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The reproductive performance of Octopus vulgaris broodstocks fed two different diets (mixed fish [F group, BW 1,048.14 g] or mixed crustaceans [C group, BW 998.44 g]) was analyzed using an experimental recirculating aquaculture system consisting of a tank equipped with spawning and incubation chambers. A total of 8 females (F1–4; C1–4), and 8 males (M1–M8) were selected. DI of the C group females was significantly (p

European eel Anguilla anguilla is among the highly valued species for aquaculture. Since its peculiar biology, it is not yet possible to complete the whole life cycle in artificial conditions and its supply depends entirely on wild catches. In the last 50 years this species has suffered a population reduction of 99 % mainly due to overfishing. In a conservation perspective, it is of fundamental importance to improve the aquaculture production of European eel, to avoid the extinction of this species and preserve its residual genetic variability, allowing at the same time the fulfilling of costumers request without increasing its harvesting pressure.In this study we aimed to deepen the knowledge about the mechanisms at the basis of reproduction of the European eel in semi-natural conditions, through direct observation of spawning behaviour and through the paternity assignment using microsatellite markers. The systematic and prolonged observation of the reproductive behaviour of European eel and the contextual parentage analyses we carried out for the very first time in this species on 39 adults and 432 F1 randomly collected. We contributed to unravel the sexual behaviour of this species in the most common artificial reproduction conditions (polyandry), and define the precise courtship sequence until the release of gametes, and the male-male hierarchy in courtship. We characterized for the first time three main types of male: dominant (the first who starts the courtship, and the one with the majority of F1 assigned), subordinate (which starts the courtship only in a second time and with a minor percentage of F1 ascribed) and ineffective (which sometime appears totally disinterested to courtship and has few F1 or none).The evidences here produced represent an important attempt for developing good reproduction practices of the critically endangered European eel, providing a good starting point for its future aquaculture production. Keywords: Anguilla anguilla, Aquaculture, Artificial breeding, Kinship analysis, Parentage assignment

The European eel has recently been included on the Red List of the International Union for Conservation of Nature (IUCN) as a critically endangered species. The rearing of Anguilla larvae is seen as a key bottleneck to the mass production of glass eels since very little ecological information is available regarding their natural nutrition. Studies of digestive physiology and ontogenetic development in eel larvae could provide useful information for solving some of the puzzles regarding larval fish culture. The aim of this study was to characterize the ontogeny of pancreatic enzymes (trypsin, lipase and amylase) and a peptide hormone regulator of pancreatic secretion (cholecystokinin) in terms of gene expression in European eel larvae from day 0 (P0) of hatching to 5, 10, 15 and 20 days post hatching during fasting. The results in the present study showed that all the genes selected were present, with different levels of expression and increasing trends, during larval development. At P0, the increase in the gene expression of lipase and amylase was higher than that of trypsin and cholecystokinin, confirming that enzymatic activity began before mouth opening and that larvae, provided with a complete enzymatic set, might have the capacity of digesting and absorbing various nutrients.

This investigation focused on an episode of chronic mortality observed in juvenile Huso huso sturgeons. The examined subjects underwent pathological, microbiological, molecular, and chemical investigations. Grossly severe body shape deformities, epaxial muscle softening, and multifocal ulcerative dermatitis were the main observed findings. The more constant histopathologic findings were moderate to severe rarefaction and disorganization of the lymphohematopoietic lymphoid tissues, myofiber degeneration, atrophy and interstitial edema of skeletal epaxial muscles, and degeneration and atrophy of the gangliar neurons close to the myofibers. Chemical investigations showed a lower selenium concentration in affected animals, suggesting nutritional myopathy. Other manifestations were nephrocalcinosis and splenic vessel wall hyalinosis. Septicemia due to bacteria such as Aeromonas veronii, Shewanella putrefaciens, Citrobacter freundii, Chryseobacterium sp., and pigmented hyphae were found. No major sturgeon viral pathogens were detected by classical methods. Next-generation sequencing (NGS) analysis confirmed the absence of viral pathogens, with the exception of herpesvirus, at the order level, also, the presence of Aeromonas veronii and Shewanella putrefaciens was confirmed at the family level by the metagenomic classification of NGS data. In the absence of a primary yet undetected biological cause, it is supposed that environmental stressors, including nutritional imbalances, may have led to immune system impairment, facilitating the entry of opportunistic bacteria and mycotic hyphae.

