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The present study supports the usefulness of ancillary techniques, such as immunohistochemistry, as a valid diagnostic tool in the field of fish oncology. The immunohistochemical patterns observed in four neoplasms on four individual teleosts belonging to different species are described. Cytokeratin, vimentin, actin, S100, calretinin, and Melan-A antibodies were used. Diagnoses of papilloma in a Bream Abramis brama, fibroma in a Sand Steenbras Lithognathus mormyrus, schwannoma in a Crucian Carp Carassius carassius, and melanoma in a spontaneously inbred Xiphophorus hybrid were made. Diagnosis of tumors in fish is not always easy to carry out, and the tool provided by antibodies used on mammalian tissue is essential for obtaining definitive, unambiguous, and inexpensive identification.

The objective of the present study was to evaluate the occurrence of pathogens and diseases in laboratory fish over a 10-year period at the Centre for Experimental Fish Pathology of Sicily, University of Messina. This report also emphasizes the adverse effects of subclinical infections on research endpoints, as well as the importance of animal health with respect to welfare. Infections in fish used for research can alter experimental outcomes, increase the variability of data, and impede experimental reproducibility. For this purpose, 411 diseased fish of different species (out of a total of 2820 fish) that belonged to four marine species ( Dicentrarchus labrax, Sparus aurata, Argyrosomus regius and Mugil cephalus) and to four fresh water species ( Danio rerio, Carassius auratus, Xiphophorus variatus and Poecilia reticulata) were examined in this study. Our results showed that mycobacteriosis and myxosporidiosis were the most important diseases found in our research fish, and the results represent a useful tool to obtain wider knowledge on the incidence of various diseases in different fish species. Further studies in this field are necessary to improve knowledge on the state of the health of fish used for research.

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Otoliths are used in taxonomy and ichthyology as they can provide a wide range of information about specimens. They are an essential tool to monitor the most sensitive species for a sustainable exploitation level. Despite the increasing use of sagittae in research, their inter- and intra-specific variability and eco-functionality are still poorly explored. This paper aims to investigate the inter- and intra-specific variability of Mugilidae sagittae using morphological and morphometrical analysis, as well as scanning electron microscopy and shape analysis. The sagittae of 74 specimens belonging to three different Mugilidae species, collected from a coastal lagoon, were analyzed to give an accurate description of their morphology, morphometry, shape and crystalline habits. The results highlighted the intra- and inter-specific variability of sagittae, showing morphometrical differences among species and slight differences between left and right sagittae in C. labrosus individuals. Moreover, SEM images showed a peculiar crystal organization, with several different crystal habits and polymorphs. This study provides an accurate description of sagittae in the studied species, deepening the knowledge on inter- and intra-specific variations and crystal habits and providing data which will be useful for future studies on otoliths. With this data, it will be possible to improve conservation and exploitation sustainability in sensitive habitats.

Metabolic dysfunction-associated fatty liver disease (MAFLD) includes several diseases, ranging from simple steatosis to steatohepatitis, fibrosis and cirrhosis. Fish-rich diets are considered helpful in the prevention of MAFLD, and the enzymatic hydrolysis of fish waste has been explored as a means of obtaining high-value protein hydrolysates, which have been proven to exert beneficial bioactivities including anti-obesity and hypocholesterol effects. This study aimed to assess the effect of the administration of protein hydrolysates from anchovy waste (APH) for 12 weeks on attenuated high-fat diet-induced MAFLD in apolipoprotein E-knockout mice (ApoE–/–). Thirty ApoE–/– mice were divided into two groups (n = 15/group) and fed a high-fat diet (HFD), with and without the addition of 10% (w/w) APH. After 12 weeks, serum and hepatic lipid profiles, hepatic enzyme activities, liver histology and immunohistochemistry were analyzed to assess hepatic steatosis, inflammation and fibrosis. Twelve-weeks on a 10% (w/w) APH diet reduces total cholesterol and triglyceride serum levels, hepatic enzyme activity and hepatic triacylglycerol content (p < 0.0001), and results in a reduction in hepatic fat accumulation and macrophage recruitment (p < 0.0001). The results suggest that a 10% APH diet has an anti-obesity effect, with an improvement in lipid metabolism, hepatic steatosis and liver injury as a result of a high-fat diet. Protein hydrolysates from fish waste may represent an efficient nutritional strategy in several diseases, and their use as nutraceuticals is worthy of future investigation.

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Otolith features are useful tools for studying taxonomy, ecology, paleontology, and fish biology since they represent a permanent record of life history. Nevertheless, the functional morphology of otoliths remains an open research question that is useful to completely understand their eco-morphology. This study aims to deepen the knowledge of intra- and interspecific variation in sagitta morphology in three congeneric seabreams, to understand how such variability could be related to the lifestyles of each species. Therefore, the sagittae (n = 161) of 24 Pagellus bogaraveo, 24 Pagellus acarne, and 37 Pagellus erythrinus specimens, collected from the south Tyrrhenian Sea, were analyzed using scanning electron microscopy and a stereomicroscope to assess morphometric features, variability between otolith pairs and the external crystalline structure the of sulcus acusticus. Statistical analysis demonstrated that, between the species, variability in sagittal otolith rostral length growth and sulcus acusticus features, correlated with increased fish total length and body weight. Moreover, slight differences between otolith pairs were detected in P. acarne and P. erythrinus (P < 0.05). The results confirm changes in otolith morphometry and morphology between different congeneric species and populations of the same species from different habitats.