Anisakis infection in allis shad, Alosa alosa (Linnaeus, 1758), and twaite shad, Alosa fallax (Lacépède, 1803), from Western Iberian Peninsula Rivers: zoonotic and ecological implications.

Spawning individuals of allis shad, Alosa alosa (Linnaeus, 1758), and twaite shad, Alosa fallax (Lacépède, 1803), were sampled from three rivers on the Atlantic coast of the Iberian Peninsula (Ulla, Minho, Mondego) during 2008 to 2013 to assess the presence of the zoonotic marine parasite Anisakis spp. larvae. The results revealed that both shad species were infected by third-larval stage Anisakis simplex s.s. and Anisakis pegreffii. The latter is reported in mixed infections in both shad species of Western Iberian Peninsula for the first time. In A. alosa, the prevalence of Anisakis infection can reach 100%, while in A. fallax, prevalence was up to 83%. Infected individuals of the former species also often contain much higher number of parasites in theirs internal organs and flesh: from 1 to 1138 Anisakis spp. larvae as compared to 1 to 121 larvae, respectively. In general, numbers of A. pegreffii were higher than those of A. simplex s.s. Our results suggest that in the marine environment of the Western Iberian Peninsula, both anadromous shad species act as paratenic hosts for A. simplex s.s. and A. pegreffii, thus widening the distribution of the infective nematode larvae from the marine to the freshwater ecosystem. This finding is of great epidemiological relevance for wildlife managers and consumers, considering the zoonotic and gastroallergic threats posed of these parasites.

Characterization of the pelagic fish community of the north-western and northern Spanish shelf waters.

This study demonstrates the utility of trawl data, collected during acoustic surveys of pelagic fish stocks as a way of confirming fish identification, to characterize the pelagic community, as well as allowing description and prediction of fish distribution patterns, based on data from Spanish Atlantic Ocean shelf surveys during spring 2005-2011. The composition of the pelagic community is described, as well as spatial and temporal patterns of variation in both the community composition and the presence and importance of two of the main exploited pelagic species, sardine Sardina pilchardus and anchovy Engraulis encrasicolus. The most important species in terms of both frequency of occurrence and standardized mass in hauls were mackerel Scomber scombrus, hake Merluccius merluccius, horse mackerel Trachurus trachurus, S. pilchardus and bogue Boops boops. Multivariate analysis indicated significant effects of depth, geographical area and year on haul composition. Descriptive generalized additive models (GAM), with latitude, longitude and depth as predictors, identified clear spatial patterns in the occurrence and abundance of both S. pilchardus and E. encrasicolus, with abundance being highest closer to the coast and, in the case of E. encrasicolus, higher near the French and Portuguese borders. Further GAM analysis, using environmental variables to explain spatial patterns, revealed significant effects of depth and sea surface temperature (SST) gradient and depth on S. pilchardus importance, while E. encrasicolus importance was related to SST. The importance of both species in hauls was higher in the years of higher spawning stock biomass (SSB) and E. encrasicolus also appeared to expand its range when SSB was higher.

Behavioural responses of sardines Sardina pilchardus to simulated purse-seine capture and slipping.

The behavioural effects of confinement of sardine Sardina pilchardus in a purse seine were evaluated through three laboratory experiments simulating the final stages of purse seining; the process of slipping (deliberately allowing fishes to escape) and subsequent exposure to potential predators. Effects of holding time (the time S. pilchardus were held or entangled in the simulation apparatus) and S. pilchardus density were investigated. Experiment 1 compared the effect of a mild fishing stressor (20 min in the net and low S. pilchardus density) with a control (fishing not simulated) while the second and third experiments compared the mild stressor with a severe stressor (40 min in the net and high S. pilchardus density). In all cases, sea bass Dicentrarchus labrax were used as potential predators. Results indicated a significant effect of crowding time and density on the survival and behaviour of slipped S. pilchardus. After simulated fishing, S. pilchardus showed significant behavioural changes including lower swimming speed, closer approaches to predators and higher nearest-neighbour distances (wider school area) than controls, regardless of stressor severity. These results suggest that, in addition to the delayed and unobserved mortality caused by factors related to fishing operations, slipped pelagic fishes can suffer behavioural impairments that may increase vulnerability to predation. Possible sub-lethal effects of behavioural impairment on fitness are discussed, with suggestions on how stock assessment might be modified to account for both unobserved mortality and sub-lethal effects, and possible approaches to provide better estimates of unobserved mortality in the field are provided.

Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: geographical trends, causal factors and effects on reproduction and mortality.