Sperm density and performance of wild and farmed male European eels were evaluated to investigate the effect of maintenance in captivity on ejaculate quality. Hormonal stimulation (with human chorionic gonadotropin) lasted for 17 weeks. Different origins of the male European eels partially influenced the quality of the ejaculates. Indeed, wild animals (i.e., collected at a natural site) had greater sperm longevity during the hormonal stimulation, whereas there was no significant effect of the origin on sperm density, spermatocrit, the percentage of motile sperm, and plasma testosterone concentrations. The different origins of the males also affected fatty acid sperm content, with greater unsaturated fatty acid and omega-6 concentrations in wild eels and lesser concentrations of saturated fatty acids and omega-3 fatty acids in farmed eels. Regarding sperm quality of European eels, this is the first study that takes into account the effect of different origins of stimulated males (wild-caught compared with farmed) on sperm quality, and these findings may help to improve the production of high-quality gametes in this endangered species.

The reproductive performances of silver European eel in term of gonad development and egg production, employing slow-release implants with the androgen 17-MT (1Â mg) in combination with traditional weekly injection of carp pituitary extract (CPE) was evaluated. Wild female European eels (Anguilla anguilla) underwent a standard induction protocol with CPE and were randomly divided into three groups (N-group, no implant; Y-group, with implant; and control, C-group, no treatment). The results showed that 17-MT-treated females (Y-group) reproduced spontaneously about 6 weeks earlier than the N-group females with a saving of almost 40% in CPE and time of induction. Concerning artificial induction of maturation in female silver eels, our study demonstrated that they positively respond to androgen exposure also in terms of eggs productivity. Indeed, Y-group was more productive than N-group: in Y-group, 11 eels ensured an eggs production that exceeded 50% of initial body weight (BW), whereas in N-group only three eels have exceeded this value. The results suggest that 17-MT should be considered in future protocols for the improvement of the artificial reproduction of female silver European eels.

This study aimed to compare the fertility of eggs between artificially matured female silver eels that spawned spontaneously and those that were spawned by manual stripping. The effects of the two methods of spawning on ovulation and fertilization rate were also investigated. For this purpose, 18 wild female European els captured in Bonello lagoon (North Adriatic Sea) were carp pituitary extract-injected to undergo sexual maturation and ovulation; a final injection of 17,20b-dihydroxy-4-pregnen-3-one (DHP) was administered when at least 30% of the oocytes were fully transparent. After the DHP-injection, nine eels were transferred to a new closed recirculating aquaculture system, where they were housed with spermiating males (sex ratio 4/1) to allow spontaneous spawning (SPT-group); the remaining nine eels were transferred to a 250 L tank and ovulation was checked at four-hourly intervals by manual stripping (STR-group). The number of eggs per female in the SPT-group was significantly greater than that in the STRgroup. Furthermore, fertilization rates in the SPT-group were notably higher than those observed in the STR-group. Significantly, the best performances were obtained among eels in which at least 50% of oocytes were fully transparent at the time DHP was administered. We conclude that the fertility of eggs from spontaneously spawning eels is superior to that of eggs acquired by strip-spawning and artificial fertilization.

Enrofloxacin (EF) is a veterinary drug for respiratory, gastrointestinal and urinary tract infections. Parenteral administration at doses higher than the manufacturer recommended dosage has induced cartilage lesions in juvenile mammals and poultry. In elasmobranchs EF is commonly used for the treatment of infectious diseases, however only one study has been performed previously to evaluate pharmacokinetics and the potential chondrotoxicity of a fluoroquinolone in adult skates. In present study juvenile lesser spotted dogfish (Scyliorhinus canicula, Linnaeus, 1758) were treated with low (LD, 5 mg/kg) and high dose (HD, 10 mg/kg) of EF daily via intramuscular injection for 15 consecutive days, as indicated in a recognized treatment. Hematological parameters, oxidative stress and histology of vertebral cartilage were evaluated. No cartilage damage was observed. Hematological parameters evaluation underlined a significant (p = 0.035), dose-dependent reduction in red blood cell count and in hematocrit (40% and 6%, respectively). Anyway, the biological significance of this reduction is doubtful, due to limited decrease observed. The evaluation of oxidative stress parameters underlined that glutathione levels, as well as glutathione S-transferase and catalase activities, were significantly increased in HD group animals, with respect to untreated and solvent control groups. Obtained data do not support a toxic effect of EF on dogfish cartilage, while concern arises from hematological and oxidative stress data.

