1,721,085 research outputs found
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
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
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
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
I valori dell'arte
No full textL’economia e la psicologia dell’arte e della cultura sono rami, tutto sommato, recenti delle discipline madri, e cioè l’economia politica e la psicologia. Ai curatori del libro è apparso utile ed opportuno cercare di far dialogare queste due discipline su di un terreno specifico dove entrambe possono trovare utili elementi di contatto. D’altro canto il dialogo tra le due discipline madri va divenendo sempre più serrato e comincia a generare ibridismi di grande interesse. Si tratta di un dialogo che si esprime sia sul terreno delle metodologie che su quello applicativo, come nel caso dei beni artistici e culturali. La comprensione delle logiche economiche che stanno alla base delle scelte compiute dai fruitori dei beni culturali ed artistici è uno dei punti essenziali della ricerca. Altrettanto rilevante è lo studio dei processi cognitivi che stanno alla base delle motivazioni di tali fruitori. Se lo studio delle logiche economiche e dei processi cognitivi è importante in sé, va anche detto che esso ha una rilevante importanza di tipo strumentale in quanto aiuta i policy makers ad affinare le tecniche organizzative e le strategie di marketing, anche in funzione di adeguate politiche di offerta turistica
Towards an Evolutionary Approach to Marshall's Reciprocal Offer and Demand Curves
No full textThis article revisits Marshall’s curves of mutual supply and demand from an evolutionary standpoint. After discussing the relationships between the neoclassical approach (in its more general sense) and the Marshallian approach, it is suggested that Marshall’s position was essentially evolutionary and that this methodological stance is clearly evident in his theory on international trade. In particular, Marshall’s treatment of mutual supply and demand curves shows that what he had in mind was actually far removed from the scheme of things in which current academic tradition has incorporated the mutual supply and demand curves
Social networks and productive connectance: modeling the organizational form of the industrial district
No full text
- …
