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1.
Abstract. A number of recent field‐based studies have investigated the possible functions of covering behaviour in a range of echinoid species. Some of these have found important relationships between covering behaviour and environmental factors, such as light (in particular, ultra‐violet light) and covering item availability. However, these studies have often shown considerable within‐species variation, thus making covering functionality both within and between species difficult to interpret. The present study experimentally investigates individual variability in covering behaviour characteristics of the sea urchin Paracentrotus lividus (Lamarck). Data were collected bimonthly over a 1‐year period at Lough Hyne, Ireland, by observing P. lividus in outdoor aquaria. Significant variations in covering behaviour characteristics were observed as a function of individual size and mobility but not as a function of sex. A significant relationship between water temperature, mobility and covering behaviour was also found and is hypothesized to have implications for grazing activity in P. lividus. In contrast to previous field studies of P. lividus at Lough Hyne, no summer ‘peak’ in the proportion of individuals covering was observed. However, there was a significant relationship between local solar radiation and ‘time to first cover’. Overall, these data highlight (i) the ecological significance of individual variation in P. lividus covering behaviour and (ii) the importance of investigating multiple factors as potential determinants of echinoid covering behaviour.  相似文献   

2.
The distribution and abundances of the following species of barnacles were established in autumn 2001 within the Lough Hyne Marine Nature Reserve: Cthamalus stellatus, Cthamalus montagui, Semibalanus balanoides, Elminius modestus, Balanus crenatus and Verruca stroemia. The results of the survey showed a clear distinction between the vertical distribution and the abundance of barnacle species inside Lough Hyne, and those sites sampled in the Rapids and outside the Lough. The Lough is now dominated by the introduced Australasian species E. modestus. This species was first recorded outside Lough Hyne in 1956. By 1988 it was found occasionally throughout the Lough, and appreciable numbers were recorded in 1990–1991. It has now replaced all other species in some parts of the North Basin. At sites subject to freshwater influence it is totally dominant, including in the highly sheltered Goleen site where intertidal barnacles have not previously been recorded. It is suggested that, once established in the North Basin, the sheltered nature of the Lough, combined with high summer temperatures and limited circulation, fostered retention of larvae and heavy spatfall of E. modestus.  相似文献   

3.
Abstract.  The so-called 'covering behaviour' of echinoids is known to vary with habitat according to the types of covering items available, but the full extent of the role played by habitat characteristics in this behaviour is not known. Moreover, whether or not different species inhabiting similar environmental conditions and habitats also show similar patterns of this particular behaviour has yet to be investigated. In this study, two prominent west coast echinoid species, Paracentrotus lividus and Strongylocentrotus purpuratus , were examined with respect to covering behaviour and spatial organisation. Populations of both species are found in exposed intertidal zones, occupying boreholes within tidepools. Important similarities were found in the spatial organisation of both species' populations, with lowest densities in upper shore pools. However, the size distributions of the two populations differed significantly; P. lividus within upper shore pools were significantly larger than those in mid or lower shore pools, whereas S. purpuratus on the lower shore were significantly larger than those at other shore heights. We found significant between-species variability in covering item use, although the number of covering items available at both sites was not significantly different. For example, greater densities of covering items were used by P. lividus than by S. purpuratus . We also found that the percent of echinoid surface area covered varied significantly in space for both species. These data emphasise the complex and multifaceted nature of covering behaviour, but most importantly, they also strongly suggest that habitat characteristics can only partly explain the extent of this behavioural variability amongst echinoid species.  相似文献   

