Co-existence of two mytilids in a heterogeneous environment: mortality, growth and strength of shell and byssus attachment

14 páginas, 1 apéndice, 5 tablas, 7 figurasThe co-existence patterns of 2 mytilid species were studied in order to evaluate the performance of the alien mussel Xenostrobus securis and the indigenous Mytilus galloprovincialis through monospecific and mixed co-habiting experiments in the Ría de Vigo (northwest Spain). Mytilus galloprovincialis was found to be the best performer in all tests. Shell growth was ~4-fold greater for the indigenous mussel when deployed without interspecific competition and regardless of density. Differences in shell growth were found to be similar within mixed populations wherein M. galloprovincialis showed greater ability for upward migratory movements on the mixed beds and distanced itself from the mud influenced layer. The alien X. securis, however, was found to inhabit underneath the M. galloprovincialis layer, which resulted in higher mortality rates. Species-specific features such as byssus filaments and lifestyle may account for such different behaviour. M. galloprovincialis secreted thicker and stronger shells and byssus regardless of their density in both monospecific and mixed experiments. This might indicate that the indigenous mussel performs better when confronted with abiotic stress or biotic pressure. The alien X. securis is currently found to establish high-density patches of individuals at the confluence of main rivers that flow into the estuary (highly heterogeneous scenario). Such behaviour favours its settlement far from the native mussel influence area. X. securis also colonises hard substrates that are not-fully occupied by other invertebrates, but its range was found to be limited by the presence of the indigenous mussel.This study was funded by the project AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government).Peer reviewe

Variability of taurine concentrations in Mytilus galloprovincialis as a function of body size and specific tissue

7 páginas, 5 figurasVariability of taurine (2-aminoethane sulfonic acid) was studied as afunction of size in the mussel Mytilus galloprovincialis and tissue specificity. Isometric and/or allometric relationships were established with regard to total soft mass of the mussels between 20 and 60 mm shell length. Relative amounts of taurine dropped significantly with increasing mass of whole soft tissues with an allometric coefficient value of − 0.15. The inverse relationship between taurine and increasing size of mussels was confirmed for gill epithelium and labial palp (allometric coefficient values of − 0.16 and − 0.10, respectively), tissues that, in turn, represented isometric functions with regard to total soft mass. Although relative amounts of taurine were significantly different in digestive gland, mantle and foot, relationships with increasing size of mussels remained unchanged in these tissues. Gill area of mussels was related to soft mass with an allometric coefficient of 0.70 by 2D Image Analysis, but increased to 0.85 when introducing a third dimension, i.e. gill thickness. Results are discussed according to gill structure analysis and taurine functionality.This study was supported by the contract-project PROINSA, Code CSIC 2004448, Galicia PGDIT03RMA13E. JMFB acknowledges funding by the Program Ramón y Cajal 2003 from Ministry of Education and Science (Spain).Peer reviewe

Importance of phenotypic plastic traits on invasion success: Response of Xenostrobus securis to the predatory dogwhelk Nucella lapillus

14 páginas, 7 figuras, 3 tablasThe ability of the invasive mussel Xenostrobus securis to activate defence mechanisms in response to the novel predatory dogwhelk Nucella lapillus was explored using field- and laboratory-based approaches. The importance of the origin of mussels was investigated in relation to different environmental conditions and levels of predation pressure (high and low). In the field, the responses of mussels were clearly asymmetrical: only individuals caged with dogwhelks at the site of high predation risk underwent phenotypical changes (stronger attachment, thicker shells and heavier adductor muscle). In contrast, shell growth was faster in mussels held in cages without dogwhelks at the high predation-risk site, suggesting trade-off patterns between growth and other energy-demanding actions. Nevertheless, X. securis activated inducible morphological defences without any detrimental effect on soft tissue growth (i.e. condition index). In the laboratory, the role of temperature on phenotypic responses of mussels exposed to dogwhelk was also evaluated. Mussels originally from the site of low predation risk showed a weaker response to the predator N. lapillus, probably because of difficulties in correctly identifying predator cues. At higher temperatures, mussels secreted stronger byssal threads regardless of their origin, while condition was poorer, shells thinner and gametogenesis activated more rapidly, particularly in the presence of dogwhelks. In summary, X. securis appears to be highly capable of activating protective mechanisms in marine environments within its geographical range of expansion through improved fitnessThis study was funded by the Spanish government through the Ministerio de Ciencia e Innovación (project AGL2010-16464) and the Autonomic government Xunta de Galicia-FEDER (project GRC2013-004)Peer reviewe

