Barnacle Amphibalanus Amphitrite Research Articles

Growth and development of the barnacle Amphibalanus amphitrite: time and spatially resolved structure and chemistry of the base plate

The radial growth and advancement of the adhesive interface to the substratum of many species of acorn barnacles occurs underwater and beneath an opaque, calcified shell. Here, the time-dependent growth processes involving various autofluorescent materials within the interface of live barnacles are imaged for the first time using 3D time-lapse confocal microscopy. Key features of the interface development in the striped barnacle, Amphibalanus (= Balanus) amphitrite were resolved in situ and include advancement of the barnacle/substratum interface, epicuticle membrane development, protein secretion, and calcification. Microscopic and spectroscopic techniques provide ex situ material identification of regions imaged by confocal microscopy. In situ and ex situ analysis of the interface support the hypothesis that barnacle interface development is a complex process coupling sequential, timed secretory events and morphological changes. This results in a multi-layered interface that concomitantly fulfills the roles of strongly adhering to a substratum while permitting continuous molting and radial growth at the periphery.

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.

Larval development and settlement of the barnacle Amphibalanus amphitrite from the Red Sea: Influence of the nauplii hatching season

Abstract Barnacle Amphibalanus amphitrite adults were collected from the Jeddah coast of the Red Sea during different seasons. The nauplii released by adults in autumn, winter, spring and summer were reared under laboratory conditions to know the larval development duration and settlement in relation to the hatching season. The nauplii reared during winter (11 days) and autumn (13 days) took longer to reach the cypris stage compared to nauplii reared in summer (6 days) and spring (7 days). The most successful settlement of larvae was observed in spring and summer and the least successful — in winter. The observations of gonads showed that summer and spring are the active breeding season for A. amphitrite in the Red Sea. The results of this study indicated that the nauplii hatching season plays a significant role in the larval development and settlement of barnacles in the Red Sea.

Histamine promotes the larval metamorphic competence of barnacle Amphibalanus amphitrite

The larvae of the typical marine-fouling barnacle develop into competent stages to settle on submerged surfaces, metamorphose to juveniles, and finally grow into adults. In this study, the presence of histamine (a neurotransmitter molecule) in both nauplii and cyprids of the barnacle Amphibalanus amphitrite was verified by analysis with High Performance Liquid Chromatography with a fluorescence detector (HPLC-FL) after O-phthalaldehyde derivatization. To clarify the functions of histamine in the larvae, two bioassays were further performed, using the nauplii and cyprids, respectively. In the presence of 5 × 10−9 M histamine, 80% of low-energy-containing cyprids settled and metamorphosed to juveniles after only 48 h of incubation, which was significantly higher than in the absence of additional histamine. Moreover, the presence of 5 × 10−10 M histamine also significantly increased and accelerated the metamorphosis of nauplii to cyprids. An antihistamine compound of triprolidine hydrochloride completely inhibited cyprid settlement and metamorphosis at a concentration of 1.3 µg ml−1, which indicated that it possessed strong antifouling effects against the barnacle A. amphitrite. These results suggest that histamine may play an important role in regulating the larval metamorphic competence of the barnacle A. amphitrite, and the antihistamine compounds are promising potential nontoxic antifouling additives.

Antifouling activities of anti-histamine compounds against the barnacle Amphibalanus (= Balanus) amphitrite

