Peracarid Crustacea Inhabiting Aegagropylae of the Red Alga Rytiphloea Tinctoria (Clemente) C. Ag. in the Stagnone Sound, Western Sicily, Italy

The peracarid Crustacea belonging to Cumacea, Tanaidacca, Isopoda and Amphipoda, inhabiting aegagropylae of Rytiphloea tinctoria were studied throughout a year in the Stagnone Sound (western Sicily, Italy). The dominant groups, tanaids (61.7%) and amphipods (32.8%), were represented by 6 and 28 species, and showed complementary trends during the 12 months, reaching their maximum of abundance in spring and autumn, respectively. Tanaids were mainly represented by Apseudes intermedius Hansen, 1895 and Parapseudes latifrons (Grube, 1864), and amphipods by Elasmopus pocillimanus (Bate, 1862), Leptocheirus guttatus (Grube, 1864), Lysianassa longicornis Lucas, 1849 and Maera inaequipes (A. Costa, …

Notes on the fish assemblages present in the areas invaded by Caulerpa spp. (Ulvophyceae, Chlorophyta) along the Sicilian coasts

Relationship between egg features and maternal body size in the simultaneous hermaphrodite Oxynoe olivacea (Mollusca, Opisthobranchia, Sacoglossa)

This paper provides information on spawn morphology and egg features of the stenophagous planktotrophic Mediterranean sacoglossan Oxynoe olivacea. Smith and Fretwell’s hypothesis, predicting that individuals of the same population growing in the same environmental conditions and varying in size should spawn eggs of a constant size, was tested in a population of O. olivacea living in the Straits of Messina. To determine whether (a) spawn mass size, (b) total egg number per spawn, and (c) egg size were related to parent size of O. olivacea, 21 egg masses (seven egg masses deposited by seven different 20 mm animals, seven egg masses deposited by seven different 25 mm animals and seven egg mass…

Dati preliminari sulla variabilità spazio-temporale di Paracentrotus lividus nell’ AMP “Capo Gallo Isola delle Femmine”

Cytogenetic characterization ofBrachidontes pharaonis(Fisher P., 1870): Karyotype, banding and fluorescentin situhybridization (fish) (Mollusca: Bivalvia: Mytilidae)

Abstract The mussel Brachidontes pharaonis (Fisher P., 1870) (Bivalvia: Mytilidae) has a diploid chromosomal set of 28 made up of 14 pairs of which eight are mono-armed (ST) and six bi-armed (M+SM). Fourteen bivalents occur in spermatocytes both at pachytene and metaphase-I. The use of combined silver and CMA3 staining reveals that nucleolus organizer regions (NORs) are located terminally on the long arm of a small subtelocentric chromosome pair (pair 14) and are compartmentalized in GC base pairs. A Paracentrotus lividus (Echinodermata) 4.3 kilobase (kb) rDNA probe (prR14) consisting of sequences from the 3′ end of 18S rDNA to the 3′ end of 26S rDNA was used to map the rDNA loci of B. phar…

Artificial Reefs in the Gulf of Castellammare (North-West Sicily): A Case Study

Most of the plans for fish stock replenishment recently undertaken in Sicily have focused on the Gulf of Castellammare. Reasons for choosing this biotope for a restocking plan include the size of the Gulf (300 km2), the importance and traditional role of its fisheries and the existence of information describing the local marine environment. The Gulf of Castellammare is the widest bay in Sicily and fishing has always played a major role in the local economy. Today income from fishing complements that from tourism.

Scheda naturalistica sul corallo rosso

Body size and mating strategies in the simultaneous hermaphrodite Oxynoe olivacea (Mollusca, Opisthobranchia, Sacoglossa).