Free amino acid composition in juveniles of Mytilus galloprovincialis: spatial variability after Prestige oil spill

10 páginas, 5 figuras, 2 tablasComposition of free amino acids (FAA) in juveniles of Mytilus galloprovincialis was analysed along a large geographical coastline area in Galicia (NW Spain). Individuals were sampled in February 2003, three months after the Prestige oil spill. Pollution values at sampling time were reported as polycyclic aromatic hydrocarbons (PAHs) concentrations in soft tissues of individuals and varied between the highest amount observed in Carrumeiro mussels (502 ng/g dw) and the lowest in Pindo mussels (196 ng/g dw), both locations being close to each other in the centre of the geographical area under study. Pollution values in the other populations varied within the range of 241–347 ng/g dw. Total free amino acids (TFAA) were highest in Aguiño–Pindo–Carrumeiro juveniles at the centre of the Coastline area studied (420–462 μmol/g dw) as compared to the other populations at North and South of Galicia (312–347 μmol/g dw). TFAA results were based on the variability observed in protein free amino acids (PFAA μmol/g dw) among populations (214–249 μmol/g dw for Aguiño–Pindo–Carrumeiro mussels and 98–149 μmol/g dw for the other populations) whereas non-protein free amino acids (NPFAA) taurine and ornithine did not show any significant spatial pattern of variation. Glycine and alanine represented the most abundant PFAA (16–29% and 2.7–11.9% of TPFAA, respectively) and significant correlations between PFAA and both the protein content of soft tissues (r=−0.82) and the condition index of juveniles (r=0.86) were observed. No significant relationships were detected, however, between pollution values in soft tissues as PAHs and FAA profiles with the exception of alanine concentrations as percentage of TFAA (r=0.88; P<0.01). The latter seemed to be an “all or nothing” effect likely due to the influence of other abiotic factors at one of the sampling sites. Such relationship was found not significant when the outlier represented by Carrumeiro mussels was removed from the analysis. The most abundant free amino acid taurine (43.2–68.5%TFAA) followed an inverse variability of that of glycine and by extension of the group PFAA most likely as a compensatory decrease in mussel populations with low protein content (and high condition index). Accordingly, taurine:glycine (t:g) ratio varied between 1 and 2 in most mussel populations but increased up to 3.2–4.2 in Miranda and Bueu mussels at both ends of the geographical interval studied with a corresponding PAHs concentrations of 261 and 304 ng/g dw, respectively. These mussel populations with the highest t:g ratios were characterised by the lowest PFAA contents (below 40%) and condition index values (below 10%). Results of the present study established a significant link between energetic status of growing juveniles and FAA concentrations in environments with different pollution degrees. Variability of the free amino acids profiles in soft tissues were related to endogenous factors of juveniles (protein content, condition index) whereas no relationship with contamination values could be observed. The utility of t:g ratio as general condition factor for M. galloprovincialis is also corroborated for in situ growing juveniles.This study was supported by the contract-project PROINSA, Code CSIC 2004448, Galicia PGDIT03RMA13E. JMFB acknowledges funding by the Program Ramón y Cajal 2003 from Ministry of Education and Sciences (Spain).Peer reviewe

Sediment mobilization and seawater warming affect ecophysiology of the clam polititapes rhomboides