Concentrations of polychlorinated biphenyls (PCBs) in blubber of female common dolphins and harbour porpoises from the Atlantic coast of Europe were frequently above the threshold at which effects on reproduction could be expected, in 40% and 47% of cases respectively. This rose to 74% for porpoises from the southern North Sea. PCB concentrations were also high in southern North Sea fish. The average pregnancy rate recorded in porpoises (42%) in the study area was lower than in the western Atlantic but that in common dolphins (25%) was similar to that of the western Atlantic population. Porpoises that died from disease or parasitic infection had higher concentrations of persistent organic pollutants (POPs) than animals dying from other causes. Few of the common dolphins sampled had died from disease or parasitic infection. POP profiles in common dolphin blubber were related to individual feeding history while those in porpoises were more strongly related to condition.

Geographic, seasonal and ontogenetic variation in cadmium and mercury concentrations in squid (Cephalopoda: Teuthoidea) from UK waters.

Cadmium (Cd) and mercury (Hg) levels were measured in the tissue samples of two loliginid (Alloteuthis sp. and Loligo forbesi) and two ommastrephid (Todarodes sagittatus and Todaropsis eblanae) squid species collected from research cruise and fishery (market) samples in UK waters during 2004-05. Concentrations of Cd were generally higher in the ommastrephids, in all tissues except muscle. Hg concentrations were higher in T. sagittatus than in the loliginids. In L. forbesi, metal concentrations differed between tissues and also varied in relation to body size, geographic origin, and season. Cd levels decreased with increasing body size. This may be related to a shift in the diet with growth, since small L. forbesi feed on benthic invertebrates that have relatively high Cd concentrations, whereas larger individuals prey mainly on fish that have low Cd concentrations. Hg levels increased with body size, indicating its retention, and they were highest at the end of the spawning season and in squid from the English Channel and the Scottish West Coast. It is likely that the ambient concentration of Hg in seawater plays an important part in its accumulation in squid tissues. As it is a short-lived species, L. forbesi may therefore function as a bioindicator species for Hg contamination of the marine environment. Our results indicate that there is no significant danger to humans from consuming squid from UK waters.

Mass-dependent predation risk and lethal dolphin-porpoise interactions.

In small birds, mass-dependent predation risk (MDPR) is known to make the trade-off between avoiding starvation and avoiding predation dependent on individual mass. This occurs because carrying increased fat reserves not only reduces starvation risk but also results in a higher predation risk due to reduced escape flight performance and/or the increased foraging exposure needed to maintain a higher body mass. In principle, the theory of MDPR could also apply to any animal capable of storing energy reserves to reduce starvation and whose escape performance decreases with increasing mass. We used a unique situation along certain parts of coastal Britain, where harbour porpoises (Phocoena phocoena) are pursued and killed but crucially not eaten by bottlenose dolphins (Tursiops truncatus), to investigate whether a MDPR effect can occur in non-avian species. We show that where high levels of dolphin 'predation' occur, porpoises carry significantly less energy reserves than would otherwise be expected and this equates to reducing by approximately 37% the length of time that a porpoise could survive without feeding. These results provide the first evidence that a mass-dependent starvation-predation risk trade-off may be a general ecological principle that can apply to widely different animal types rather than, as is currently thought, only to birds.

Breaking symmetry: the marine environment, prey size, and the evolution of asymmetry in cetacean skulls.

Skulls of odontocetes (toothed whales, including dolphins and porpoises) are typified by directional asymmetry, particularly in elements associated with the airway. Generally, it is assumed this asymmetry is related to biosonar production. However, skull asymmetry may actually be a by-product of selection pressure for an asymmetrically positioned larynx. The odontocete larynx traverses the pharynx and is held permanently in place by a ring of muscle. This allows prey swallowing while remaining underwater without risking water entering the lungs and causing injury or death. However, protrusion of the larynx through the pharynx causes a restriction around which prey must pass to reach the stomach. The larynx and associated hyoid apparatus has, therefore, been shifted to the left to provide a larger right piriform sinus (lateral pharyngeal food channel) for swallowing larger prey items. This asymmetry is reflected in the skull, particularly the dorsal openings of the nares. It is hypothesized that there is a relationship between prey size and skull asymmetry. This relationship was examined in 13 species of odontocete cetaceans from the northeast Atlantic, including four narrow-gaped genera (Mesoplodon, Ziphius, Hyperoodon, and Kogia) and eight wide-gaped genera (Phocoena, Delphinus, Stenella, Lagenorhynchus, Tursiops, Grampus, Globicephala, and Orcinus). Skulls were examined from 183 specimens to assess asymmetry of the anterior choanae. Stomach contents were examined from 294 specimens to assess prey size. Results show there is a significant positive relationship between maximum relative prey size consumed and average asymmetry relative to skull size in odontocete species (wide-gape species: R2 = 0.642, P = 0.006; narrow-gape species: R2 = 0.909, P = 0.031). This finding provides support for the hypothesis that the directional asymmetry found in odontocete skulls is related to an aquatic adaptation enabling swallowing large, whole prey while maintaining respiratory tract protection.

