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In this study we investigated the ability to associate chemosensory cues with a stressful event in the common acorn barnacle (Semibalanus balanoides). The ecological benefit of associative learning relies on accurate assessment of predictive cues. There are no reports available on experience-dependent behavioral changes in adult barnacles’ autonomic responses. We demonstrated that repetitive aversive conditioning elicited a significant increase in the retraction rate of the cirrus and closure of the operculum after presentation of a cue. These results indicate that adult acorn barnacles are able to anticipate an aversive event through associative learning.

Anelasma squalicola is a parasitic barnacle of members of the deep-water shark families Etmopteridae, Pentanchidae and Scyliorhinidae. We report the first published confirmation of this species in the Eastern Pacific Ocean, based on material collected off Costa Rica, its first record as a parasite of the Ninja lantern shark, Etmopterus benchley (Etmopteridae), and a new size record for the host. The information presented herein expands the knowledge (distribution and host usage) of this enigmatic species.

The settlement of intertidal barnacles Chthamalus spp. was measured for an entire recruitment season at 3 sites separated by 100 m in Baja California, Mexico. During a 10 d pulse that accounted for nearly 30% of yearly settlement, coastal wind speed and direction, nearshore water column temperature, and current velocities were also measured. During this period, strong internal tidal forcing was observed, with short episodes (1-1.5 h) of rapid fluctuations in water column temperature, stratification, and currents. Chthamalus spp. settlement was significantly and positively correlated with cumulative high-frequency fluctuations in temperature, thermal stratification, and surface current flows, but not with onshore winds. Furthermore, the spatial pattern in the number of settlers was correlated with the angle of propagation estimated for onshore-moving internal waves, potentially modulated by nearshore bathymetry. This relationship between Chthamalus spp. settlement and high-frequency changes in water column temperature was also shown for a site in La Jolla, California, USA, but not for a similar barnacle, Balanus glandula, suggesting that interspecific differences in larval behavior and nearshore depth distribution may translate into differences in transport. Our results suggest that both the number of settlers at shore and their spatial pattern can be modulated by the intensity and direction of internal wave events, at least during peak settlement periods. Future research should consider both the intensity and geometry of internal-wave-induced variability in the nearshore, as well the small-scale features of coastal geomorphology and bathymetry.

During larval development of the intertidal barnacle Fistulobalanus albicostatus, larvae in the naupliar stages I and II (NII where the highest absorbance was within 550 to 600 nm. The phototaxis of each stage was determined under light irradiation at six wavelengths (375, 470, 515, 525, 660, and 735 nm) and at three intensities (5, 15, and 25 W/m2), except for the 735 nm treatment which was irradiated at 25, 50, and 100 lx. NI&II larvae showed no clear pattern of phototaxis under the assessed light conditions. NVI and cyprids exhibited strong positive phototaxis under the assessed light conditions, except under 375 nm at 5 and 15 W/m2 where negative phototaxis was detected. Furthermore, the settlement behavior of cyprids was examined under 375 nm at the three intensities, and under the other five wavelengths at 25 W/m2 or 100 lx. The highest and lowest rates of settlement occurred at 470 and 375 nm, respectively. The results provide a valuable insight into the light-response mechanisms that potentially determine the distribution of barnacle larvae.

Most organisms experience ontogenescence (high and decreasing mortality from conception to the age of maturity) in spite of the clear evolutionary disadvantage of dying prior to reproducing. One hypothesis that may help to explain the prevalence and persistence of ontogenescence is the Transitional Timing Hypothesis, which states that developmental transitions are dangerous and concentrated in the earliest phases of life (e.g., hatching or birth). This study's goal was to examine the transitional dangers of early development and hatching in the barnacle Chthamalus fragilis. Barnacle egg lamellae were monitored for 2 weeks after extraction from their parents, and all hatching events were recorded along with whether each hatched larva was a successful swimmer or not. The total number of eggs that failed to hatch from each egg lamella was also determined. Results showed significant brood mortality prior to hatching as well as a large proportion of newly-hatched larvae that were unable to swim well. There was also a clear pattern in the timing of hatching events from egg lamellae. However, there was no effect of delayed hatching on either hatching success or swimming ability of larvae. The high proportion of non-hatching and poor-swimming larvae lend support to the Transitional Timing Hypothesis, suggesting that early developmental stages and hatching in barnacles (and probably other organisms, too) are potentially dangerous transitional events that cannot be avoided and should be taken into account when studying the population ecology of these species.

The role of cascades in natural communities has been extensively studied, but interactions between trophic and facilitation cascades are unexplored. In the White Sea (65°N) shallow subtidal, bivalve primary facilitators provide hard substrate for secondary facilitator barnacles, that, in turn, provide substrate for conspecifics, ascidians, red algae and multiple associated organisms, composing a multi-level facilitation cascade. Previous research revealed that predation by the whelk Boreotrophon clathratus accounts for ~7% of adult barnacle mortality. Low whelk abundance limits their effect, with barnacles living on conspecifics several times more vulnerable to predation than those living on primary substrate. Trophic cascades can selectively shield foundation species from consumers, and hence may affect the structure and length of facilitation cascades. We tested the hypothesis that low abundance of the whelks results from mesopredator predation on their juveniles. Depending on the magnitude of the effect, this would mean that a trophic cascade controls the abundance of barnacles on all substrates or only barnacles living on conspecifics. We also suggested that barnacles on primary substrates and conspecifics facilitate different dependent assemblages. We manipulated the presence of crab and shrimp mesopredators in field caging experiments to assess their effect on whelk recruitment. In a field survey, we compared the assemblages of sessile macrobenthic organisms associated with barnacles living on different substrates. Caging experiments evidenced that crab and shrimp mesopredators reduce whelk recruitment by 4.6 times. Field data showed that barnacles on primary substrate and on conspecifics promote different dependent assemblages including secondary facilitator ascidians. Although mesopredators do not shield barnacles from elimination, their absence would restrict them from living on conspecifics. Barnacles on conspecifics are functionally different from barnacles on primary substrate, and can be considered a separate level of the facilitation cascade. Trophic cascades thus can generate community-wide effects on facilitation cascades by affecting their structure and possibly length.

