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1.
Distribution and abundance as a function of depth, and population parameters such as sex and size structure of the population and aspects of reproductive biology have been studied in the deep-sea polychelid lobsters Polycheles typhlops and Stereomastis sculpta. Samples were taken by otter trawl in the Balearic Sea, a deepsea basin in the northwestern Mediterranean Sea from 1985 to 1989. In both species the largest size classes were dominated by females. In S. sculpta, male and female sizes were very similar. In P. typhlops, ovigerous females and those with external spermatophores were 23 and 25 mm in carapace length (CL), respectively; males with external spermatophores were 17 mm in CL. In S. sculpta, ovigerous females and those with external spermatophores were 24 and 19 mm CL, respectively, and males with external spermatophores 19 mm CL. Highest densities of P. typhlops occurred along the middle slope at depths between 500 and 1000 m. Only small-sized individuals were found at the deepest depths sampled; some recruitment must therefore occur in waters much deeper than those usually inhabited by the adult population. The sex-ratio was 1:1 in most samples, but in some of the shallowest samples females predominated. The depth distribution range of S. sculpta was 981 to 2253 m: densities clearly increased with increasing depth. There were no apparent variations in size distribution as a function of depth. Since very few adult males and females were captured, the population in the survey area would seem to be comprised mainly of juveniles. As a function of depth, females were numerically dominant only in some of the shallowest samples taken in the distribution range of this species. There is strict habitat partitioning between the two species. In both species, the variation in the sex-ratio as a function of depth suggests differential migration between the sexes, probably related to egg incubation and hatching.  相似文献   

2.
The spatial strategies and activity patterns of two populations of Pachygrapsus marmoratus (Fabricius), from Italy and Portugal, were studied in the field. The Mediterranean site was a non-tidal splash zone about 30 cm wide, while the Atlantic site was a 30 m wide intertidal belt. Almost all P. marmoratus of both populations were active on the emerged rocks, rarely entering the sea. The Mediterranean crabs actively fed on the algal turf throughout the 24 h, while in Portugal active crabs were more numerous at night. In the Italian population, all crabs were packed together, although large males had larger activity areas than females and smaller males. In Portugal, the large males were more concentrated in the sublittoral fringe, while both small males and females were confined to the eulittoral and littoral fringe. The Italian P. marmoratus performed feeding loops within areas smaller than 9 m2. Although most Portuguese crabs showed the same spatial strategy, some of them performed feeding migrations to the sublittoral fringe, covering distances of up to 20 m. Environmental factors (e.g. temperature), physical factors (e.g. refuge availability) and biotic factors (e.g. competitors and predators) of the different shores probably determine the behavioural plasticity of␣P.␣marmoratus. Received: 1 February 1998 / Accepted: 13 November 1998  相似文献   

3.
Attempts to identify predictors and mechanisms of invasion success have been weakened by poor data quality, mostly because monitoring does not begin immediately after introduction events. To overcome this issue, we used data from conservation translocations of threatened bird species. We analyzed information on >1200 translocation events of >150 bird species to investigate how life-history traits affect population establishment measured based on rates of survival and reproduction. Species position along the slow–fast life-history continuum was a key predictor of translocation success. Species with fast-paced life histories were less likely to survive (over both short- and mid-term) and more likely to breed successfully than species with slow life histories. The temporal partitioning of reproductive effort (number of clutches per year) also affected the probability of successful reproduction. Our results illustrate how conservation-motivated reintroduction programs can provide proxies for the initial stages of the invasion process, enabling empirical tests of predictions from life-history theory and informing management.  相似文献   

