Luigi Musco

Taxonomic sufficiency in the detection of natural and human-induced changes in marine assemblages: a comparison of habitats and taxonomic groups.

Taxonomic Sufficiency (TS) is a promising analysis technique, particularly in light of the current need for rapid and reliable procedures in marine impact assessment and monitoring. However, generalizations are still difficult and there are few studies comparing the effectiveness of TS under different environmental settings. The present study investigates whether reduced taxonomy can be used to detect natural and human-driven patterns of variation in mollusk and polychaete assemblages from subtidal soft and hard bottoms in the Mediterranean. Results showed that, unlike in polychaetes, mollusk families represent effective taxonomic surrogates across a range of environmental contexts. These findings suggest that the mechanisms behind TS in mollusks could act homogeneously across habitats and environmental conditions. In contrast, multiple factors could interact to determine the robustness of polychaetes to taxonomic aggregation. This study highlights the need to go beyond the current pragmatism in this field of work and focus on the reasons underlying TS effectiveness in order to provide a general framework on the application of taxonomic surrogates in marine systems.

Inventory and distribution of hard bottom fauna from the marine protected area of Porto Cesareo (Ionian Sea): Porifera and Polychaeta

Abstract The hard bottom fauna of the marine protected area of Porto Cesareo (Salento Peninsula) was examined considering two representative benthic groups, Porifera and Polychaeta. Sampling was performed by SCUBA divers from the surface to a depth of 25 m in a variety of environments. Sponge and polychaete assemblages were rich and diversified, with a total of 160 taxa collected (66 and 94, respectively), representing the first large contribution to the knowledge of the two groups in the marine protected area. This was particularly true for polychaetes, 80% of which had not been previously reported in the literature for this area. The distribution of the species in the examined environments is also given.

A new species of Sphaerosyllis (Polychaeta, Syllidae, Exogoninae) from the coasts of Italy and Cyprus (eastern Mediterranean Sea)

Abstract The faunistic analysis of hard and soft benthic materials collected from the Marine Reserve of Porto Cesareo (Ionian Sea, Salento Peninsula, Italy) and the coast of northern Cyprus (Levant Sea) revealed a new species of Sphaerosyllis, S. boeroi sp. n. (Polychaeta, Syllidae, Exogoninae). This species is mainly characterized by having compound chaetae with discernable subdistal spine, a strong dorso‐ventral gradation in size of blades throughout the body, elongated slender blades of superior compound chaetae on anterior and middle parapodia, parapodial glands with fibrillar material, and the distributional pattern of papillae on the body surface. Sphaerosyllis boeroi is described and compared to the other morphologically similar species, with emphasis on its ecological and reproductive patterns.

The effects of an invasive seaweed on native communities vary along a gradient of land-based human impacts

The difficulty in teasing apart the effects of biological invasions from those of other anthropogenic perturbations has hampered our understanding of the mechanisms underpinning the global biodiversity crisis. The recent elaboration of global-scale maps of cumulative human impacts provides a unique opportunity to assess how the impact of invaders varies among areas exposed to different anthropogenic activities. A recent meta-analysis has shown that the effects of invasive seaweeds on native biota tend to be more negative in relatively pristine than in human-impacted environments. Here, we tested this hypothesis through the experimental removal of the invasive green seaweed, Caulerpa cylindracea, from rocky reefs across the Mediterranean Sea. More specifically, we assessed which out of land-based and sea-based cumulative impact scores was a better predictor of the direction and magnitude of the effects of this seaweed on extant and recovering native assemblages. Approximately 15 months after the start of the experiment, the removal of C. cylindracea from extant assemblages enhanced the cover of canopy-forming macroalgae at relatively pristine sites. This did not, however, result in major changes in total cover or species richness of native assemblages. Preventing C. cylindracea re-invasion of cleared plots at pristine sites promoted the recovery of canopy-forming and encrusting macroalgae and hampered that of algal turfs, ultimately resulting in increased species richness. These effects weakened progressively with increasing levels of land-based human impacts and, indeed, shifted in sign at the upper end of the gradient investigated. Thus, at sites exposed to intense disturbance from land-based human activities, the removal of C. cylindracea fostered the cover of algal turfs and decreased that of encrusting algae, with no net effect on species richness. Our results suggests that competition from C. cylindracea is an important determinant of benthic assemblage diversity in pristine environments, but less so in species-poor assemblages found at sites exposed to intense disturbance from land-based human activities, where either adverse physical factors or lack of propagules may constrain the number of potential native colonizers. Implementing measures to reduce the establishment and spread of C. cylindracea in areas little impacted by land-based human activities should be considered a priority for preserving the biodiversity of Mediterranean shallow rocky reefs.

