the fabrics, with special attention to barnacles; 2) the identification of which fabric type provides the most desirable environment for colonisation; and 3) the identification of factors that affect the growth rate of the different species. Three species of barnacles, Balanus trigonus Darwin, Amphibalanus reticulatus (Utinomi) and A. variegatus (Darwin), were present in varying numbers and sizes. The colonisation process of the barnacles occurred rapidly, with the first sighting of barnacles observed within the first month on neoprene and control floats. The surface that attracted the largest number of barnacles was neoprene, followed by satin and cotton, while velvet showed an inconsistent colonisation rate. The largest size barnacles were observed on the control floats, while all fabrics showed a similar smaller size. Overall, time spent in water and water temperature had a significant positive relationship with both number and size of the colonising barnacles. This study is the first to provide information that will aid in the investigation of human remains recovered from Western Australian marine waters, using the barnacle colonisation on different fabric types.

The interactions of oil droplets with filter feeders: A fluid mechanics approach

Filter feeding animals capture and lose oil droplets using cilia or ramified appendages. Here we demonstrate that copepod and barnacle appendages capture fish, canola and 1-decanol oil droplets up to 11μm without selectivity for size, chemistry, density, viscosity, or interfacial tension. Following capture, the droplets are ingested or lost via detachment. Capture and detachment did not differ between a barnacle appendage and stainless-steel wires of radii R_f=50 and 250μm. Key parameters to detachment include the ratio of oil droplet radius to fiber radius, and the Weber number. Smaller oil droplet size to fiber size ratio r=R_o∕R_f, required a higher We for detachment. These data plot as a curve that predicts whether a droplet will remain captured or detach and re-enter the fluid stream, based on the fluid, the droplet radius to fiber radius ratio, and the oil droplet properties. Significantly, this curve may be used to plan responses to oil spills in marine environments.

Barnacles as potential bioindicator of microplastic pollution in Hong Kong

Microplastic (MP) pollution is an emerging problem in the marine environment and the assessment of the presence and abundance of microplastics in wild organisms is essential for risk assessment. The occurrence of microplastics in four species of barnacles at 30 sites in Hong Kong waters was investigated. The median number of microplastics ranged between 0 and 8.63 particles g^-1 wet weight, or 0 and 1.9 particles individual^-1, with fibers being the most abundant type of microplastics. The chemical composition of 152 pieces out of 606 potential microplastics was analyzed using micro-Fourier Transform Infrared Spectroscopy (μ-FTIR). Fifty-two of them were synthetic polymers, 95 natural cotton fibers and five unknowns. Eight types of polymer were identified with cellophane being the most abundant (58%). Correlation analysis was conducted between the abundance of MPs in sediments obtained in our previous study and that in individual barnacle species in this study, and a positive correlation was established for the barnacle Amphibalanus amphitrite, highlighting the potential of using this species as a bioindicator of microplastics.

Transcriptome analyses suggest a molecular mechanism for the SIPC response of Amphibalanus amphitrite

Barnacles are notorious marine fouling organisms. Their successful attachment to a substrate requires that they search for an appropriate habitat during their cyprid stage. A chemical cue called SIPC (Settlement-Inducing Protein Complex) has been shown to play a key role in the induction of cyprid gregarious settlement; however, the underlying biochemical mechanism remains unclear. Here, RNA-seq was used to examine the gene expression profiles of Amphibalanus amphitrite cyprids in response to SIPC and to identify SIPC-activated intracellular signaling pathways. A total of 389 unigenes were differentially expressed in response to SIPC, and cement protein genes were not among them. KEGG enrichment analysis suggested that SNARE interactions in the vesicular transport pathway were significantly influenced by SIPC treatment, indicating a possible role for SIPC in triggering protein transportation and secretion. Several genes with specific functions in metamorphosis were found among the differentially expressed genes (DEGs). GO (Gene Ontology) enrichment analysis revealed that the DEGs were significantly enriched in enamel mineralization pathways, suggesting that SIPC may also be involved in the activation of mineralization.