Synopsis Larvae of barnacles typically pass through naupliar and cyprid planktonic stages before settlement and metamorphosis. As the final larval stage, cyprids swim much faster than nauplii and in turbulent fluid environments with high shears as they seek habitat. Cyprids swim with six pairs of reciprocating thoracic appendages and use two anterior antennules during settlement. Our understanding of how thoracic appendages generate movement is limited due to short stroke intervals (∼5 ms) that impede observations of the shape and trajectory of appendages. Here, we used high-speed videography to observe both free-swimming and tethered cyprids of the intertidal acorn barnacle Balanus glandula to produce a comprehensive description of thoracic appendage swimming kinematics. Cyprids used a drag-based method of swimming: their six pairs of thoracic appendages moved through metachronal power strokes and synchronous recovery strokes similar to the thoracopod motions in calanoid copepods during escape swimming. During the power stroke, plumose setae on each appendage pair spread laterally into a high surface area and high drag paddle composed of a meshwork of fused setules. This interconnected setal array collapsed into a low surface area and low drag shape during the recovery stroke. These effective swimming appendages allowed cyprids to move upward at an average speed of 1.4 cm/s (∼25 body lengths/s) with an average beat frequency of 16 beats/s, and reach an instantaneous velocity of up to 6 cm/s. Beat frequency of the thoracic appendages was significantly associated with speed, with higher beat frequencies indicating faster swimming speed. At their average speed, cyprids moved at the intermediate Reynolds number of ∼10, in which both viscous and inertial forces affected movement. Cyprids could alter swimming direction by sweeping the posterior-most appendage pair to one side and beating the remaining thoracic appendages synchronously through the power stroke with greater motion on the outside of their turn. These results greatly enhance our understanding both of cyprid motility and how small planktonic organisms can use swimming appendages with fused setule arrays to reach high swimming speeds and affect directional changes.

Breakdown of skeletal and lithic hard substrates by organisms, a process referred to as bioerosion, is part of the global carbon cycle and receives increased attention, but little is known about bioerosion in polar environments. Here, we study bioerosion traces (addressed by their respective ichnotaxa) recorded in the barnacle Bathylasma corolliforme from the Ross Sea, Antarctica. Traces were visualized via scanning electron microscopy of epoxy casts prepared with the vacuum cast-embedding technique. In 50 samples from shallow 37 m to bathyal 1680 m water depths, 16 different bioerosion traces were found, classified into microborings presumably produced by cyanobacteria (1), chlorophytes (1), fungi (9), foraminifera (1), unknown organotrophs (5), and macroborings produced by cirripeds (1). Statistical ichnodiversity analysis resulted in a significant (p = 0.001) ANOSIM with moderate differences (R = 0.5) between microbioerosion trace assemblages at different water depths and revealed two main clusters (NMDS, SIMPROF) corresponding to the photic and aphotic stations. A comparison between this study and a corresponding study from the Svalbard archipelago, Arctic Ocean, shows that the ichnodiversity in calcareous barnacle skeletons is similar in polar waters of both hemispheres. This includes several ichnotaxa that are indicative for cool- to cold-water environments, such as Flagrichnus baiulus and Saccomorpha guttulata. Nine of the investigated ichnotaxa occur in both polar regions and seven ichnotaxa show an extensive bathymetrical range down to the deep sea at bathyal 1680 m water depth.

Although diatoms colonize a vast diversity of immersed hard-surfaced objects and organisms, many diatom species, and sometimes entire genera, show a clear preference towards a particular type of su...

Xenobalanus globicipitis is a commensal barnacle located on cetacean fin edges. The commensal-host interaction between Xenobalanus globicipitis and the bottlenose dolphin (Tursiops truncatus) has been poorly studied in Mexico. The main objective was to estimate the relative barnacle prevalence and abundance in bottlenose dolphins in three areas and seasons of the Gulf of Mexico. Tamiahua zone showed the higher prevalence (42.4%) and relative abundance (0.60 barnacles/individual/hr-1)compared to Tuxpan and Nautla zones. Whereas, in dry season there were higher prevalence (55.6%) and relative abundance (0.53 barnacles/individual/hr-1)than rainy and winter storm seasons. Therefore, zones and seasons of the Gulf of Mexico influence the barnacle-dolphin interactions.

Sea turtles are partners in commensal relationships with a variety of epibionts, including barnacles. The acorn barnacle Chelonibia testudinaria is one species commonly found associated with sea turtles and other marine fauna throughout temperate to tropical waters including the Indo-Pacific. We conducted a study to assess the occurrence of this barnacle, relative to host life stage and species in a mixed foraging population of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles (juvenile, sub-adult, adults (female and male)) in Mabul Island, Sabah, Malaysia (Celebes Sea). Expecting similar relative abundance by life stage, we found instead a significant effect between the combined dependent variables (abundance and size of barnacles) and the life stages of sea turtles in Mabul after controlling for the covariates of size and species of sea turtles (F(8, 428) = 5.77, P < 0.001, Pillai = 0.19). Among green turtles with barnacles, though adult males had larger barnacles compared with the female turtles, the mean barnacle abundance on adult females (43.4 individuals ± 5.19 SD) was higher than all other life stages. Most of the barnacles (85.6%; N = 1931) were found on the plastron of the sea turtles. The highest number of barnacle reacquisition was found among the juvenile turtles. In assessing the complemental males of the barnacles, we found they were consistently attached to the shells of the larger of the hermaphrodites from each region of the host's body despite average shell-size differences with each region.

This paper describes a new species of sponge-inhabiting barnacle, Neoacasta liui sp. nov., collected in Fukuoka, Kyushu, Japan. In the present study we used both the morphological examination and DNA barcode (cytochrome c oxidase I gene) to distinguish this new species from acastine species including its congeners from Neoacasta Kolbasov, 1993. Neoacasta liui sp. nov. is similar to Neoacasta glans (Lamarck, 1818) in shell morphology, but the divergence in COI gene between them reached inter-specific differences. N. liui sp. nov. is characterized by externally latticed, narrow scutum, beak-shaped tergum with wider spur, and lack of six inwardly prominent teeth on margin of basis. N. glans having an Indo-West Pacific distribution may represent a complex of cryptic species.

Barnacles are common epibionts on a wide range of marine organisms, including turtles. Chelonibia testudinaria is a successful epibiotic barnacle species, and mainly turtles are responsible for their wide range dispersal. In the present study, the mitochondrial Cytochrome Oxidase I (COI) gene haplotypes of C. testudinaria from Caretta caretta hosts were evaluated. The samples were collected from three dead C. caretta turtle carapaces in 2014 from the Middle East Technical University, Institute of Marine Sciences coastline. Results were also compared with those samples submitted to databases (NCBI and BOLD-system, 139 in total). By comparison, three clades were recorded like previous studies: the Atlantic-Mediterranean clade (Clade-α), the IndianPacific Ocean clade (Clade-β), and Magdalena Bay (Eastern Pacific- Clade-) clade; all samples collected from Turkish shores clustered in the Atlantic-Mediterranean group (Clade-α). The gene flow between the three clades was deficient and highly significant (0.02, 0.03, and 0.03, respectively). According to network age estimation, present study samples’ clade (Clade-α) diverged from the Clade-β approximately 200 kya (SDs=0.22, SDy=4402.90) and Clade- 130 kya (SDs=0.17, SDy=3494.55). In the present study, eight haplotypes were observed in total, two of which were specific to the region.

