Mitochondrial genome of Esox flaviae (Southern pike): announcement and comparison with other Esocidae.

Pikes are fish species belonging to order Esociformes, family Esocidae, genus Esox. Species of the genus Esox are common, large, and economically important for food and fishing activities. Recently, a new species, southern pike E. flaviae, was described for a well-studied area such as Italy, using also two mtDNA markers: cox1 and cytb. A scant number of remnant populations of the species persist in Italy, threatened by habitat loss and degradation and by competition and possible hybridization with E. lucius, massively and recurrently stocked to sustain angling pressure. The availability of new mtDNA markers will possibly contribute to the conservation of the species. Currently, whole mitogenome information for the genus is available only for E. lucius and for E. reichertii. The aim of the present paper is to report novel mitogenomic information for southern pike.

Transferability of oxytetracycline (OTC) from feed to carp muscle and evaluation of the antibiotic effects on antioxidant systems in liver and kidney.

Oxytetracycline (OTC) is employed in fish farms to contest or prevent bacterial infections. We simulated an OTC treatment at therapeutic level (75 mg kg(-1)) and at higher doses (150, 300 mg kg(-1)) for 10 days. A withdrawal period of 10 days was considered for treated carp, carrying out the same chemical and biochemical analyses (total glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase and malondialdehyde). The aim was to obtain data related to the carryover in muscle and on variations in the antioxidant indicators in liver and kidney. The OTC residual levels in muscle showed a dose-response relationship. After 10 days of treatment at the recommended dose (75 mg kg(-1)), the mean value in muscle was 295 µg kg(-1). After 10 withdrawal days, residues in all treated groups were not entirely eliminated by fish. Residues of recommended 75 mg kg(-1) OTC dose were lower than the maximum permitted by EEC regulation: 100 µg kg(-1). Disturbance in the antioxidant systems in liver and kidney was recorded in (150, 300 mg kg(-1)) carp, as well as during the withdrawal period. A lowered superoxide dismutase activity and higher levels of catalase, glutathione peroxidase, glutathione reductase and glutathione were evaluated in liver, while in kidney only higher malondialdehyde and glutathione S-transferase concentrations were recorded for 300 mg kg(-1) dose. The therapeutic OTC dose exerted lower effects, and only in liver, enhancement of GPx and GR activities was recorded. After the withdrawal period, altered antioxidant responses in tissues were restored for all three OTC doses.

Effects of selenium supplemented diets on growth and condition indexes in juvenile red swamp crayfish, Procambarus clarkii.

Effects of selenium diets (Se, 0.3 and 1.2mgkg(-1)) on juvenile red swamp crayfish Procambarus clarkii were observed for eight weeks. Growth, condition factors and Se levels in exoskeleton and hepatopancreas for both sexes and diets were evaluated at three endpoints. The specific growth rate (SGR) showed a faster, but not statistically significant growth in Se exposed specimens. Se levels were higher in exoskeleton and hepatopancreas of both Se exposed males and females, when compared to controls. The abdomen-total weight relationship (Tw/B) showed no significant differences between Se exposed and control groups. A constant decline of HI values was recorded in both Se exposed sexes and the same trend was observed in control males. Se exposed females evidenced lower HI after 4 and 8 weeks when compared to controls. Therefore, evident reductions of the health indicator values HI suggested that selenium can deplete the hepatopancreas energy reserves, mainly in juvenile male crayfish.

Detoxifying response in juvenile tench fed by selenium diet.

The effects of a selenium (Se) diet (1.0 mg Se kg⁻¹) were investigated on growth, accumulation and antioxidant response in juvenile Tinca tinca at three endpoints (0, 4 and 8 weeks). Growth and condition factor (K>1.5) for both control (0.25 mg Se kg⁻¹) and Se tench were not significantly affected. Se exposed fish exhibited the highest Se level in the kidney and the liver after 4 weeks. By feeding more Se the accumulation capacity of tench did not increase and a plateau, mainly for the liver, was thus reached. Se level remained almost constant in the muscle if compared to own control and for each endpoint. Superoxide dismutase activity in both tissues was not affected by Se supplementation and the higher catalase level in the kidney might support the hypothesis that the enzyme was adequate to remove the hydrogen peroxide production following Se exposure. However, supplemented diet with higher Se level could be critical for tench, as it may cause a lowering of glutathione peroxidase and glutathione reductase activities facilitating the onset of oxidative damage. The enhancement of thiol level and glutathione S-transferase activity, mainly in the liver, could be the signals of the only protection against the oxidative damage induced by Se.

Molecular and phenotypic evidence of a new species of genus Esox (Esocidae, Esociformes, Actinopterygii): the southern pike, Esox flaviae.

We address the taxonomic position of the southern European individuals of pike, performing a series of tests and comparisons from morphology, DNA taxonomy and population genetics parameters, in order to support the hypothesis that two species of pike, and not only one, exist in Europe. A strong relationship emerged between a northern genotype supported by COI, Cytb, AFLP and specific fragments, and a phenotype with round spot skin colour pattern and a large number of scales in the lateral line, clearly separated from a southern genotype with other skin colour pattern and a low number of scales in the lateral line. DNA taxonomy, based on a coalescent approach (GMYC) from phylogenetic reconstructions on COI and Cytb together with AFLP admixture analysis, supported the existence of two independently evolving entities. Such differences are not simply due to geographic distances, as northern European samples are more similar to Canadian and Chinese samples than the southern Europe ones. Thus, given that the differences between the two groups of European pike are significant at the phenotypic, genotypic and geographical levels, we propose the identification of two pike species: the already known northern pike (Esox lucius) and the southern pike (E. flaviae n.sp.). The correct identification of these two lineages as independent species should give rise to a ban on the introduction of northern pikes in southern Europe for recreational fishing, due to potential problems of hybridisation.