Morphological and molecular evidence support the intertidal barnacle Octomeris intermedia Nilsson-Cantell, 1921 (Thoracica, Chthamalidae) as a valid species in Indo-Pacific waters

Octomeris is a chthamalid intertidal barnacle with eight shell plates. There are currently two species of such barnacles: O. brunnea Darwin, 1854 (type locality in the Philippines), common in the Indo-Pacific region, and O. angulosa Sowerby, 1825, only recorded in South Africa. Octomeris intermedia Nilsson-Cantell, 1921, identified from the Mergui Archipelago in Myanmar, was considered to be conspecific with O. brunnea by Hiro (1939) based on samples collected in Taiwan. The morphological differences in shell and opercular plates between O. brunnea and O. intermedia are believed to be intra-specific variations due to different degrees of shell erosion. In the present study, the genetic and morphological differentiations of Octomeris in the Indo-Pacific region were examined. This study found two molecular clades (with inter-specific differences) based on the divergence in the COI genes, and the species also have distinct geographical distributions. The Octomeris brunnea clade covers samples collected from the Philippines and Taiwan waters and the other clade, which we argue is O. intermedia, is distributed in Phuket and Krabi, Thailand and Langkawi, Malaysia. Phuket and Krabi are located approximately 300 km south of the Mergui Archipelago, the type locality of O. intermedia. The morphology of samples collected from Thailand fits the type description of O. intermedia in Nilsson-Cantell (1921). Our study concludes that O. intermedia is a valid species based on morphological and molecular evidence.

Towards a barnacle tree of life: integrating diverse phylogenetic efforts into a comprehensive hypothesis of thecostracan evolution

Barnacles and their allies (Thecostraca) are a biologically diverse, monophyletic crustacean group, which includes both intensely studied taxa, such as the acorn and stalked barnacles, as well as cryptic taxa, for example, Facetotecta. Recent efforts have clarified phylogenetic relationships in many different parts of the barnacle tree, but the outcomes of these phylogenetic studies have not yet been combined into a single hypothesis for all barnacles. In the present study, we applied a new "synthesis" tree approach to estimate the first working Barnacle Tree of Life. Using this approach, we integrated phylogenetic hypotheses from 27 studies, which did not necessarily include the same taxa or used the same characters, with hierarchical taxonomic information for all recognized species. This first synthesis tree contains 2,070 barnacle species and subspecies, including 239 barnacle species with phylogenetic information and 198 undescribed or unidentified species. The tree had 442 bifurcating nodes, indicating that 79.3% of all nodes are still unresolved. We found that the acorn and stalked barnacles, the Thoracica, and the parasitic Rhizocephala have the largest amount of published phylogenetic information. About half of the thecostracan families for which phylogenetic information was available were polyphyletic. We queried publicly available geographic occurrence databases for the group, gaining a sense of geographic gaps and hotspots in our phylogenetic knowledge. Phylogenetic information is especially lacking for deep sea and Arctic taxa, but even coastal species are not fully incorporated into phylogenetic studies.

The complex barnacle perfume: identification of waterborne pheromone homologues in Balanus improvisus and their differential expression during settlement

A key question in barnacle biology is the nature of cues that induce gregarious settlement. One of the characterised cues is the waterborne settlement pheromone (WSP). This study aimed to identify WSP homologues in Balanus improvisus and to investigate their expression during settlement. Six WSP homologues were identified, all containing an N-terminal signal peptide, a conserved core region, and a variable C-terminus comprising several -GR- and -HDDH- motifs. The B. improvisus WSP homologues were expressed in all settlement stages but showed different expression patterns. The homologue most similar to the B. amphitrite WSP was the most abundant and was constantly expressed during settlement. In contrast, several of the other WSP homologues showed the greatest expression in the juvenile stage. The presence of several WSP homologues suggests the existence of a pheromone mix, where con-specificity might be determined by a combination of sequence characteristics and the concentration of the individual components.