Barnacles strongly adhere to immersed solid substrates using a mixture of cement proteins (CP) that self-assembles into a permanently bonded layer and binds the barnacles’ shells to foreign surface...

Spatiotemporal relationships between developmental stages (cydippid, transition and adult) of the comb jelly Mnemiopsis leidyi and environmental parameters were seasonally evaluated using the random forest (RF) model along the Iranian coasts of the Caspian Sea. The mean density of M. leidyi in spring, summer, autumn and winter were 8, 54, 130, and 15 ind m−3, respectively. The density of various stages, particularly cydippid, showed a decreasing trend with increase in depth. Cydippids had the highest abundance with a lower percentage in the deeper layers and colder seasons. Temperature was found to be the most influential parameter on the distribution of M. leidyi’s life stages, particularly cydippids, with a stronger effect in spring and summer. The highest densities for all life stages were observed above 20 °C with an explosive growth at above 25 °C for the cydippids. Moreover, cydippids were strongly influenced by all the three stages of the copepod Acartia tonsa (nauplius, copepodite and adult), especially its later developmental stages. Due to the presence of M. leidyi, the maximum zooplankton abundance has shifted to cold seasons. There was also a relationship between M. leidyi with barnacle larvae and rotifers in the cold seasons. The interrelationships among the life stages of M. leidyi, particularly between the transition and cydippid, was a major factor in its population dynamics. The relationship curves between these environmental parameters and the life stages of M. leidyi were nonlinear and mostly sigmoidal (not absolutely linear). The magnitude of parameter importance and relationships curves varied with season and life stage.

Anaerobic metabolism is an important response to stress in many organisms. Intertidal species often face heat stress during low tide. Balanus glandula (Darwin, 1854) is a high-shore intertidal barnacle common to the Pacific that experiences prolonged low-tide air exposure. It is not known whether B. glandula uses anaerobic metabolism during emersion, or if its use varies by latitude. We measured low tide D-lactate production in two US west coast populations of B. glandula separated by 14 degrees of latitude. We exposed barnacles to seven low-tide air temperatures (10, 15, 20, 25, 30, 35, and 38 °C) for which aerobic respiration has been previously measured. Our northern population of B. glandula increased D-lactate production at high air temperatures where aerobic metabolic depression is known to occur, indicating sublethal stress. In contrast, our southern population showed little increase in D-lactate over the same temperature range, coincident with high aerobic respiration across those temperatures. In a second experiment, we quantified D-lactate at 1, 2, and 6 hours post-emersion for northern B. glandula exposed to either a 10 or 38 °C low tide, to measure their potential lactate usage. While D-lactate was elevated at 38 °C compared to the 10 °C control immediately following low tide exposure, it dropped to control levels, and was likely excreted, within 1 hour of re-immersion. Our results suggest that the low latitude population of B. glandula may be more resilient to climate change than its high latitude counterpart in the absence of adaptation, which has strong implications for species distribution.

Acorn barnacle adults experience environmental heterogeneity at various spatial scales of their circumboreal habitat, raising the question of how adaptation to high environmental variability is maintained in the face of strong juvenile dispersal and mortality. Here we show that 4% of genes in the barnacle genome experience balancing selection across the entire range of the species. Many of these genes harbor mutations maintained across 2 million years of evolution between the Pacific and Atlantic oceans. These genes are involved in ion regulation, pain reception, and heat tolerance, functions which are essential in highly variable ecosystems. The data also reveal complex population structure within and between basins, driven by the trans-Arctic interchange and the last glaciation. Divergence between Atlantic and Pacific populations is high, foreshadowing the onset of allopatric speciation, and suggesting that balancing selection is strong enough to maintain functional variation for millions of years in the face of complex demography.

The intertidal isopod Dynoides dentisinus is a sexually dimorphic species; males are much larger than females and have a large, horn-like pleonal process (hereafter referred to as a "horn") and large, posteriorly extended uropods. Here, we investigated the function of these structures with regard to their mating system. Behavioral interactions were observed between a male occupying a small tube (resident) and a newly introduced individual (a female or male visitor). When the visitor was male, the resident repeatedly struck the visitor with his horn; each swing was accompanied by a short sound produced by stridulation. The resident also used his uropods to strike the male visitor and then rejected the visitor. The resident struck the female visitor in a similar fashion but eventually accepted her into the tube; during this process, the resident frequently emitted stridulatory sounds. Our field survey found that the members shared a single shelter (barnacle shell) containing groups composed of several males and females. This suggests that the mating system of this species is polygynandry. The number of females in a single barnacle shell was positively associated with the basal diameter of the barnacle shell. However, the number of females was not associated with the body size, horn size, or uropod size of the largest male in the barnacle shell. These results suggest that male body size, horns, and uropods might have evolved as weapons through male-male competition for large barnacle habitats and more females, but that they have not evolved as ornaments via female choice.

Molecular and morphological methods are used to describe Lernaeodiscus rybakovi, a new rhizocephalan species parasitizing the porcellanid crab Pachycheles stevensii Stimpson, 1858, collected in Russian waters of the Sea of Japan. Molecular analysis of three species, including the new one, confirms the monophyly of the genus Lernaeodicus Muller, 1862 and its recent transfer to the family Peltogastridae. The main morphological features of the new species are also common with characters of the other species of the genus Lernaeodiscus Muller, 1862. Externa of L. rybakovi differs from the well studied Lernaeodiscus porcellanae from the E. Pacific by molecular markers, color and the absence of pronounced marginal lobes. Retinacula on the internal cuticle of L. rybakovi are found in the genus Lernaeodiscus for the first time. Some of the female hosts with adult externae were unusual in also carrying their own eggs on the pleopods, a rare situation among rhizocephalans. The complete larval development in the genus Lernaeodiscus is described here for the first time and includes five naupliar and one cypris instar. The main morphological features of Lernaeodiscus nauplii (the presence of flotation collar, morphology of the frontolateral horns and furcal spines, and the arrangement of dorsal setae on the shield head) are common with those of other known peltogastrid larvae, but also resemble nauplii of Peltogasterella in the presence of naupliar eyes and thin structure of the flotation collar. The sizes of male and female cyprids of L. rybakovi overlap slightly. In summer months, larval sex ratio is male-biased. We briefly review important larval characters in the Rhizocephala.

