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The Mar Menor is a hypersaline coastal lagoon representing one of the most iconic natural areas in Southeastern Spain. However, it has suffered several catastrophic environmental events causing an exceptional eutrophication status. A study was performed to assess the recruitment of oysters in the Mar Menor, determine their taxonomic allocation and evaluate functionality in filtration and growth A total of 45 spat collectors were installed in June 2020 and posteriorly retrieved in October 2020. In total, 3431 oyster recruits were counted. Two species of oyster Ostrea edulis and O. stentina, inhabit the Mar Menor, but they are indistinguishable at the morphological level when they are small. Thus, a genetic tool was developed to identify both species. From a total of 90 oyster recruits, 95% of them corresponded to O. stentina. Finally, growth rate and clearance measurements were conducted on 661 oysters over 6 months under laboratory conditions to explore their possible use in the bioremediation of the lagoon.

[EN] Syngnathid fishes (Actinopterygii, Syngnathidae), including seahorses and pipefishes, are flagship vulnerable species highly associated with seaweed and seagrass habitats. Our multidisciplinary study provides the first insights for syngnathid populations in Atlantic Islands of Galicia (Cíes Archipelago, Atlantic Ocean) and Cabrera Archipelago (Mediterranean Sea) Spanish National Parks. Syngnathid fishes were collected on several sites in the first year of the study, and habitat characteristics were also determined. From the results achieved, a further two-years monitoring was performed seasonally in selected sites. The fishes were analyzed for size, weight, sex and sexual maturity, stable isotope signatures and genetics. Epifauna and gut contents were also analyzed for further dietary assessment of syngnathids. Diversity and abundances were generally low, with four species (including seahorses) identified in the Atlantic Islands of Galicia National Park and five (only pipefishes) at Cabrera National Park. Syngnathids from both national parks differed in size, isotopic values and prey regime. Syngnathids preferred less exposed sites in macroalgal assemblages (Atlantic) or Cymodocea meadows (Mediterranean). Population characteristics in the Atlantic Islands of Galicia National Park suggests that syngnathids mainly comprise breeders that migrate seasonally, with preference for less exposed sites on shallow complex rocky-sandy substrates covered by macroalgae. Prey preferences would rely mainly on the consumption of copepods and gammarids. In the Mediterranean, syngnathids were likely limited by the depth of the studied sites, showing preference for Cymodocea meadows over Posidonia, and for the capture of a wider range of prey compared to the Atlantic populations. Borrón (Atlantic) and Es Burri (Mediterranean) would be preferential sites to undertake conservations plans for syngnathids. Several research topics are suggested for further management of syngnathids pop, [ES] Los signátidos (Actinopterygii, Syngnathidae) son una familia de peces que incluye caballitos de mar y peces pipa. Se trata de especies vulnerables estrechamente asociadas a las comunidades vegetales. Este estudio multidisciplinar en signátidos es el primero realizado en los Parques Nacionales Marítimo-Terrestres de las Islas Atlánticas de Galicia (Archipiélago de Cíes, Atlántico) y del Archipiélago de Cabrera (Mediterráneo). En el primer año de estudio, se estudiaron los signátidos en diversas zonas de ambos parques nacionales, así como las características de sus hábitats. Los resultados alcanzados permitieron establecer zonas preferentes para la realización de un estudio bianual posterior. En los peces capturados se determinaron las siguientes características: talla, peso, sexo y madurez sexual, isótopos estables y características genéticas. También se analizó la epifauna y los contenidos digestivos para determinar preferencias alimentarias. La diversidad y las abundancias fueron reducidas, con cuatro y cinco especies identificadas en el Atlántico y Mediterráneo, respectivamente, con presencia de caballitos de mar solo en la vertiente atlántica. Se observaron diferencias importantes en los signátidos de ambas zonas en lo relacionado con talla, valores isotópicos y preferencias alimentarias, Los signátidos atlánticos mostraron preferencia por zonas someras menos expuestas en hábitats macroalgales complejos arenoso-rocosos, con preferencia por el consumo de gammáridos y copépodos. Las especies del mediterráneo estuvieron mejor representadas en praderas de Cymodocea comparado con las de Posidonia, con una mayor variedad de fuentes alimenticias que en el atlántico, dependiendo de la especie. Las zonas de mayor interés, de cara a futuros planes de conservación, fueron Borrón (Atlántico) y Es Burri (Mediterráneo). Se proponen diversas actuaciones para el estudio futuro de las poblaciones estudiadas

