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Freshwater crayfish are amongst the largest macroinvertebrates and play a keystone role in the ecosystems they occupy. Understanding the global distribution of these animals is often hindered due to a paucity of distributional data. Additionally, non-native crayfish introductions are becoming more frequent, which can cause severe environmental and economic impacts. Management decisions related to crayfish and their habitats require accurate, up-to-date distribution data and mapping tools. Such data are currently patchily distributed with limited accessibility and are rarely up-to-date. To address these challenges, we developed a versatile e-portal to host distributional data of freshwater crayfish and their pathogens (using Aphanomyces astaci, the causative agent of the crayfish plague, as the most prominent example). Populated with expert data and operating in near real-time, World of Crayfish™ is a living, publicly available database providing worldwide distributional data sourced by experts in the field. The database offers open access to the data through specialized standard geospatial services (Web Map Service, Web Feature Service) enabling users to view, embed, and download customizable outputs for various applications. The platform is designed to support technical enhancements in the future, with the potential to eventually incorporate various additional features. This tool serves as a step forward towards a modern era of conservation planning and management of freshwater biodiversity.

Abstract Narrow clawed crayfish, Pontastacus (Astacus) leptodactylus, represents an ecologically and economically valuable freshwater species. Despite the high importance of artificial breeding for conservation purpose and aquaculture potential, hatching protocols have not been developed so far in this species. Further, limited knowledge exists regarding the artificial egg incubation, the temperature effect on embryonic development, hatching synchronization and hatching rate. In the present study we investigated the temperature increase (from 17 oC to 22oC) effects in two different embryonic developmental stages of P. leptodactylus. Furthermore, two primer pairs for the Fibroblast Growth Factor Receptor 4 (FGFR4) gene cDNA amplification were successfully designed, characterising for the first time the FGFR4 gene in P. leptodactylus in relation to different developmental stages and temperatures. Apart from the FGFR4 gene, the Na+/K+-ATPase α-subunit expression was also explored. Both the FGFR4 and Na+/K+-ATPase α-subunit expression levels were higher in embryos closer to hatching. Egg incubation at 22oC for seven days led to significant increase of FGFR4 expression in embryos from earlier developmental stages. Nevertheless, temperature increase did not affect FGFR4 expression in eggs from latter developmental stages and Na+/K+-ATPase α-subunit expression in all developmental stages. Temperature increase represents therefore probably a promising strategy for accelerating hatching in freshwater crayfish particularly in early developmental stages. Specifically, our results indicate that FGFR4 expression increased in embryonic stages closer to hatching and that temperature influences significantly its expression in embryos from earlier developmental stages. Overall, these findings can provide a better understanding of artificial egg incubation of P. leptodactylus, and therefore can be employed for the effective management of this species, both for economic and biodiversity retention reasons.

Biofloc technology (BFT) offers an innovative eco-friendly approach that is particularly applicable in shrimp farming. Penaeus vannamei is the most important seafood species in terms of global economic value. Nevertheless, its increasing global demand highlights the necessity for sustainable production of P. vannamei shrimps outside their native range, assuring the avoidance of genetic pollution risk. Towards this direction, the present study focuses on the feasibility of tropical shrimp species aquaculture in indoor systems evaluating BFT application in temperate zones. The achievability of P. vannamei cultivation inside greenhouses in temperate latitudes is thoroughly examined and a representative experimental biofloc setup for P. vannamei within a greenhouse in Northern Greece is demonstrated. Nevertheless, there are two major limitations, related to economy and ecology, namely the energy demand for high seawater temperature and the fact that most reared shrimps are non-indigenous species setting risk for genetic pollution, respectively. To overcome the former, energy-saving measures such as tank and greenhouse insulation in combination with a microclimate chamber construction were implemented to optimize water temperature at minimal cost. Concerning the latter, there is clear evidence that P. vannamei populations cannot be established in the Mediterranean, setting aside any environmental risk. Overall, based on the developed and tested pilot prototype, employment of optimal management practices, innovative manufacturing and clean energy alternatives, and the utilization of ecosystem services could reduce the environmental impact and maximize the profitability of biofloc operations. These actions could probably permit sustainable and economically viable farming of P. vannamei employing BFT within greenhouses in the Mediterranean.

Ascidian biofouling generates significant challenges to bivalve aquaculture. Their rapid spread across almost every available surface leads to increased maintenance costs and reduced yields in shellfish farming. In addition, ascidians may introduce pathogens or toxins, further compromising the health and marketability of bivalve stocks and thereby necessitating strict management strategies to manage these impacts. The aim of this study was the evaluation of different management practices for eliminating ascidian fouling and the identification of the best method for Mytilus galloprovincialis (Lamarck, 1819) aquaculture farms. The effects of different anti-fouling treatments as well as their interactive outcomes were examined by conducting two experiments. Various experimental procedures were applied, including the temporally differential washing of mussels, air exposure and immersion in 50 ppt and 70 ppt salinity solutions, as well as the combination of these applications. All treatments reduced the number of ascidian colonies on mussel socks but at varying proportions. Immersing mussel socks in a 70 ppt salinity solution followed by air exposure for 1 day was the most efficient method and led to a 93% eradication.