4.
Plankton samples collected in November 2002, February, May and August 2003 were used to examine seasonal variation in tidal exchange of zooplankton biomass, abundance and species composition between Lough Hyne Marine Nature Reserve and the adjacent Atlantic coast. Micro- to mesozooplankton were collected by pump over 24-h sampling periods during spring and neap tides from the narrow channel connecting the semi-enclosed water body to the Atlantic. Sample biomass (dry weight) and total zooplankton abundance peaked in the summer and were lowest in winter, showing a positive relationship with temperature. Zooplankton biomass, total abundance and numbers of holo- and meroplankton revealed import during some diel cycles and export in others. However, the tidal import of these planktonic components was generally dominant, especially during May. The greatest import of numbers of holoplankters and meroplanktonic larvae occurred during May and August, respectively. There was no significant variation in sample biomass between periods of light and dark, but some variation in zooplankton abundance could be explained by this diel periodicity. Significant differences in sample assemblage composition between flood and ebb tide samples were always observed, except during winter neap tides. There was a net import of the copepods Temora longicornis and Oithona helgolandica and the larval stages of Mytilus edulis during spring and summer. Proceraea cornuta and Capitellid trochophores were imported during winter, and a hydrozoan of the genus Obelia during the spring spring tides. Seasonal export from the lough was shown by Pseudopolydora pulchra larvae (autumn and spring), Serpulid trochophores (autumn) and veligers of the bivalve Anomia ephippium (summer). It is suggested that the direction of tidal exchange of meroplanktonic taxa is related to the distribution of the adult populations. Copepod naupliar stages dominated the assemblages except during May spring tides when the copepod Pseudocalanus elongatus made up over 22% of the abundance. The general import of micro- to mesozooplankton may, in part, explain the higher densities of this size-class of zooplankton within the semi-enclosed system of Lough Hyne.  相似文献   

5.
Abstract. The sponge communities inhabiting a temperate semi-submerged sea cave were investigated at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. Thirty-one species of sponge were reported, the majority of which exhibited either an encrusting or massive morphology. Sponge density (averaged over depth) increased with horizontal distance (5  m intervals) into the cave until approximately 30  m, corresponding to the maximum algal intrusion (algal information from Norton et al. , 1971) . Species diversity and richness (averaged over depth) were highest at 10  m horizontal distance from the cave entrance. Variability in sponge density, diversity and richness was observed with increasing vertical depth (0.5  m intervals) at most horizontal intervals sampled (5  m apart). These three variables increased initially with depth, but then decreased towards the seabed. Bray-Curtis Similarity Analysis and Multi-Dimensional Scaling (MDS) showed cave sponge community composition to have greater similarity (50 %) with local loose rock habitats than the nearby cliffs. Similar processes structuring cave and loose rock sponge communities may account for this situation. Information collected from this and previous studies on the biotic (algal communities, other fauna and competition) and abiotic factors (water flow rate, depth, aerial exposure, light, cave morphology, nutrient depletion and humidity) affecting this and other caves is discussed with respect to its influence on the sponges inhabiting different parts of the cave. Although horizontal zonation patterns have been considered analogous to vertical distribution patterns for algal communities (due to similar decreases in light), this was not the case for the studied sponge communities.  相似文献   

6.
Abstract. Settlement panels immersed at Lough Hyne, County Cork, Ireland, at six stations with widely different flow regimes were retrieved at monthly intervals. Between 40 and 62 taxa were identified at each station during the study period. Percentage cover, number of interactions and number of recruits were recorded. Space occupied was found to vary more than 2.5 orders of magnitude between stations and seasons (0.3 – 82 %). Competition for space was most intense during summer, when recruitment was highest. More than 3600 interactions between pairs of species were recorded and competitive matrices are presented for the two stations with the most interactions. Both number of interactions and % cover were significantly higher at sites with greater water flow. The nature and the degree of competition varied between sites, with the most intense competition occurring in the very high flow sites with a large proportion of intra­specific encounters. Colonial species were more evident at the sites with high flow. Certain solitary species (notably Anomia ephippium and Pomatoceros spp.) were successful competitors in encounters with cheilostomatid bryozoans. Solitary species may prevent space monopolisation by the faster-growing bryozoans. 'Typical' early successional species, notably bryozoans such as Celleporella hyalina and Microporella ciliata, were more abundant at the more disturbed sites, implying either a larger adult population and/or preferential settlement of these species at such sites.  相似文献   