Biological and ecological factors related to trace element levels in harbour porpoises (Phocoena phocoena) from European waters.

Selected trace elements (Cd, Cu, Hg, Se, Zn) were measured in the kidneys and the liver of 104 harbour porpoises (Phocoena phocoena) stranded along the coasts of France, Galicia (Spain), Ireland, Scotland (UK), and the Netherlands. Generally, relatively low concentrations of toxic elements were encountered in the tissues of European porpoises, except for two individuals, which displayed high hepatic Hg concentrations. Also, elevated Cd levels obtained in Scottish porpoises could be related to their feeding preferences and this result suggests an increase of the proportion of cephalopods in their diet with latitude. Moreover, significant geographical differences were seen in hepatic Zn concentrations; the elevated Zn concentrations displayed by porpoises from the Netherlands may relate their poor health status. Variation in metal concentrations within porpoises from the North Sea is likely to reflect a long-term segregation between animals from northern (Scotland) and southern areas (the Netherlands), making trace elements powerful ecological tracers.

New insights from age determination on toxic element accumulation in striped and bottlenose dolphins from Atlantic and Mediterranean waters.

This study aimed at comparing toxic element (Hg, Cd) bioaccumulation in relation to age for bottlenose (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) from Mediterranean and Atlantic waters. Metal concentrations were also measured in selected prey to infer metal exposure through the diet. As expected, Mediterranean prey exhibited the highest Hg levels, probably as a consequence of the Hg enrichment of the Mediterranean Sea. Comparing the predators from each area and taking age into account, Mediterranean bottlenose dolphins displayed higher Hg levels than Atlantic dolphins (p = 0.032), whereas Mediterranean striped dolphins did not (p = 0.691). The consumption of Myctophid fish, which showed the highest Hg levels (105+/-80 ngg(-1) w.wt.) among Atlantic prey, may explain the high Hg levels in the liver of the Atlantic striped dolphins and suggested a preferential offshore feeding behaviour in this area. Concerning Cd, no clear differences were found between geographical areas.

A C. elegans orphan nuclear receptor contributes to xenobiotic resistance.

Lipophilic endocrine signals in metazoans, including the steroid, thyroid, and retinoid hormones, alter gene expression in target cells by binding to and modulating the activity of nuclear receptor (NR) transcription factors [1]. In vertebrates, xenobiotic and pharmacologic compounds can regulate the expression of protective metabolic enzymes via specific "xenobiotic sensing" NRs [2-4]. Here, we report evidence suggesting that this activity is an ancient conserved function for the NR class containing these receptors. Specifically, we show that a Caenorhabditis elegans member of this NR class, nhr-8, is required for wild-type levels of resistance to the toxins colchicine and chloroquine. The nhr-8 promoter is active in the nematode gut, a tissue that also expresses the ABC transporter, PGP-3, which contributes to defense against these toxins [5]. In contrast to pgp-3 mutants, nhr-8 mutants are not more sensitive than wild-type to pyocyanin-dependent killing by the pathogenic bacterium Pseudomonas aeruginosa. We conclude that NHR-8 functions in the nematode xenobiotic defense system and that NHR-8 and PGP-3 have overlapping, but distinct, spectra of toxin specificity.

Diet selection by common shrews Sorex araneus in a depleting environment.

Common shrews (Sorex araneus L.) were presented with two prey types at various densities in a depleting environment. Observed diet choice was compared to predictions of the classical optimal diet model and of "shrew-specific" simulations incorporating patch depletion. Two strategies were simulated: expansion of the diet from taking only profitable prey to taking both types, and fixed partial preference. The simulations predict partial preference over a narrow range of initial densities of profitable prey. However, within this range, energetic benefits are relatively insensitive to diet composition. Shrews preferred more profitable prey and were more selective when encounter rate with profitable prey was higher, broadly as predicted by all the models. Partial preference was observed, but neither of the mechanisms simulated was strongly supported by results for the shrews. Univariate and multivariate analyses were used to identify cues involved in selecting prey. Instantaneous measures of encounter rates and encounters per unit search distance were the best predictors of subsequent prey choice, but decisions appear to have been made on a probabilistic basis.