The barnacle Amphibalanus (=Balanus) amphitrite is a typical marine fouling invertebrate, with adults releasing planktonic larvae that settle and further metamorphose into juveniles on submerged surfaces. The mechanisms regulating larval selection for settlement surface and metamorphosis initiation have been proposed to have a close relationship to neurotransmitters. In this study, a total of 35 signal-influencing pharmaceutical compounds affecting several neurotransmitters were examined in an antifouling bioassay using cyprid larvae of A. amphitrite to search for new antifouling compounds. The results indicated that 18 of the 35 compounds were effective against the larval settlement and metamorphosis of the barnacle A. amphitrite, with nontoxic effects at concentrations of 20μgmL−1. By reducing the treatment concentrations, a 5-HT3 receptor antagonist of Ondansetron; two epinephrine β2 receptor agonists of Propranolol and Clorprenaline; and five histamine H1 receptor antagonists, including Loratadine, Antazoline, Clemastine, Azelastine, and Triprolidine were found to be very active against the larval settlement and metamorphosis of A. amphitrite, with EC50 values lower than 1.6μgmL−1. In a recovery bioassay, the larvae treated with a histamine H1 receptor antagonist of Triprolidine regained the ability to settle and to metamorphose into juveniles in fresh artificial seawater. The settlement and metamorphosis of the recovered larvae were further enhanced by the addition of 5×10−9M histamine. The results of the present study indicated that some of the compounds influencing neurotransmitter signaling, especially histamine H1 receptor antagonists, are promising new antifouling candidates.

A survey on bioconcentration capacities of some marine parasitic and free-living organisms in the Gulf of Oman

During the course of the present study 21 rays including Himantura cf. gerrardi and Glaucostegus granulatus infected with the four cestode species Tetragonocephalum sp., Polypocephalus sp., Rhinebothrium sp1., and Rhinebothrium sp2. as well as three species of free living animals including the barnacle Amphibalanus amphitrite, and the two bivalve species Saccostrea cucullata and Barbatia obliquata were studied from the Gulf of Oman in respect to their cadmium and lead concentrations. All specimens were analyzed using graphite furnace atomic absorption spectrometry (GFAAS) for metal concentrations. In all cases, Cd and Pb concentrations in cestodes were higher than those in the tissues of the respective fish. The cosmopolitan barnacle species A. amphitrite showed the highest bioconcentration for all metals. However, the cestode species and especially Polypocephalus sp. could be an additional reliable metal indicator. The combination of “mobile” parasites together with sedentary species (i.e. barnacles) might be the most effective way to indicate local pollution levels and to relate this to an estimation of the average pollution level in larger geographical zones.

MKK3 was involved in larval settlement of the barnacle Amphibalanus amphitrite through activating the kinase activity of p38MAPK.

The p38 mitogen-activated protein kinase (p38MAPK) plays a key role in larval settlement of the barnacle Amphibalanus amphitrite. To study the signaling pathway associated with p38MAPK during larval settlement, we sought to identify the upstream kinase of p38MAPK. Three MKKs (MKK3, MKK4 and MKK7) and three MAPKs (p38MAPK, ERK and JNK) in A. amphitrite were cloned and recombinantly expressed in E. coli. Through kinase assays, we found that MKK3, but not MKK4 or MKK7, phosphorylated p38MAPK. Furthermore, MKK3 activity was specific to p38MAPK, as it did not phosphorylate ERK or JNK. To further investigate the functional relationship between MKK3 and p38MAPK in vivo, we studied the localization of phospho-MKK3 (pMKK3) and MKK3 by immunostaining. Consistent with the patterns of p38MAPK and phospho-p38MAPK (pp38MAPK), pMKK3 and MKK3 mainly localized to the antennules of the cyprids. Western blot analysis revealed that pMKK3 levels, like pp38MAPK levels, were elevated at cyprid stage, compared to nauplii and juvenile stages. Moreover, pMKK3 levels increased after treatment with adult barnacle crude extracts, suggesting that MKK3 might mediate the stimulatory effects of adult barnacle extracts on the p38MAPK pathway.

Functional polymer brushes via surface-initiated atom transfer radical graft polymerization for combating marine biofouling

