The Mediterranean benthic herbivores show diverse responses to extreme storm disturbances

Catastrophic storms have been observed to be one of the major elements in shaping the standing structure of marine benthic ecosystems. Yet, little is known about the effect of catastrophic storms on ecosystem processes. Specifically, herbivory is the main control mechanism of macrophyte communities in the Mediterranean, with two main key herbivores: the sea urchin Paracentrotus lividus and the fish Sarpa salpa. Consequently, the effects of extreme storm events on these two herbivores (at the population level and on their behaviour) may be critical for the functioning of the ecosystem. With the aim of filling this gap, we took advantage of two parallel studies that were conducted before, during and after an unexpected catastrophic storm event. Specifically, fish and sea urchin abundance were assessed before and after the storm in monitored fixed areas (one site for sea urchin assessment and 3 sites for fish visual transects). Additionally, we investigated the behavioural response to the disturbance of S. salpa fishes that had been tagged with acoustic transmitters. Given their low mobility, sea urchins were severely affected by the storm (ca. 50% losses) with higher losses in those patches with a higher density of sea urchins. This may be due to a limited availability of refuges within each patch. In contrast, fish abundance was not affected, as fish were able to move to protected areas (i.e. deeper) as a result of the high mobility of this species. Our results highlight that catastrophic storms differentially affect the two dominant macroherbivores of rocky macroalgal and seagrass systems due to differences in mobility and escaping strategies. This study emphasises that under catastrophic disturbances, the presence of different responses among the key herbivores of the system may be critical for the maintenance of the herbivory function.

High-throughput sequence analysis of turbot (Scophthalmus maximus) transcriptome using 454-pyrosequencing for the discovery of antiviral immune genes

Turbot (Scophthalmus maximus L.) is an important aquacultural resource both in Europe and Asia. However, there is little information on gene sequences available in public databases. Currently, one of the main problems affecting the culture of this flatfish is mortality due to several pathogens, especially viral diseases which are not treatable. In order to identify new genes involved in immune defense, we conducted 454-pyrosequencing of the turbot transcriptome after different immune stimulations.

Response of hexokinase enzymes and the insulin system to dietary carbohydrates in the common carp, Cyprinus carpio.

The response of the common carp to diets with varying amounts of digestible starch, provided either as pea meal (LP, HP, 30 and 46% peas, respectively) or as cereal (LW, HW, 30 and 46% wheat, respectively), was studied and compared with the response to a carbohydrate-free protein-rich diet (CF). Here we focused on the utilisation of dietary carbohydrates by examining the relationship between dietary starch intake, hepatic hexokinase activities, circulating insulin and muscle insulin receptor system. Plasma glucose concentration and hepatic high Km hexokinase (glucokinase, GK) activity were not affected by the content of digestible starch, but 6 h after feeding enzyme activity was higher in the fish fed carbohydrate diets. Similarly, low Km hexokinase (HK) activity was also higher in the fish 24 h after feeding. Fat gain and protein retention were significantly improved by increased digestible starch intake, especially in the HP group, which in turn, presented the highest plasma insulin levels. Glycogen stores were moderately increased by the ingestion of digestible starch. The number of insulin receptors was greater in the CF group than in fish on carbohydrates, except the HP group. Our results confirmed that the common carp uses dietary carbohydrates efficiently, especially when there are provided by peas. This efficiency might be related to the enhanced response of postprandial insulin observed in the HP group.

AMP-activated protein kinase plays an important evolutionary conserved role in the regulation of glucose metabolism in fish skeletal muscle cells