[EN] This project addressed a genetic evaluation of syngnathid fish (seahorses and pipefish) in the Maritime and Terrestrial National Parks of the Atlantic Islands of Galicia (Cíes Islands) and the Cabrera Archipelago, as well as their respective adjacent unprotected areas (Ría de Vigo and Majorca Island), using mitochondrial and microsatellite markers. The genetic analysis between 2016 and 2018 identified a diversity of species distributed differentially in the National Parks and adjacent areas, with limited presence of seahorses (Hippocampus guttulatus) and predominance of pipefish (Syngnathus acus, S. abaster, S. typhle, Entelurus aequoreus, Nerophis lumbriciformis, N. maculatus and N. ophidion). ntegrative genetic and morphological data allowed clarifying in situ identification difficulties between some species and detecting a cryptic differentiated lineage of S. abaster in Cabrera Islands with respect to more eastern Mediterranean populations of this species. The levels of population genetic diversity and structure were evaluated within each species, providing useful information to trace individuals, and as a basis for delineating management units. For preferential species in each National Park, signs of population genetic stability were detected on a temporal scale and gene flow with adjacent areas, but significant differentiation between Atlantic and Mediterranean populations of the species analyzed in both slopes. Parental assignment analysis of pipefish progenies in the Cíes Islands and their adjacent area demonstrated multiple maternity events, compatible with a preferential polygamous genetic mating system in these populations. This study provides useful reference genetic data for future monitoring and conservation of syngnathid populations in marine protected areas, as reservoirs of valuable associated ecosystems and habitats, [ES] Este proyecto abordó la caracterizaron genética de peces signátidos (caballitos de mar y peces pipa) en los Parques Nacionales Marítimo-Terrestres de las Islas Atlánticas de Galicia (Islas Cíes) y Archipiélago de Cabrera, así como en sus respectivas áreas adyacentes no protegidas (Ría de Vigo e Isla de Mallorca), mediante marcadores mitocondriales y microsatélite. El análisis genético entre 2016 y 2018 permitió identificar una diversidad de especies distribuidas diferencialmente en los Parques Nacionales y áreas adyacentes, con presencia muy limitada de caballitos de mar (Hippocampus guttulatus) y preferente de peces pipa (Syngnathus acus, S. abaster, S. typhle, Entelurus aequoreus, Nerophis lumbriciformis, N. maculatus y N. ophidion). La integración de datos genéticos y morfológicos permitió clarificar dificultades de identificación in situ entre algunas especies, así como detectar un linaje críptico diferenciado de S. abaster en el Archipiélago de Cabrera respecto a poblaciones mediterráneas más orientales de esta especie. Para cada especie, se evaluaron los niveles de diversidad y estructura genética poblacional, aportando información útil para la trazabilidad individual y como base para delinear unidades de gestión. En las especies con distribución preferente en cada Parque Nacional se detectaron signos de estabilidad genética poblacional a escala temporal y flujo génico con áreas adyacentes, pero diferenciación significativa entre poblaciones atlánticas y mediterráneas de las especies analizadas en ambas vertientes. El análisis de asignación parental de progenies de peces pipa en las Islas Cíes y su área adyacente demostró eventos de maternidad múltiple, compatible con un sistema de apareamiento genético polígamo preferente en estas poblaciones. Este estudio aporta datos genéticos de referencia útiles para el futuro seguimiento y conservación de las poblaciones de signátidos presentes en áreas marinas protegidas, como reservorios de ecosistemas y hábitats

Enteromyxoses are relevant diseases for turbot and gilthead sea bream aquaculture. The myxozoan parasites invade the intestinal mucosa, causing a cachectic syndrome associated with intestinal barrier alteration; nonetheless, their pathological impact is different. Turbot infected by Enteromyxum scophthalmi develop more severe intestinal lesions, reaching mortality rates of 100%, whereas in E. leei‐infected gilthead sea bream, the disease progresses slowly, and mortality rates are lower. The mechanisms underlying the different pathogenesis are still unclear. We studied the distribution and expression changes of E‐cadherin, a highly conserved protein of the adherens junctions, in the intestine of both species by immunohistochemistry and quantitative PCR, using the same immunohistochemical protocol and common primers. The regular immunostaining pattern observed in control fish turned into markedly irregular in parasitized turbot, showing an intense immunoreaction at the host–parasite interface. Nevertheless, E‐cadherin gene expression was not significantly modulated in this species. On the contrary, no evident changes in the protein distribution were noticed in gilthead sea bream, whereas a significant gene downregulation occurred in advanced infection. The results contribute to the understanding of the different host–parasite interactions in enteromyxoses. Host and parasite cells appear to establish diverse relationships in these species, which could underlie the different pathological picture.