Utilization of muddy detritus as organic matter source by the fan mussel Pinna nobilis.

The knowledge of the feeding habits in marine species is fundamental to better understand their relationship with the environment. Although phytoplankton has been traditionally reported as the main food source consumed by the Mediterranean fan mussel Pinna nobilis, recent studies have revealed that detritus represents an important food source for this species. We analysed the degree of acceptance of muddy detritus and the utilisation of its organic matter (OM) by P. nobilis on a group of 21 individuals (30.3-59.7 cm of total shell height (Ht)). The specimens were collected between July and September 2012 in two areas (43°04´25” N; 5°46´7” E and 43°04´34” N; 5°47´32” E) of the Embiez archipelago, northwestern Mediterranean (France). Our studies show that P. nobilis retains high quantities of OM from muddy detritus (47.50 ± 11.23% of filtered OM) irrespectively of shell size. Smaller individuals, however, actively filter more detritus than large ones. The values of retained OM, together with previous studies on stomach contents, suggest that muddy detritus is a more important OM source than phytoplankton for this species

Scope for growth and dietary needs of Mediteranean Pinnids maintained in captivity

Abstract Background: The measurement of the energy available for growth (scope of growth, SFG) can be used in bivalves to make a long-term prediction in a short-term experiment of the condition of the individual. In order to tackle the best conditions for captive maintenance of Mediterranean Pinnids, a SFG study was conducted using Pinna rudis as a model species. Three diets were examined to test the viability of live microalgae and commercial products: i) a control diet using 100% of live microalgae based on the species Isochrysis galbana (t-ISO), ii) a 100% of commercial microalgae diet based on the product Shellfish Diet 1800®, and iii) a 50/50% mix diet of I. galbana (t-ISO) and Shellfish Diet 1800®. Results: SFG results showed significant differences among diets in the physiological functions measured and suggested lower acceptability and digestibility of the commercial product. Negative SFG values were obtained for the commercial diet which indicates that it should be rejected for both Pinnid maintenance. The mixed diet showed improved physiological performance compared to the commercial diet, resulting in a higher SFG that had no significant differences with the control diet. However, in the long-term, the lower digestibility of the mixed diet compared to the control diet could lead to a deterioration of individuals’ conditions and should be considered cautiously. Conclusions: This work represents the first case study of SFG in Pinna spp. and provides fundamental data on dietary needs for the critically endangered species, P. nobilis.En prens

In situ biomonitoring shows seasonal patterns and environmentally mediated gaping activity in the bivalve, Pinna nobilis

The rhythms and responses of animals to environmental factors are important issues for their adaptation to natural cycles. These rhythms assure an optimum synchrony between organisms and their environment. Bio-logging enables monitoring these activity cycles remotely. To characterize rhythms and responses of fan mussels (Pinna nobilis) to environmental factors, six individuals were monitored from April 2009 to October 2011. The study was conducted at a station in the western Mediterranean at 11 m depth in Tabarca Island Marine Reserve (Alicante, Spain). Sensors at the station monitored dissolved oxygen (mg l−1), turbidity (ntu), temperature (°C), chlorophyll a concentration (chl a) (mg m−3), current speed (cm s−1), and direction (°). One pattern of gaping activity (P1) occurred from mid-July–early August–early November, whereas another pattern (P2) occurred the rest of the time (i.e., from early November–mid-July–early August). The activity was synchronized among the fan mussels and showed autocorrelation peaks at a period of 21.9–24 h. In P1, the fan mussels opened their valves according to the position and illumination of the sun and moon. In P2, however, individuals did not track sun and moonlight, although their gaping activity was regular and synchronized. Likewise, individuals were unaffected by high-frequency (daily) variation in dissolved oxygen and (chl a). Gaping activity was directly influenced by current intensity and direction. The shift between the two patterns and the presence of similar periods of autocorrelation in the activity time series indicate that P. nobilis has an internal clock