Green turtle (Chelonia mydas) population demographics at three chemically distinct foraging areas in the northern Great Barrier Reef

The catchments of the Great Barrier Reef (GBR) have experienced significant modifications in recent decades, leading to increases in sources of pollutants and declines in coastal water quality. As coastal waters of the GBR support some of the highest density green turtle (Chelonia mydas) foraging populations in the western Pacific Ocean, understanding the effects of contaminants on GBR green turtle populations is a priority. In 2012, elevated strandings of green turtles in the Upstart Bay region instigated the WWF's collaborative Rivers to Reef to Turtles (RRT) project to investigate if coastal pollutants are compromising green turtle health. Important to interpreting these investigations into toxicology and health is understanding the demographics of the green turtle populations being investigated. In three green turtle foraging grounds, Cleveland Bay (CLV), Upstart Bay (UPB) and the Howick Group of Reefs (HWK), this study explored population size, age class structure, sex ratio, growth rates, body condition and diet, as well as indices of turtle health, such as plastron barnacle loads and eye lesions. The three foraging populations had similar age class structure and adult sex ratios to other green turtle foraging populations in the GBR. Somatic growth rate was nonlinear, peaking in immature turtles, and was much slower in turtles foraging at HWK compared to the other two sites. This may have been due to differences in food source, which was supported by the observed dietary shifts between seagrass and algae in HWK turtles, compared to a consistently seagrass diet in CLV and UPB turtles. There were also small differences in body condition between sites, as well as differences in barnacle loads, eye lesions and occurrence of fibropapilloma tumors. This study provides important information on green turtle foraging ground population dynamics in the northern GBR, and context for the other papers in this special issue.

Parasite and host biomass and reproductive output in barnacle populations in the rocky intertidal zone

The rocky intertidal zone has a long history of ecological study with barnacles frequently serving as a model system to explore foundational theories. Parasites are often ignored in community ecology studies, and this particularly holds for true for the rocky intertidal zone. We explore the role of the isopod parasite, Hemioniscus balani, on its host, the acorn barnacle, Chthamalus fissus. We use the currencies of biomass and reproduction measured at the individual level, then applied to the population level, to evaluate the importance of this parasite to barnacle populations. We found H. balani can comprise substantial biomass in 'apparent' barnacle populations, sometimes even equaling barnacle biomass. Additionally, parasite reproduction sometimes matched barnacle reproduction. Thus, parasites divert substantial energy flow from the barnacle population and to near-shore communities in the form of parasite larvae. Parasites appeared to decrease barnacle reproduction per area. Potentially, this parasite may control barnacle populations, depending on the extent to which heavily infected barnacle populations contribute to barnacle populations at larger scales. These findings regarding the importance of a particular parasite for host population dynamics in this well studied ecosystem call for the integration of disease dynamics into community ecological studies of the rocky intertidal zone.

Spatial and temporal shifts in the diet of the barnacle Amphibalanus eburneus within a subtropical estuary

The success of many sessile invertebrates in marine benthic communities is linked to their ability to efficiently remove suspended organic matter from the surrounding water column. To investigate the diet of the barnacle Amphibalanus eburneus, a dominant suspension feeder within the Indian River Lagoon (IRL) of central Florida, we compared the stable isotopes ratios (δ¹³C and δ¹⁵N) of barnacle tissue to those of particulate organic matter (POM). Collections were carried out quarterly for a year from 29 permanent sites and at sites impacted by an Aureoumbra lagunensis bloom. δ¹³C and δ¹⁵N values of Amphibalanus eburneus varied across sites, but δ¹⁵N was more stable over time. There was a range of δ¹⁵N values of Amphibalanus eburneus tissue from 6.0‰ to 10.5‰ across sites. Because land-based sources such as sewage are generally enriched in ¹⁵N, this suggests a continuum of anthropogenic influence across sites in the IRL. Over 70% of the variation in δ¹⁵N values of Amphibalanus eburneus across sites was driven by the δ¹⁵N values of POM, supporting a generalist feeding strategy on available sources of suspended organic matter. The dominance of this generalist consumer in the IRL may be linked to its ability to consume spatially and temporally variable food resources derived from natural and anthropogenic sources, as well as Aureoumbra lagunensis cells. Generalist consumers such as Amphibalanus eburneus serve an important ecological role in this ecosystem and act as a sentinel species and recorder of local, site-specific isotopic baselines.