Long-term changes in North Adriatic soft-bottom polychaete assemblages following a dystrophic crisis

Abstract In the Northern Adriatic Sea, the combination of natural and anthropogenic processes causes periodic hypoxia and anoxia, which can cause mass mortality of benthic organisms. Here, we report the results of a 20-year monitoring programme carried out after an anoxic event in 1989 that caused benthic mass mortality over an area of about 1200 km2. The recovery dynamics of the polychaete fauna was followed at three stations (including one sampled a year before the anoxic event). Samples (0.1 m2 Van Veen grab, 2-mm sieve) were collected from 1989 to 1994 and from 2003 to 2008. A total of 6519 specimens belonging to 186 species were identified. The analyses of univariate biodiversity indexes highlighted higher temporal variation of assemblage diversity in the period following the dystrophic crisis, followed by higher stability in the next decade. PERMANOVA suggested that the highest component of assemblage variation belonged to the factor year. However, differences across years varied in magnitude, depending on stations and were portrayed by non-metric multidimensional scaling plots of each years centroids for each of the three stations. SIMPER analysis identified the species most characterizing the assemblages in each year for each of the three stations. Our results highlight the importance of analysing long-term data sets in order to understand assemblage dynamics following strong disturbance events. Assuming the 1989 anoxia as the event determining the biodiversity change, and considering our outcomes, which suggest that the assemblages still show a pattern of non-random changes through years, our data indicate that the polychaete fauna is still recovering without having reached a pattern of among-years stability. Focusing on the biology of the species characterizing the different periods might help in understanding the ecological processes that have determined the observed pattern.

Sperm ultrastructure of three Syllinae (Annelida, Phyllodocida) species with considerations on syllid phylogeny and Syllis vittata reproductive biology

Phylogeny of Syllidae is under debate due to new studies based on molecular and morphological data. The noticeable taxonomic diversity of syllids (about 700 listed species) is also mirrored in the array of reproductive strategies as well as in sperm morphology, counting a display of forms already supposed to reflect phylogenetic relationships between the species. The sperm ultrastructure of Syllis gerlachi, S. prolifera and S. vittata is herein presented and compared to the Syllinae species studied previously. Moreover, the egg structure and the gamete allocation within stolons of S. vittata are particularly investigated. Both male germinal cells at different level of maturation and oocytes were found in the same individual of S. vittata, suggesting simultaneous hermaphroditism. The ultrastructural analysis revealed that the observed spermatozoa belong to the ect-aquasperm type resembling those of the similar studied species (Syllis sp., S. pigmentata and S. krohni). Differences in the acrosome structure and nucleus shape are in accordance with a recent phylogenetic reconstruction and suggest a trend in the evolution of spermatozoa in Syllinae toward the development of the apical part. However, further molecular and ultrastructural analyses are needed to support this hypothesis. This is the first record of simultaneous hermaphroditism within Syllinae.

