347 research outputs found
Foraging behaviour and mutual interference in the Mediterranean shore crab, Carcinus aestuarii, preying upon the immigrant mussel Musculista senhousia
No full textPredator-prey dynamics between the Mediterranean shore crab Carcinus aestuarii and the non-indigenous mussel Musculista senhousia were examined in laboratory experiments to assess the effects of varying predator and prey densities upon predator foraging rates and prey survival. The factorial design involved 3 predator and 3 prey densities, with 4 trial per treatment combination. Functional responses were differentiated statistically by analysis of the exponent of a general functional response model. Shore crabs displayed type II (decelerating rise to an upper asymptote) inversely density-dependent functional responses at low and moderate predator densities, while a nontraditional model was probably more appropriate at high predator density. No density-dependent refuge was observed for M. senhousia, whereas, at high predator density, mutual interference among crabs was evident and prey mortality was lowered. Mediterranean shore crab's combined functional and interference response, by affecting foraging rates, was important to the outcome of interactions between predators and the bivalve prey, and might play an important role in determining crab's predatory behaviour and dispersion and prey persistence in the fiel
Organic content in gorgonian axis: Structural function and implications for energy budget estimates
No full textThe organic content of the proteinaceous portion of the skeleton of two Mediterranean gorgonian corals was estimated by means of two different methods: a gravimetric one (combustion and incineration) and by elemental analysis. Paramuricea clavata was investigated at a granitic shoal at the northern entrance to the Strait of Messina (Tyrrhenian Sea); Lophogorgia ceratophyta at a rocky station located off Tinetto Rock (Ligurian Sea). Both gorgonians were the visually dominant macrobenthic species in their habitat. Twenty colonies per species were collected in 1993, ages were estimated by counting axial annual growth increments, and the total content of the organic matrix of the skeleton was determined. The degree of axis mineralization was found to be different in the two species, suggesting different stiffening strategies to withstand water velocities. Annual weight increment of P. clavata due to skeletal organics was estimated in 12.72 g AFDW (ash free dry weight) m-2, while the total resident amount was 78.93 g AFDW m-2. L. ceratophyta yielded, respectively, 47.84 g AFDW m-2 yr-1 and 268.45 g AFDW m-2. Gorgonian corals can be thought of as ‘energy storer’ organisms, since only a minor part of the organic matter of the colony (i.e., coenenchymal tissue) is immediately available to consumers, while most of it is sequestered in the axial structures, and becomes available to decomposers only after the death of the colony. © 1996 Taylor & Francis Group, LLC
Recensione a M. Mistri, La Città Metropolitana, Vicenza, La Gru, 2013, pp. 178
No full textquesto articolo evidenzia in modo analitico i problemi principali connessi al problema della confusa riforma
italiana in tema di Città metropolitane così come ben individuati dall'autore M. Mistri nel libro "La Città Metropolitana". Il problema della nascita della città metropolitana, intrecciandosi con la questione
del riassetto delle Province, suscita non pochi problemi di natura politica in
quanto coinvolge l’intera governance del territorio. L’Autore mette sotto la
lente critica i recenti provvedimenti che hanno toccato il sistema delle autonomie locali, i
quali dimostrano la mancanza di una reale e coerente visione riformatrice in materia.This article stress the main problems about the confusing Italian reform of metropolitan cities, as well identified by the author M. Mistri in the book "La Città Metropolitana"
Effects of Musculista senhousia mats on clam growth and survival: much ado about nothing?