4.
Several aspects of the biology of Bathypolypus sponsalis were studied from 297 individuals (115 males, 180 females and 2 indeterminates) caught in a depth range of 200–800 m depth in the western Mediterranean Sea. The paper presents data on sizes (length-weight relationships, size-frequency distributions) and reproduction (sex ratio, maturation, condition), and also analyses of the diet of B. sponsalis from samples taken throughout the year. Length-weight relationships showed that females are heavier than males at the same mantle length. Although mature individuals were found all year round, the maximum number occurred in spring and summer. Sexual maturation data revealed that males mature at smaller sizes than females. The gonadosomatic index increased with maturity in both sexes; the increase was gradual in males, but abrupt in females. The digestive gland index was used as a condition index and showed a differential behaviour with maturity; it increased gradually in females, but decreased in males. Like other octopus species, B. sponsalis appears to be an opportunistic predator, feeding on a great variety of preys. Stomach content analysis yielded a total of 19 different prey items belonging to four major groups (Crustacea, Mollusca, Ophiuroidea and Osteichthya). The first three groups were the more frequent preys, since crustaceans, molluscs and ophiuroids appeared in 76%, 49% and 30% of the stomachs, respectively. Decapoda Reptantia (among crustaceans) and cephalopods and bivalves (among molluscs) constituted the more abundant prey items. While the Decapoda Reptantia group was significantly more abundant in stomach contents of females, gastropods were taken more frequently by males. These differences in diet could reveal females as a more active predators than males. Received: 5 March 2000 / Accepted: 7 November 2000  相似文献   

5.
R. T. Bauer 《Marine Biology》1977,40(3):261-276
Preening (cleaning, grooming) of the antennules and other cephalothoracic appendages by the third maxillipeds was observed in several species of shrimp. Distribution and ultrastructure of serrate grooming setae on the third maxillipeds, which scrape the antennules, was studied with light and scanning electron microscopy. The motor patterns of antennular cleaning were similar for all species. Antennular preening was the most frequent grooming behavior observed, but the duration of other grooming behaviors was greater. Tidepool shrimps (Heptacarpus pictus) experimentally prevented from grooming the antennules by ablation suffered fouling of the olfactory hairs of the antennules with their subsequent breakage and loss; antennules of controls remained clean and undamaged. Antennular preening, a frequent and widespread behavior of caridean shrimps and other decapod crustaceans, is suggested as having high adaptive value in keeping sensory sites free of epizoic and sedimentary fouling which might render them inoperative.  相似文献   

6.
Sabella spallanzanii (Gmelin) is one of the best known and widely distributed Mediterranean polychaetes, but available data on its general biology has been inferred mostly from populations recently introduced to Australia. In the present paper, data on gametogenesis and larval development of a Mediterranean population from the Gulf of Taranto (Ionian Sea, Italy) are reported. Histological and electron microscopical analysis of gametogenesis showed that oogenesis, a long process beginning soon after spawning in February, is of extraovarian type. By contrast spermatogenesis is a very fast process lasting from September to December, when the coelomic cavity is completely packed with mature gametes and almost devoid of coelomocytes. During the period of spawning, some experiments of in vitro fertilisation were performed, always without success, while some of the collected females naturally spawned fertilised eggs (100%). Particularly interesting was the discovery of a small percentage of eggs which appeared fertilised but unspawned within the coelomic cavity of female. Investigation of the S. spallanzanii life cycle, from the naturally spawned fertilised eggs to embryonic and juvenile stages, was performed by daily microscopical observations and by SEM. Despite the presence of large eggs giving rise to a lecithotrophic larva, a long pelagic phase was observed, the longest found among Sabellidae. The larval development pattern is also described. Settlement began after about 2 weeks; metamorphosis occurred 10 d after settlement, when mucus was secreted abundantly and an external tube was formed. The long larval pelagic period and the development pattern, suggesting a high potential for dispersal, support both the introduction and invasive behaviour of the species in Australian waters. Received: 28 May 1999 / Accepted: 10 December 1999  相似文献   