Stable isotopes demonstrate the effectiveness of a tidally-staged sewage release system

Nutrient loading from sewage wastewater discharge contributes to the eutrophication of coastal waters. Wastewater from the Gold Coast, Australia is discharged into the Gold Coast Seaway (GCS) for 13.5 h d^-1 primarily on the ebbing tide to disperse wastewater seawards. Nitrogen stable isotopes were used to assess how effectively the tidally staged release system dispersed wastewater out of the GCS and identified pathways by which sewage-N was incorporated into food webs. Turf algae, limpets and barnacles were sampled at the GCS, at two coastal sites and at the mouth of a control estuary that lacked point-source discharge. In the GCS δ¹⁵N values of algae and limpets returned to coastal baseline levels within 250 m of the diffusers. In contrast, δ¹⁵N of filter-feeding barnacles did not significantly vary indicating wastewater-N does not dominate the pelagic food web. Nitrogen stable isotopes clearly demonstrated that the tidally-staged wastewater release system effectively disperses wastewater offshore.

The fluid dynamics of Balanus glandula barnacles: Adaptations to sheltered and exposed habitats

Suspension feeders use a wide range of appendages to capture particles from the surrounding fluid. Their functioning, either as a paddle or a sieve, depends on the leakiness, or amount of fluid that passes through the gaps between the appendages. Balanus glandula is the most common species of barnacle distributed along the Pacific coast of North America. It shows a strong phenotypic response to water flow velocity. Individuals from exposed, high flow sites have short and robust cirral filters, whereas those from sheltered, low velocity sites have long, spindly appendages. Computational fluid dynamics (CFD) simulations of these two ecophenotypes were done using a finite volume method. Leakiness was determined by simulating flow velocity fields at increasing Reynolds numbers, results that have been unattainable at higher velocities by observation. CFD also allowed us to characterize flow in hard to see regions of the feeding legs (rami). Laser-illumination experiments were performed at low to medium flow velocities in a flume tank and corroborated results from CFD. Barnacle filters from a sheltered site become completely leaky at Re=2.24(0.16m/s), well above the maximum habitat velocity, suggesting that this ecophenotype is not mechanically optimized for feeding. Barnacles from exposed environments become fully leaky within the range of habitat velocities Re=3.50(0.18m/s). Our CFD results revealed that the drag force on exposed barnacles feeding appendages are the same as the sheltered barnacles feeding appendages despite their shape difference and spacing ratio.

Bioerosive and bioprotective role of barnacles on rocky shores

Bioerosion and bioprotection (bio-remodeling) is the action exerted by biota colonizing rocky shores. It represents an important component among processes responsible for shaping coastal landforms, and a clear evidence of interaction between the biosphere and the solid earth. Barnacles extensively colonize the midlittoral belt of rocky shores in the Mediterranean Basin. Previous research, mostly based on laboratory evidence, suggests that barnacles are bioprotectors, in that they protect the rock surface from different types of physical and chemical weathering. In this paper, we present the results of a field experiment carried out at different spatial scales at two study areas along the moderately energetic and microtidal coast of NW Italy. Barnacles were removed from the sandstone bedrock in replicated plots (manipulated plots) arranged according to a hierarchical spatial design. After four months rock hardness was tested on each plot with both Schmidt hammer and Equotip Piccolo devices, as well as on a corresponding number of control plots. Data were processed by means of a multifactorial analysis of variance (ANOVA). In control plots, rock hardness tested with Schmidt hammer exceeded that measured in previously manipulated plots. Testing with Equotip yielded the opposite results. This experimental evidence confirmed that barnacles play a bio-protective role in the midlittoral at sub-surficial level, while adding the key aspect that this effect is generalizable to spatial scales ranging from a few centimeters up to tens of kilometers. In addition, our results showed, for the first time, that at surface level they can simultaneously act as bioeroders, likely causing corrosion of the rock surface by fostering dissolution of the sandstone carbonate matrix.

Galkinius Perreault, 2014 or Darwiniella (Anderson, 1992)? A new coral-associated barnacle sharing characteristics of these two genera in Pacific waters (Crustacea, Cirripedia, Thoracica, Pyrgomatidae)

A new species of coral associated barnacle (Balanomorpha: Pyrgomatidae) sharing morphological features of Darwiniella (Anderson, 1992) and Galkinius Perreault, 2014 is described. It has a fused shell and opercular plates, characteristic of Darwiniella. However, the morphology of the tergum and somatic body are closer to Galkinius. Sequence divergence of mitochondrial DNA 12S rDNA and COI reveals this new species clusters with the Galkinius clade. Therefore this new form is assigned to the genus Galkinius, as G.maculosussp. n. Concomitantly the diagnosis of Galkinius is emended to include species with fused or four- plated shells and fused opercular plates. The new species is distinct from all Galkinius species in having a fused shell. It inhabits the corals Lobophyllia spp. and is distributed from the Dongsha Atoll in the South China Sea, Orchid Island of Taiwan in the Pacific Ocean, to Madang in Papua New Guinea waters.