Summary 1To better understand the role and importance of body size in hermaphroditic mating system theory, the mating behaviour of the shelled sacoglossan Oxynoe olivacea was studied. This simultaneous hermaphrodite exhibits bilateral and unilateral sperm transfer and thus it is particularly suitable for studies on hermaphrodite sexual conflict. 2In this study three hypotheses on body size were tested: that O. olivacea partner size has an effect on (i) mating mode choice, (ii) duration of mating modes, and (iii) choice of sexual role. Furthermore, we tested Charnov's hypothesis that in O. olivacea, like many simultaneous hermaphrodites, a sexual conflict exists and the male role is preferre…

Cultural and socio-economic impacts of Mediterranean marine protected areas

Marine protected areas (MPAs) may be important for protecting the marine environment, but they may also have substantial socio-cultural impacts about which very little is currently known, or acknowledged. In the Mediterranean, few data are available on the socio-economic consequences of MPAs. The present study reviews the existing data on MPAs in Spain, France, Italy and Greece. A general increase in tourist activities in Mediterranean MPAs is evident, as are increases in the abundances of larger fish species, although there are no data indicating yields for fisheries increase adjacent to MPAs. A large increase in the number of divers and vessels using MPAs has already had impacts on natura…

Human recreational activities within Mediterranean marine protected areas: lessons learnt in the Ustica Island MPA.

La "pomelia", immagine gentile di una terra difficile

Distribution and diet of Marthasterias glacialis at Ustica Island MPA

Distribution and diet of Marthasterias glacialis was studied at Ustica Island MPA. We conducted observations of the asteroid along the upper infralittoral zone using random parallel transects. M. glacialis was more abundant at study sites characterized by low densities of erect algae. Most frequent prey species was a bivalve and sea urchins

Protection effect on distribution patterns of Paracentrotus lividus and Arbacia lixula in the “Plemmirio” Marine Protected Area

First record of Sphoeroides pachygaster (Tetraodontidae) in the south Tyrrhenian (N/W Sicily)

Il progetto S.E.P.I.A. (Sperimentazione sull’Educazione Pubblica ed Informazione Ambientale) nell’Area Marina Protetta “Isola di Ustica”.

NUOVA CATTURA DI LOBOTES SURINAMENSIS (BLOCH,1790) IN TIRRENO MERIDIONALE (OSTEICHTHYES: LOBOTIDAE).

The operational sex ratio of the sea urchin Paracentrotus lividus populations: the case of the Mediterranean marine protected area of Ustica Island (Tyrrhenian Sea, Italy)

We investigated, with a series of field and laboratory observations, the possible effect of the starfish Marthasteria glacialis predation on the operational sex ratio (OSR), i.e. the number of sexually mature males divided by the total number of sexually mature adults of both sexes at any one time, of the edible sea urchin Paracentrotus lividus. The OSR was estimated three times during the sea urchin summer spawning period (July 2004, June 2005 and July 2006) on barren substrates of Ustica Island Marine Protected Area (Southern Tyrrhenian Sea, Italy). Four sites were selected: two characterized by high M. glacialis density (take zone C) and two controls with low starfish density (no-take zo…

Food partitioning between Serranus scriba and Scorpaena porcus (Perciformes) on the infralittoral ground of the South Tyrrhenian Sea.

Food preferences of Scorpaena porcus and Serranus scriba were investigated from the stomach contents of fish caught with trammel nets in the Gulf of Palermo (Tyrrhenian Sea). Decapoda Natantia and Decapoda Brachyura were the main preferred prey in the diet of S. porcus whereas Decapoda Natantia, Decapoda Galatheidae and Pisces were the preferred prey for S. scriba. These results and the values of the index of overlapping alimentary requirements suggested competition for food resources between the two species. A more precise investigation, at species level, of the food remains of the most abundant taxon (Crustacea Decapoda) made it possible to demonstrate that the trophic niche overlap betwe…

Effetti della raccolta ricreativa sulla distribuzione di Paracentrotus lividus e Arbacia lixula nell’amp “Isola di Ustica” (Mediterraneo occidentale, Italia).

Cytogenetics in the sacoglossan Oxynoe olivacea (Mollusca: Opisthobranchia): karyotype, chromosome banding and fluorescent in situ hybridization

Developing embryos and sexually mature follicles of the male portion of ovotestis proved to be a suitable material as a source of cleaving cells for advanced cytological investigations on the sacoglossan species Oxynoe olivacea Rafinesque, 1819 (Mollusca: Opisthobranchia). O. olivacea has a diploid chromosomal number of 30 made up of 15 pairs of which six are metacentric/submetacentric (M/SM), four subtelocentric (ST) and five on the borderline between SM and ST. Correspondingly, 15 bivalents occur in spermatocytes at Metaphase I. Constitutive heterochromatin is scarce and restricted to small C-bands seen in five pachytene bivalents. The use of combined silver staining and fluorescent in si…

The rise of thermophilic sea urchins and the expansion of barren grounds in the Mediterranean Sea

Recent ecological studies have shown a strong relation between temperature, echinoids and their grazing effects on macro-algal communities. In this study, we speculate that climate warming may result in an increasingly favourable environment for the reproduction and development of the sea urchin Arbacia lixula. The relationship between increased A. lixula density and the extent of barren grounds in the Mediterranean Sea is also discussed.