Identification of a plant’s pollen components can be used to establish its geographical provenance, while also providing insights into the diet and foraging preferences of the honeybee (Apis mellifera L.). The diversity and amount of pollen represent crucial factors for pollinators. Here, we identified plant species visited by honeybees by analyzing the pollen pellets collected from honeybees in Kastoria, Greece. The results indicate that pollen from different periods was identified by means of floral composition. An interesting observation is that all identified plants belonged to different genera. Among the identified plants, native ones, such as the Macedonian pine, Pinus peuce, present a distinct foraging profile for local honeybees.

Freshwater crayfish are considered as aquatic products of high quality and high nutritional value. The increasing demand has led to populations reduction in several locations throughout their range. Thus, the development of appropriate rearing conditions is considered necessary, among which, optimization of their diet is a basic part. Towards this direction, in the present study, a 98-day feeding trial was carried out to evaluate the impact of dietary fishmeal substitution by Hermetia illucens meal on Pontastacus leptodactylus juveniles kept under laboratory conditions. Insect meals represent an environmentally friendly alternative solution, considered as a high-value feed source, rich in nutrients such as protein and fat. Three dietary regimens were utilized with a fishmeal-based without Hermetia meal (HM) defined as the control diet (HM0), and two diets, the first with 50% (HM50) and the second with 100% (HM100) of fishmeal substitution by HM, respectively. Growth performance, whole-body composition, and fatty acid profiles of individuals were studied in the different treatments. At the end of the feeding trial, statistically significant differences were observed in the mean survival rate (SR), specific growth rate (SGR), feed conversion ratio (FCR) and weight gain (WG) values. More specifically, animals fed with HM-based diets had higher mean SR, while the control group performed better regarding FCR and SGR. The HM inclusion in the diet significantly altered the whole-body chemical composition of the crayfish signifying a different metabolic utilization compared to fishmeal (FM). The fatty acid analysis revealed that 16:0 (palmitic acid) was the predominant saturated fatty acid (SFA), 18:1ω9 (oleic acid) was found to be the main monounsaturated fatty acid (MUFA), while 18:2ω6 (linoleic acid) represented the major polyunsaturated fatty acid (PUFA) followed by C20:3 cis ω3 (cis-11-14-17-eicosatrienoate) and C22:6 cis ω3 (cis-4,7,10,13,16,19-Docosahexaenoic) fatty acids. The inclusion of dietary HM significantly reduced the contents of ∑SFAs, ∑PUFAs and ∑ω6 fatty acids, as well as those of C22:6 cis ω3 and increased the ω6/ω3 and hypocholesterolemic to hypercholesterolemic ratios in the body. In parallel with improvements in balanced diets and in culture conditions that need to be optimised for rearing of freshwater crayfish, our study provides new data that enlighten the suitability of insect meals in the nutrition of P. leptodactylus.

Mediterranean finfish aquaculture is mainly represented by the production of the gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) growing in marine cage farms. Despite the numerous benefits of fish farming, the ecological risk potentially caused by fish escapes to the wild populations is occasionally high. In the current study, an integrated review of fish escapes is presented regarding S. aurata and D. labrax escapes and their potential effect on the genetic composition of wild populations. The collected data from the literature are combined and discussed along with recorded escapes in a fish farm located in the Aegean Sea, Greece. According to these records, fish escapes present a generally stable rate, ranging between 0 and 2% in each escape event, which occur 5–8 times per year. Although for other farmed fish species worldwide, the ecological risk may be higher, this risk is probably lower in Mediterranean finfish populations, which are characterized by generally low levels of genetic differentiation. Nevertheless, the risk of genetic introgression still exists. Particularly in sea bream and sea bass farming, genetic structure and differentiation in wild populations seem to be unaffected for now. Nevertheless, suitable management measurements would be a useful strategy to avoid future negative effects of fish escapes. These strategies should be focused on further efforts towards recapture program development, reduced escapees’ survival, and proper legislation. Furthermore, more data on escapees’ survival percentage, their migration pathways, and the way these pathways relate to mortality, the type of escape event, and the season of release would be also valuable.

