Showing papers by "Ferdinando Boero published in 2006"

Spatial and temporal variability of sessile benthos in shallow Mediterranean marine caves

Abstract: Hypotheses on the spatial and temporal distribution of sessile assemblages in sub- merged marine caves have rarely been tested. Classically, the distribution of cave benthos has been related mainly to the physical gradients along the exterior-interior axis. Using a multifactorial sam- pling design, we examined the distribution of species assemblages within 3 different caves in South- ern Italy. Non-destructive sampling was repeated at 4 different times over a period of 11 mo. Results showed an overall pattern of change in the structure of the assemblages along the exterior-interior axis of the 3 caves (i.e. among sectors). Significant differences in species assemblages, however, were also observed within sectors (i.e. among areas), and changes in assemblages varied inconsistently with time and among caves. This result suggests a high complexity of the processes determining spatio-temporal distribution patterns in marine caves, which are context- and scale-dependent. Results also showed the uniqueness of these assemblages, which has important implications for their conservation and management.

Mitigating human disturbance: can protection influence trajectories of recovery in benthic assemblages?

Abstract: 1. Understanding whether Marine Protected Areas (MPAs) can be considered as a suitable tool for restoring the structure and function of populations and assemblages is urgently needed to achieve an effective policy of mitigation of human impact in coastal management. However, to date, the role played by MPAs in enhancing ecosystems resilience has been more advocated than unambiguously documented. 2. This study was designed to test whether full protection in marine reserves facilitates recovery of benthos impacted by the date mussel Lithophaga lithophaga fishery, one of the most harmful human activities affecting subtidal rocky habitats in the Mediterranean Sea. 3. The effects of this destructive fishery were reproduced at one fully protected location (P) and at two unprotected control locations (Cs) in the SW Mediterranean Sea. At each location, three plots (4 m2) of rocky surface at 4-6 m depth were disturbed experimentally, while another three plots served as reference. In each plot, the species composition and relative cover of the sessile benthic assemblages were sampled photographically on each of five occasions during a period of 20 months. 4. Over and above variation in habitat features among locations, multivariate and univariate analyses revealed significant differences between P-vs.-Cs in patterns of assemblage recovery and showed that, at the fully protected location, recovery was faster than at the unprotected control locations. 5. Our results suggest that MPAs have the potential to change the trajectories of recovery of disturbed assemblages by accelerating the processes of recolonization and call for further investigation to identify the specific mechanisms underlying increased resilience.

Vibrio harveyi associated with Aglaophenia octodonta (Hydrozoa, Cnidaria).

Abstract: A previously unknown association between a luminous bacterium, Vibrio harveyi, and a benthic hydrozoan, Aglaophenia octodonta, is described. Aglaophenia hydrocladia showed a clear fluorescence in the folds along the hydrocaulus and at the base of the hydrotheca, suggesting the presence of luminous bacteria. This hypothesis was confirmed by isolation of luminous bacteria from Aglaophenia homogenates. Phenotypic characterization of bacterial isolates was performed by several morphological, biochemical, and cultural tests, completed with 16S rDNA sequence analysis. All the isolates were referred to a single species: V. harveyi. The association between V. harveyi and A. octodonta has epidemiological as well as ecological significance. Therefore, A. octodonta may function as habitat "islands" providing a unique set of environmental conditions for luminous bacteria colonization, quite different from those already recorded from the plankton for other Vibrio species.

Evidence of reverse development in Leptomedusae (Cnidaria, Hydrozoa): the case of Laodicea undulata (Forbes and Goodsir 1851)

Abstract: Laboratory rearing and reconstruction of Laodicea undulata (Hydrozoa) life cycle led to the discovery for the first time in Leptomedusae of the potential for ontogeny reversal, i.e. the medusa stage can asexually transform back into the polyp stage. In turn, each rejuvenated polyp stage can newly activate the standard developmental programme towards colony morphogenesis and budding of secondary medusae. These can be considered as clonemates of the initial medusa batch, since they originate by asexual processes. In combination with the ordinary medusa budding process, the potential for reverse development might represent a tool to increase jellyfish population growth rate during the favourable season, but eventually it does not avoid jellyfish to die. Comparably to polyembryony, reverse development leads to offspring multiplication from a single fertilization event, with a wider dispersal of each single genotype; eventually, it favours the enhancement of the overall genetic diversity at small spatial scale. The life cycle of L. undulata from the Mediterranean Sea is re-described, linking previously uncoupled descriptions of either the polyp or the early medusa stages. Taxonomic considerations of the genus Laodicea and a comparison among the known Mediterranean species are also provided.