A survey of ovarian maturation in a population of Aristeus antennatus [Crustacea: Decapoda)

Le aree di transizione siciliane: stato dell’arte e sviluppi futuri

Feeding strategy of the sacoglossan opisthobranch Oxynoe olivacea on the tropical green alga Caulerpa taxifolia.

The feeding behaviour of the shelled sacoglossan Oxynoe olivacea was investigated to better understand the role and importance of this species in influencing encroachments of the alien alga Caulerpa taxifolia in the Mediterranean sea. We tested whether this slug preferred, as preliminary field observations suggested, an aggregative feeding behaviour and which part of the algal thallus, phylloid vs rhizoid, it preferred. Results showed that O. olivacea fed in groups and actively selected phylloid. This outcome poses important questions regarding the possibility that this species, fragmenting the alga thallus, could enhance dispersion and regeneration of C. taxifolia.

Investigations on gonadal maturation in Pagellus acarne (Pisces, Sparidae) in the strait of Messina (Sicily)

Sicilian transitional waters: Current status and future development

To appraise the current knowledge of Sicilian transitional waters (TWs), a review was undertaken of the information available on these ecosystems. In detail, a synthesis of the current status is reported, highlighting for each area the ecological features and status, historical data, conservation regime, environmental emergencies and anthropic pressures to which they are subject. The Sicilian TWs reviewed include coastal ponds and lakes, mires and areas with active and nonactive saltworks. Almost all of these ecosystems are affected by several protection regimes because of their high naturalistic value, although current knowledge is limited and fragmented. A few areas have received more att…

Remarkable presence of Aplysia punctata (Mollusca, Opisthobranchia, Anaspidea) in the Ustica Island MPA (Western Mediterranean, Italy)

Espansione di Caulerpa taxifolia (Caulerpales, Ulvophyceae) lungo le coste dell'Isola di Favignana

Artificial Reefs in North-West Sicily: Comparisons and Conclusions

The most notable features of the biotic colonization and fishing yield of artificial reefs are a straightforward response to local environmental conditions. When applying this assumption to the artificial reefs of north-west Sicily, the features that distinguish the reefs from each other are largely consistent with the major hydrographic characteristics of the Gulf of Castellammare, the Bay of Carini and the Gulf of Palermo. The differences in environmental conditions in the three biotopes have made it possible to compare the colonization of artificial reefs in unpolluted oligotrophic water (Bay of Carini), eutrophic water (Gulf of Palermo) and water with heavy siltation rates (Alcamo Marin…

Convergence of roles among peracarids in critical environments.

Sea temperature and echinoid Arbacia lixula (L.) population fluctuations on Ustica Island MPA

Nuova Cattura di Lobotes surinamensis (Bloch, 1790) in Tirreno Meridionale (Osteichthyes: Lobotidae).

Relazioni tra parametri biometrici in Marthasterias glacialis (L.) (Asteroidea)

Biometric parameters of the Asteroid echinoderm Marthasterias glacialis (L.) were measured at Ustica Island MPA (SW Tyrrhenian Sea). Wet weight was correlated with tip-to-tip (arm-span) diameter, central disk, arm length, arm width and arm height. Results show high positive correlation between weight and arm height, suggesting a new useful method to estimate starfish size also for in situ measurements.

Patterns of algal recovery and small-scale effects of canopy removal as a result of human trampling on a Mediterranean rocky shallow community.

