Anguillicola crassus impairs the silvering-related enhancements of the ROS defense capacity in swimbladder tissue of the European eel (Anguilla anguilla).

In a process called silvering, European eels prepare for their long-distance migration from European freshwater systems to the Sargasso Sea for reproduction. During this journey, eels perform extended diel vertical migrations, and the concomitant changes in hydrostatic pressure significantly affect the swimbladder, functioning as a buoyancy organ. As the swimbladder is primarily filled with oxygen, the tissue has to cope with extreme hyperoxic conditions, which typically are accompanied by the generation of reactive oxygen species (ROS) and oxidative stress. In addition, since the introduction of the parasitic nematode Anguillicola crassus in the early 1980s, swimbladder function of most of the European eels is impaired by the infection with this parasite. However, the exact pathways to detoxify ROS and how these pathways are affected by silvering or the infection are still unknown. In swimbladder and muscle tissue from uninfected and infected yellow, and from uninfected and infected silver eels, we measured the level of lipid peroxidation, which increases with ROS stress. To assess the capacity of the ROS defense systems, we analyzed the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and glutathione reductase (GR), and determined the concentration of the antioxidant glutathione (GSH + GSSG). In swimbladder tissue, we found increased concentrations of GSH + GSSG as well as higher activities of SOD, GPx and GR, suggesting that SOD and the glutathione cycle are important for ROS detoxification. Comparing swimbladder tissue of uninfected yellow with uninfected silver eels, the concentration of GSH + GSSG and the activity of SOD were higher after silvering, corresponding with lower levels of lipid peroxidation. Whereas in yellow eels the infection with A. crassus had no effect, in silver eels the capacity to cope with ROS was significantly impaired. In muscle tissue, silvering or the infection only affected the activity of SOD but in exactly the same way as in swimbladder tissue.

Effects of Anguillicola novaezelandiae on the levels of cortisol and hsp70 in the European eel.

The nematodes Anguillicola novaezelandiae and Anguillicola crassus are both alien parasites of the European eel with severe adverse effects on their new host. Both species differ in terms of their invasiveness and their severity of harmful effects on the European eel. The purpose of this study was to determine under laboratory conditions whether stages of A. novaezelandiae induce stress in European eels (Anguilla anguilla) and if these levels differ from stress levels induced by A. crassus. We analysed levels of plasma cortisol and hepatic hsp70 of eels experimentally infected with A. novaezelandiae and compared them to uninfected eels as well as to eels experimentally infected with A. crassus. Larval stages of A. novaezelandiae induced higher levels of plasma cortisol compared to uninfected controls, while adult parasites increased the levels of hepatic hsp70 above those of uninfected controls. The eels' cortisol response is induced by larval stages of A. novaezelandiae, while adult stages elevate levels of hepatic hsp70. Levels of stress induced by A. novaezelandiae are comparable to those induced by A. crassus.

Comparative study of the metal accumulation in Hysterothalycium reliquens (nematode) and Paraphilometroides nemipteri (nematode) as compared with their doubly infected host, Nemipterus peronii (Notched threadfin bream).

In February 2013, forty-seven Notched threadfin bream, the Nemipterus peronii, were sampled from the eastern coastal waters of the South China Sea. The concentration of various elements, namely cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), strontium (Sr), manganese (Mn), selenium (Se), Lead (Pb), nickel (Ni), aluminum (Al), arsenic (As), iron (Fe), and Zinc (Zn) were analyzed in the liver, muscle, and kidney organs of the host, as well as in their parasites Hysterothalycium reliquens (nematode) and the Paraphilometroides nemipteri (nematode), using inductively coupled plasma mass spectrometry (ICP-MS). The former group of parasites showed highest accumulation capacity for Cr, Cu, Fe, Mn, Se, Ni, and Zn while the latter group had high accumulation potential of As, Hg, Cd, Al, Pb, and Sr. The divergence in heavy-metal accumulation profiles of both nematodes is linked with the specificity of microhabitats, cuticle morphology, and interspecific competition. The outcome of this study indicates that both parasite models can be used for biomonitoring of metal pollution in marine ecosystems.

Serum acute phase proteins in dogs with symptomatic esophageal spirocercosis.

Canine spirocercosis (CS) is a helminthic infection caused by the nematode Spirocerca lupi. The clinical hallmark of the disease is esophageal dysphagia due to parasite-induced esophageal nodules. Currently, there is limited information on the involvement of serum acute phase proteins (APPs) in the symptomatic CS. The objective of this study was to investigate whether C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp) and albumin are involved in CS, and if their concentrations measured on admission reflect the severity of benign esophageal lesions. Nineteen dogs with spontaneous symptomatic esophageal spirocercosis and 7 clinically healthy dogs were studied retrospectively. The most consistently increased APP in the symptomatic dogs was Hp (95% of the dogs), followed by CRP (68%). The SAA concentrations were infrequently increased (5% of the dogs), while albumin concentrations were decreased in 58% of the affected dogs. The dogs with spirocercosis had significantly higher median concentrations of Hp (p=0.0001) and CRP (p=0.02) compared to healthy dogs. Median albumin concentrations did not differ between the two groups of dogs. The median concentrations of Hp, CRP and albumin did not differ significantly between the dogs having a single or multiple esophageal nodules. The results of this study indicate that in symptomatic CS, Hp and CRP are significantly and consistently increased, while SAA and albumin may be of limited value as diagnostic markers. No association was established between the concentrations of Hp, CRP and albumin measured on admission and the number of esophageal nodules.

Contents of several inorganic substances in European eel infected and uninfected by Anguillicola crassus (Nematoda).

The content of 5 macroelements and 5 microelements were analyzed using the atomic absorption method in muscle samples of European eels infected and uninfected by Anguillicola crasus. The mean contents of these substances in infected eels were statistically highly significantly lower in Ca, P, Fe, Mn, but only statistically significantly lower in Na, Mg, Zn and Cu as compared to uninfected fishes. These differences are discussed in relation to hematophagus feeding and pathogenity of the parasite.