Dense and uniform polymer brush coatings were developed to combat marine biofouling. Nonionic hydrophilic, nonionic hydrophobic, cationic, anionic and zwitterionic polymer brush coatings were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-hydroxyethyl methacrylate, 2,3,4,5,6-pentafluorostyrene, 2-(methacryloyloxy)ethyl trimethylammonium chloride, 4-styrenesulfonic acid sodium and N,N′-dimethyl-(methylmethacryloyl ethyl) ammonium propanesulfonate, respectively. The functionalized surfaces had different efficacies in preventing adsorption of bovine serum albumin (BSA), adhesion of the Gram-negative bacterium Pseudomonas sp. NCIMB 2021 and the Gram-positive Staphylococcus aureus, and settlement of cyprids of the barnacle Amphibalanus amphitrite (=Balanus amphitrite). The nonionic hydrophilic, anionic and zwitterionic polymer brushes resisted BSA adsorption during a 2 h exposure period. The nonionic hydrophilic, cationic and zwitterionic brushes exhibited resistance to bacterial fouling (24 h exposure) and cyprid settlement (24 and 48 h incubation). The hydrophobic brushes moderately reduced protein adsorption, and bacteria and cyprid settlement. The anionic brushes were least effective in preventing attachment of bacteria and barnacle cyprids. Thus, the best approach to combat biofouling involves a combination of nonionic hydrophilic and zwitterionic polymer brush coatings on material surfaces.

Heavy Metals Accumulation in the Barnacle Amphibalanus amphitrite from Alexandria, Mediterranean Sea

Heavy Metals Accumulation in the Barnacle Amphibalanus amphitrite from Alexandria, Mediterranean Sea

Metal toxicity, uptake and bioaccumulation in aquatic invertebrates—Modelling zinc in crustaceans

We use published data on the different patterns of the bioaccumulation of zinc by three crustaceans, the caridean decapod Palaemon elegans, the amphipod Orchestia gammarellus and the barnacle Amphibalanus amphitrite, to construct comparative biodynamic models of the bioaccumulation of zinc into metabolically available and detoxified components of accumulated zinc in each crustacean under both field and laboratory toxicity test conditions. We then link these bioaccumulation models to the onset of toxic effects on exposure of the crustaceans to high dissolved zinc bioavailabilities, using the tenets that toxicity effects are related to the total uptake rate of the toxic metal, and that toxicity is not usually dependent on the total accumulated metal concentration but always on the concentration of accumulated metal that is metabolically available. We dismiss the general concept that there is a critical accumulated body concentration of a metal in an invertebrate at which toxicity ensues, except under specific circumstances involving a rare lack of storage detoxification of accumulated metal. We thus propose a theoretical framework that can be extended to other metals and other aquatic invertebrates (indeed other animals) to explain the variation in the relationship between bioaccumulated body concentrations and toxicity, and subsequently to predict this relationship in many other species for which we have bioaccumulation modelling data.

Evaluation of the antifouling properties of 3-alyklpyridine compounds

One of the most promising alternative technologies to antifouling (AF) biocides based on toxic heavy metals lies in the development of natural eco-friendly biocides. The present study evaluates the AF potential of structurally different compounds containing a 3-alkylpyridine moiety. The products, namely poly 3-alkylpyridinium salts, saraine, and haminols, were either extracted or derived from natural sources (the sponges Haliclona sp. and Reniera sarai and the mollusc Haminoea fusari), or obtained by chemical synthesis. All the molecules tested showed generally good anti-settlement activity against larvae of the barnacle Amphibalanus (=Balanus) amphitrite (EC50 values between 0.19 and 3.61 μg ml−1) and low toxicity (LC50 values ranging from 2.04 to over 100 μg ml−1) with non-target organisms. For the first time, the AF potential of a synthetic monomeric 3-alkylpyridine was demonstrated, suggesting that chemical synthesis is as a realistic way to produce large amounts of these compounds for future research and development of environmentally-friendly AF biocides.

Reversible anti-settlement activity against Amphibalanus (=Balanus) amphitrite, Bugula neritina, and Hydroides elegans by a nontoxic pharmaceutical compound, mizolastine

