0000000000463582
AUTHOR
Davide Agnetta
Hydrodynamism and its influence on the reproductive condition of the edible sea urchin Paracentrotus lividus
Despite the large body of work published in the last two decades on the reproduction of the sea urchin Paracentrotus lividus, the reproductive aspects linked to hydrodynamic conditions and their influence on gonad production remain poorly understood. The present paper aims to evaluate the effect of hydrodynamism on the reproductive cycle of P. lividus. Variability in the gonadosomatic index (GSI) of P. lividus was estimated seasonally from 2007 to 2008 at two shallow sub-littoral flat basaltic areas at Ustica Island (Western Mediterranean). GSI was higher in the sites characterized by low hydrodynamism than in those with high hydrodynamism. Results also suggest a possible role for hydrodyna…
Preliminary data on movement of sea-urchins Paracentrotus lividus and Arbacia lixula in two habitats with different structural complexity.
Dati preliminari sulla variabilità spazio-temporale di Paracentrotus lividus nell’ AMP “Capo Gallo Isola delle Femmine”
Influenza della protezione sulla struttura dei popolamenti algali dell’AMP “Isola di Ustica”, un caso di studio.
Fish-seastar facilitation leads to algal forest restoration on protected rocky reefs
AbstractAlthough protected areas can lead to recovery of overharvested species, it is much less clear whether the return of certain predator species or a diversity of predator species can lead to re-establishment of important top-down forces that regulate whole ecosystems. Here we report that the algal recovery in a Mediterranean Marine Protected Area did not derive from the increase in the traditional strong predators, but rather from the establishment of a previously unknown interaction between the thermophilic fish Thalassoma pavo and the seastar Marthasterias glacialis. The interaction resulted in elevated predation rates on sea urchins responsible for algal overgrazing. Manipulative ex…
Functional traits of two co-occurring sea urchins across a barren/forest patch system
Abstract Temperate rocky reefs may occur in two alternative states (coralline barrens and erect algal forests), whose formation and maintenance are often determined by sea urchin grazing. The two sea urchin species Paracentrotus lividus and Arbacia lixula are considered to play a similar ecological role despite their differing morphological traits and diets. The patchy mosaic areas of Ustica Island, Italy, offer an ideal environment in which to study differences in the performance of P. lividus and A. lixula in barren versus forest states. Results show that the two sea urchin species differ in diet, trophic position, grazing adaptation, movement ability and fitness in both barren and forest…
Protection effect on distribution patterns of Paracentrotus lividus and Arbacia lixula in the “Plemmirio” Marine Protected Area
Il progetto S.E.P.I.A. (Sperimentazione sull’Educazione Pubblica ed Informazione Ambientale) nell’Area Marina Protetta “Isola di Ustica”.
Effetti della raccolta ricreativa sulla distribuzione di Paracentrotus lividus e Arbacia lixula nell’amp “Isola di Ustica” (Mediterraneo occidentale, Italia).
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.
Macroalgal assemblage type affects predation pressure on sea urchins by altering adhesion strength.
In the Mediterranean, sea breams are the most effective Paracentrotus lividus and Arbacia lixula predators. Generally, seabreams dislodge adult urchins from the rocky substrate, turn them upside down and crush their tests. Sea urchins may respond to fish attacks clinging tenaciously to the substratum. This study is the first attempt to investigate sea urchin adhesion strength in two alternative algal assemblages of the rocky infralittoral and valuated its possible implication for fish predation. We hypothesized that (1) sea urchin adhesion strength is higher in rocky shores dominated by encrusting macro-algae (ECA) than in erected macro algae (EMA); (2) predation rates upon sea urchins are …
Diet and trophic interactions of Paracentrotus lividus and Arbacia lixula in two alternative stable states of the Mediterranean rocky sublittoral community
Sea temperature and echinoid Arbacia lixula (L.) population fluctuations on Ustica Island MPA
Size-dependent predation of the mesopredator Marthasterias glacialis (L.) (Asteroidea)
Asteroids are largely recognized as important predators in all of the world’s oceans and for this reason, they play a crucial role in shaping the structure and functioning of benthic ecosystems. The spiny starfish Marthasterias glacialis is generally considered a voracious predator of molluscs, in particular bivalves. Using field observations and carbon (δ13C) and nitrogen (δ15N) stable isotopes, we explored possible changes in diet in relation to size of M. glacialis. Data were collected at Ustica Island (Southern Tyrrhenian Sea) from June 2008 to June 2010. M. glacialis showed a size shift in feeding preferences due to different use of food items: bivalves, Columbella rustica, Euthria cor…
Role of two co-occurring Mediterranean sea urchins in the formation of barren from Cystoseira canopy
Abstract In the Mediterranean Sea the co-occurring sea urchins Paracentrotus lividus and Arbacia lixula are usually considered to share the same ecological role in the formation of barren from Cystoseira canopy. However, their foraging ability may vary due to feeding behavior and species-specific morphological traits. The relative effects of P. lividus and A. lixula on Cystoseira canopy was tested experimentally both in the laboratory, at a density of about 20 ind./m 2 , and in the field by gut content analysis. Field and laboratory results show that A. lixula is unable to affect Cystoseira spp. Furthermore, these results confirmed the great ability of P. lividus to consume Cystoseira canop…
Influenza della protezione sulla struttura dei popolamenti algali. AMP "Isola di Ustica", un caso di studio
Hiding behaviour ofOxynoe olivacea(Mollusca: Opisthobranchia: Sacoglossa) in the invasive seaweedCaulerpa taxifolia
The occurrence of the invasive seaweed Caulerpa taxifolia in the Straits of Messina (Italy) provides an excellent opportunity to examine the spatial and temporal patterns of abundance of the endemic Mediterranean sacoglossan Oxynoe olivacea. Densities of this species were recorded in March, June and October 2000 on three different habitats: the underside of boulders (UNB), the upper side of boulders (UPB), and the surface of concrete blocks (CB). Results showed that in March, O. olivacea was consistently more abundant on UNB whereas in June it was present exclusively on CB. The density of O. olivacea was similar in the three habitats in October. The hiding behaviour of O. olivacea and its s…
Sizing up the role of predators on Mullus barbatus populations in Mediterranean trawl and no-trawl areas
Abstract Fishing leads to drastic changes in ecosystems with a net loss of predatory biomass. This issue has been evidenced from historical ecological studies and from the evaluation of the effects of effective and large marine protected areas. In two fishery reserves off the northern Sicily coast the red mullet Mullus barbatus underwent an impressive biomass increment and a few piscivores fish species recovered after a trawl ban. The red mullet, more than 20% of all demersal fish in the untrawled areas, represented a huge food resource to its potential predators. By contrasting two trawled and two untrawled gulfs we figured out predator - prey relationships through the use of a combined ap…