7.
Man-made defence structures (e.g., breakwaters, jetties) are becoming common features of marine coastal landscapes all around the world. The ecology of assemblages of species associated with such artificial structures is, however, poorly known. In this study, we evaluated the density and size of fish predators of echinoids (i.e., Diplodus sargus, Diplodus vulgaris, Sparus aurata), and the density of sea urchins (i.e., Paracentrotus lividus) at defence structures (i.e., breakwaters) inside and outside the marine protected area of Miramare (northern Adriatic Sea) in order to: (1) assess possible differences in fish predator density and size between protected and fished breakwaters; (2) assess whether fish predation may have the potential to affect sea urchin density in artificial rocky habitats. Surveys were carried out at four random times over a period of two years. Total density, and density of medium- and large-sized individuals of the three predatory fishes were generally greater at the protected than at the fished breakwaters, whereas no differences were detected in the density of small-sized individuals. Density of the sea urchin P. lividus did not show any difference between protected and fished breakwaters. The results of this study suggest that: (1) protection may significantly affect predatory fishes in artificial rocky habitats; (2) differences in predatory fish density, and size may be unrelated with the density of the sea urchin P. lividus; (3) protected artificial structures such as breakwaters, originally planned for other purposes, could represent a potential tool for fish population recovery and enhancement of local fisheries.  相似文献   

8.
Sea urchin embryo-larval development (ELD) and fertilization tests have been widely used in ecotoxicity studies and are included in regulatory frameworks. Biological processes occur naturally within a range of salinity that depends on the species considered. In an attempt to determine the optimum range of salinity, ELD and fertilization bioassays were performed at different salinities (15-40.5‰) with two species of Atlantic sea urchin: Arbacia lixula and Paracentrotus lividus. In the ELD assay, the optimum range of salinity was wider for A.?lixula (29-35.5‰) than for P.?lividus (29-33‰). In the fertilization assay with P.?lividus as a bioindicator species, the highest percentage of fertilization (90%) was obtained at salinities of between 29 and 33‰. More research on A.?lixula is required, since the fertilization success was below 60%. The results of the present study demonstrate that salinity may be a confounding factor in interpreting ELD test results.  相似文献   

9.
Abstract. Monthly soluble and insoluble protein, carbohydrate, lipid and ash levels and energetic content were measured in tissues of Paracentrotus lividus adults living in a lagoonal environment over a 1-year period to increase our understanding of resource allocation to the different tissues. The biochemical composition of P. lividus individuals in this environment is similar to that observed in other environments. The gonad and gut contained a high level of proteins soluble or insoluble, a lesser amount of lipids and, finally, a low level of carbohydrates. The main component of the test was ash, followed by protein levels. The lipid and carbohydrate levels in the test were very low. Seasonal variability in the biochemical composition of the different body parts was observed. In the gonad, an increase in the level of lipids was recorded concomitant to an increase in gonad weight. The lipids and carbohydrates, after an initial increase, decreased with the maturation of the gonad. The biochemical variations observed in the gut seem to be linked to both the reproductive cycle and the sea urchin's trophic activity. Variability in the test was low and irregular for all of the observed biochemical components. As P. lividus is an important member of the benthic community in the Urbinu lagoon, this echinoid represents an important store of materials and energy within this lagoonal environment.  相似文献   