The ecological importance of marine algae is widely known but in shallow coastal areas the composition and structure of algal communities may be affected by different human activities. Recovery from different trampling disturbances of two competing morphological groups (i.e. macroalgae and algal turfs) and effects of macroalgal canopy removal on the dominant associated fauna were examined using controlled trampling experiments. Six months after trampling disturbance was removed, the two morphological groups closely resembled control (untrampled) conditions, both in terms of cover and canopy (%). In particular, macroalgal recovery seemed to be very rapid: the higher the impact on the system …

Sex ratio operativa della popolazione di Paracentrotus lividus (Lam.) nell’AMP Isola di Ustica

Nell’AMP ”Isola di Ustica” l'instaurazione del regime di protezione, e quindi del divieto di prelievo, ha provocato un aumento della densità del riccio edule Paracentrotus lividus (Lam.) con conseguenze negative sulle comunità algali. L’intenso pascolo di questi echinidi regolari ha infatti trasformato la fascia superficiale sommersa in un barren ground, area a bassa complessità e diversità. Una buona stima della sex ratio operativa (OSR) di P. lividus può chiarire aspetti importanti della dinamica di popolazione di questa specie ed essere di notevole aiuto in una logica di intervento gestionale. Scopo del lavoro è stato quello di valutare la OSR della popolazione di P. lividus presente nel…

Species richness and coastal biodiversity of Ustica island (pg Tyrrhenian Sea, Mediterranean)

Il paesaggio e la biodiversità

Ricchezza specifica e biodiversità marina nell’isola di Ustica. Naturalista siciliano

New record of Caulerpa taxifolia (Caulerpales, Ulvophyceae) in the South-western Sicilian waters (Italy).

Evaluating the ecological effects of Mediterranean marine protected areas: habitat, scale and the natural variability of ecosystems

The capability to detect and predict the responses of marine populations and communities to the establishment of marine protected areas (MPAs) depends on the ability to distinguish between the influences of management and natural variability due to the effects of factors other than protection. Thus, it is important to understand and quantify the magnitude and range of this natural variability at each scale of observation. Here we review the scale of responses of target populations and communities to protection within Mediterranean MPAs, against their ‘normal’ spatio-temporal heterogeneity, and compare those with documented cases from other temperate and tropical marine ecosystems. Additiona…

Molluscan assemblages associated with photophilic algae in the Marine Reserve of Ustica Island (Lower Tyrrhenian Sea, Italy)

Abstract Very few studies have addressed the effect of protection on macrozoobenthos in marine protected areas, and particularly for sites in the Mediterranean Sea. In the present study, the molluscan assemblages associated with photophilic algal communities of the Marine Reserve of Ustica Island, were investigated. A survey was carried out along transects from 1 to 15 m in depth, during the spring of 1996 at three different sites, subjected to different levels of reserve protection. Species richness and number of individuals reflected the level of protection, and both variables were significantly higher in the integral (most heavily protected) part of the reserve compared with the less wel…

Sex allocation in the simultaneous hermaphrodite Aplysia punctata (Mollusca, Opisthobranchia).

Protection effects on feeding and reproduction of Paracentrotus lividus and Arbacia lixula on barren grounds at Ustica Island MPA (Western Mediterranean, Italy).

Traditional and experimental floating fish aggregating devices in the Gulf of Castellammare (NW Sicily): Results from catches and visual observations

Floating fish aggregating devices (FADs) have long been used to attract fish in NW Sicily since antiquity. Recently, a number of changes have been made to the type of material employed to construct FADs, with the aim of increasing their effectiveness. In this paper we compare the catches made at eight experimental floating FADs (polypropylene ropes frayed at the ends) with those obtained at eight traditional FADs in the Gulf of Castellammare. A total of 672 samples were collected during summer and autumn in 1995 and 1996 at the 16 FADs using a surrounding net. Visual observations of fishes associated with the FADs were also conducted to obtain qualitative information about the spatial distr…

Dendropoma lower intertidal reef formations and their palaeoclimatological significance, NW Sicily

Abstract Most carbonate rocky shores of NW Sicily are marked by a coalescence of shells of the gastropod Dendropoma in a construction that is variably developed as a response to wave impact. Here, we review all the available information on these constructions and find that the fossil reefs are reliable sea-level indicators. The thickness of the reef samples never exceeds 30–40 cm below sea-level, whereas all 14 C dates fall within a range of few centuries. Some small fragments ejected by violent sea storms date back to 2500 years cal BP. No samples older than 6200 years cal BP have been detected so far. The present distribution of Mediterranean vermetid platforms should result from a northw…

A preliminary study on temporal and spatial patterns of variability in Paracentrotus lividus and Arbacia lixula in the Ustica Island MPA (western Mediterranean, Italy). “ Le scienze naturali,economiche e giuridiche nello studio per la gestione degli ambienti acquatici.