Biomonitoring of trace metal bioavailabilities to the barnacle Amphibalanus amphitrite along the Iranian coast of the Persian Gulf

The fouling barnacle Amphibalanus amphitrite is a cosmopolitan biomonitor of trace metal bioavailabilities, with an international comparative data set of body metal concentrations. Bioavailabilities of As, Cd, Cr, Cu, Fe, Mn, Pb, V and Zn to A. amphitrite were investigated at 19 sites along the Iranian coast of the understudied Persian Gulf. Commercial and fishing ports showed extremely high Cu bioavailabilities, associated with high Zn bioavailabilities, possibly from antifouling paints and procedures. V availability was raised at one port, perhaps associated with fuel leakage. Cd bioavailabilities were raised at sites near the Strait of Hormuz, perhaps affected by adjacent upwelling off Oman. The As data allow a reinterpretation of the typical range of accumulated As concentrations in A. amphitrite. The Persian Gulf data add a new region to the A. amphitrite database, confirming its importance in assessing the ecotoxicologically significant trace metal contamination of coastal waters across the world.

Molecular phylogeny of the acorn barnacle family Tetraclitidae (Cirripedia: Balanomorpha: Tetraclitoidea): validity of shell morphology and arthropodal characteristics in the systematics of Tetraclitid barnacles

Shell structure is a crucial aspect of barnacle systematics. Within Tetraclitidae, the diametric and monometric growth patterns and number of rows of parietal tubes in the shells are key characteristics used to infer evolutionary trends. We used molecular analysis based on seven genes (mitochondrial COI, 16S and 12S rRNA, and nuclear EF1, RPII, H3, and 18S rRNA) to test two traditional phylogenetic hypothesis: (1) Tetraclitid barnacles are divided into two major lineages, which are distinguished according to monometric and diametric shell growth patterns, and (2) the evolutionary trend in shell parietal development began with a solid shell, which developed into a single tubiferous shell, which then developed into multitubiferous shells. The results indicated that Tetraclitinae and Newmanellinae are not monophyletic, but that Austrobalaninae and Tetraclitellinae are. The phylogram based on the genetic data suggested that Bathylasmatidae is nested within the Tetraclitidae, forming a sister relationship with the Austrobalaninae and Tetraclitinae/Newmanellinae clade. Within the Tetraclitinae/Newmanellinae clade, the genera Tetraclita (multitubiferous shell), Tesseropora (single tubiferous shell), and Yamaguchiella (multitubiferous shell) are polyphyletic. The results suggested that shell morphology and growth patterns do not reflect the evolutionary history of Tetraclitidae, whereas the arthropodal characteristics are informative.

Minimal incorporation of Deepwater Horizon oil by estuarine filter feeders

Natural abundance carbon isotope analyses are sensitive tracers for fates and use of oil in aquatic environments. Use of oil carbon in estuarine food webs should lead to isotope values approaching those of oil itself, -27‰ for stable carbon isotopes reflecting oil origins and -1000‰ for carbon-14 reflecting oil age. To test for transfer of oil from the 2010 Deepwater Horizon spill into estuarine food webs, filter-feeding barnacles (Balanus sp.) and marsh mussels (Geukensia demissa) were collected from Louisiana estuaries near the site of the oil spill. Carbon-14 analyses of these animals from open waters and oiled marshes showed that oil use was <1% and near detection limits estimated at 0.3% oil incorporation. Respiration studies showed no evidence for enhanced microbial activity in bay waters. Results are consistent with low dietary impacts of oil for filter feeders and little overall impact on respiration in the productive Louisiana estuarine systems.