10.
The climate‐envelope approach to predicting climate‐induced species range shift is limited. There are many possible reasons for this, but one novel explanation is that species adapt to changes in temperature at the expense of adaptation to other stressors. Here we test this hypothesis using the limpet Patella depressa (Mollusca, Patellidae), over a large geographical area covering most of the Atlantic coast of the Iberian Peninsula, known to consist of a genetically inter‐connected population. We examine limpet shell morphology on four shores in each of three regions, from Northern Spain to Southern Portugal. Within each region, shell morphology (measured as maximum shell profile to length ratio) varied between shore types differing in their insolation, wave action, microhabitat availability and biological factors. However, this ratio, which is known to be an adaptive response to heat stress, was found to be consistently higher in more southern latitudes despite differences between shore types being found in all regions. This implies that localized adaptation to shore type (most likely through phenotypic plasticity) is compromised by factors that change over latitudinal or regional scales, or which could occur in response to climate change. Although such climate‐induced changes may initially be localized, compromised adaptation (through phenotypic or genetic plasticity) may result in altered community interactions and potentially large shifts in community structure.  相似文献   

11.
Observations on the behaviour of the common octopus Octopus vulgaris were made during daytime and night-time sampling on an unexploited rocky reef habitat in Baía dos Tigres, southern Angola. The relative numerical abundance sampled was 0.47 octopus person–1 h–1 during the day and 5.33 octopus person–1 h–1 during the night, suggesting that the population under study was nocturnal. The activity patterns differed between sizes of octopus. Small octopus (<20 cm total length [TL]) were observed roaming during the night, whereas the large individuals (>20 cm TL) generally fed in their dens. This ontogenetic behavioural shift may be due to tidal constraints or could be a strategy to avoid cannibalism. Octopus inhabiting a shallow, small-boulder substratum made extensive modifications to their habitat, excavating dens of up to 1 m deep in the sand below the boulders. These dens were not visible during the day as the octopus appeared to retract the small boulders over their den entrances. This unique behavioural strategy is thought to be a means to reduce predation and reduce light intensity during the day. Octopus were not observed in the small-boulder habitat during the five hours of daytime sampling. With nocturnal activity and extensive habitat modification, it is likely that avoidance of predation may be an important driver influencing the behaviour of the octopus population under study.  相似文献   

12.
Studies on the feeding behaviour of large predatory sharks are inherently problematic because of the size of the animals, the difficulty in observing and handling them and the risks to the investigator. Observations on the feeding behaviour of the sevengill shark Notorynchus cepedianus over a seven-year period revealed this species to display at least four distinct foraging strategies. A particular strategy, or a combination of two or more, was employed depending on the size and type of prey being subdued. The four primary factors that appear to influence prey selection were prey size, availability and density, and scavenging. The behaviour of a prey species influences the predator's foraging and hunting behaviour. The success of the sevengill shark as an apical predator can be attributed, in part, to the feeding strategies it employs to subdue prey.  相似文献   

13.
Settlement of Ostrea lutaria on sand‐cement‐plastered asbestos plates held in steel frames on the bottom of Foveaux Strait was studied from March 1965 to April 1967. Spat mortality over the period of plate exposure (about one month) was very low (maximum of 3 percent) and was greatest shortly after settlement. There was no evidence that mortality was due to predation. Essentially the same seasonal pattern of settlement was observed each year. Eighty to 90 percent of spat settled between mid December and mid February in both summers; settlement occurred as early as October; some was observed as late as July.

Results of field experiments suggest some very tentative conclusions on the settlement behaviour of O. lutaria: (1) The larvae are benthopelagic and remain on the bottom in strong current conditions. (2) Light stimulates swimming of larvae in still water. (3) In still water and low light intensities of the area larvae tend to swim upward toward the light. (4) In still water and dim light of the area larvae settle predominantly on under surfaces. (5) In still water in the absence of light larvae settle predominantly on upper surfaces. (6) Under the conditions of current and light in the multiplate frames used to sample spatfall here, larvae settle mainly on upper surfaces. (7) Larvae tend to crawl up inclined surfaces before settling.