Wide-Geographic and Long-Term Analysis of the Role of Pathogens in the Decline of Pinna nobilis to Critically Endangered Species

A mass mortality event (MME) affecting the fan mussel Pinna nobilis was first detected in Spain in autumn 2016 and spread north- and eastward through the Mediterranean Sea. Various pathogens have been blamed for contributing to the MME, with emphasis in Haplosporidium pinnae, Mycobacterium sp. and Vibrio spp. In this study, samples from 762 fan mussels (necropsies from 263 individuals, mantle biopsies from 499) of various health conditions, with wide geographic and age range, taken before and during the MME spread from various environments along Mediterranean Sea, were used to assess the role of pathogens in the MME. The number of samples processed by both histological and molecular methods was 83. The most important factor playing a main role on the onset of the mass mortality of P. nobilis throughout the Mediterranean Sea was the infection by H. pinnae. It was the only non-detected pathogen before the MME while, during MME spreading, its prevalence was higher in sick and dead individuals than in asymptomatic ones, in MME-affected areas than in non-affected sites, and it was not associated with host size, infecting both juveniles and adults. Conversely, infection with mycobacteria was independent from the period (before or during MME), from the affection of the area by MME and from the host health condition, and it was associated with host size. Gram (-) bacteria neither appeared associated with MME.En prens

Suspended culture of Pinna rudis enhances survival and allows the development of a seasonal growth model for Mediterranean Pinnids

A two-year growth study of 80 Pinna rudis individuals was conducted in offshore cages in the western Mediterranean Sea. A Von Bertalanffy growth model was fitted to monthly measured data of 40 individuals (Group 1), whereas length-dry weight relationship was established with the other 40 individuals (Group 2). Oceanographic data were sampled bimonthly. The individuals showed the fastest growth reported for a bivalve (1.32 mm day−1). Temperature acted as the main factor controlling growth, which showed strong seasonality, but phytoplankton availability acted as a limiting factor during the warmest periods of year. These data will be useful to understand P. rudis ecology. Furthermore, the length-dry weight regression is proposed as a tool for captivity diet confection of the critically endangered species P. nobilis. Natural mortality was 0% during the study period.info:eu-repo/semantics/acceptedVersio

Age and growth of the endangered fan mussel Pinna nobilis in the western Mediterranean Sea

International audienceThe present work, which is the first comparative study of the growth of the fan mussel Pinna nobilis in the western Mediterranean, encompasses 12 populations of this species living in different environments in France and Spain. Two hundred nine shells were processed and used to obtain growth records from the posterior adductor muscle scar. Size-at-age data were fitted to the Von Bertalanffy growth model. Considerable variability in growth parameters and age was detected among the populations. The results show that the only two fan mussel populations remaining in Spain, which live in an estuary and a coastal lagoon, occupy habitats that are optimal for fast growth, but individuals show low longevity, complicating the long-term conservation of the species. Multivariate analyses groups the populations into three groups (SO, EO and LG), and a general model is proposed for each group; the model can be used as an approximation to calculate the ages of individuals living in similar environments

Scope for growth and dietary needs of Mediteranean Pinnids maintained in captivity

Background The measurement of the energy available for growth (scope of growth, SFG) can be used in bivalves to make a long-term prediction in a short-term experiment of the condition of the individual. In order to tackle the best conditions for captive maintenance of Mediterranean Pinnids, a SFG study was conducted using Pinna rudis as a model species. Three diets were examined to test the viability of live microalgae and commercial products: i) a control diet using 100% of live microalgae based on the species Isochrysis galbana (t-ISO), ii) a 100% of commercial microalgae diet based on the product Shellfish Diet 1800®, and iii) a 50/50% mix diet of I. galbana (t-ISO) and Shellfish Diet 1800®. Results SFG results showed significant differences among diets in the physiological functions measured and suggested lower acceptability and digestibility of the commercial product. Negative SFG values were obtained for the commercial diet which indicates that it should be rejected for both Pinnid maintenance. The mixed diet showed improved physiological performance compared to the commercial diet, resulting in a higher SFG that had no significant differences with the control diet. However, in the long-term, the lower digestibility of the mixed diet compared to the control diet could lead to a deterioration of individuals’ conditions and should be considered cautiously. Conclusions This work represents the first case study of SFG in Pinna spp. and provides fundamental data on dietary needs for the critically endangered species, P. nobilis.info:eu-repo/semantics/publishedVersio