Mizolastine, an antihistamine pharmaceutical, was found to significantly inhibit larval settlement of the barnacle Amphibalanus (=Balanus) amphitrite, the bryozoan Bugula neritina, and the polychaete Hydroides elegans with EC50 values of 4.2, 11.2, and 4.1 µg ml−1, respectively. No toxicity against the larvae of these three species was observed at the concentration range tested during incubations with mizolastine. To determine whether the anti-settlement activity of mizolastine is reversible, recovery bioassays using these three species were conducted. More than 70% of the larvae that had been exposed for 4 h to mizolastine at concentrations four-fold greater than their respective EC50 values completed normal metamorphosis. The results of the recovery bioassay provide evidence that the anti-settlement effect of mizolastine is reversible in addition to being nontoxic. The anti-settlement activities of several intermediates of the synthesis process of mizolastine were also examined. One of the intermediates, 2-chloro-1-(4-fluorobenzyl)-1H-benzo[d]imidazole, inhibited larval settlement and metamorphosis with low toxicity. These results may improve the understanding of the key functional group responsible for the anti-settlement activity of mizolastine.

Effects of ocean acidification over the life history of the barnacle Amphibalanus amphitrite

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 385:179-187 (2009) - DOI: https://doi.org/10.3354/meps08099 Effects of ocean acidification over the life history of the barnacle Amphibalanus amphitrite Michelle R. McDonald1, James B. McClintock1,*, Charles D. Amsler1, Dan Rittschof2, Robert A. Angus1, Beatriz Orihuela2, Kay Lutostanski2 1Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294-1170, USA 2Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516-9721, USA *Corresponding author. Email: mcclinto@uab.edu ABSTRACT: Increased levels of atmospheric CO2 are anticipated to cause decreased seawater pH. Despite the fact that calcified marine invertebrates are particularly susceptible to acidification, barnacles have received little attention. We examined larval condition, cyprid size, cyprid attachment and metamorphosis, juvenile to adult growth, shell calcium carbonate content, and shell resistance to dislodgement and penetration in the barnacle Amphibalanus amphitrite reared from nauplii in either ambient pH 8.2 seawater or under CO2-driven acidification of seawater down to a pH of 7.4. There were no effects of reduced pH on larval condition, cyprid size, cyprid attachment and metamorphosis, juvenile to adult growth, or egg production. Nonetheless, barnacles exposed to pH 7.4 seawater displayed a trend of larger basal shell diameters during growth, suggestive of compensatory calcification. Furthermore, greater force was required to cause shell breakage of adults raised at pH 7.4, indicating that the lower, active growth regions of the wall shells had become more heavily calcified. Ash contents (predominately calcium carbonate) of basal shell plates confirmed that increased calcification had occurred in shells of individuals reared at pH 7.4. Despite enhanced calcification, penetrometry revealed that the central shell wall plates required significantly less force to penetrate than those of individuals raised at pH 8.2. Thus, dissolution rapidly weakens wall shells as they grow. The ramifications of our observations at the population level are important, as barnacles with weakened wall shells are more vulnerable to predators. KEY WORDS: Ocean acidification · Barnacle · Life history · Larval ecology · Intertidal ecology · Calcification Full text in pdf format PreviousNextCite this article as: McDonald MR, McClintock JB, Amsler CD, Rittschof D, Angus RA, Orihuela B, Lutostanski K (2009) Effects of ocean acidification over the life history of the barnacle Amphibalanus amphitrite. Mar Ecol Prog Ser 385:179-187. https://doi.org/10.3354/meps08099Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 385. Online publication date: June 18, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Breeding biology of the barnacle Amphibalanus amphitrite (Crustacea: Cirripedia): influence of environmental factors in a tropical coast

Barnacles are the common fouling organisms encountered in coastal waters around the world. In the present study, breeding biology of the intertidal barnacle Amphibalanus amphitrite (=Balanus amphitrite) was studied for a period of two years (July 2003 to June 2005) in the Kudankulam coastal waters. Results showed that A. amphitrite breeds throughout the year in the study area. A high percentage of individuals with free nauplii in the mantle cavity was observed during March 2004 (47.6%) and May 2004 (41.7%). Barnacles with fertilized eggs in the ovary were high during November 2004 (56%), March 2005 (46.7%) and April 2005 (42.8%). Overall, a peak breeding activity was observed during the March–May period. The breeding activity showed a significant positive correlation with surface water temperature and phytoplankton abundance.