Successo di fecondazione di Arbacia lixula: limitazione da sperma e longevità dei gameti

Artificial Reefs in Sicily: An Overview

Sicilian cave drawings from the Grotta del Genovese, Isle of Levanzo (west Sicily) ca. 12 000 B.C. show silhouettes of dolphins, tuna, groupers and bass which, together with remains offish (tuna, groupers, bass and others), limpets and oysters from Grotta dell Uzzo, north-western Sicily, indicate the importance of fish and shellfish in the diet of coastal populations of that time (Villari, 1992a, 1992b). Remains of turtles (Caretta caretta), tuna and sharks are evidence of fishing activity during this period (Villari, 1995).

Colonisation process of vegetative fragments of Posidonia oceanica (L.) Delile on rubble mounds

Seagrass colonise new areas via the dispersion of seeds or vegetative fragments. Independent of the manner of colonization, habitat requirements need to be met for the successful establishment of seagrasses. Here we report on the colonization process of Posidonia oceanica in a highly disturbed area: a gas pipeline trench at Capo Feto (SW Sicily, Italy). A trench dredged through a P. oceanica bed was back-filled with rubble added from dump barges leading to the formation of a series of rubble mounds on the seabed. Over time, these mounds became colonised with P. oceanica. In order to understand the pattern of P. oceanica colonization, shoot density was quantified over 3 years (2001-2003) on …

Population structure of the sea urchins Paracentrotus lividus and Arbacia lixula across a depth gradient

Sea urchins are considered to have a paramount role in structuring rocky shallow communities. Under certain conditions, grazing by sea-urchins has been reported to produce a shift from macroalgae-dominated communities to barren habitat dominated by encrusting algae. However, this process is not recorded at all depths. The effect of depth on the structure of the sea-urchin populations may be thus a key feature to understand the origin and maintenance of the barren habitat within certain depths. In the present study, the structure of Paracentrotus lividus (Lam.) and Arbacia lixula (L.) populations are analyzed across a depth gradient in the Ustica Island MPA (NW Mediterranean), where the barr…

Short-term effect of human trampling on the upper infralittoral macroalgae of Ustica Island MPA (western Mediterranean, Italy)

The short-term response of Mediterranean upper infralittoral macroalgal species to experimental human trampling was investigated. Disturbances of six different intensities were applied within the integral reserve of the Ustica Island marine protected area (Italy, Mediterranean Sea). The dominant macroalgal species Cystoseira brachicarpa v. balearica and Dictyota mediterranea were strongly affected by human trampling. Higher levels of disturbance significantly affected both algal percentage cover and canopy at an increasing rate. Three months after trampling, for both variables it was highlighted that the algal recovery from disturbance was incomplete, being significantly different among tra…

Species richness and coastal biodiversity of Ustica Island (Tyrrhenian Sea, Mediterranean)

Helminth infestation of three fishes (Serranus scriba, Mullus surmuletus, Scorpaena porcus)from a coastal seaground in the Gulf of Palermo (Tyrrhenian Sea)

Abstract The results of a year's survey on the parasitic infestation of the gastrointestinal tract of three species of benthic fish, namely Serranus scriba, Mullus surmuletus, and Scorpaena porcus, living in a restricted coastal seaground in the N/W sector of the Gulf of Palermo, are reported and critically discussed. Fish populations were sampled monthly by means of a trammel net, according to the local fishing usage. As many as nine helminth species, five of them trematodes and four nematodes, were collected from the gastrointestinal tract of 625 individuals. Infestation was most intense in M. surmuletus, with a peak in the spring. S. scriba was especially parasitized during the spring an…

Ecologia di un "superorganismo": la salina come "macchian intelligente"

Ciclo riproduttivo di Arbacia lixula (Linneo, 1758) (Echinodermata: echinoidea) nella AMP “Isola di Ustica”

Ricchezza specifica e biodiversità marina nell’isola di Ustica.

The Impact of Human Recreational Activities in Marine Protected Areas: What Lessons Should Be Learnt in the Mediterranean Sea?

