Hepatoxylon trichiuri (Cestoda: Trypanorhyncha) plerocercoids in cage-reared northern bluefin tuna, Thunnus thynnus (Osteichthyes: Scombridae)
Northern bluefin tuna (Thunnus thynnus) were caught by purse seine boats and brought to a farm for a rearing cycle of 1.5 years. Mortalities occurred in the first weeks of acclimatization at the facility. Parasitological examination revealed plerocercoids of the cestode Hepatoxylon trichiuri embedded in the stomach mucosa. The larvae were found in 28.4% of the fish and the mean abundance was 3.12 per fish. Histopathology revealed disseminated erosion at the site of attachment, atrophy of fundic glands, lymphocytic migration, and hyperplasia of connective tissue in the lamina propria. These symptoms, however, together with the parasite abundance, could not have triggered the mortalities. This is the first record of this parasite in northern bluefin tuna.
Tuna Aquaculture in Europe
Abstract Among Mediterranean fishes, the Atlantic bluefin tuna (ABFT, Thunnus thynnus) is remarkably well adapted to its habitat. Many consider it and its relatives to be physiological wonders, owing to their warm-bodied nature and capacity for rapid growth and fast swimming. ABFT today are threatened by the one thing to which this species has not been able to adapt, overfishing. The superb taste of the ABFT’s flesh has made it a prized target for human consumption in the Mediterranean world, over the ages. Europe is rich in historic accounts and traditions involving human–tuna interactions. As one of the most valuable fishery species in the world, the ABFT has attracted international interest in assuring its permanence and sustainability of its stocks. Attention to both wild and ranched ABFT populations has accelerated since the late 1990s, and significant strides have been made toward true aquacultural farming to replace ranching of wild-caught animals. Building on previously successful aquaculture models, European aquaculture is now on the verge of closing the life cycle for this species. Significant advances have also been made, through collaborative research, on other fronts also related to tuna aquaculture. This chapter provides an up-to-date and comprehensive account of the state-of-the-technology in tuna aquaculture in Europe.
Applications of nanocomposite hydrogels for biomedical engineering and environmental protection
Nanocomposite hydrogels are polymeric networks that possess a unique property of hydration. The presence of alcohols, carboxylic acids and amides as hydrophilic moieties in structure of nanocomposite hydrogels enhances their stiffness and water-absorbing capacity. Addition of cross-linker in the synthesis of hydrogels increases their stability under extreme conditions of temperature, pH and pressure. Natural polymer-based nanocomposite hydrogels are biodegradable, highly hydrophilic and possess good mechanical strength. Gelatin, chitin, cellulose, pectin, carrageenan, starch and alginate are natural polymers commonly used to fabricate nanocomposite hydrogels. Nanocomposite hydrogels have special characteristics such as high swelling rate, selectivity and stimuli-sensitive nature. Here we review nanocomposite hydrogels for environmental protection and biomedical engineering. Applications in biomedical engineering include drug delivery agents, wound dressing, tissue engineering and antibacterials. Applications in environmental protection include ion exchangers, adsorption, photocatalysis and soil conditioning. Many nanocomposite hydrogels show excellent adsorption selectivity for heavy metal ions: Cu2+ up to 30.35 mg/g, Pb2+ up to 35.94 mg/g, and Zn2+ and Fe3+ up to 94.34 mg/g. Xanthan gum-based nanocomposite hydrogel has removed 96% dye from industrial effluent as reported. In addition, most of the nanocomposite hydrogels showed better adsorption capacity for pollutants in the pH range from 5 to 7. The nanocomposite hydrogels could also be regenerated and successfully utilized for several times. Nanocomposite hydrogels are therefore good bio-absorbent materials for environmental detoxification.