7.
While studies on a wide diversity of organisms have demonstrated the importance of female behavior during matings, in crustacean studies, a strong bias towards male mating behavior prevails. Reproductively mature rock shrimp (Rhynchocinetes typus) exist as several ontogenetic stages that differ in their morphological and physiological capacities. In natural populations, the majority of males are in early ontogenetic stages (termed typus), many are in intermediate stages (intermedius), and few are in the terminal molt stage (robustus). Dominant robustus males, which have already demonstrated their biological fitness by surviving to this stage, have previously been shown to have a higher potential than subordinate typus males to defend receptive females against other males, and fertilize the entire clutch of a female. While females should thus show a preference for robustus males, they nevertheless frequently receive sperm from typus males. These observations suggested that females might have mechanisms to discriminate against sperm from subordinate males. In laboratory experiments, we observed that females avoided being seized by typus males for longer time periods in the absence of robustus males than in their presence. Following seizure, females that were initially held by typus males, required more time to initiate spawning than those held by robustus males. Many typus males transferred spermatophores to females before these started to spawn while robustus males waited until females began to spawn before they transferred spermatophores. Females manipulated spermatophores received from typus males for long time periods (minutes), but not those they received from robustus males. By accepting sperm from subordinate typus males, females may avoid further harassment (convenience polyandry), but they subsequently may discriminate against these subordinate males by delaying spawning and removing their sperm. These observations suggest that female behavior influences the outcome of matings, favoring fertilization of eggs by sperm from dominant males. Convenience polyandry and cryptic female choice may be common in other crustaceans as well.Electronic Supplementary Material Supplementary material is available in the online version of this article at .Communicated by T. Czeschlik  相似文献   

8.
The carbon transfer through the microbial community in two areas of the Northern Adriatic Sea was estimated by proteolytic and respiratory activities during four oceanographic surveys carried out in June, 1996, 1997 and February, 1997, 1998. In front of the Po Delta (area A), the mean rates of proteolytic activity range from 4.9 to 9.9 r µg r C r h r l; near Ancona (area B), they range from 3.1 to 7.6 r µg r C r h r l. Respiratory rates vary between 0.19 and 2.29 and between 0.24 and 1.40 r µg r C r h r l in areas A and B, respectively. In general, high rates occur in the surface layers, within the first 10 r m of depth. In area A, proteolytic and respiratory rates undergo seasonal course, with high activity in warm periods. In area B, respiration and bacterioplankton abundance increase from the first to the second year, whilst proteolytic activity decreases. The sequence of metabolic steps in the carbon transfer within the bacteria, from the biotic vs . the abiotic compartment, was drawn in order to define the actual role of bacterial biomass in the biogeochemical fluxes in an ecosystem which often suffers distrophic crises. Respiratory turnover rates, in the upper 10 r m depth, reach low values in cold periods and high values in June, 1997. The carbon transfer versus mineralization flows better in the summer period, in particular in June, 1997. However, the bacterial growth efficiency ranges from 17 to 38% in area A and from 13 to 44% in area B with highest values in February, 1997, when bacteria contribute in a relevant way to the overall respiration.  相似文献   

9.
Oh  C.-W.  Hartnoll  R. G. 《Marine Biology》2004,144(2):303-316
Aspects of the reproductive biology of the common shrimp Crangon crangon (L.) were studied in Port Erin Bay, Isle of Man, Irish Sea. Size at sexual maturity was determined from the proportions of ovigerous females and of females with maturing ovaries. The size at which 50% of females are mature is estimated (±95% confidence intervals) as 12.5±0.48 mm carapace length. Based on the proportions of ovigerous females and of mature females, the main breeding season was from January to June. Mean ovarian dry weights indicated two broods (winter and summer), with females bearing winter broods (WB) having higher gonad indices than those with summer broods (SB). WB females with non-eyed eggs and with eyed eggs differed in the regression of ovarian dry weight on carapace length, indicating preparation for laying a second brood. In both broods the moult stages of berried females were related to egg stage. Moulting will occur following the release of the brood. During embryonic development, mean egg length and egg volume were larger in all stages, and the mean dry weight of individual eggs of all stages heavier, in WB than in SB; there was no difference in egg number, however. Consequently, reproductive investment, the proportion of female weight devoted to egg production, was 67% higher in WB (0.20±0.04) than in SB (0.12±0.03). There is a significant effect of egg volume on brood weight, but not on egg number. In both broods, egg number was a negatively allometric function of female body size in non-eyed eggs and an isometric function of female body size in eyed eggs. Brood mortality during incubation was higher in SB (17%) than WB (10%). Differences in the reproductive variables and investment between the two broods of C. crangon are discussed in the light of reproductive strategies and life history.Communicated by J.P. Thorpe, Port Erin  相似文献   