Although parasitic castration is widespread among rhizocephalan barnacles, Boschmaella japonica Deichmann & Høeg, 1990 does not completely sterilise the host barnacle Chthamalus challengeri Hoek, 1883. As little information is available on the relationships with the host in “barnacle-infesting parasitic barnacles” (family Chthamalophilidae), we studied the life cycles of both B. japonica and C. challengeri and the effects of the parasite on the host reproduction. Specimens of C. challengeri were collected from an upper intertidal shore at Shirahama, Wakayama, western Japan from April 2017 to September 2018 at 1–3 mo intervals. We recorded the body size, number of eggs, egg volume, and the presence of the parasite for each host. Moreover, settlement and growth of C. challengeri were followed in two fixed quadrats. Chthamalus challengeri brooded from February to June. The prevalence of B. japonica was high (often exceeded 10%) from April to July, and was rarely observed from September to next spring. The life cycle of the parasite matched well with that of the host. The parasite reduced the host’s brooding rate and brood size, to the extent that no hosts brooded in 2018.

Assessment of unique and potentially significant fossils may be considerably compromised by surrounding matrix. This paper assesses a fossil barnacle group from the mid to late Eocene of Seymour Island, off the Antarctic Peninsula, that potentially has very significant phylogenetic importance. It discusses why the specimen could be significant, and describes and applies as a proof of concept an advanced imaging technique, using X-ray Computed Tomography (CT), that was effectively employed to confirm systematic taxonomy with virtual 3-D sections through the specimen. In this case, the Antarctic barnacle's complex internal plate morphologies were resolved by advanced 3-D imaging, such that a taxonomic attribution could be made to either the Archaeobalanidae or Austrobalanidae, excluding the initial assessment of Coronulidae, which would have otherwise been allusive.

How larvae of whale and dolphin epibionts settle on their fast-swimming and migrating hosts is a puzzling question in zoology. We successfully reared the larvae of the whale and dolphin barnacle Xenobalanus globicipitis to the cyprid stage. We studied the larval developmental ecology and antennular morphology in an attempt to assess whether an epibiotic lifestyle on this extreme substratum entails any unique larval specializations. Morphological parameters were compared with five other barnacle species that also inhabit extreme substrata. We found no larval specializations to a lifestyle associated with marine mammals. The external morphology of the antennules in Xenobalanus cyprids is morphologically similar to species from strikingly different substrata. We found variation only in the structures that are in physical contact with the substratum, i.e., the third segments carrying the villi-covered attachment disc. The third segments of the Xenobalanus cyprid antennules are not spear-shaped as in the stony coral barnacles, which are here used to penetrate the live tissue of their hosts. The presence of a cyprid cement gland implies that Xenobalanus uses cement protein when attaching to its cetacean host. Naupliar instars developed outside of the mantle cavity, indicating dispersal is planktonic. Our results militate against the idea that the cyprids settle during ocean migrations of their hosts. We suggest cyprids settle during coastal aggregations of the cetacean hosts. We conclude that the ecological success of barnacles has ultimately depended on a larva that with little structural alteration possesses the ability to settle on an amazingly wide array of substrata, including cetaceans.

The sessile barnacle Xenobalanus globicipitis was observed on multiple cetacean species during field surveys off the northern coast of Sao Paulo state, Brazil. However, the occurrence of X. globici...

Sea turtles are long-lived migratory species that are sensitive to anthropogenic impacts. Their condition reflects that of marine ecosystems and can serve as an indicator for environmental monitoring. However, evaluating body condition parameters, as a proxy for health, is challenging and often overlooked. The purpose of this study was to validate a straightforward method for assessing the body condition of nesting loggerhead sea turtles (Caretta caretta), and to investigate whether body condition was correlated with epibiont loading. To achieve this, 60 nesting loggerhead sea turtles were sampled and categorized into five body conditions ranging from very poor to very good. Injuries, skin deformities and plastron shape were used for this classification. Epibionts were collected from the same turtles and identified, with species richness, diversity, community structure and barnacle loading compared among body conditions. Epibiont communities were correlated with body condition as both species richness and abundance increased with a decline in turtle body condition. Barnacle epibionts showed great variation among different body conditions, having significantly higher numbers on turtles in poor condition. All parameters in this study showed similar distinctive relationships with body condition of loggerhead turtles from poor to very good body condition. The body condition index used in this study can be applied readily and, along with barnacle counts, can provide basic baseline information on turtle health.

Capitulum mitellais a tropical/sub-tropical intertidal barnacle of high economic value. However, no studies have yet focused on the effects of the extrinsic and intrinsic factors that affect the metamorphosis of this species. The current study stored cyprids at room temperature (24–26°C) and low temperature (7°C) and then compared the effects of age and storage temperature on cyprid metamorphosis. The effects of salinity and temperature on cyprid metamorphosis and survival were examined. Results showed the following. (1) Young 0-day cyprids were not competent to metamorphose, andC. mitellacyprids had a pre-competent phase. (2) The cyprid metamorphosis percentage at different storage temperatures with the same age was higher at room temperature than at 7°C. Low temperature storage of cyprids appeared to be unsuitable forC. mitella. The ideal storage time at room temperature for cyprids was 3–5 days. (3) The cyprids could complete metamorphosis at a salinity range of 20–45 mg l−1, and the optimum salinity range for metamorphosis was 25–35 mg l−1. At 15 mg l−1salinity, the cyprids could survive but failed to metamorphose. (4) The cyprids could survive and complete metamorphosis at 18–36°C, and the optimum temperature range for metamorphosis was 21–33°C. The metamorphosis ofC. mitellacyprids can tolerate a wide spectrum of salinity and temperature, which is related to the distribution location, habitat environment and lifestyle. Results of this study may provide a basis for the settlement biology, recruitment ecology and aquaculture of this species.

The Portuguese oyster (Crassostrea angulata) is an important fishery resource in Taiwan. This study investigated oyster cultures at two locations along the coast of Taisi Township from March 2012 to July 2014. The average recruitment density, measured once every two weeks, of the oyster larvae was 256.4 ± 236.6 individuals/shell (N = 62) at site A and 118.5 ± 140.2 individuals/shell (N = 39) at site B. The average adherence density of the barnacle larvae was 187.1 ± 251.2 individuals/shell (N = 60) at site A and 60.9 ± 112.5 individuals/shell (N = 37) at site B. In Taiwan, C. angulata spawned all year. The primary spawning season was from March to September. The primary of adherence spawning season of barnacles was from March to October. Rainfall was the major factor that influenced oyster C. angulata and barnacle settlement, the eigenvalue of PC1 was 1.83 and could explain 61.0%. There are two main culturing seasons that move oyster larvae from coast of Taisi to farms in other places: from March to May and from August to September. Although the oyster larvae are more abundant in spring, fishermen prefer harvesting the larvae in autumn to avoid the typhoon season (July-September).

Balanomorph Eochionelasmus species are hydrothermal vent endemic barnacles. In the genus Eochionelasmus, three species are known to date and they distribute at three different vent fields in Pacifi...

