Role of food availability in the bathymetric distribution of the starfish "Marthasterias glacialis" (Lamk.) on reefs of northern Portugal

[EN] We examined whether the abundance and size of the starfish Marthasterias glacialis (Lamk.) exhibit a depth-dependent partitioning on subtidal reefs. We tested the hypothesis that differences in food availability can result in habitat partitioning along a depth gradient. The abundance and size of M. glacialis was registered at 4 depth strata: 0-4 m, 4-8 m, 8-12 m, and >12 m; we also recorded the number of food items that they were preying on. The abundance and size of M. glacialis decreased with depth. Mussels (Mytilus galloprivincialis) were the most preyed food item across all depth strata, followed by gastropods, sea urchins and barnacles; M. glacialis also consumed a significantly larger amount of mussels in feeding experiments compared with sea urchins and gastropods. The abundance of M. galloprivincialis beds decreased with depth. The clear link between the decrease in abundance and size of M. glacialis with depth and the decay of the most consumed prey (mussels) suggest that food availability may play an important role in the vertical distribution of this starfish, though wave-associated turbulence in the first few metres of the subtidal could also limit the abundance of M. glacialis.

Discussion about the validity of virtual practices in subjects in the radioccomunication area. Results of the educational experience

[EN]Nowadays we are living a virtual learning boom. Mainly, it is due to two facts: first, easy spreading of the knowledge and second, virtual learning is cheaper than classic instrumentation laboratories. This cost is even bigger in radiocommunication and high frequency area. In fact, time and time again there are more universities that give up offering the realization of laboratory practice. In the present report we propose a discussion about the increase of virtual practices when contact with instrumentation and circuits is basic. The experience of seven lecturers of the Communications Engineering Group (GIC) will be exposed.