Search results for " Marthasterias"
showing 5 items of 5 documents
Distribution and diet of Marthasterias glacialis at Ustica Island MPA
2009
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
New body metrics to determine asteroid size and weight directly in the field
2015
Asteroids are an important group of predators in many marine ecosystems. The measure of body size is crucial in studying asteroid biology as this variable affects both prey selection and predation impact. Current field techniques for estimating asteroid size (i.e. total length TL, total weight TW) include the measure of correlated variables, such us the central disk (CD) and arm length (AL). However, these variables are often time-consuming and require a direct handling of the organism. We tested the accuracy of new asteroid body metrics, the arm height (AH) or arm width (AW), to rapidly estimate body size in asteroids. AH and AW were measured in three of the most common Mediterranean aster…
Relazioni tra parametri biometrici in Marthasterias glacialis (L.) (Asteroidea)
2013
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.
Relative role of fish vs. starfish predation in controlling sea urchin populations in Mediterranean rocky shores
2009
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
2009
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…