The Sea Urchin Arbacia lixula: A Novel Natural Source of Astaxanthin

Several echinoderms, including sea urchins, are valuable sources of bioactive compounds but their nutraceutical potential is largely unexplored. In fact, the gonads of some sea urchin species contain antioxidants including carotenoids and polyhydroxylated naphthoquinones (PHNQ’s), such as echinochrome A. Astaxanthin is known to have particular bioactivity for the prevention of neurodegenerative diseases. This carotenoid is produced by microalgae, while several marine invertebrates can bioaccumulate or synthetize it from metabolic precursors. We determined the carotenoid content and analyzed the bioactivity potential of non-harvested Atlantic-Mediterranean sea urchin Arbacia lixula. The comparison of methanol crude extracts obtained from eggs of farmed and wild specimens revealed a higher bioactivity in farmed individuals fed with a customized fodder. HPLC-analysis revealed a high concentration of astaxanthin (27.0 μg/mg), which was the only pigment observed. This study highlights the potential of farmed A. lixula as a new source of the active stereoisomer of astaxanthin.

Planktonic Assemblages in a Coastal Mediterranean Area Subjected to Anthropogenic Pressure

In marine environment phytoplankton and picoplankton are responsible for a bulk of production and nutrient cycling and may give important information about the different seawater habitats. In the present paper, the temporal changes of phytoplankton as well as autotrophic and heterotrophic picoplankton abundance and biomass in two coastal areas in the Gulf of Taranto (Mediterranean Sea) subjected to different levels of anthropogenic pressure were studied and related to the main environmental variables. The two analysed areas were significantly different as regards the abiotic conditions which also varied temporally. Univariate analyses revealed that larger phytoplankton and heterotrophic picoplankton abundance and biomass varied as well. The multivariate analyses showed a complex distribution of the whole planktonic assemblages, which varied in time and space without a decipherable pattern, presumably due to the peculiar spatial-temporal dynamics of the sole autotrophic picoplankton abundance. Significant correlations between planktonic assemblages and environmental variables were discussed by taking into account also the potential role of the considered planktonic components as useful environmental monitoring parameters.

Food Modulation Controls Astaxanthin Accumulation in Eggs of the Sea Urchin Arbacia lixula

The carotenoid astaxanthin has strong antioxidant properties with beneficial effects for various degenerative diseases. This carotenoid is produced by some microalgae species when cultivated in particular conditions, and, interestingly, it is a predominant carotenoid in aquatic animals throughout a broad range of taxa. Recently, astaxanthin was detected in the eggs of the sea urchin Arbacia lixula in relevant concentrations when this organism was maintained in culture. These results have paved the way for deeper research into astaxanthin production by this species, particularly in regards to how astaxanthin production can be modulated by diet. Results showed that the highest content of astaxanthin in eggs was observed in sea urchins fed on a diet enriched with Spirulina platensis. This result was confirmed by the high antioxidant activity recorded in the egg extracts of these animals. Our results suggest that (i) the sea urchin A. lixula is able to synthesize astaxanthin from precursors obtained from food, and (ii) it is possible to modulate the astaxanthin accumulation in sea urchin eggs by modifying the proportions of different food ingredients provided in their diet. This study demonstrates the large potential of sea urchin cultivation for the eco-sustainable production of healthy supplements for nutraceutical applications.

Worming its way into Patagonia: an integrative approach reveals the cryptic invasion by Eulalia clavigera (Annelida: Phyllodocidae)

A phyllodocid polychaete belonging to the genus Eulalia is reported from Nuevo Gulf, Patagonia (South-western Atlantic Ocean) with abundant populations thriving in the intertidal zone. Morphological and molecular data allowed assigning this population to Eulalia clavigera (Audouin & Milne-Edwards, 1834), a species typically occurring along the north-eastern Atlantic coast. The absence of genetic structuring between north-eastern and south-western Atlantic E. clavigera strongly supports a non-native origin of the Patagonian population. Conversely, the majority of the Mediterranean Eulalia cf. clavigera analysed in this study turned out to belong to a different, probably undescribed species, suggesting that the diversity and taxonomy of green Eulalia is more complex than previously supposed. The high adaptation capabilities to stressed environments showed by E. clavigera, along with its possible high impact on native assemblages through predation, compel to carefully monitor its spread along the Patagonian coasts.