Poster.-- Poster.-- VIII International Symposium on Marine Science, Las Palmas de Gran Canaria, 6-8 July 2022High-energy hydrodynamic events associated to currents and waves may disturb bivalve mollusks´ ecophysiology, especially those buried in the the sea bed due to sediment mobilization. Evidences of massive mortality for the clam Polititapes rhomboides (banded carpet shell clam) in Galicia (NW Spain) have been associated to warm water temperatures and high wave magnitudes above climatic averages and the presence of rickettsias (intracellular prokaryotic colonies) in gills (Villalba et al. 1999; Darriba et al. 2019; Villacieros-Robineau et al. 2021)Project PID2019-106008RB-C21 financed by MCIN/AEI/10.13039/501100011033N

The killer within: Endogenous bacteria accelerate oyster mortality during sustained anoxia

16 pages, 5 figures, 2 tablesSustained periods of anoxia, driven by eutrophication, threaten coastal marine systems and can lead to mass mortalities of even resilient animals such as bivalves. While mortality rates under anoxia are well-studied, the specific mechanism(s) of mortality are less clear. We used a suite of complementary techniques (LT50, histology, 16S rRNA amplicon sequencing, and valvometry) to show that the proliferation of anaerobic bacteria within eastern oysters (Crassostrea virginica) accelerates mortality rate under anoxic conditions. Manipulative laboratory experiments revealed that oyster survival under anoxic conditions was halved when bacteria were present compared to when they were excluded by the broad-spectrum antibiotic chloramphenicol. Histological assessments supported this mechanism and showed infiltration of bacteria in oysters that were not treated with antibiotics compared to a general lack of bacteria when oysters were treated with antibiotics. 16S rRNA amplicon sequencing failed to identify any particular genera of bacteria responsible for mortality, rather a diversity of endogenous anaerobic and/or sulfate-reducing bacteria were common among oysters. In addition, monitoring of oyster valve gaping behavior in the field revealed that oysters showed remarkable valve closure synchrony when first exposed to anoxia. However, oysters periodically opened throughout anoxia/hypoxia in both the lab and field, suggesting that the infiltration of exogenous bacteria from the environment may also influence mortality rates under natural settings. Coupled with previous studies, we posit that mass mortality events in a wide range of coastal bivalves are likely the result of co-morbidity from asphyxiation and bacterial processesThis study was funded by L'Étang Ruisseau Bar Ltd. in partnership with the Department of Fisheries and Oceans of Canada (Aquaculture Collaborative Research and Development Program, project 17-G-02 led by M.R.S.C.), a NSERC Discovery Grant to R.F. (RGPIN-2017-04294), and a Total Development Fund from the New Brunswick Department of Agriculture, Aquaculture and Fisheries to R.F.Peer reviewe

Byssus secrection of Mytilus galloprovincialis: Effect of site at macro and micro-geographical scales within Ría of Vigo (NW Spain)

The effect of the abiotic environment on byssus tenacity and associated features was investigated for Mytilus galloprovincialis in the Ría de Vigo (NW Spain). The effect of site was examined at macro-geographical (outer exposed Cabo Estay vs. inner sheltered San Simón Ensenada sites) and micro-geographical (intertidal vs. subtidal locations) scales. Site significantly influenced byssus tenacity, shape and byssus thread diameter, whereas location did not. Qualitative analysis of the byssus corroborated the importance of site; mussels inhabiting the rougher outer Ría secreted stronger and stiffer threads regardless of location and had a higher potential to form cross-links or metal chelation in the byssal collagen to gain structural integrity when needed. When mussels were transplanted between exposed and sheltered sites, asymmetrical changes were observed in tenacity, endogenous indices, byssus morphology and mechanical properties after 3 mo. Individuals transferred from the sheltered to the exposed site shifted all variables, suggesting that mussels have a plastic response to rougher environments by increasing byssus size and mechanical integrity. In contrast, mussels transplanted from the exposed to the sheltered site shifted tenacity, endogenous indices and thread length but not thread diameter nor mechanical properties. In summary, we report the highly dynamic nature of the mussel ability to modify byssus tenacity when subjected to abrupt environmental changes. Mussels have the potential to change byssus diameter and mechanical properties to increase strength in stressful abiotic conditions, and can re-allocate energy for vital structures such as gonadal and soft tissue growth in more benign environmentsThis study was partly funded by “National Science Foundation EF1041213 to E. 600 Carrington. JMF Babarro acknowledges the funding of the projects AGL2006-06986/ACU and 601 AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government). 602 603Peer reviewe

