DOI: 10.3391/ai.2026.21.1.180751

Authors: Marco Boschiero, Chiara Facca, Francesco Cavraro, Simone Redolfi Bristol, Anna Gavioli, Federico Riccato, Matteo Zucchetta, Piero Franzoi

Abstract: The Atlantic blue crab (Callinectes sapidus) is among the 100 worst invasive species in the Mediterranean Sea, causing significant ecological and economic impacts. The aim of this study is to investigate key aspects of the species’ biology and ecology during its demographic outbreak in a Northern Adriatic area significantly affected by the species’ invasion. Year-round sampling was carried out across a short spatial gradient encompassing lagoon, estuarine, and marine habitats. This comprehensive approach aimed to elucidate the invasive success of the blue crab. Our findings shows that the species resulted widely distributed across all habitat types, with significant differences among stations, seasons, and sexes, with females being prevalent in higher salinity marine and outer lagoon waters during spawning season. These findings, along with the spatiotemporal analyses of the condition factor and the presence in the lagoon of various cohorts of juveniles over the year, highlight the completion of the complex life cycle of the blue crab on an extremely small spatial scale. Moreover, with an average of over 2 million eggs laid per female and a prolonged spawning season, the species reveals a robust reproductive potential, likely favoured by the short distance between mating and spawning habitats. In conclusion, the results of this study underscore the critical role of the short spatial environmental mosaic in facilitating the invasive success of C. sapidus, providing relevant data for managing this unprecedented demographic explosion.

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DOI: 10.3391/ai.2024.19.2.117212

Authors: Emanuele Pelella, Flaminia Mariani, Beatrice Questino, Simona Ceschin

Abstract: Freshwater ecosystems are among the most susceptible to biological invasions. The South American Ludwigia hexapetala is an aquatic plant that is becoming an increasing threat in many European waterbodies, recently including Italy. This study aimed to define the main parameters influencing the early colonization stage of L. hexapetala by overlapping the percentage cover of this species with environmental parameter data collected at 24 aquatic sites from six waterbodies in north-central Italy. At each site, chemical and physical characteristics of the water (temperature, pH, dissolved oxygen, conductivity, nitrates, phosphates, ammonia, depth, transparency), grain size of the substrate and level of anthropogenic disturbance were evaluated. The results showed that although L. hexapetala prefers shallow, warm, alkaline, moderately rich in ions and nutrients (especially phosphates) and oxygen-poor waters, it can grow in a wide range of environmental conditions. Moreover, as a typical invasive alien species, it spreads opportunistically in disturbed, unstable sites. Thus, L. hexapetala can invade freshwater habitats with different environmental conditions and subjected to anthropogenic disturbance. However, the results suggest that water depth may be a limiting factor in the early colonization stage of this species, which does not seem to be able to colonise waters deeper than 1 m in investigated sites, while it has been observed in significantly deeper waters in other European countries with a longer invasion history. Detecting the environmental parameters that most influence the growth of L. hexapetala becomes crucial both to identify the sites most at-risk of invasion in which to initiate timely monitoring actions for the species, and to be able to develop better management and control actions for this alien species in sites that have already been invaded.

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DOI: 10.3391/ai.2023.18.3.108128

Authors: Robin P. M. Gauff, Marc Bouchoucha, Amelia Curd, Gabin Droual, Justine Evrard, Nicolas Gayet, Flavia Nunes

Abstract: Introduced species constitute a critical bio-security issue worldwide and the precise monitoring of their spread is crucial for their management. For species forming cryptic complexes this may remain difficult. Using integrative taxonomy, we formally report for the first time, well-established populations of the cosmopolitan introduced bryozoan Watersipora subatra in the French Mediterranean Sea and compile worldwide existing genetic data for Watersipora species alongside newly acquired data to establish the most complete phylogeny of the genus to date. This revealed pervasive erroneous identifications in Genbank, which in turn perpetrate further errors in recent studies, primarily misidentifying W. subatra as W. subtorquata. High abundance and geographic spread of W. subatra in our Mediterranean sampling sites suggest that this species has been present for some time but has been misidentified until now. We provide an updated species identification for all current reference sequences in the Watersipora genus, which may help future monitoring of W. subatra and other Watersipora species.

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DOI: 10.3391/ai.2023.18.1.103438

Authors: Aylin Ulman, Hasan Deniz Akbora, Ozgur Çanak, Elaine Chu, Burak Ali Çiçek, Hasan Ersönmez, Sinan Mavruk, Caner Enver Özyurt, Taner Yildiz, Amy Liu, Nazli Demirel, Daniel Pauly

Abstract: The highly toxic orange-spotted toadfish Torquigener hypselogeneion (Bleeker 1852) [conspecific Torquigener flavimaculosus Hardy & Randall, 1983] is now a very common invasive fish in the Eastern Mediterranean. Its small size, well under 20 cm, may have concealed the danger it represents, and little is known about its biology or ecology. Here, the spawning seasons, gonado- and hepato-somatic index and condition factors of T. hypselogeneion from 3 locations of the Eastern Mediterranean are presented, based on a total of 1360 individuals sampled, i.e., 216 from Finike, 817 from Fethiye (both Turkey), and 327 from Cyprus. Our results show that T. hypselogeneion is a carnivorous species that forages on sandy bottoms, with a preference for small invertebrates, especially the small invasive gastropod Cerithium scabridum, crustaceans (hermit crabs, other crabs and barnacles), and sea urchins; however, at least in some localities, they appear to forgo eating during their peak reproductive period. The parameters of the von Bertalanffy Growth Function for T. hypselogeneion in the Eastern Mediterranean were: asymptotic length = 17.4 cm (total length; TL) and K = 0.96 year-1, implying a longevity of about 4 years, while the mean length at first maturity was about 10 cm (TL) for both sexes. An average-sized adult female (13 cm TL, 45.7 g live weight) was found to contain 1,250 eggs per gram body weight. Based on its high invasiveness and negative impacts to ecology of the Eastern Mediterranean and the human health, we suggest that T. hypselogeneion should be listed as a priority invasive species and that its population closely monitored within the Mediterranean Sea.

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