Background The barnacles are a group of >2,000 species that have fascinated biologists, including Darwin, for centuries. Their lifestyles are extremely diverse, from free-swimming larvae to sessile adults, and even root-like endoparasites. Barnacles also cause hundreds of millions of dollars of losses annually due to biofouling. However, genomic resources for crustaceans, and barnacles in particular, are lacking. Results Using 62× Pacific Biosciences coverage, 189× Illumina whole-genome sequencing coverage, 203× HiC coverage, and 69× CHi-C coverage, we produced a chromosome-level genome assembly of the gooseneck barnacle Pollicipes pollicipes. The P. pollicipes genome is 770 Mb long and its assembly is one of the most contiguous and complete crustacean genomes available, with a scaffold N50 of 47 Mb and 90.5% of the BUSCO Arthropoda gene set. Using the genome annotation produced here along with transcriptomes of 13 other barnacle species, we completed phylogenomic analyses on a nearly 2 million amino acid alignment. Contrary to previous studies, our phylogenies suggest that the Pollicipedomorpha is monophyletic and sister to the Balanomorpha, which alters our understanding of barnacle larval evolution and suggests homoplasy in a number of naupliar characters. We also compared transcriptomes of P. pollicipes nauplius larvae and adults and found that nearly one-half of the genes in the genome are differentially expressed, highlighting the vastly different transcriptomes of larvae and adult gooseneck barnacles. Annotation of the genes with KEGG and GO terms reveals that these stages exhibit many differences including cuticle binding, chitin binding, microtubule motor activity, and membrane adhesion. Conclusion This study provides high-quality genomic resources for a key group of crustaceans. This is especially valuable given the roles P. pollicipes plays in European fisheries, as a sentinel species for coastal ecosystems, and as a model for studying barnacle adhesion as well as its key position in the barnacle tree of life. A combination of genomic, phylogenetic, and transcriptomic analyses here provides valuable insights into the evolution and development of barnacles.

Background Barnacles are sessile crustaceans that attach to underwater surfaces using barnacle cement proteins. Barnacles have a calcareous or chitinous membranous base, and their substratum varies from biotic (e.g. corals/sponges) to abiotic surfaces. In this study, we tested the hypothesis that the cement protein (CP) composition and chemical properties of different species vary according to the attachment substrate and/or the basal structure. We examined the histological structure of cement glands and explored the variations in cement protein homologs of 12 barnacle species with different attachment habitats and base materials. Results Cement gland cells in the rocky shore barnacles Tetraclita japonica formosana and Amphibalanus amphitrite are eosinophilic, while others are basophilic. Transcriptome analyses recovered CP homologs from all species except the scleractinian coral barnacle Galkinia sp. A phylogenomic analysis based on sequences of CP homologs did not reflect a clear phylogenetic pattern in attachment substrates. In some species, certain CPs have a remarkable number of paralogous sequences, suggesting that major duplication events occurred in CP genes. The examined CPs across taxa show consistent bias toward particular sets of amino acid. However, the predicted isoelectric point (pI) and hydropathy are highly divergent. In some species, conserved regions are highly repetitive. Conclusions Instead of developing specific cement proteins for different attachment substrata, barnacles attached to different substrata rely on a highly duplicated cementation genetic toolkit to generate paralogous CP sequences with diverse chemical and biochemical properties. This general CP cocktail might be the key genetic feature enabling barnacles to adapt to a wide variety of substrata.

Barnacles are sessile suspension feeders whose feeding efficiency and behavior is largely determined by the movement of water through their environment. Barnacles expend energy to feed actively in environments with low flow velocity, whereas they may feed passively at higher flow velocities, which is more efficient than active feeding. Many intertidal barnacles have been shown to switch between active and passive feeding modes as water velocities change, but little is known about the behavior of epibiotic species attached to mobile hosts, which are exposed to more consistent feeding currents. To assess the response of epibiotic barnacles to flow, laboratory-reared sea-turtle barnacles, Chelonibia testudinaria (Linnaeus, 1758), were subjected to a wide range of water velocities in both the presence and absence of food particles. Their behaviors were video-recorded and categorized using an automated behavior recognition algorithm compiled in R. Individuals of C. testudinaria only displayed passive feeding behavior, but did not feed at lowest test velocities. This species fed most at flow velocities between 25 cm s–1 and 40 cm s–1 (linear mixed effects model, F = 19.30, P < 0.001), a range that correlates well with the average swimming speed of two common host species, the loggerhead and green sea turtles, on which C. testudinaria resides. Chelonibia testudinaria displayed longer average feeding durations when food particles were absent than when food was abundant (linear mixed effects model, F = 11.76, P = 0.001), a result that is in line with the expectations of optimal foraging theory for suspension-feeding invertebrates. Lack of active feeding in this species may have evolved following the establishment of its epibiotic nature and may make this obligate epibiotic species entirely reliant on its hosts’ movements to provide a feeding current. This is the only barnacle species known to not facultatively switch between active and passive feeding modes.

Movement is a fundamental characteristic of life, yet some invertebrate taxa, such as barnacles, permanently affix to a substratum as adults. Adult barnacles became ‘sessile’ over 500 Ma; however, we confirm that the epizoic sea turtle barnacle, Chelonibia testudinaria , has evolved the capacity for self-directed locomotion as adults. We also assess how these movements are affected by water currents and the distance between conspecifics. Finally, we microscopically examine the barnacle cement. Chelonibia testudinaria moved distances up to 78.6 mm yr −1 on loggerhead and green sea turtle hosts. Movements on live hosts and on acrylic panels occasionally involved abrupt course alterations of up to 90°. Our findings showed that barnacles tended to move directly against water flow and independent of nearby conspecifics. This suggests that these movements are not passively driven by external forces and instead are behaviourally directed. In addition, it indicates that these movements function primarily to facilitate feeding, not reproduction. While the mechanism enabling movement remained elusive, we observed that trails of cement bore signs of multi-layered, episodic secretion. We speculate that proximal causes of movement involve one or a combination of rapid shell growth, cement secretion coordinated with basal membrane lifting, and directed contraction of basal perimeter muscles.