. The aesthetic appeal of marine reserves and the facilities provided, together with the increased public awareness of nature, all contribute to creating massive tourism in MPAs. Human activities are being changed inside MPAs in two ways: humans as top predators are generally being removed, but in turn they could come back at great numbers as visitors. Many authors have studied the impact of visitors, and the results highlight that the consequences can be very substantial and may represent a severe threat to the overall diversity of marine communities. To date, the documented effects of human recreational activities on natural communities are restricted to assessing the consequences of tram…

Synapseudes Shiinoi Riggio, 1973, a Species of Tanaidacea Found in the Mediterranean

During the bionomic survey carried out in the course of 1968 on the biogenic platform bordering the rocky shore of Mount Pellegrino in the Bay of Palermo (northwestern Sicily) some individuals of a species of Synapseudes Miller (1940) were found in samples of Tanaidacea taken during the winter at station no. 1. This find is of considerable interest as no Synapseudes species had hitherto been described from the Mediterranean, although the presence of this genus on the coast of southern France has been mentioned by Bellan-Santini (1962, 1969). Careful examination of the specimens revealed that they belonged to a new species, which was named after Prof. Sueo M. Shiino in gratitude for his kind…

Relative role of fish vs. starfish predation in controlling sea urchin populations in Mediterranean rocky shores

In the Mediterranean, fishing bans generally allow the recovery of populations of sea urchin predators, such as the seabreams Diplodus sargus and D. vulgaris, promoting the transformation of overgrazed communities into ones dominated by erect macroalgae. However, in the marine reserve on Ustica Island (SW Italy) the opposite trend has occurred in the upper infralittoral community, and urchin barrens formed after the cessation of fishing activities. We hypothesized that (1) the natural scarcity of the 2 seabream species leads to a low predation rate on sea urchins at Ustica, and (2) predation rate varies with depth, due to differences in the predator assemblages. Tethering experiments were c…

Ruolo ecologico degli Asteroidei in due comunità dell'infralitorale superiore dell'Isola di Ustica

Gli asteroidi sono predatori che si ritrovano comunemente negli ecosistemi marini di fondo duro e mobile. Nell’Area Marina Protetta “Isola di Ustica” il divieto di raccolta del riccio edule Paracentrotus lividus nell’infralitorale superiore, ha determinato la sostituzione della comunità ad alghe fotofile erette con una comunità dominata da alghe incrostanti e ricci (barren) in gran parte dell’isola. Tre specie di asteroidi, Marthasterias glacialis, Ophidiaster ophidianus e Coscinasterias tenuispina, si ritrovano comunemente sia nell’habitat dominato dal barren che in quello dove rimangono elevate coperture ad alghe fotofile erette. Sono state studiate la distribuzione e le abitudini aliment…

First record of Caulerpa taxifolia (Caulerpales, Ulvophyceae) in the western Sicilian waters (Italy).

The effects of recreational Paracentrotus lividus fishing on distribution patterns of sea urchins at Ustica Island MPA (Western Mediterranean, Italy)

This study evaluated the effects of recreational Paracentrotus lividus fishing on average density and size of this edible sea urchin, and its indirect effects on Arbacia lixula on barren substrates of Ustica Island MPA (SW Italy, Mediterranean Sea). Size, single and pooled species densities, density of large individuals (>40 mm long) and small individuals (<20 mm long) of the two species were estimated by scuba diving in autumn 2003, spring and summer 2004 at two sites impacted by P. lividus fishing (Punta Cavazzi and Pagliaro, take zone C) and one control (Cala Sidoti, no take zone). Two samplings were performed in each season. We found that reduced densities of P. lividus and A. lixula oc…

Larval Development of Arbacia lixula (Linneo, 1758) in two Marine Protected Area: preliminary data.

The sea urchin Arbacia lixula is a crucial species in driving the algal assemblages dynamic of the infralittoral zone. A. lixula is considered a thermophilic species and its increase in abundance in western Mediterranean waters, probably is due to an increase in seawater temperature. The aim of this study was to examine the reproductive success of A. lixula by larval development. The study was conducted within two Sicilian MPA (Capo Gallo-Isola delle Femmine and Ustica), characterized by photophilic algae, the same exposure and seawater temperature. In each area, twenty random specimens was sampled from May to September 2010, and mature gametes were collected from six males and six females …

Effetto della complessità del substrato sulla distribuzione di Paracentrotus lividus e Arbacia lixula nel barren dell?A.M.P. "Isola di Ustica"

Effects of Paracentrotus lividus removal on the co-occurring Arbacia lixula at Ustica Island MPA (Western Mediterranean, Italy)