10.
11.
About 2,500 specimens of the Kamchatka king crab Paralithodes camtschatica (Tilesius), ca. 5 to 15 years old, and about 10,000 juveniles, ca. 1 to 3 years old, were released into the Barents Sea from 1961 to 1969. One large berried female was caught in 1974, and the number of records increased in 1976 (at least 100 records, including 6 reliable ones). The crab therefore seems to have become a permanent inhabitant of the Barents Sea. It will be important in future to continually record new occurrences of the crabs, especially of juveniles, in order to document the extent of their distributional range and to obtain evidence of successful reproduction of the species.  相似文献   

12.
Loggerhead turtles nesting in the Mediterranean Sea exhibit remarkable genetic structuring. This paper tests the hypothesis that young loggerhead turtles from different rookeries do not distribute homogeneously among the major Mediterranean foraging grounds, due to a complex pattern of surface currents. We extracted long fragments of mitochondrial DNA from 275 stranded or bycaught juvenile turtles from six foraging grounds (Catalano-Balearic Sea, Algerian basin, Tyrrhenian Sea, Adriatic Sea, northern Ionian Sea and southern Levantine Sea). We used a Bayesian mixed-stock analysis to estimate the contributions from rookeries in the Mediterranean, the North-west Atlantic and Cape Verde to the studied foraging grounds. Differences were found in the relative contribution of juvenile turtles of Atlantic and Mediterranean origin to each foraging ground. A decreasing proportion of Atlantic juveniles was detected along the main surface current entering the Mediterranean, with a high prevalence of turtles from eastern Florida in the Algerian basin and lower numbers elsewhere. In regard to the turtles of Mediterranean origin, juveniles from Libya prevailed in central and western Mediterranean foraging grounds other than the Algerian basin. Conversely, the Adriatic Sea was characterised by a large presence of individuals from western Greece, while the southern Levantine Sea was inhabited by a heterogeneous mix of turtles from the eastern Mediterranean rookeries (Turkey, Lebanon and Israel). Overall, the distribution of juveniles may be related to surface circulation patterns in the Mediterranean and suggests that fisheries might have differential effects on each population depending on the overlap degree between foraging and fishing grounds.  相似文献   

13.
Abstract:  Evidence for severe declines in large predatory fishes is increasing around the world. Because of its long history of intense fishing, the Mediterranean Sea offers a unique perspective on fish population declines over historical timescales. We used a diverse set of records dating back to the early 19th and mid 20th century to reconstruct long-term population trends of large predatory sharks in the northwestern Mediterranean Sea. We compiled 9 time series of abundance indices from commercial and recreational fishery landings, scientific surveys, and sighting records. Generalized linear models were used to extract instantaneous rates of change from each data set, and a meta-analysis was conducted to compare population trends. Only 5 of the 20 species we considered had sufficient records for analysis. Hammerhead ( Sphyrna spp.), blue ( Prionace glauca ), mackerel ( Isurus oxyrinchus and Lamna nasus ), and thresher sharks ( Alopias vulpinus ) declined between 96 and 99.99% relative to their former abundance. According to World Conservation Union (IUCN) criteria, these species would be considered critically endangered. So far, the lack of quantitative population assessments has impeded shark conservation in the Mediterranean Sea. Our study fills this critical information gap, suggesting that current levels of exploitation put large sharks at risk of extinction in the Mediterranean Sea. Possible ecosystem effects of these losses involve a disruption of top-down control and a release of midlevel consumers.  相似文献   

14.
Extracts from marine sponges collected along the French coast of Mediterranean in 1983 have been tested for antibacterial and antifungal activities. The distribution of antimicrobial activities against five classes of microorganisms (5 Gram-positive and 5 Gram-negative terrestrial bacteria, 10 marine bacteria, 15 human pathogenic fungi and 5 phytopathogenic fungi) among 28 species of marine demosponges is reported. Antibacterial activity against Gram-positive bacteria (77%) is much more frequent than against Gram-negative bacteria (53%). Activity against marine bacteria and yeast is less frequent (32%). Those sponges which contain a large quantily of symbiotic bacteria display a weak antifungal activity.  相似文献   