Aquaculture is affected by numerous factors that may cause various health threats that have to be controlled by the most environmentally friendly approaches. In this context, prebiotics, probiotics, and synbiotics are frequently incorporated into organisms’ feeding rations to ameliorate the health status of the host’s intestine, enhancing its functionality and physiological performance, and to confront increasing antimicrobial resistance. The first step in this direction is the understanding of the complex microbiome system of the organism in order to administer the optimal supplement, in the best concentration, and in the correct way. In the present review, pre-, pro-, and synbiotics as aquaculture additives, together with the factors affecting gut microbiome in crayfish, are discussed, combined with their future prospective outcomes. Probiotics constitute non-pathogenic bacteria, mainly focused on organisms’ energy production and efficient immune response; prebiotics constitute fiber indigestible by the host organism, which promote the preferred gastrointestinal tract microorganisms’ growth and activity towards the optimum balance between the gastrointestinal and immune system’s microbiota; whereas synbiotics constitute their combination as a blend. Among pro-, pre-, and synbiotics’ multiple benefits are boosted immunity, increased resistance towards pathogens, and overall welfare promotion. Furthermore, we reviewed the intestinal microbiota abundance and composition, which are found to be influenced by a plethora of factors, including the organism’s developmental stage, infection by pathogens, diet, environmental conditions, culture methods, and exposure to toxins. Intestinal microbial communities in crayfish exhibit high plasticity, with infections leading to reduced diversity and abundance. The addition of synbiotic supplementation seems to provide better results than probiotics and prebiotics separately; however, there are still conflicting results regarding the optimal concentration.

Table olives are a major component of the Mediterranean diet and are associated with many beneficial biological activities, which are mainly related to their phenolic compounds. Olive fruit debittering process defines the quantitative and qualitative composition of table olives in biophenols. The aim of the present study was to evaluate the in vitro antioxidant capacity and DNA-protective activity of an extract originated from brine samples, according to the Greek style debbitering process of Kalamon olive fruits. The main phenolic components determined in the brine extract were hydroxytyrosol (HT), verbascoside (VERB) and tyrosol (T). The in vitro cell-free assays showed strong radical scavenging capacity from the extract, therefore antioxidant potential. At cellular level, human endothelial cells (EA.hy296) and murine myoblasts (C2C12) were treated with non-cytotoxic concentrations of the brine extract and the redox status was assessed by measuring glutathione (GSH), reactive oxygen species (ROS) and lipid peroxidation levels (TBARS). Our results show cell type specific response, exerting a hormetic reflection at endothelial cells. Finally, in both cell lines, pre-treatment with brine extract protected from H2O2-induced DNA damage. In conclusion, this is the first holistic approach highlighted table olive wastewaters from Kalamon- Greek style debittering process, as valuable source of bioactive compounds, which could have interesting implications for the development of new products in food or other industries.

The objective of this study was to assess the resting values of the physiological oxidative stress exhibited by lambs and kids reared in Greece, and the potential correlations between redox biomarker levels in blood and other tissues (liver, diaphragm, quadriceps, psoas major muscle). For this purpose, lambs and kids at different developmental stages (d.s.) were used. The latter corresponded to four live weight categories (LWC), each representing 25%, 35%, 70% and 100% of mature body weight. In each of the above tissues, the levels of five common redox biomarkers were determined: glutathione (GSH), catalase (CAT), total antioxidant capacity (TAC), thiobarbituric reactive substances (TBARS), and protein carbonyls (CARBS). The results revealed that lambs and kids belonging to the 35% LWC had weaker endogenous antioxidant pools, while animals in the 70% and 100% LWC had elevated intrinsic antioxidant defense systems. Blood redox biomarkers were associated with the respective ones measured in the diaphragm, liver, quadriceps, and psoas major of both species. Importantly, TBARS levels in blood of animals in the 25% and 100% LWC are correlated with the TBARS levels in all other tissues tested. Blood antioxidant parameters might be used as potential biomarkers to predict the antioxidant status of tissues that affect meat quality. The latter would facilitate quality assessment prior to slaughter, allowing for timely nutritional interventions that can improve meat products.

The impact of climate change on both terrestrial and aquatic ecosystems tends to become more progressively pronounced and devastating over the years. The sector of aquaculture is severely affected by natural abiotic factors, on account of climate change, that lead to various undesirable phenomena, including aquatic species mortalities and decreased productivity owing to oxidative and thermal stress of the reared organisms. Novel innovative technologies, such as aquaponics that are based on the co-cultivation of freshwater fish with plants in a sustainable manner under the context of controlled abiotic factors, represent a promising tool for mitigating the effect of climate change on reared fish. The rainbow trout (Oncorhynchus mykiss) constitutes one of the major freshwater-reared fish species, contributing to the national economies of numerous countries, and more specifically, to regional development, supporting mountainous areas of low productivity. However, it is highly vulnerable to climate change effects, mainly due to the concrete raceways, in which it is reared, that are constructed on the flow-through of rivers and are, therefore, dependent on water’s physical properties. The current review study evaluates the suitability, progress, and challenges of developing innovative and sustainable aquaponic systems to rear rainbow trout in combination with the cultivation of plants. Although not commercially developed to a great extent yet, research has shown that the rainbow trout is a valuable experimental model for aquaponics that may be also commercially exploited in the future. In particular, abiotic factors required in rainbow trout farming along, with the high protein proportion required in the ratios due to the strict carnivorous feeding behavior, result in high nitrate production that can be utilized by plants as a source of nitrogen in an aquaponic system. Intensive farming of rainbow trout in aquaponic systems can be controlled using digital monitoring of the system parameters, mitigating the obstacles originating from extreme temperature fluctuations.