The results indicate that larval behaviour may be changed by small alterations of light intensity and current. The contradictory nature of surface angle preferences found by other workers for various species of Ostrea and Crassostrea may have been due to such small variations caused by the experimental techniques. It is possible that the settlement behaviour of all species of these genera is similar.  相似文献   

14.
The bioaccumulation of four metals (Cd, Cu, Pb, Zn) dissolved in water was assessed measuring the concentrations recorded within sea-urchin larvae (Paracentrotus lividus, Lmk.) after a 48-h exposure period. Concurrently, the frequencies of abnormalities were evaluated at the 48-h pluteus stage to check the actual toxicity of such contaminants with regards to larval development. Maximum metal concentrations in the larvae reached 43.8 +/- 6.7 micrograms Cd g-1 dry weight (d.w.), 1269 +/- 392 micrograms Cu g-1 d.w., 3106 +/- 679 micrograms Pb g-1 d.w., 534 +/- 62 micrograms Zn g-1 d.w. Bioconcentration factors (BCFs) reached very high values for Pb (maximum value: 16,282 +/- 973) and indicated that the concentrations of Pb and Cd were directly related to the water concentration at least in the range of concentrations tested. Zn appeared to be partially regulated above a certain threshold concentration (between 5 and 25 micrograms l-1). Cu was accumulated with an active uptake at least below lethal threshold level (100 micrograms l-1). Nevertheless, above these thresholds, high mortality of embryos prevent any interpretation of Zn and Cu bioconcentration factors. Concurrent studies carried out on embryotoxicity confirmed the high toxicity of Cu towards sea-urchin pluteus larvae and highlighted the different behaviour of Cd. The internal Cd concentrations were directly related to the external ones, comparable to other non-essential metals, but Cd had little toxic effect on the initial larval development.  相似文献   

15.
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 zone A). Mature sea urchins were independently collected by SCUBA diving and sexed. The adult sex ratio was skewed towards males at high M. glacialis density sites, whereas it was balanced (1:1) at predator low-density sites. Results of sex-selective feeding experiments in the laboratory showed that females of P. lividus were more vulnerable to M. glacialis predation. These outcomes underline the possible importance of M. glacialis in regulating the OSR of P. lividus populations.  相似文献   

16.
Based upon an under-representation of second time spawners on the spawning grounds between 1935 and 1973, researchers have suggested that Norwegian spring-spawning (NSS) herring (Clupea harengus) frequently skip their second spawning event. In order to evaluate this claim with direct evidence, herring were collected over a period of three years from statutory surveys and commercial catches over a wide area covering the feeding, over-wintering and spawning grounds. The development stage of the ovaries was assessed and the intensity of atresia quantified. Only a negligible number of the analysed herring caught were considered likely to skip spawning, thus this phenomenon does not appear to be a common feature of the NSS herring stock at present. In addition, considering the reproductive strategy of herring, it seems doubtful that skipping the second spawning event has ever frequently occurred in this stock.  相似文献   

17.
The recovery capacity of shallow Posidonia oceanica meadows degraded by beach replenishment eighteen years before was assessed in two impacted meadows and compared with other two undisturbed localities. Inside each locality, we selected randomly three sites separated by 500–1000 m. At site level we study the vitality of P. oceanica meadow assessing the vegetative growth, leaf characteristics, and non-structural carbohydrates of the plants. Additionally, at locality level, silt-clay fraction, organic matter, pH and light intensity incident on the sea bottom were measured to evaluate the environmental conditions. Covering of P. oceanica was significantly lower at the impacted localities while amount of dead “matte” was higher. Leaf production of horizontal rhizomes (14.6 ± 1.11 vs 19.47 ± 1.45 leaves y−1), net total rhizomes recruitment (2.33 ± 0.17 vs 4.3 ± 0.33 branches y−1) and starch concentration (43.625 ± 0.67 vs 54.45 ± 0.74 mg per g of rhizome) at impacted meadows were significantly lower than controls. Leaf features, epiphytes biomass, colonization, elongation and horizontal and vertical rhizome production did not show significant differences. Sediments at impacted localities contained higher silt-clay fraction and higher organic matter load while pH was lower. Light intensity on the sea bottom measured at all localities was over the minimum light requirements estimated for P. oceanica. Our results show that the press impact produced by beach replenishment was enduring in the time slowing natural recovery by 45%. This impact may be related with changes in the sediment features.  相似文献   