AMPK, a master metabolic switch, mediates the observed increase of glucose uptake in locomotory muscle of mammals during exercise. AMPK is activated by changes in the intracellular AMP:ATP ratio when ATP consumption is stimulated by contractile activity but also by AICAR and metformin, compounds that increase glucose transport in mammalian muscle cells. However, the possible role of AMPK in the regulation of glucose metabolism in skeletal muscle has not been investigated in other vertebrates, including fish. In this study, we investigated the effects of AMPK activators on glucose uptake, AMPK activity, cell surface levels of trout GLUT4 and expression of GLUT1 and GLUT4 as well as the expression of enzymes regulating glucose disposal and PGC1α in trout myotubes derived from a primary muscle cell culture. We show that AICAR and metformin significantly stimulated glucose uptake (1.6 and 1.3 fold, respectively) and that Compound C completely abrogated the stimulatory effects of the AMPK activators on glucose uptake. The combination of insulin and AMPK activators did not result in additive nor synergistic effects on glucose uptake. Moreover, exposure of trout myotubes to AICAR and metformin resulted in an increase in AMPK activity (3.8 and 3 fold, respectively). We also provide evidence suggesting that stimulation of glucose uptake by AMPK activators in trout myotubes may take place, at least in part, by increasing the cell surface and mRNA levels of trout GLUT4. Finally, AICAR increased the mRNA levels of genes involved in glucose disposal (hexokinase, 6-phosphofructokinase, pyruvate kinase and citrate synthase) and mitochondrial biogenesis (PGC-1α) and did not affect glycogen content or glycogen synthase mRNA levels in trout myotubes. Therefore, we provide evidence, for the first time in non-mammalian vertebrates, suggesting a potentially important role of AMPK in stimulating glucose uptake and utilization in the skeletal muscle of fish.

Protocol de conservació ex situ del Centre Ictiològic del Parc Natural del Delta de l'Ebre

En aquest Treball de Fi de Grau es pretén establir un protocol per a la conservació ex situ de les espècies que hi ha en el Centre Ictiològic del Parc Natural del Delta de l’Ebre. Les espècies que es troben en el CI són espècies vulnerables o en perill: espinós, samaruc, fartet, rabosa, llopet de riu i tritó palmat. Els objectius d’aquest protocol són: que el CI tingui un protocol propi, aprendre com funciona tot el centre, totes les espècies, com alimentar-les, com manipular-les i com tractar-les durant tot el seu cicle de vida. Un altre objectiu és el de veure si a finals d’any s’obté una alta població de cada espècie, quines són reintroduïdes, les patologies sorgides i els valors dels paràmetres químics de les basses naturals exteriors. El protocol s’elabora a partir de les pràctiques realitzades durant l’estiu del 2013 i els coneixements adquirits, la bibliografia i les dades del CI. Gràcies a això s’ha elaborat el treball. S’ha tractat la conservació ex situ; la problemàtica que sofreixen les espècies; cadascuna d’aquestes espècies; com funciona el CI a nivell de centre i a nivell de personal; les tasques que hi ha diàriament, setmanalment i ocasionalment segons les necessitats de l’estoc; el maneig sanitari; les patologies i com tractar-les; i l’anàlisi genètic. Els resultats obtinguts d’aquest protocol són els resultats numèrics obtinguts de l’any 2013 que són: 1. El gran nombre de cries nascudes de samaruc i fartet, menys de raboseta de riu, poques d’espinós i tritó palmat, i menys de llopet que tot just comença ara en el CI. 2. El total d’uns 5700 individus reitnroduits (samaruc, raboseta de riu i espinós de Girona). 3. La patologia més sorgida és el punt blanc. 4. I els paràmetres químics (amoni, nitrits, nitrats i fòsfor) no són molt elevats. La conclusió final i més important a la que arribo en fer el protocol és la gran importància que té el CI per a conservar aquestes espècies que no es saben apreciar fins que comencen a desparèixer. La existència del CI és més aviat una mesura correctora de tots els impactes que han sofert els habitatges de les espècies tractades i de la introducció d’espècies exòtiques que són una amenaça per les autòctones.

[Notes breus (fauna)] Primera citació de brema blanca (Abramis bjoerkna) a Catalunya i noves introduccions de peixos exòtics (Alburnus alburnus, Sander lucioperca i Silurus glanis) a diverses conques catalanes = First record of white bream (Abramis bjoerkna) in Catalonia (Spain) and new introductions of exotic fish (Alburnus alburnus, Sander lucioperca and Silurus glanis) into Catalan river basins

En aquesta nota es recullen noves observacions de diverses espècies de peixos exòtics obtingudes en un mostreig efectuat de febrer a maig de 2003, en catorze embassaments de Catalunya

Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past

The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs.

Small but powerful: Top predator local extinction affects ecosystem structure and function in an intermittent stream.

Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators' extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1) leads to a 'mesopredator release', affects primary consumers and changes whole community structures, and (2) triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the topdown effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel), conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire.We found that top predator absence led to 'mesopredator release', and also to 'prey release' despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers' extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been extirpated, to restore ecosystem structure and function.

Fish colonization of artificial reefs in a large Neotropical reservoir: material type and successional changes

Artificial reefs have barely been used in Neotropical reservoirs (about five studies in three reservoirs), despite their potential as a fishery management tool to create new habitats and also to understand fish ecology. We experimentally assessed how reef material (ceramic, concrete, and PVC) and time modulated fish colonization of artificial reefs deployed in Itaipu Reservoir, a large reservoir of the mainstem Parana´ River, Brazil. Fish richness, abundance, and biomass were significantly greater in the reef treatments than at control sites. Among the experimental reefs, ceramic followed by the concrete treatments were the materials most effectively colonized, harboring the majority of the 13 fish species recorded. Although dependent on material type, many of the regularities of ecological successions were also observed in the artificial reefs, including decelerating increases in species richness, abundance, mean individual size, and species loss rates with time and decelerating decreases of species gain and turnover rates. Species composition also varied with material type and time, together with suites of life history traits: more equilibrium species (i.e., fishes of intermediate size that often exhibit parental care and produce fewer but larger offspring) of the Winemiller-Rose model of fish life histories prevailed in later successional stages. Overall, our study suggests that experimental reefs are a promising tool to understand ecological succession of fish assemblages, particularly in tropical ecosystems given their high species richness and low seasonality

Invasive species and habitat degradation in Iberian streams: an analysis of their role in freshwater fish diversity loss

Mediterranean endemic freshwater fish are among the most threatened biota in the world. Distinguishing the role of different extinction drivers and their potential interactions is crucial for achieving conservation goals. While some authors argue that invasive species are a main driver of native species declines, others see their proliferation as a co-occurring process to biodiversity loss driven by habitat degradation. It is difficult to discern between the two potential causes given that few invaded ecosystems are free from habitat degradation, and that both factors may interact in different ways. Here we analyze the relative importance of habitat degradation and invasive species in the decline of native fish assemblages in the Guadiana River basin (southwestern Iberian Peninsula) using an information theoretic approach to evaluate interaction pathways between invasive species and habitat degradation (structural equation modeling, SEM). We also tested the possible changes in the functional relationships between invasive and native species, measured as the per capita effect of invasive species, using ANCOVA. We found that the abundance of invasive species was the best single predictor of natives’ decline and had the highest Akaike weight among the set of predictor variables examined. Habitat degradation neither played an active role nor influenced the per capita effect of invasive species on natives. Our analyses indicated that downstream reaches and areas close to reservoirs had the most invaded fish assemblages, independently of their habitat degradation status. The proliferation of invasive species poses a strong threat to the persistence of native assemblages in highly fluctuating environments. Therefore, conservation efforts to reduce native freshwater fish diversity loss in Mediterranean rivers should focus on mitigating the effect of invasive species and preventing future invasions

L'Impacte ecològic dels peixos introduïts a Catalunya

We review the invasive fish species introduced to Catalonia (Spain) and their mechanisms of ecological impact. Catalonia has about 15 established foreign fish species along with many others that have been translocated. These fish species, which are identical to those that have been introduced worldwide (thereby contributing to biotic homogenization), include: common carp (Cyprinus carpio), largemouth bass (Micropterus salmoides), eastern mosquitofish (Gambusia holbrooki) and many European cyprinids that are not native to the Iberian Peninsula. There are some well-documented repercussions to the native fauna, such as the impact of mosquitofish on endangered, endemic cyprinodonts. The illegal introduction by anglers continues to be one of the main culprits of this environmental problem, one that has been barely addressed by local and state authorities

Quantifying seasonality along a latitudinal gradient: from stream temperature to growth of invasive mosquitofish