No full textBy means of manipulative experiments, growth and mortality of the clams Tapes decussatus and Ruditapes philippinarum were assessed in the presence and absence of Musculista senhousia (Mytilidae) in its mats. The experiment was arranged as a randomized complete block design, with eight blocks of nine cages each: four blocks contained T. decussatus, and four blocks R. philippinarum. The experimental units received one of the following treatments: T. decussatus (or R. philippinarum) with no mats, with mats of M. senhousia in high density, with mats in low density. The experiment ran for 100 days. The growth of both clam species was not affected by the presence of mussel mats. Mortality was higher for T. decussatus than for R. philippinarum, but the presence of mats, both in high and low density, seemed to exert no significant effect on clam mortality. It is hypothesized that deeper-dwelling species, as the carpet-shell and the Manila clam, are much less affected than other bivalves by mussel mat
Prey preference of Carcinus aestuarii: possible implications with the control of an invasive mytilid and Manila clam culture in a northern Adriatic lagoon
No full textThe cultivated Manila clam, Ruditapes philippinarum, and the accidentally introduced Asian date mussel, Musculista senhousia, are nowadays the most abundant bivalve species in the Sacca di Goro (northeastern Italy). M. senhousia, with its sub-surficial extended mats, creates quite a heavy economical impact to clam shellfish culture. Individual Mediterranean shore crabs Carcinus aestuarii were allowed to forage on the 2 bivalve species to examine crab's preference in light of the optimal foraging theory. Crabs preferred M. senhousia over R. philippinarum: mortality was higher for the former (34.6%) than for the latter bivalve species (9.5%). It is suggested that the marked preference of C. aestuarii for Asian date mussels over Manila clams could be advantageously exploited to control or to reduce the extension of mats, especially where these create management problems to infaunal, burrowing bivalve culture
Predatory behavior and preference of a successful invader, the mud crab Dyspanopeus sayi (Panopeidae), on its bivalve prey
No full textPredator-prey relationships between the panopeid crab, Dyspanopeus sayi, and the mytilid Musculista senhousia, were investigated. Through laboratory experiments, prey-handling behavior, prey size selection, predator foraging behavior, and preferences for two types of prey (M. senhousia and the Manila clam Ruditapes philippinarum), were assessed. Handling time differed significantly with respect to the three prey sizes offered (small: 15.0 - 20.0 mm shell length, SL, medium: 20.1 - 25.0 mm SL, and large: 25.1 - 30.0 mm SL); mud crabs were more efficient in predating medium-small than large prey. Although differences in prey profitability were not evident, D. sayi exhibited a marked reluctance to feed on larger-sized prey whilst smaller, more easily predated mussels were available. Size selection may be the result of a mechanical process in which encountered prey are attacked but rejected if they remain unbroken after a certain number of opening attempts. D. sayi exhibited inverse density-dependent foraging. A significant higher mortality of prey was evident at low prey density. Thus, at low predator density, the D. sayi-M. senhousia interaction was a destabilizing Type II functional response. Interference responses affected the magnitude of predation intensity by D. sayi on M. senhousia, since as the density of foraging crabs increased, their foraging success fell. At high density (4 crabs tank-1), crabs engaged in a high amount of agonistic activity when encountering a conspecific specimen, greatly diminished prey mortality. Finally, presenting two types of prey, Manila clam juveniles were poorly predated by mud crabs, which focused their predation mostly on M. senhousia. It is hypothesized that, when more accessible prey is available, mud crabs will have a minimal predatory impact on commercial R. philippinarum juvenile stock
Production of the meiobentic harpacticoid copepod Canuella perplexa
No full textSecondary production of C. perplexa was estimated in a brackish water lagoon of the Po River Delta (Italy). Three generation peaks and a nonproductive overwintering population were observed. Estimates of the annual production of copepodites and adults using 3 methods are similar: 6.76, 6.09 and 6.78 g dry wt m-2. Egg production was 0.02 g dry wt m-2; nauplii production was 0.38 g dry wt m-2. These values show a relatively constant P/B ratio per generation (3-4). -from Author
[Recensione a:] Maurizio Mistri, The Euro Crisis. An Institutionalist Approach, Padova, Padova University Press, 2021, 196 pp.
No full textThe book by Maurizio Mistri deals above all with the complex institutional system of the EU and the Euroland in particular. As the author wrote ‘the euro is an opportunity to deal with a pivotal issue, namely the determination of institutional and supranational system to ensure the governance of economic and monetary integration processes’ (p. 9). Consequently, the purpose of the book is to present some analytical tools mainly derived from a careful use of Thomas Schelling’s contributions. The centrality that Mistri gives to the author of ‘The Strategy of Conflict’ (1960) is significant: Embracing the theoretical results reached by many economists and political scientists who have followed Shelling’s lesson, Mistri clearly brings out the controversial relationship between national institutions and supranational institutions in the European reality
A 20 YRS-LONG ANALYSIS OF THE MACROBENTHOS IN A LTER SITE: THE VALLI DI COMACCHIO STUDY CASE
No full textThe analysis of the benthic community of the Valli di Comacchio revealed similar general patterns across all studied sites, albheit strong interannual variability was evident. The ecological quality status resulted almost constantly unsatisfactory: the overlapping effects of natural and anthropogenic disturbance may challange the environmental assessment of the Valli
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