15.
The frostfish Lepidopus caudatus (Euphrasen, 1788) is a mesopelagic species; it occurs along the shelf and slope down to 450 m in the Catalan Sea. Its' fishery, population structure, growth, diet and reproduction was studied on the basis of commercial statistics from 1984 to 1990 and on samplings made in 1988 and 1989. L. caudatus is fished by two types of commercial method, trawl and long-line; catches by the latter method display a marked seasonality. The minimum size of fish caught is 26 cm total length by trawling and 71 cm by long-line. Maximum sizes are similar for both gears: 196 and 188 cm, respectively. L. caudatus exhibits fast growth and attains an age of 8 yr. It feeds on small mesopelagic prey. It is a partial spawner reproductive activity occurring from April to November. Males attain sexual maturity at 97 cm and females at 111 cm total length.  相似文献   

16.
Meganyctiphanes norvegica (M. Sars)is a pelagic crustacean that plays a key role in marine food webs of North Atlantic Ocean and marginal seas. We studied eight population samples collected in the European Atlantic and Mediterranean Sea. By means of single strand conformation polymorphism analysis (SSCP) and direct sequencing, we investigated a segment of 158 base pairs of the mitochondrial gene coding for the subunit 1 of NADH dehydrogenase. We found 12 sequence variants among the 385 individuals studied. Analysis of molecular variance (AMOVA) showed that 14.75% of the total genetic variability was explained by differences between populations, thus indicating absence of panmixia for these populations. Pairwise comparisons revealed three distinct genetic pools: the first one represented by Cadiz Bay, the second one by the Ligurian Sea, and the third one included all the NE Atlantic samples. We also investigated one population from the Alboran Sea (within the Mediterranean basin, east of the Strait of Gibraltar). This population was found to be genetically intermediate between the NE Atlantic samples and the Ligurian sample, suggesting that the restriction to the gene flow is not associated with the Strait of Gibraltar, but possibly with the Oran–Almeria oceanographic front. The present work indicates that M. norvegica, although endowed with a high dispersal capacity because of its pelagic habit, can develop separate breeding units inside the same oceanic basin (the Atlantic). Furthermore, the Ligurian sample should be considered as a distinct evolutionary entity, separated from the Atlantic population. Received: 2 May 1999 / Accepted: 26 November 1999  相似文献   

17.
T. Madurell  J.E. Cartes 《Marine Biology》2006,148(6):1325-1338
Daily and seasonal changes in dietary habits, resource partitioning and daily food consumption of Coelorhynchus coelorhynchus, Hymenocephalus italicus and Nezumia sclerorhynchus, the three dominant macrourids coexisting at mid-slope depths (between 473 and 603 m) in the eastern Ionian Sea, were analysed. The three species showed very diverse diets, based mainly on suprabenthic prey and infauna. Day–night changes in the diet and feeding intensity were more apparent in H. italicus and N. sclerorhynchus, preying mainly on mobile prey (suprabenthos), than for C. coelorhynchus that preyed largely on infauna. Dietary overlap was very low among species. The highest daily ration (DR) obtained for N. sclerorhynchus (in April) coincided with maximum concentration of its preferred prey (i.e. Boreomysis arctica). H. italicus, displaying a more pelagic diet than N. sclerorhynchus, showed higher DR (between 1.47–1.51%wetW and 0.47–0.71%wetW, respectively) probably due to higher metabolic activity because it may swim up in the water column to eat. C. coelorhynchus, having the most benthic diet, showed the highest DR (between 2.92 and 2.53%wetW). This rather unexpected high DR would be attributable to a continuous feeding on more uniformly distributed prey (benthos) and to a high rooting activity on the sediment in search of infauna. The influence of the type of resources exploited in the overall trends obtained in the diet of macrourids is discussed and compared with those of other deep-sea species. As a general conclusion, results suggest that food consumption of bathyal fish are probably influenced by or coupled with the type of resources exploited.  相似文献   