Attachment strength of the mussel Mytilus galloprovincialis: effect of habitat and body size

9 páginas, 6 figuras, 4 tablasMarine organisms adapt to a wide variety of environments, often altering their morphology and behavior in response to local habitat. This study addressed the effects of habitat (wave exposure) and body size on the morphology and byssal attachment of mussels within the same estuary. Tenacity of the mussel Mytilus galloprovincialis was higher at the exposed site, particularly for the smaller size classes. This was largely due to differences in thread thickness; mussels from the exposed site produced thicker and stronger byssal threads. For a given shell length, exposed mussels also produced thicker and smaller shells and had lower gonadal condition. In laboratory flume experiments, both thread production and mechanical performance (strength and extensibility) decreased with increased flow, suggesting that flow alone does not explain tenacity differences between sites. Altogether, these analyses suggest that mussels at exposed sites allocate resources to reduce risk of dislodgment (smaller and thicker shell, stronger byssal threads) instead of growth and reproduction, and these allocation differences between sites are less apparent in larger size classes. The lack of the largest size class (8 cm) at the exposed site may reflect an upper limit to size imposed by wave induced mortality, where attachment strength does not keep pace with hydrodynamic loading.MF Babarro acknowledges the funding of the projects AGL2006-06986/ACU and AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government).Peer reviewe

Narrow valve gaping in the invasive mussel Limnoperna securis: implications for competition with the indigenous mussel Mytilus galloprovincialis in NW Spain

13 páginas, 3 figuras, 1 tablaThe black pygmy mussel Limnoperna securis (Lamarck 1819) is endemic to the brackish waters of New Zealand and Australia, but over the past decade, it has successfully invaded the inner Galician Rias of NW Spain. There is growing concern that L. securis will expand its range to the outer zones of the Rias, where it would pose a threat to the intensive raft culture of the indigenous mussel Mytilus galloprovincialis (Lamarck 1819). In this paper, we compare the valve-opening behaviour of the two mytilids under simulated raft conditions, i.e. full-strength seawater (35 g l−1) and a low current flow regime (2–5 cm s−1). Modes of valve-opening amplitudes that were most frequently observed in both species were in the range of 60–90 %, indicating a tendency towards full valve openness. Both species displayed circadian periodicity (τ = 24 h): maximal gaping was generally observed during periods of darkness and minimum gaping during daylight hours. The only prominent difference in behaviour between the two species was related to the degree of valve opening. The maximum recorded gape angle was 8.2° (SE = 0.9) for L. securis versus 14.8° (SE = 1.4) for M. galloprovincialis. This difference may place L. securis at a competitive disadvantage on substrates, where the two species coexist, such as over rocky shores or potentially mussel culture ropesThis study was funded by the project AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government).Peer reviewe

Byssus attachment strength of two mytilids in mono-specific and mixed-species mussel beds

Póster presentado en el ICES Anuual Science Conference, A Coruña, Spain, 15-19 September 2014There is a growing interest to understand co-existence processes between marine species in the bio-invasion scenario. Xenostrobus securis is a small mussel endemic to the brackish waters of New Zealand and Australia and has been listed among the “100 Worst Invasive Species”. The mussel Mytilus galloprovincialis is successfully cultivated in Galician Rías. Mussel byssus secretion and its functional strength when subjected to distinct substrate and salinity values were evaluated as the basis to understand dominance patterns within mixed-species beds.This study was funded by the project AGL2010-16464 (Ministerio de Ciencia e Innovación, Spanish Government).Peer reviewe