Nur I, Aris EA, Yusnaini Y, Beavis S. 2021. The potential use of Octolasmis spp. parasites in mud crabs Scylla spp. as a bioindicator for mercury pollution. Biodiversitas 22: 3764-3772. Artisanal small-scale gold mining and the use of mercury is widespread across Indonesia, often characterized by relatively short-lived gold rushes. In the late and post-mining phases, mercury stored in mine tailings and river beds was transported down catchment, posing risks to ecosystems and human health over much longer time scales. These risks can be under-rated when mercury concentrations in water, sediments, and aquatic species are low enough to meet relevant guideline thresholds. In this study in Southeast Sulawesi, Indonesia, we have investigated the Costraca barnacle, Octolasmis, as a bioindicator of mercury contamination. The presence of Octolasmis parasites in mud crabs, Scylla spp., and the accumulation of mercury (Hg) in the hosts, parasites, and the ambient environment, were analyzed across both dry and wet seasons. Severe infestation of Octolasmis was assessed using prevalence, abundance, and intensity. Hg concentrations were significantly higher in the Octolasmis parasites than in the host tissues, water and sediments. The mean bioconcentration factor (BCF) of Hg equaled 7938.21 from water to parasites, and 28.91 from the host’s gill tissue to the parasites. The results suggest that Octolasmis spp. can be used effectively as a bioindicator in coastal catchments impacted by mercury contamination, even when concentrations of mercury are low in water and river sediments. The study provides the first report of Octolasmis spp. parasitized to mud crabs as a reliable bioindicator of Hg contamination and pollution.

Causes and consequences of jellyfish bloom formation are subject to controversial discussions worldwide. While medusae have been studied to a broader extent, the knowledge on polyp stages of scyphozoans is limited thus hampering reliable prediction of jellyfish bloom formation. This study describes the occurrence, abundance, habitat characteristics and interactions of scyphozoan Aurelia sp. polyp colonies with other fouling organisms in intertidal and subtidal sectors of Trondheimsfjorden (Norway). In total, 982 polyps were found on 70 substrata of varying material types during a field survey in spring-summer 2018 along a longitudinal gradient within and outside Trondheimsfjorden. The polyps were identified as Aurelia sp. based on molecular species identification. Most polyps were found in bays with macroalgae canopy on the down facing side of artificial and natural substrata (rocks, concrete, iron) and inside rock cracks. Polyp microhabitats included the surface of Ascidia mentula (solitary ascidian), increments of Pomatoceros triqueter (polychete) tubes and dead Balanus balanoides (barnacle) shells. Based on the deployment of settling plates, abundance of Aurelia sp. polyps ranged from 1.2 (± 0.7) to 0.12 (± 0.07) polyps cm–2. Settlement occurred either directly on the PVC settling plates or as epibionts on the ascidian Ascidia mentula and on barnacle shells of Balanus balanoides. This study provides insights into the potential of local Aurelia sp. polyps contributing to the seasonal occurrence and abundance of Aurelia sp. in fjord systems, where intensive blooms occur annually.

Environmental controls on the biogeographic distribution of species are becoming increasingly relevant under the present climate change conditions. The reproductive cycle of the acorn barnacle Semibalanus balanoides at its southernmost European distribution limit in Galicia (Northwest Iberian Peninsula) was studied in two locations (42.57°N 8.96°W, 42.61°N 8.89°W) with different temperatures during a 4-year time series (2012–2016), where an isolated population breeds even though the temperature thresholds documented for northern populations of the species are exceeded. Ovary production, total number of embryos and pre-hatching developmental stage were significantly higher in the colder location than in the warmer one. Fecundity was higher in colder reproductive seasons mediated by upwelling regime and food supply 3 months prior to fertilization. Investment in ovary tissue was favored by high temperatures and food availability, whereas suspended sediment was negatively correlated with investment in ovary tissue. Larvae release was associated with high temperatures and suspended sediment. Phenology of reproductive events was similar to what was described in farther north populations. Results indicated that reproductive output of the species at its southernmost European distribution limit is comparable to that reported in northern latitudes and suggest adaptation or acclimatization to local environmental conditions as maturation of gonads and fertilization was successfully carried out at higher temperatures than documented in northern European populations.

Here we present the complete mitochondrial genome of Tetraclita squamosa squamosa, which is 15,191 bp in length with 67.20% AT content. It contains 13 protein-coding genes, 2 ribosomal-RNA genes an...

Limpets and barnacles are important components of intertidal assemblages worldwide. This study examines the effects of barnacles on the foraging behaviour of the limpetPatella vulgata, which is the main algal grazer in the North-west Atlantic. The behaviour of limpets on a vertical seawall on the Isle of Man (UK) was investigated using autonomous radio-telemetry, comparing their activity patterns on plots characterized by dense barnacle cover and plots from which the barnacles had been removed. Limpet behaviour was investigated at mid-shore level, but two different elevations were considered. This experiment revealed a significant effect of barnacle cover on the activity ofP. vulgata. Limpets on smooth surfaces spent a greater proportion of total time active than did limpets on barnacles. Movement activity was also greater in areas that were lower down in the tidal range. In general, limpets were either predominantly active during diurnal high or nocturnal low tides and always avoided nocturnal high tides. Individuals on barnacles at the higher elevation concentrated their activity during nocturnal low water. All the other groups of limpets (smooth surfaces on the upper level and all individuals on the lower shore) had more excursions centred around daylight hours with an equal distribution of activity between periods of low and high water. Inter-individual variability was, however, pronounced.

Waterfowl occupied the prominent rating with respect to abundance among the birds on the Dolgiy Island in the south-eastern part of the Barents Sea in land habitats and coastal water habitats. Comparison of the number of clutches and broods of waterfowl per 10 km of walking trails in different years on the island shows that in recent years (2014, 2016 and 2017), compared to 2004, there was an increase in abundance of the breeding populations of the Barnacle Goose, the White-fronted Goose, the Bean Goose, the Long-tailed Duck and the King Eider. There was a particularly rapid growth in the abundance of the Barnacle Goose for the studied period which, in the land habitats of the island, occupied a leading position in terms of abundance among other geese. An increased abundance of the Barnacle Goose on the island was accompanied by changes in its choice of nesting habitat type and its distribution in the parental care and moulting periods. The results of our study show that with an increase in the nesting density of the Barnacle Goose, the similarity of its nesting habitat types with those of the White-fronted Goose also increased. Some links between the abundance of clutches and broods of waterfowl and weather parameters were observed in different years. The abundance of waterfowl clutches and broods on the island was highest in 2016, which was characterised by the highest average monthly temperature of June and the longest frost-free period for all the years of observation.

Annually, shipworms and other biofouling species cause millions of dollars in damage to wooden marine infrastructure across the world. Given their abundant larval supply and high dispersal potential, bioeroders and biofoulers are ubiquitous threats that shorten the lifespan of wooden docks, piers, boats and shoreline stabilization structures in coastal environments. Despite these impacts, there are no treatments that completely protect wood against shipworms and biofouling. To explore potential approaches for extending the lifespan of wooden shoreline stabilization structures, we conducted two field experiments to evaluate the resistance to shipworms and biofouling of small and large diameter branches of four trees – laurel oak (Quercus hemisphaerica), sweetgum (Liquidambar styraciflua), crepe myrtle (Lagerstroemia spp.), and black mangrove (Avicennia germinans) – positioned at varying distances from the sediment surface in southeastern US estuaries. We discovered that the wood volume lost to shipworm burrows was concentrated near the sediment surface, more prevalent in tree species with lower wood densities, and varied markedly between years. Barnacle fouling was far higher on branches > 30 cm from the surface and on laurel oak and sweetgum branches. In a third field experiment, we tested two chemical and two non-chemical wood treatments and found chemical treatments to be more effective at deterring barnacle fouling and shipworm burrowing of wooden posts, especially beneath the sediment surface. By identifying desirable characteristics of the wood employed and elevations at which the impacts of shipworms and biofouling are especially prevalent, this experimental study informs the design of more durable wooden stabilization structures in coastal environments.

