Competing barnacle species with a time dependent reproduction rate

A simple competition model with time varying periodic coefficients, in which two species use different reproduction strategies, is explored in this paper. The two species considered comprise a native species which reproduces once a year over a short time period and an invasive species which is capable of reproducing throughout the entire year. A monotonicity property of the model is instrumental for its analysis. The model reveals that the time difference between the peak of reproduction for the two species is a critical factor in determining the outcome of competition between these species. The impact of climate change and an anthropogenic disturbance, comprising the creation of additional substrate, is also investigated using a modified model. The results of this paper describe how climate change will favour the invasive species by reducing the time period between the reproductive peaks of the two species and how the addition of new substrates is likely to endanger a small population of either of the two species, depending on the timing of the introduction of the substrates.

The Gut Microbiota of Marine Fish

The body of work relating to the gut microbiota of fish is dwarfed by that on humans and mammals. However, it is a field that has had historical interest and has grown significantly along with the expansion of the aquaculture industry and developments in microbiome research. Research is now moving quickly in this field. Much recent focus has been on nutritional manipulation and modification of the gut microbiota to meet the needs of fish farming, while trying to maintain host health and welfare. However, the diversity amongst fish means that baseline data from wild fish and a clear understanding of the role that specific gut microbiota play is still lacking. We review here the factors shaping marine fish gut microbiota and highlight gaps in the research.

The novel use of pop-off satellite tags (PSATs) to investigate the migratory behaviour of European sea bass Dicentrarchus labrax

A total of 12 adult European sea bass Dicentrarchus labrax were tagged with pop-off satellite archival tags (PSAT) in Irish coastal waters and in offshore waters in the north-east Celtic Sea between 2015 and 2016. Archived data were successfully recovered from five of the 12 tags deployed, three from fish released in inshore Irish waters and two from fish released offshore in the eastern Celtic Sea. All three fish tagged in inshore waters were found to undertake migrations into the open ocean coinciding with the spawning period. These fish also exhibited fidelity to inshore sites post-migration, returning to the same general location (within c. 73 km, which is roughly the predicted mean accuracy of the method) of their original release site. Although the number of tracks obtained here was limited, some degree of aggregation between inshore and offshore tagged fish in the eastern Celtic Sea was noted during the expected spawning period suggesting PSATs can provide new information on specific spawning locations of European sea bass.

Characterization of protein hydrolysates from blue whiting (Micromesistius poutassou) and their application in beverage fortification

Enzymatic hydrolysis of fish proteins has been employed as a principle method for converting under-utilised fish into valuable products for the pharmaceutical and health food industries. In this study, six commercial enzymes were tested for their ability to make fish protein hydrolysate powders from whole blue whiting. The chemical and functional properties of these powders were compared. The powders all had high solubility (>80%) across a wide pH range in water and their solubility improved further within a vitamin-tea beverage matrix (>85%). Varying degrees of anti-oxidant activities were recorded for the powders using three model systems (DPPH, ferrous chelating and reducing power). This study demonstrates that commercial enzymes are useful for the extraction and alteration of fish protein from a low value source to produce highly digestible, low molecular weight peptide powders that could be used as a fortifying health ingredient, especially in beverages.

Neutral red retention time assay in determination of toxicity of nanoparticles

The neutral red retention time (NRRT) assay is useful for detecting decreased lysosomal membrane stability in haemocytes sampled from bivalves, a phenomenon often associated with exposure to environmental pollutants including nanomaterials. Bivalves are popular sentinel species in ecotoxicology and use of NRRT in study of species in the genus Mytilus is widespread in environmental monitoring. The NRRT assay has been used as an in vivo test for toxicity of carbon nanoparticles (Moore MN, Readman JAJ, Readman JW, Lowe DM, Frickers PE, Beesley A. 2009. Lysosomal cytotoxicity of carbon nanoparticles in cells of the molluscan immune system: An in vivo study. Nanotoxicology. 3 (1), 40-45). We here report application of this assay adapted to a microtitre plate format to a panel of metal and metal oxide nanoparticles (2 ppm). This showed that copper, chromium and cobalt nanoparticles are toxic by this criterion while gold and titanium nanoparticles are not. As the former three nanoparticles are often reported to be cytotoxic while the latter two are thought to be non-cytotoxic, these data support use of NRRT as a general in vitro assay in nanotoxicology.

Toxicity of copper oxide nanoparticles in the blue mussel, Mytilus edulis: a redox proteomic investigation

Relatively little is known about the fate and effects of nanomaterials even in relatively simple organisms such as Mytilus edulis. Here, copper oxide nanoparticles (CuO NP) are shown to induce dose-dependent toxic effects at the biochemical, physiological and tissue levels in the blue mussel. Stable CuO NP suspensions were sized by differential light scattering and nanoparticle tracking analysis to yield average particle diameters of approximately 100 nm. These were administered to M. edulis, at doses of 400, 700 and 1000 ppb. Ingested copper was predominantly located in the gill tissue with small amounts in digestive gland. Fifteen coomassie-stained spots were excised from two dimensional gel electrophoresis separations of gill tissue extacts and identified by peptide mass fingerprinting. These contained six unique proteins (alpha- and beta-tubulin, actin, tropomyosin, triosephosphate isomerase and Cu-Zn superoxide dismutase). Of these, two spots (actin and triosephosphate isomerase) showed decreased protein thiols while three (alpha-tubulin, tropomyosin and Cu-Zn superoxide dismutase) showed increased carbonylation which is indicative of protein oxidation of cytoskeleton and enzymes in response to CuO NP. The neutral red retention time (NRRT) assay revealed toxicity due to the CuO NPs which was comparable with toxic metal oxide nanoparticles such as chromium and cobalt. In contrast, non-toxic titanium and gold metal oxide nanoparticles gave no NRRT effects at similar NP concentrations. Histology revealed deposition of pigmented brown cells in response to CuO NP, located predominantly along the mantle and gill margin but also lining digestive tubules and some of the sinuses and distributed throughout the connective tissue and in the adductor muscle.

Pseudodiarrhoea in zebra mussels Dreissena polymorpha (Pallas)exposed to microcystins

Microcystins are produced by bloom-forming cyanobacteria and pose significant health and ecological problems. In this study we show that zebra mussels respond differently to different strains of Microcystis aeruginosa, and that a highly toxic strain causes zebra mussels to produce large quantities of mucous pseudofaeces, `pseudodiarrhoea', that are periodically expelled hydraulically through the pedal gape by shell valve adductions rather than by the normal ciliary tracts. Analysis of the pseudofaecal ejecta showed that the proportion of Microcystis aeruginosa relative to Asterionella formosa was high in the pseudofaeces and even higher in the `pseudodiarrhoea' when a mixed diet was given to the mussels. This confirms that very toxic Microcystis aeruginosa were preferentially being rejected by comparison with the non-toxic diatom in the pseudofaeces and even more so in the`pseudodiarrhoea'. Such selective rejection was not observed with low or non-toxic strains and would therefore tend to enhance the presence of toxic Microcystis aeruginosa in mixed Microcystis aeruginosacyanobacterial blooms, as well as transferring toxins from the water column to the benthos.

The observed acute irritant response to the toxin represents the first demonstration of an adverse sublethal effect of microcystins on invertebrate ecophysiology. Our results also suggest that it could be a specific response to microcystin-LF, a little studied toxin variant.