Swimming physiology of European silver eels (Anguilla anguilla L.): energetic costs and effects on sexual maturation and reproduction

The European eel migrates 5,000–6,000 km to the Sargasso Sea to reproduce. Because they venture into the ocean in a pre-pubertal state and reproduce after swimming for months, a strong interaction between swimming and sexual maturation is expected. Many swimming trials have been performed in 22 swim tunnels to elucidate their performance and the impact on maturation. European eels are able to swim long distances at a cost of 10–12 mg fat/km which is 4–6 times more efficient than salmonids. The total energy costs of reproduction correspond to 67% of the fat stores. During long distance swimming, the body composition stays the same showing that energy consumption calculations cannot be based on fat alone but need to be compensated for protein oxidation. The optimal swimming speed is 0.61–0.67 m s−1, which is ~60% higher than the generally assumed cruise speed of 0.4 m s−1 and implies that female eels may reach the Sargasso Sea within 3.5 months instead of the assumed 6 months. Swimming trials showed lipid deposition and oocyte growth, which are the first steps of sexual maturation. To investigate effects of oceanic migration on maturation, we simulated group-wise migration in a large swim-gutter with seawater. These trials showed suppressed gonadotropin expression and vitellogenesis in females, while in contrast continued sexual maturation was observed in silver males. The induction of lipid deposition in the oocytes and the inhibition of vitellogenesis by swimming in females suggest a natural sequence of events quite different from artificial maturation protocols

Abundance and distribution of the white shark in the Mediterranean Sea

Conservation of apex predators is a key challenge both in marine and terrestrial ecosystems, and sharks represent one of the most endangered groups in the ocean as a consequence of fishing exploitation, high vulnerability and a generalized lack of data on ecology and conservation status. This situation is particularly critical in the Mediterranean Sea due to its millenarian history of exploitation. Even if the white shark is a rare but persistent inhabitant of the Mediterranean Sea, its ecology in the area is still largely unknown. We have scarce information about white shark distribution and habitat use, aspects that are critical for conservation and management. The species is currently assessed as “Critically Endangered” according to the IUCN Regional Redlist criteria. In this study, we built the most comprehensive database of white shark occurrence records in the area (773 observations) and used them to characterize the spatial and temporal patterns of abundance of Mediterranean white sharks within a large temporal window (1860-2016). We fitted generalized additive models to standardized occurrence rates and used spatially disaggregated information on human coastal population abundance as a proxy of observation effort. Our results suggest a complex trajectory of population change characterized by a historical increase and a more recent steep reduction (61.5%) since the second half of 20th-century. Declines ranged between 52% and 97% across different Mediterranean sectors, with a contemporary regional contraction of the spatial distribution. For the first time, these results would inform conservation assessments, underlining the importance to produce status assessments based on population trends that are not suspected but quantitatively inferred. Furthermore, our analyses resulted instrumental to advance new hypotheses on the white shark occurrence and ecology in the Mediterranean Sea and to plan tagging programs with the purpose of collecting high-quality ecological data such distribution, population structure, foraging and habitat use

A New Approach to Evaluate the Biomechanical Characteristics of Osseointegrated Dental Implants

Tooth loss is a common pathology that affects many people. Dental osseointegrated implants are the ideal solution to restore normal functionality in partially or completely edentulous patients. The not perfect osseointegration and the fixture fracture are the main causes of failure for these kinds of implant. To avoid these drawbacks, several studies have been conducted to analyse the behaviour of dental implants. Aim of this work is to analyse the biomechanical behaviour of three different endosseous dental implants. For this purpose, a new numerical model has been developed to simulate different levels of osseointegration and to evaluate the stress values on the bone at different times. In this way, it can be investigated the possibility of anticipating the use of dental implants that usually is delayed three months after surgery. Obtained results confirm the validity of the proposed approach and can provide useful guidelines for dentists