Ten blue swimming crabs Portunus segnis (Forskal, 1775) were collected from the north west of the Arabian Gulf off the Iraqi marine waters from October to November 2017 at 29ᵒ 37′ N to 48ᵒ 47′ E. The barnacle Octolasmis angulata (Aurivillius, 1894) was found on the gills of the present species of crab, the mean incidence of infestation was 30%, while the mean Intensity of infestation was 12.3. The barnacle have a long and slim shaped calcareous plate with the presence of carina and the absence of tergum, in addition to the elongated shape of carina and scutum. The current study represents the first record of the barnacle O. angulata in the Arabian Gulf.

Cu nanoparticles (CuNPs) have been widely used in numerous products, and may become a potential threat to marine organisms, but their behavior in the marine environments and potential toxicity to marine organisms remain little known. In the present study, we investigated the behavior of CuNPs in seawater, as well as the toxicity and bioaccumulation of CuNPs and copper sulfate (CuSO4) in barnacle larvae (Balanus amphitrite), a dominant fouling invertebrate in marine environment. CuNPs tended to aggregate in natural seawater and released Cu ion rapidly into seawater. The aggregation and release were especially higher at a lower concentration of CuNPs, e.g., 94–96% of CuNPs were released as Cu ions at 20 μg/L after 24 h. The larger size of CuNPs (40 nm) tended to display a higher solubility than the 20 nm CuNPs did. Humic acids enhanced the aggregation and inhibited the dissolution of CuNPs, and had a protective effect on the survival of nauplii II at higher Cu concentrations (100–200 μg/L). Comparison of the lethal concentrations showed that CuNPs were generally less toxic to the two stages of barnacle larvae (nauplii II and VI) than the Cu ions. The calculated 48-h LC50 values for nauplii II were 189.5 μg/L, 123.2 μg/L, and 89.8 μg/L for 20 nm CuNPs, 40 nm CuNPs, and CuSO4, respectively. However, the lethal concentrations of Cu bioaccumulation in the barnacle larvae were comparable between CuNPs and Cu ions when expressed by the actual tissue Cu bioaccumulation. Barnacle larval settlement decreased with an increase of Cu concentrations of both CuNPs and CuSO4, and was significantly inhibited at 100 μg/L CuSO4 and 150 μg/L CuNPs. Our results indicated that the toxicity of CuNPs could not be solely explained by the released Cu ions, and both CuNPs and the released Cu ion contributed to their toxicity and bioaccumulation in barnacle larvae.

Pelagic larvae of benthic organisms comprise a substantial part of the coastal Arctic zooplankton community in spring–summer. We studied the timing, growth, and pelagic duration of Cirripedia larvae in Adventfjorden, a high-Arctic fjord in Spitsbergen, Svalbard. Two distinct abundance peaks were found: one in early May (~ 25.000 ind. m−3) and another one in late May (~ 35,580 ind m−3). DNA barcoding based on the COI gene was used to identify the barnacle larvae to species. Whereas both Balanus balanus and Semibalanus balanoides were present, the first one dominated (50–100%) the barnacle abundance. High resolution sampling and size measurements of Cirripedia larvae revealed that these larvae most likely originated from a single spawning event. Development of the larvae suggested a pelagic residence time of roughly 2 months for B. balanus and at least 1 month for S. balanoides in the Arctic. Long pelagic residence time, large potential for biofouling on ships and larger plastic debris, combined with the disappearance of landfast sea ice and less ice scouring opens up new opportunities for barnacles to colonize the high-Arctic littoral zone. In a future warmer Arctic, we therefore expect establishment of new, more temperate Cirripedia species in Svalbard.

Introduced species are a major threat to coastal ecosystems worldwide. Thus, understanding biotic resistance (i.e. the ability of native species to limit introduced species) is a central goal of invasion biology. This paper examines mechanisms underlying biotic resistance. Consumption can limit introduced prey provided that native predators prefer such prey. Furthermore, predator nonconsumptive effects (NCEs), mediated through predator-released cues perceived by prey, can limit prey recruitment, a key demographic process for prey populations. However, information on predator NCEs is largely absent in the context of recruitment in introduced prey. Working on the Pacific coast of Hokkaido (Japan), we addressed this knowledge gap using native predatory dogwhelks (Nucella lima) that prey on native barnacles (Chthamalus dalli) and introduced barnacles (Balanus glandula). We experimentally examined dogwhelk preferences for barnacles in the laboratory and dogwhelk NCEs on barnacle recruitment in the field. We found that N. lima preferred B. glandula over C. dalli, likely as B. glandula prey is more profitable, as suggested by previous findings in congeneric dogwhelks. Moreover, we found that N. lima NCEs limited recruit density in C. dalli and B. glandula, likely as barnacle larvae moved away from dogwhelk cues to reduce future predation risk. Our study suggests that predator prey preferences and predator nonconsumptive limitation of prey recruitment are two mechanisms that can contribute to predator-driven biotic resistance against introduced prey.