MONITORING THE MARINE RESERVE OF FISHING INTEREST OF SERRA D\u2019IRTA (SPAIN) USING MARINE MACROPHYTES

Serra d'Irta (Castell\uf3n, Spain) was declared marine reserve of fishing interest (MRFI) in 2003 with the objective of favouring the regeneration of marine resources. This work presents the results obtained in the monitoring studies carried out in this reserve during summer 2017 using different marine macrophytes indexes. The aim of this study was to evaluate the ecological status of the macrophytes as a biological quality element, as a proxy of the water quality of the marine reserve in the contex of the Water Framework Directive (WFD) and to detect anthropogenic pressures. Two species of seagrasses, Posidonia oceanica and Cymodocea nodosa are found in the reserve. To estimate their conservation status, 9 localities were sampled and structural and morphological descriptors were analized. After a multifactorial analysis, results showed that the two localities studied with Posidonia oceanica meadows showed a good ecological status (EQR>0,55). In the case of Cymodocea nodosa only 4 of the 7 localities sampled presented living plants probably as a result of intense storms ocorred in autumn 2016 that altered sedementary bottoms of areas below 10m. The ecological status for the localities with meadows was moderate (EQR>0,41) except for one of them that was good (EQR>0,61). Environmental quality of the marine reserve waters was also estimated using macroalgal littoral community by means of the application of the CARLIT index. Two sectors were distinguished in the reserve costal: a North Sector dominated by Corallina elongata and other opportunistic species favoured by the nutrients provided by freshwater upwellings and limited by the coastal nature of the cliff; and a South Sector dominated by Laurencia spp. that proliferates through all the extensive coastal platforms battered by waves and sprinkled by fronds of Cystoseira spp. indicating a very good water quality. The EQR obtained for the entire extension analized (86,4% of the total coast) was of 0,769 indicating a very good ecological status for the studied area

Recruitment and Growth of the Fan Mussel Pinna nobilis in the Montenegrin Adriatic Coast and Comparison with the Western Mediterranean

In this study, the comparative results of the fan mussel Pinna nobilis larvae collection during 3 years (2016–2019) on the sites of the Montenegrin Adriatic coast and the Western Mediterranean, France are presented. In both countries, growth studies of collected fan mussel juveniles were carried out as well. After 1 year growth measurement of P. nobilis recruits in their natural habitat on the site Dobrota, Montenegro, mean shell length was 198.58 ± 17.77 mm for the recruits from Sv. Nedjelja and 206.73 ± 16.40 mm for the recruits collected from Ljuta. The growth study carried out in a laboratory tank in France indicated that the mean shell length of P. nobilis recruits after a 9 month period was 100.50 ± 7.59 mm for the recruits from Bomasse, 96.33 ± 11.06 mm from Basse Renette 1, and 95.75 ± 8.45 mm for recruits from Basse Renette 2, respectively. In spite of much larger mean shell lengths obtained in Montenegro, mean monthly growth rate of P. nobilis recruits bred in France was higher due to more stable conditions and access to food within the tank in contrast to variations of environmental parameters in their natural habitat. We have presented first data on P. nobilis recruitment and growth in Montenegro and showed higher growth rate in comparison with the other sites in the Adriatic Sea and Mediterranean. It was shown that the temperature is of high importance for the growth rate of P. nobilis juveniles in their natural habitat due to lower growth during winter. Anthropogenic pressure was the main obstacle for development of P. nobilis populations during the study period, while biological pollution as the main threat for P. nobilis survival will be the subject of further studies in the Montenegrin Adriatic coast