The effect of water temperature and flow on respiration in barnacles: patterns of mass transfer versus kinetic limitation

In aquatic systems, physiological processes such as respiration, photosynthesis and calcification are potentially limited by the exchange of dissolved materials between organisms and their environment. The nature and extent of physiological limitation is, therefore, likely to be dependent on environmental conditions. Here, we assessed the metabolic sensitivity of barnacles under a range of water temperatures and velocities, two factors that influence their distribution. Respiration rates increased in response to changes in temperature and flow, with an interaction where flow had less influence on respiration at low temperatures, and a much larger effect at high temperatures. Model analysis suggested that respiration is mass transfer limited under conditions of low velocity (<7.5 cm (-1)) and high temperature (20-25°C). In contrast, limitation by uptake reaction kinetics, when the biotic capacity of barnacles to absorb and process oxygen is slower than its physical delivery by mass transport, prevailed at high flows (40-150 cm s(-1)) and low temperatures (5-15°C). Moreover, there are intermediate flow-temperature conditions where both mass transfer and kinetic limitation are important. Behavioral monitoring revealed that barnacles fully extend their cirral appendages at low flows and display abbreviated 'testing' behaviors at high flows, suggesting some form of mechanical limitation. In low flow-high temperature treatments, however, barnacles displayed distinct 'pumping' behaviors that may serve to increase ventilation. Our results suggest that in slow-moving waters, respiration may become mass transfer limited as temperatures rise, whereas faster flows may serve to ameliorate the effects of elevated temperatures. Moreover, these results underscore the necessity for approaches that evaluate the combined effects of multiple environmental factors when examining physiological and behavioral performance.

Description of a new species of coral-inhabiting barnacle, Darwiniella angularis sp. n. (Cirripedia, Pyrgomatidae) from Taiwan

The present study has identified a new species from the previously monotypic genus Darwiniella Anderson, 1992. Darwiniella angularissp. n. is similar to Darwiniella conjugatum (Darwin, 1854) in external shell morphology and arthropodal characters. Darwiniella conjugatum, however, has a sharper tergal spur and a less obvious adductor plate angle when compared to Darwiniella angularissp. n. Molecular analyses on mitochondrial DNA 12S rDNA and COI regions also support the morphological differences. Sequence divergences in 12S rDNA and COI between Darwiniella conjugatum and Darwiniella angularissp. n. are 5% and 13% respectively, which are equivalent to the inter-specific sequence divergences in other barnacles. Both Darwiniella species are common on Cyphastrea Milne-Edwards and Haime, 1848 corals and Darwiniella angularissp. n. is also collected from Astreopora de Blainville, 1830 corals in Taiwan.

Nutritional interaction in an alga-barnacle association

Nitrogen is the major growth-limiting nutrient for marine algae. One potential source of nitrogen for marine algae is ammonium released by invertebrates. Many mid-intertidal reefs in northeastern New Zealand are dominated by a close association between the honeycomb barnacle Chamaesipho columna and an encusting brown alga Pseudolithoderma sp. Growth of Pseudolithoderma was enhanced in the presence of live C. columna, which released ammonium at a greater rate than the maximum rate of ammonium uptake by Pseudolithoderma. Algal tissue on barnacle tests had a lower C:N ratio than tissue located more than 2 cm from the nearest barnacle, suggesting the barnacle is an important source of nitrogen for the alga. The role of nutrient exchange in determining ecological patterns of species in marine communities is discussed.

Desiccation, predation, and mussel-barnacle interactions in the northern Gulf of California

Field experiments were conducted in order to determine the potential for desiccation and predation to mediate the effect of mussels (Brachidontes semilaevis) on barnacles (Chthamalus anisopoma) in the highly seasonal northern Gulf of California. We did this by removing both mussels and a common mussel predator (Morula ferruginosa: Gastropoda) and by spraying selected sites with sea water during summertime spring low tides. We also determined the effect of crowding on resistance to desiccation in barnacles, and the effect of barnacles on colonization by mussels. The mussel-barnacle community was not affected by keeping experimental quadrats damp during daytime low tides throughout the summer. Exposure to summertime low tides, however, did affect the survivorship of isolated, but not crowded, barnacles; and barnacle clumps enhanced the recruitment of mussels. Hence crowding in barnacles had a positive effect on both barnacle survivorship and mussel recruitment. Morula had a negative effect on mussel density, and mussels had a negative effect on barnacle density. The effect of Morula on barnacle density was positive, presumably due to its selective removal of mussels. These results suggest an indirect mutualism between barnacles and the gastropod predator, because barnacles attract settlement or enhance the survival of mussels, and the predator reduces the competitive effect of mussels on barnacles.