Involvement of reactive oxygen species in the electrochemical inhibition of barnacle (Amphibalanus amphitrite) settlement

The role of reactive oxygen species (ROS) in electrochemical biofouling inhibition was investigated using a series of abiotic tests and settlement experiments with larvae of the barnacle Amphibalanus amphitrite, a cosmopolitan fouler. Larval settlement, a measure of biofouling potential, was reduced from 43% ± 14% to 5% ± 6% upon the application of pulsed electric signals. The application of ROS scavengers such as glutathione and catalase counteracted the inhibitory effects of the electric signals, allowing settlement, and thus indicating that ROS are antifouling agents. Based on the experimental evidence, the proposed mechanism for ROS-based fouling prevention with interdigitated electrodes involved the electrochemical generation of hydrogen peroxide by oxygen reduction, and its likely reduction to hydroxyl radicals. Either hydroxyl radicals or products of hydroxyl radical reactions appeared to be the main deterrents of larval settlement.

Nanoscale structures and mechanics of barnacle cement

Polymerized barnacle glue was studied by atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and chemical staining. Nanoscale structures exhibiting rod-shaped, globular and irregularly-shaped morphologies were observed in the bulk cement of the barnacle Amphibalanus amphitrite (=Balanus amphitrite) by AFM. SEM coupled with energy dispersive X-ray (EDX) provided chemical composition information, making evident the organic nature of the rod-shaped nanoscale structures. FTIR spectroscopy gave signatures of β-sheet and random coil conformations. The mechanical properties of these nanoscale structures were also probed using force spectroscopy and indentation with AFM. Indentation data yielded higher elastic moduli for the rod-shaped structures when compared with the other structures in the bulk cement. Single molecule AFM force-extension curves on the matrix of the bulk cement often exhibited a periodic sawtooth-like profile, observed in both the extend and retract portions of the force curve. Rod-shaped structures stained with amyloid protein-selective dyes (Congo red and thioflavin-T) revealed that about 5% of the bulk cement were amyloids. A dominant 100 kDa cement protein was found to be mechanically agile, using repeating hydrophobic structures that apparently associate within the same protein or with neighbors, creating toughness on the 1–100 nm length scale.

Fluctuating asymmetry of Amphibalanus (Balanus) amphitrite (Cirripedia: Thoracica) in association with shore height and metal pollution

The level of fluctuating asymmetry (FA), which is defined as random deviations from perfect bilateral symmetry in the morphological traits of an organism, increases with increasing developmental instability, and it may be used as an indicator of environmental and/or genetic stresses. This study attempted to relate FA levels in the opercular plates of the barnacle Amphibalanus (Balanus) amphitrite with shore height and body trace metal concentrations. Barnacles were collected from both low and mid shores at six coastal locations with various degrees of marine pollution in Hong Kong. Four opercular traits, namely scutum length, tergum length, scutum width, tergum width were measured in the specimen while concentrations of five common trace metals (Cd, Cu, Cr, Mn and Zn) were determined in their body tissues using inductively coupled plasma-atomic emission spectrophotometry. Among the four traits, only tergum length and scutum width fulfilled the assumption of FA while their measurement errors were low. Across all sites, mid-shore A. amphitrite consistently exhibited a significantly higher FA level in scutum width than that in low-shore barnacles, but FA levels in tergum length were similar between the two shore heights. These results suggested that FA was trait-dependent, and mid-shore barnacles were possibly under high physical stress, such as desiccation and high temperature, leading to high developmental instability. Although no positive association was observed between FA and metal contamination in low-shore A. amphitrite, FA level in tergum length significantly increased with decreasing body concentration of manganese (Mn) in these barnacles. Such a negative relationship may be explained by the mechanism of bioaccumulation and physiological role of Mn in A. amphitrite with respect to the formation of barnacle shell plates.

