This research investigates the occurrence of Pinna nobilis (Linnaeus, 1758) in the Mediterranean Sea, where it is an endemic and the largest bivalve species. Such a species is protected under the European Council Directive 92/43/EEC since 1992, being exposed to anthropogenic impacts. The distribution of this species has been known, in the past, only from reports in scientific literature. Presently, the concerns, threats and risks for P. nobilis are increasing and a more detailed mapping of the actual distribution from a largest to a local spatial scale is essential for the implementation of monitoring, management and conservation actions. Here we provide a systematic review on the occurrence of P. nobilis, employing and combining different sources of information, such as scientific and grey literature, NATURA 2000 geodata and citizen science records. The methodological approach is a pilot test based on a scaling down of the geographical area of study, from the whole of the Mediterranean Sea to the Italian and Apulian coastline (South-East Italy); accordingly, the above mentioned sources of data have been gradually included. The results show that the combination of multiple sources of information provide a more exact determination of the species distribution at a local scale, identifying sites where in-depth actions are required to ensure the species conservation and restoration. Also, the IUCN has recently underlined that the conservation of P. nobilis has become a difficult challenge, so that each of the spatial scales for the investigation is crucial to enable a better preservation and conservation of the species in the Mediterranean Sea.

Information on the presence of Pinnanobilis (Linnaeus, 1758) in the Mediterranean Sea is largely reported in literature because it is an endemic and, at the same time, endangered species. Besides, this record contributes to enlarge the spatial distribution of this species in the South-East Italian coastline (Adriatic Sea). P.nobilis is a protected species under the EU Habitats Directive (1992). In particular, P.nobilis has been recorded for the first time in the Aquatina Lagoon, a transitional water ecosystem included in the NATURA 2000 site “Aquatina di Frigole” (IT9150003). Therefore, this finding underlines the role of transitional water ecosystems as “nursery habitats” for P.nobilis as well as the relevance of conservation actions introduced by the EU with the NATURA 2000 network for preserving the biodiversity.

The behavioural choices made by foragers regarding the use of resource patches have a direct influence on the energy balance of the individual. Given that several individual traits linked to the acquisition of spatially distributed resources increase with body size (e.g., energy requirements, resource ingestion rates, and movement capacity), it is reasonable to expect size dependencies in overall foraging behaviour. In this study, we tested how body size influences the number, duration, and frequency of foraging episodes in heterogeneous resource patches. To this end, we performed microcosm experiments using the aquatic amphipod Gammarus insensibilis as a model organism. An experimental maze was used to simulate a habitat characterised by resource-rich, resource-poor, and empty patches under controlled conditions. The patch use behaviour of 40 differently sized specimens foraging alone in the experimental maze was monitored via an advanced camera setup. Overall, we observed that individual body size exerted a major influence on the use of resource patches over time. Larger individuals had stronger preference for the resource-rich patches initially and visited them more frequently than smaller individuals, but for shorter periods of time. However, larger individuals subsequently decreased their use of resource-rich patches in favour of resource-poor patches, while smaller individuals continued to prefer resource-rich patches for the whole experimental time. With body size being a key organismal trait, our observations support the general understanding of foraging behaviours related to preference, patch use, and abandonment.

Elucidating the underlying mechanisms behind variations of animal space and resource use is crucial to pinpoint relevant ecological phenomena. Organism's traits related to its energy requirements might be central in explaining behavioral variation, as the ultimate goal of a forager is to fulfill its energy requirements. However, it has remained poorly understood how energy requirements and behavioral patterns are functionally connected. Here we aimed to assess how body mass and standard metabolic rate (SMR) influence behavioral patterns in terms of cumulative space use and time spent in an experimental patchy environment, both within species and among individuals irrespective of species identity. We measured the behavioral patterns and SMR of two invertebrate species, that is, amphipod Gammarus insensibilis, and isopod Lekanesphaera monodi, individually across a range of body masses. We found that species of G. insensibilis have higher SMR level, in addition to cumulatively exploring a larger space than L. monodi. Cumulative space use scaled allometrically with body mass, and it scaled isometrically with SMR in both species. While time spent similarly in both species was characterized by negative body mass and SMR dependence, it was observed that L. monodi individuals tended to stay longer in resource patches compared to G. insensibilis individuals. Our results further showed that within species, body mass and metabolic rate explained a similar amount of variation in behavior modes. However, among individuals, regardless of species identity, SMR had stronger predictive power for behavioral modes compared to body mass. This suggests that SMR might offer a more generalized and holistic description of behavioral patterns that extend beyond species identity. Our study on the metabolic and body mass scaling of space and resource use behavior sheds light on higher‐order ecological processes such as species' competitive coexistence along the spatial and trophic dimensions.

Home range is the spatial evolutionary arena where an individual can succeed or fail. Its size reflects the balance between individual energy requirements and acquisitions. Since various behavioural traits can affect individual energy demand, we investigated how these traits affect individual space‐use behavior and resulting home range size of aquatic organisms. We compiled data for 172 freshwater and marine species, ranging from invertebrates to marine mammals, spanning 8 orders of magnitude in body size and 13 in home range size. Across all taxa, home range size scaled allometrically with body size ( R ² = 0.78, exponent = 1.68 ± 0.07). Behavioural traits explained an additional 27.15% of the variance beyond that explained by body size alone. In particular, carnivorous and pelagic species exhibited significantly larger home ranges than herbivorous and benthic ones, whereas migration and sociality were not retained as significant predictors beyond body size, despite migration affecting the intercept of the scaling relationship. We show that while body size is a strong predictor of home range, behavioural categories significantly modulate the allometric relationship. Our findings provide new insights into the behavioural constraints shaping spatial ecology in aquatic environments. These results underscore the role of energy‐demanding behaviours in shaping spatial ecology, with implications for individual density, the intensity of intra‐specific interactions, and patterns of interspecific coexistence.