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.

The European eel (Anguilla anguilla, Linnaeus 1758) is a catadromous fish with significant cultural, scientific, and commercial value. The protection of this species is particularly difficult because the biology of the eel life cycle remains unknown in many aspects. The European eel (A. anguilla) population has declined alarmingly over the past 30 years; this condition has led to questions about the long-term welfare of this species. This work aims to perform a histological analysis on gonad samples from European eels coming from four different lagoons of the North Adriatic at different stages of silvering, and to evaluate the maturation of the gonads. For this study, a total of 859 wild eels were captured from four different lagoons using the “lavoriero”. Subsequently, the biometric parameters were collected. Seventy-nine female eels were randomly selected, dissected, and the gonads were removed for histological analysis. Sections of 4 µm were cut and stained with hematoxylin and eosin (H&E). Histological observations of germ cells at the light microscopy level allowed for the characterization of six steps of oocyte maturation. Valle di Comacchio had the highest levels of oocyte maturation, while Valle Ca’ Pasta had the lowest. Eels with silver index III had an oocyte maturation nearly equal to that of eels at stages IV and V of silvering. Considering the results, we can affirm that eels from North Adriatic lagoons have high oocyte maturation levels and high GSI value indices at silvering stage III. The following experimental work shows that the levels of oocyte maturation are higher even at lower silver index levels. It can be hypothesized that in these eels, the transition from yellow to silver eel occurs faster in relation to the high trophic availability in North Adriatic lagoons.

The European eel, Anguilla anguilla (Linnaeus, 1758), is a species of high conservation and commercial value. Also, with a high aquacultural value, it was one of the most farmed species in Europe before its decline. Conservation measures for this species are currently being implemented, some of which are the release of adults to allow them to migrate to spawning grounds and artificial reproduction to minimise the impact of overfishing. Much progress has been made regarding the closing of the life cycle, but several problems remain to be solved, such as the weaning and growth of larvae. In this regard, the study of local populations and the identification of the best spawners could be a good way forward as it would help to identify spawners with high reproductive potential and good offspring quality. In this study, we compared the reproductive performance of female eels from migratory areas of the Northern Adriatic Sea at different maturation stages (10 pre-migrant stage; 10 migrant stage), treating both groups with the same hormonal protocol (weekly carp pituitary extract, injection of 17α,20β-Dihydroxy-4-pregnen-3-one at complete oocyte maturation). The research showed that eels at the beginning of metamorphosis (SI III), i.e., eels not yet ready to undertake migration, achieve reproductive performance equal to that of eels ready for migration (SI IV). Their performance was on par in both qualitative and quantitative terms. The optimal results in hatching (with values of 65.8 ± 3.2% for pre-migrant and 68.2 ± 4.1% for migrant) and survival rates (with value of 25.7 ± 5.4% pre-migrants; 27.2 ± 3.7% migrants), as well as the results about the time to reach full gonadal maturation, may have positive implications when considering release and restocking measures.

Octopus vulgaris is a commercially valuable species. It is overexploited in the natural environment and is considered to be an innovative species for aquaculture. However, large-scale farming is generally designed only based on economic requirements, disregarding any form of enrichment that induces the natural behavior of aquatic species. Although many studies have shown the influence of environmental enrichment on terrestrial vertebrates, fish, and cephalopod mollusks, information on the effect of environmental enrichment on the body patterns of O. vulgaris is limited. Therefore, in this study, we assessed how different environmental conditions (Basic vs. Enriched) affect sub-adults of O. vulgaris kept in recirculation systems, through qualitative–quantitative studies of the main body patterns and their potential application in the commercial production of this species. The results indicated that octopuses kept in the enriched environment showed several body patterns and gained a significantly higher weight than those kept in the basic environment. The body patterns displayed by the individuals kept in the basic environment were similar to those exhibited under situations of hostility and inter/intra-specific conflict. Hence, the environment of octopuses needs to be enriched, especially for the large-scale production of this species.

Background and Aim: Seasonal changes, especially temperature and photoperiod, are well-known determining factors of swine reproductive capacity, but the underlying mechanisms remain unknown. This study aimed to investigate the effect of age and seasonal variations on boar seminal plasma steroids (dehydroepiandrosterone [DHEA], cortisol [CORT], and testosterone [TEST]) over 1 year. Materials and Methods: Four commercial hybrid adult boars (Large White × Duroc), aged between 12 and 44 months, were repeatedly evaluated at the Department of Veterinary Medical Sciences of the University of Bologna. Daily temperature and light hours relating to the collection date were considered for each observation within the four astronomical seasons: Winter, spring, summer, and autumn. Hormones were quantified using radioimmunoassay. The association between seasonal factors and hormone concentrations was evaluated using linear regression models. Univariate models were estimated for each hormone to assess the influence of the independent variables; two multivariate models were assessed to evaluate the effect of temperature and daylight hours, including boar and season factors. Results: Age significantly affected all analyzed hormones (CORT p < 0.0001; DHEA p < 0.0001; and TEST p < 0.0001). The highest average levels were found for each hormone during summertime, suggesting a positive correlation between steroid concentrations with temperature and light hours. Conclusion: The results of this study support the hypothesis that the increase in external temperature and light hours is somehow associated with higher levels of steroid concentrations in the seminal plasma of in-housed boars. These findings may help further investigate seasonal fluctuations in reproductive outcomes, which are well-known for porcine species. Keywords: boar, ejaculate, reproduction, seasonal parameters, steroids, swine.