Barnacles are symbiont and harm to the crabs when they are in large numbers. They will affect the respiration, normal activity and growth of the crabs. The prevalence, mean intensity and identification of pedunculate barnacle, Octolasmis spp. on blue swimming crab, Portunus pelagicus from the coastal area of Kuala Terengganu were studied. The site specificity of the different species of Octolasmis attached was examined. The crabs were measured and weight. The crabs were euthanized by put in ice until no movement. The Octolasmis were observed from the surfaces and gills or brachial chamber. The Octolasmis were observed from each gill. The prevalence and mean intensity was calculated. The Octolasmis were preserved in 70% alcohol and mounting using glycerine jelly to make the permanent slide. A total of all 13 crabs were infested by four species of Octolasmis which is 218 Octolasmis angulata, 191 Octolasmis warwickii, 16 Octolasmis tridens and 218 Octolasmis lowei. Octolasmis angulate showed the highest prevalence (84.62%) and lowest prevalence was O. lowei (23.08%) and O. warwickii (23.08%). The barnacles were attached to the gill, carapace, abdomen and also walking legs. Barnacle occurred most frequently on the gill part by having 371 (57.70%) barnacles compared to other areas, 272 (42.30%) barnacles. The distributions of barnacle in this study suggest distal areas are more susceptible in infestation by Octolasmis spp. However, they did not show site specificity on the gill areas because it depends on the water current.AbstrakBarnacle (teritip) adalah simbion yang dalam jumlah besar akan membahayakan kepiting. Teritip tersebut berpengaruh pada pernapasan, aktivitas normal dan pertumbuhan kepiting. Prevalensi, intensitas rata-rata dan identifikasi pedunculate barnacle, Octolasmis spp. pada rajungan, Portunus pelagicus dari daerah pesisir Kuala Terengganu telah diteliti. Kekhasan lokasi dari berbagai spesies Octolasmis telah diperiksa. Kepiting telah diukur dan ditimbang. Kepiting dieuthanasi dengan cara dimasukkan kedalam es sampai tidak bergerak. Octolasmis diamati dari permukaan tubuh dan insang (branchial chamber). Octolasmis diamati pada tiap insang. Prevalensi dan intensitas rata-rata dihitung. Octolasmis diawetkan dalam alcohol 70 % dan mounting menggunakan Jeli gliserin untuk membuat slide permanen. Semua kepiting 13 ekor telah terinfestasi oleh empat spesies Octolasmis, yaitu 218 Octolasmis angulata, 191 Octolasmis warwickii, 16 Octolasmis tridens dan 218 Octolasmis lowei. Octolasmis angulate menunjukkan prevalensi paling tinggi (84,62%) dan prevalensi paling rendah adalah O. lowei (23,08%) dan O. warwickii(23,08%). Teritip menyerang insang, karapas, abdomen dan juga kaki jalan.Teritip paling sering ditemukan pada bagian insang 371 ekor (57,70%) dibandingkan pada bagian lain, 272 ekor (42,30%). Distribusi teritip pada penelitian ini menunjukkan bahwa bagian distal lebih rentan mengalami infestasi Octolasmis spp. Namun, teritip tidak menunjukkan kekhasan lokasi pada daerah insang bergantung pada arus air.

Between 2014 and 2017, the Rivers to Reef to Turtles (RRT) project examined the health of green turtles at two coastal sites impacted by urban and agricultural human activities (Cleveland and Upstart Bays) and one proposed pristine site (Howick Group of Reefs) in northern Queensland, Australia, through blood biochemistry and haematology, plasma protein electrophoresis, and clinical assessments including body condition and barnacle counts. Furthermore, cases of mortality were subjected to comprehensive postmortem examination. In an attempt to advance diagnostics, associations between specific contaminants and health of turtles in this region were tested. No comprehensive health assessments had been conducted at these sites prior to this study. The coastal Cleveland and Upstart Bays both demonstrated effects likely to be in response to stressors suspected to be anthropogenic in origin (elevated total white cell counts and creatinine kinase levels across the populations, respectively). This was associated with a suite of trace elements, in particular cobalt. While these indicators of stress resolved by the final year of the study, a chronic stressor was suspected to be persisting with ongoing low albumin: globulin. Necropsies did not elucidate any specific diseases. Although body condition index did not closely correlate with site health, barnacle counts in juvenile turtles may prove a reliable indicator of site health. Based on previously established indicators of poor health, barnacle counts showed that 10% of the population was in poor health at Upstart Bay and nearly 20% of the population at Cleveland Bay. This is above what would be expected for a normal population. Overall, the health component of this study suggested that the pristine turtle population was healthy and the coastal turtle populations were under active stressors, possibly caused by anthropogenic effectors such as chemical pollutants, when initially examined in 2014. These stressors resolved by the conclusion of the study in 2017; but chronic stressors remained absent in the pristine site and present within each of the studied coastal populations.

Gregarious settlement in barnacles has been attributed to chemical cues originating from the associated microorganisms, lectins, and settlement-inducing protein complex from arthropodin, a glycoprotein present in their conspecifics/adults. In this study, we explored the influence of haemolymph haemocytes on the metamorphosis of barnacle, Amphibalanus amphitrite cyprids. The barnacle haemocytes were also characterized for the first time using flow cytometry. Cyprid metamorphosis was significantly higher in the presence of surface-bound haemocytes compared to water-borne cues from haemolymph or adult glycoprotein, a known settlement inducer. The flow cytometry-assisted haemocyte characterization, sorting and their subsequent microscopic evaluation indicated the presence of hyalinocytes and granulocytes. Tagging of these haemocytes with lectins revealed that a significant number of haemocytes had d-glucose/d-mannose and N-acetyl-d-galactosamine, which are important settlement cues. These glycoconjugates were also detected in the cyprid larva pointing out the origin of conspecific cues. The retention of these glycoconjugates in the adult haemocytes and their occurrence in adult leachants indicate pelago-benthic coupling in sessile barnacles wherein these glycoconjugates play a significant role in their gregarious settlement. Characterization of such a coupling process in other sessile benthic invertebrates will pave the way to the understanding of complexities in their population dynamics.

As heavy metals are easy to accumulate and have strong biological toxicity, they pose a potential threat to human health by entering the human body through the cumulative effect of marine life. Land-based input is an important source of heavy metals in the ocean, which has a great influence on coastal water quality. In this study, the spatial distribution characteristics of heavy metals (Zn, Cu, Cd, Pb, Cr, As) in the coastal waters of the desulfurization process outlet of a power plant in Zhanjiang Bay were investigated, and the enrichment behavior of heavy metals by organisms (oysters and barnacles) were also studied. The results showed that, before the seawater desulfurization system was closed, there were high concentrations of heavy metals (Cu, Zn, Cd, Pb and Cr) in the surface seawater near the drainage outlet. The concentrations of these heavy metals in the surface seawater were higher than those in the bottom seawater within 100 m of the drainage outlet. After the seawater desulfurization system was closed, the average concentrations of Cu, Cr and As in seawater at each station decreased by 17.04%, 37.52% and 29.53%, respectively, while the average concentrations of Zn, Cd and Pb increased by 17.05%, 32.87% and 48.77%, respectively. Single factor pollution index (SFI) and bio-concentration factor (BCF) showed that there was a potential high accumulation risk of Zn in oysters and barnacles near the drainage outlet of desulfurization wastewater (0.5 < SFI < 1 and BCF > 1000). The SFI and BCF of each metal in oysters and barnacles decreased with the increase in distance from the drainage outlet. Generally, the coastal water quality of desulfurization process drainage area in Zhanjiang Bay were below the class Ⅱof the “Seawater quality standard” (GB 3097-1997) of China. However, the heavy metals content in seawater and organisms near the drainage outlet is slightly higher. This suggested that if the seawater desulfurization process runs for a long time, it will have a negative impact on the coastal water and organisms.