Most ecosystems undergo substantial variation over the seasons, ranging from changes in abiotic features, such as temperature, light and precipitation, to changes in species abundance and composition. How seasonality varies along latitudinal gradients is not well known in freshwater ecosystems, despite being very important in predicting the effects of climate change and in helping to advance ecological understanding. Stream temperature is often well correlated with air temperature and influences many ecosystem features such as growth and metabolism of most aquatic organisms. We evaluated the degree of seasonality in ten river mouths along a latitudinal gradient for a set of variables, ranging from air and water temperatures, to physical and chemical properties of water and growth of an invasive fish species (eastern mosquitofish, Gambusia holbrooki ). Our results show that although most of the variation in air temperature was explained by latitude and season, this was not the case for water features, including temperature, in lowland Mediterranean streams, which depended less on season and much more on local factors. Similarly, although there was evidence of latitude-dependent seasonality in fish growth, the relationship was nonlinear and weak and the significant latitudinal differences in growth rates observed during winter were compensated later in the year and did not result in overall differences in size and growth. Our results suggest that although latitudinal differences in air temperature cascade through properties of freshwater ecosystems, local factors and complex interactions often override the water temperature variation with latitude and might therefore hinder projections of species distribution models and effects of climate change

La biota de los ríos : los peces

Capítol 15 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix als peixos dels sistemes fluvials

Anatomia macroscòpica i microscòpica de l'aparell genital femení d'Ophidion barbatum (L.) (Pisces, Ophididae)

S'ha realitzat un estudi de l'anatomia macroscòpica i microscòpica de I'ovari d'Ophidion barbatum (L.) (Pisces, Ophidiidae), utilitzant material recollit per pescadors del port de Blanes (mar català) durant el mes d'octubre de 1985. L'absència d'òrgan copulador en els mascles d'aquesta espècie i la posició de l'orifici nasal anterior, a una certa alçada respecte al llavi superior, ens permet identificar-la com una espècie ovípara, del subordre Ophidioidei, dins de l'ordre Ophidiiformes. L'ovari és únic i continuat caudalment per l'oviducte. Els nombrosos cordons intraovarics que tapien la cavitat augmenten considerablement la superfície germinal. El desenvolupament de l'ovari es correspon amb el tipus asincrònic (Marza, 1938) i la fresa repetida al llarg d'una estació reproductiva més o menys llarga és una estrategia que augmenta la fecunditat, normalment limitada pel volum corporal de la femella. Dins de l'ordre Ophidiiformes, el tipus d'ovari únic sense restes de paret mitjana sembla ser la norma entre les espècies de reproducció ovípara. Aquest fet esta en contradicció amb la teoria de Mendoza (1943) que, fora d'algunes excepcions, l'ovari únic es troba principalment en els teleostis vivípars

Homogenization Dynamics and Introduction Routes of Invasive Freshwater Fish in the Iberian Peninsula

Nonnative invasive species are one of the main global threats to biodiversity. The understanding of the traits characterizing successful invaders and invasion-prone ecosystems is increasing, but our predictive ability is still limited. Quantitative information on biotic homogenization and particularly its temporal dynamics is even scarcer. We used freshwater fish distribution data in the Iberian Peninsula in four periods (before human intervention, 1991, 1995, and 2001) to assess the temporal dynamics of biotic homogenization among river basins. The percentage of introduced species among fish faunas has increased in recent times (from 41.8% in 1991 to 52.5% in 2001), leading to a clear increase in the similarity of community composition among basins. The mean Jaccard's index increase (a measure of biotic homogenization) from the pristine situation to the present (17.1%) was similar to that for Californian fish but higher than for other studies. However, biotic homogenization was found to be a temporally dynamic process, with finer temporal grain analyses detecting transient stages of biotic differentiation. Introduced species assemblages were spatially structured along a latitudinal gradient in the Iberian Peninsula, with species related to sport fishing being characteristic of northern basins. Although the comparison of fish distributions in the Iberian Peninsula and France showed significant and generalized biotic homogenization, nonnative assemblages of northeastern Iberian basins were more similar to those of France than to those of the rest of the Iberian Peninsula, indicating a main introduction route. Species introduced to the Iberian Peninsula tended to be mainly piscivores or widely introduced species that previously had been introduced to France. Our results indicate that the simultaneous analysis of the spatial distribution of introduced assemblages (excluding native species that reflect other biogeographical patterns) and their specific traits can be an effective tool to detect introduction and invasion routes and to predict future invaders from donor regions