18.
Abstract. We estimated the abundances of the three common littoral echinoid species Paracentrotus lividus, Arbacia lixula and Sphaerechinus granularis in a littoral zone between 0 and 10m depth on the Catalan shores NE Spain. Densities of each species were estimated from a total number of 11 571× 1 m2 sampling units deployed at 152 sites along the 13 zones into which the coast was divided. The surface area available in each of these zones was estimated at the scale of the sampling unit 1 m2 taking into account the fractal dimension of the shore. The stocks individuals > 2cm test diameter of these species for the whole Catalan shore ≅ 300 km, straight-line distance were estimated to be about 279.1 × 106 individuals for P. lividus , 28.9 × 106 individuals for A. lixula and 10.9 × 106 individuals for S. granularis. These sea-urchins are key species in the regulation of algal communities and some of them P. lividus. S. granularis are of commercial interest. This information will provide a tool for the future monitoring and management of this resource, which now faces diverse pressures of human origin.  相似文献   

19.
The day–night cycle is one of the strongest geophysical cycles modulating species' behavioral rhythms. However, in deep-water continental margins, where light intensity decreases over depth, interspecific competition may alter behavioral responses to day–night cycles. The burrowing decapod crustacean Nephrops norvegicus is a large-size predator in benthic communities, exerting despotic territorial behavior. In this study, we analysed how the effect of light intensity cycles on decapod behavioral rhythms is reduced as one moves from shelves to slopes. In the Western Mediterranean, the predatory behavior and interspecific competition for substrate use of Nephrops increases moving from the shelf (100–110 m) to the slope (400–430 m). Vector fitting and generalized additive models were used to assess the effect of light intensity and behavioral rhythms of N. norvegicus on the temporal variation of prey decapods co-occurring in trawl tow catches carried out on the shelf and the slope during October 1999 and June 2000. The combination of diel variations in light intensity and N. norvegicus abundance influences the activity rhythms of prey decapods in a depth- and seasonal-dependent manner. Light modulation is stronger on the shelf and weaker on the slope, where Nephrops population size is greater. Although present regression analysis does not necessarily imply a direct cause–effect relationship between rhythms of predators and prey, we suggest that Nephrops alters the temporal patterning in the behavior of its prey on the slope, where light intensity is reduced. This alteration is stronger in endobenthic species than in benthopelagic species; the former rely on bottom substrate for the expression of behavioral rhythms, experiencing stronger interspecific competitions with Nephrops at time of activity.  相似文献   

20.
Replacing traditional light sources with light-emitting diode (LED) light modules is a global trend, especially for underwater illumination. The light intensity is dispersed evenly at all emission angles in traditional underwater light sources that use the radiative transfer model, resulting in the inclusion of scattering factors in the attenuation coefficient. The high directionality of LED light source modules causes the light intensity transfer in water to vary according to varying emission angles. This renders traditional underwater optical transfer theory irrelevant as an underwater LED light module design reference. Therefore, this study constructs an underwater LED light source transfer model using the light-field average cosine and the light transfer scattering probability method, and imports the LED luminous intensity distribution curve (LIDC) and axial luminous intensity. Experimental results showed that the illumination intensity of the underwater LED illumination module was less than 10% of the simulation. Therefore, this design method can be used to design the required illumination light modules for different underwater environments. Finally, the LED light module has been used for under water fish attractor lighting and enhanced the illumination zone efficiency (m3 per Watt) of 81% compared to the traditional high intensity discharge (HID) underwater fish attractor lamp.  相似文献   

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