Release characteristics of reattached barnacles to non-toxic silicone coatings

Release mechanisms of barnacles (Amphibalanus amphitrite or Balanus amphitrite) reattached to platinum-cured silicone coatings were studied as a function of coating thickness (210–770 μm), elastic modulus (0.08–1.3 MPa), and shear rate (2–22 µm s−1). It was found that the shear stress of the reattached, live barnacles necessary to remove from the silicone coatings was controlled by the combined term (E/t)0.5 of the elastic modulus (E) and thickness (t). As the ratio of the elastic modulus to coating thickness decreased, the barnacles were more readily removed from the silicone coatings, showing a similar release behavior to pseudobarnacles (epoxy glue). The barnacle mean shear stress ranged from 0.017 to 0.055 MPa whereas the pseudobarnacle mean shear stress ranged from 0.022 to 0.095 MPa.

Inhibition of barnacle (Amphibalanus amphitrite) cyprid settlement by means of localized, pulsed electric fields

The increasing needs for environmental friendly antifouling coatings have led to investigation of new alternatives for replacing copper and TBT-based paints. In this study, results are presented from larval settlement assays of the barnacle Amphibalanus (= Balanus) amphitrite on planar, interdigitated electrodes (IDE), having 8 or 25 μm of inter-electrode spacing, upon the application of pulsed electric fields (PEF). Using pulses of 100 ms in duration, 200 Hz in frequency and 10 V in pulse amplitude, barnacle settlement below 5% was observed, while similar IDE surfaces without pulse application had an average of 40% settlement. The spacing between the electrodes did not affect cyprid settlement. Assays with lower PEF amplitudes did not show significant settlement inhibition. On the basis of the settlement assays, the calculated minimum energy requirement to inhibit barnacle settlement is 2.8 W h m−2.

Sugar compound products of the periphytic diatom Navicula ramosissima induce larval settlement in the barnacle, Amphibalanus amphitrite

This study investigated the response of cyprids of the barnacle Amphibalanus amphitrite to 23 strains of laboratory cultured periphytic diatoms isolated from microbial biofilms that formed on glass slides immersed in Tachibana bay, Nagasaki, and those from mass-production tanks in the Fisheries Center of Nagasaki City, Japan. In addition, periphytic diatoms were subjected to various treatments, in order to investigate the nature of the chemical cue in periphytic diatoms. Cyprids of A. amphitrite responded differently to the 23 different periphytic diatom strains and settled in high percentages on Cocconeis sp. and Navicularamosissima strain A. On the other hand, nine strains of diatoms significantly inhibited settlement. The settlement inducing activity of N. ramosissima strain A increased linearly with diatom density, and its activity was enhanced by culturing the diatom under a bacteria-free condition, suggesting that specific diatom species, i.e., N. ramosissima strain A, may play an important role on larval settlement of the barnacle. Subjecting N. ramosissima strain A biofilm to hydrochloric acid (HCl) and ethanol (EtOH) treatments or heating it at 100°C did not inactivate the film, indicating that the settlement cue was a stable surface bound compound that did not decompose from the above treatments. Moreover, of the various lectins, enzymes, and drugs [H5IO6 and sodium dodecyl sulfate or (SDS)] used, only Lentil Agglutinin (LCA) treatment of N. ramosissima strain A biofilm resulted in the reduction its settlement inducing activity. A positive correlation was observed between the settlement inducing activity and the amount of LCA conjugated fluorescein isothiocyanate (FITC-LCA) of N. ramosissima strain A. On the other hand, subjecting biofilms of N. ramosissima strain B, an inactive strain, to various types of treatments resulted in the induction of A. amphitrite larval settlement but LCA treatment also reduced the activity of these treated N. ramosissima strain B biofilms. These findings suggest that a cue containing an LCA-binding sugar chain is present in both A and B strains of N. ramosissima but the large amount of mucous substance covering N. ramosissima strain B biofilm probably makes the sugar chain containing active subunit in strain B unavailable to A. amphitrite cyprids. In conclusion, periphytic diatoms such as N. ramosissima play an important role in larval settlement of the barnacle A. amphitrite. The cue in the diatom was an LCA-binding sugar chain(s) compound that may have similarities to the settlement inducing protein complex (SIPC) from adult shell of the barnacle.