Inclusion of sustained-release androgen implants into fertility treatment regimes of female freshwater eels has been proposed to benefit artificial maturation outcomes. This study sought to test whether co-administration of the androgen 17-methyltestosterone (17-MT) in combination with ‘traditional’ hypophysation of female European silver eels would affect egg quality and subsequent larval survival. Implants, containing 1 mg 17-methyltestosterone (17α-methyl-4-androsten-17β-ol-3-one in a matrix of cholesterol:cellulose = 95:5), were administered twice, at 1 and 5 weeks after onset of experimentation (MTA- and MTB-groups); control eels (Ctrl) were given a blank implant. Female eels received weekly injections with carp pituitary homogenates (CPH) from either Week 1 (MTA- and Ctrl groups) or Week 5 onwards (MTB-group). First 4 injections were made with 10 mg CPH/kg body weight (BW) in sterile physiological saline (0.9% NaCl); the subsequent 12 injections with 30 mg/kg CPH and thereafter, 40 mg/kg CPH was injected until fish were considered ready for induction of final maturation. Bi-weekly blood samples were collected (Day 0 onwards) and analyzed for levels of testosterone (T) and estradiol-17β (E2) by radioimmunoassay. After reaching maturity, fertilized eggs were obtained upon spontaneous spawning of co-housed breeders and egg performance (fertilization, hatching, survival rates) was recorded. No differences were observed between eels from the MTA- and MTB-groups; however, egg performance was notably better in eels treated with 17-MT + CPH compared to eels receiving CPH only, with hatching rates reaching mean values as high as around 70% for both 17-MT and CPH co-treated groups, but only averaging 21.0 ± 8.4% for eggs from the Ctrl-group. Furthermore, 17-MT treated eels displayed a more distinct pre-spawning peak for levels of plasma T and E2 and for body weight, the latter being indicative of increased batch fecundity. We conclude that androgen co-treatment holds promise for future development of eel captive breeding technologies. Statement of relevance Artificial propagation of the European eel is increasingly urgent to release the strain on natural populations. This study presents a novel approach to artificial maturation of female eels: centered around the incorporation of androgens during fertility treatment. Accordingly, increased performance was observed in terms of fertilization, hatching and survival rates, which contributes to completing the life cycle of this fish in captivity. © 2017 Elsevier B.V.

This study aimed to set up a method for the long-term management of Adriatic sturgeon, through the analysis of sex steroids and the genetic profiling of individuals in order to maximize the already reduced genetic variability of this species. Ten A. naccarii adults (nine of captive origin, one captured in the Ticino river and then moved into captivity) and eight subadults located in a semi-natural land-locked pond in Abbiategrasso (Milan, Italy) were analysed. Plasma testosterone differed significantly in the eight analysed subadults allowing their differentiation into two groups: the first group with an average testosterone concentration of 5.42 ± 1.31 ng/ml (probably female) and the second group with an average of 423.14 ± 75.97 ng/ml (probably male), as subsequently confirmed by artificial stripping. The plasma testosterone level was also significantly different between adult males and females (371.37 ± 43.58 vs. 95.34 ± 51.10 ng/ml), while the E2 levels showed no significant differences. Animals were genotyped on the basis of 10 microsatellite loci and their parental relationships were defined: four adults, two females and two males, generated the eight subadults. On the basis of pedigree analyses and genetic distances, 15 unrelated couples were identified for the future breeding seasons. Finally, the adult female captured in the Ticino River showed an interesting genetic profile, widely different from all of the other 17 specimens analysed, and represents a valuable source of genetic diversity.

Florfenicol (FF) is employed in fish farms to contest or prevent bacterial infections. However, this pharmaceutical may produce reactive oxygen species that may cause biochemical changes in antibiotic-treated fish. The aim of this study was to evaluate the effect of FF on Rainbow Trout Oncorhynchus mykiss treated for 10 d with 7.5 and 15 mg/kg FF followed by a withdrawal period of 5 d. Superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, glyoxalase I and glyoxalase II, total glutathione, lactic dehydrogenase, and alkaline phosphatase were investigated in the livers of treated and untreated fish. A general impairment of antioxidant enzymes and metabolic indicators was measured in FF-treated Rainbow Trout. Onset of oxidative damage may have occurred during the antibiotic treatment as a consequence of the effect of FF toxicity at mainly the highest dose. Nevertheless, the rise in levels of total glutathione and glutathione S-transferase even after the withdrawal period may shield the antibiotic-mediated oxidative processes. Received December 22, 2015; accepted May 26, 2016.