18.
George Skoufas 《Marine Biology》2006,149(6):1365-1370
The two forms of Eunicella singularis sclerites, spindles and clubs, were examined in two sites in East Mediterranean Sea, Greece. The comparison of the sclerites size was based on the hydrodynamic profile of the sites (the site of Arethoussa was exposed and the Phidonissi site was sheltered), on the sites bathymetry (AR 5–8 m, AR 9–13 m, PH 5–10 m, PH 11–13 m) and on the position occupied by the sclerites on the gorgonian colonies (top, middle and base). With the usage of image system analysis the following microfeatures were measured or calculated: projection, length, width, elongation factor, compactness factor, length × width and length/width. The present study confirms the hypothesis that spindles are involved in the recovering of the gorgonian colonies and clubs contribute to the flexion capacity of the colonies. The spindles of the shallow E. singularis colonies (AR 5–8 m) were significantly bigger (length, width) compared with the others, in order to assure the best recovery of the colonies after their flexion, induced by higher water current velocity in shallow water. The clubs occupy the intern part of the mesoglea and their size (length, width) increased in colonies from the shallow exposed site in order to facilitate the gorgonian flexion. The present study demonstrates the gorgonian adaptation (in a microscopic scale) to the environmental pressure of hydrodynamic conditions.  相似文献   

19.
In the shrimp Crangon crangon, an important fishery resource and key species in the southern North Sea, we studied temporal variations in size, biomass (dry weight, W) and chemical composition (C, N, protein and lipid) of eggs in an initial embryonic stage. Data from 2 years, 1996 and 2009, consistently revealed that egg size and biomass varied seasonally, with maxima at the beginning of the reproductive season (January), decreasing values throughout spring, minima in June–July, and a slight increase thereafter. This cyclic pattern explains why “Winter eggs” are on average larger and heavier than “summer eggs”. Using a modelling approach, we estimated the duration of oogenesis in relation to seasonally changing seawater temperatures. According to an additive model of multiple explanatory variables, the C content per newly laid egg showed in both years a highly significant negative relationship with day length (r2 = 0.38 and 0.40, respectively; P < 0.0001), a weak positive relationship with temperature (r2 = 0.08 and 0.09; P < 0.05), and a weak negative relationship with phytoplankton biomass (r2 = 0.11 and 0.12; P < 0.05) at the estimated time of beginning oogenesis. Phenotypic plasticity in initial egg size and biomass is interpreted as an adaptive reproductive trait that has evolved in regions with strong seasonality in plankton production and periods of larval food limitation. In contrast to biomass per egg, the percentage chemical composition remained similar throughout the reproductive period. Both the absolute and percentage values also showed significant interannual variations, which caution against generalizations based on short-term studies of reproductive traits of C. crangon and other species of shrimp.  相似文献   

20.
The brown shrimp Crangon crangon is a key species in the coastal areas of the North Sea. It constitutes a significant food source for fishes. Simultaneously, it is an important predator on a wide range of invertebrates. C. crangon shows a variety of digestive enzymes that allow to utilizing a wide range of food items. The initial step of alimentary protein digestion, that is the degradation into peptides, is facilitated by set of endopeptidases which are expressed by the midgut gland. In crustaceans, these endopeptidases are often dominated by serine proteinases. C. crangon, however, predominantly express cysteine proteinases, while only some specimens show a highly variable pattern of serine proteinases. The composition of these serine endopeptidases was investigated using liquid chromatography, substrate gel electrophoresis and inhibitor assays. Distinctly elevated activities were present only in about 10% of the samples. When activity was detected, two peaks, one with tryptic activity and the other one with chymotryptic activity, could be separated by anionic exchange chromatography. Moreover, specimens with elevated tryptic activities often showed highly polymorphic patterns of endopeptidases after electrophoretic separation. Overall, 30 different bands of endopeptidases were identified. There was no similarity between animals from the same sampling sites, neither between animals of similar size, weight or nutritive state. The polymorphism of proteinase from the midgut gland seems to reflect the high adaptive potential of this species to variable trophic conditions in a continuously changing environment.  相似文献   

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