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1.
Andrea Gori Cristina Linares Sergio Rossi Rafel Coma Josep-Maria Gili 《Marine Biology》2007,151(4):1571-1584
Paramuricea clavata (Risso, 1826) and Eunicella singularis (Esper, 1794) are the most representative gorgonian species in hard bottoms sublittoral communities in the Western Mediterranean
Sea. Reproductive cycles of two populations of both species were studied in two distinct locations approximately 600 km apart
(Medes Islands and Cape of Palos), in order to assess interpopulation variability on a relevant geographic scale. Seasonal
variation of lipid concentration levels in the gorgonian tissue was used as a tool to quantify energy storage by each studied
population in order to explain possible interpopulation differences in gonadal output. Sex ratio in Medes Islands populations
of both species was 1:1, while in Cape of Palos sex ratio was significantly male biased (1:7) in P. clavata, and female biased (1.7:1) in E. singularis populations. Spawning timing occurred in all cases coinciding with a marked increase in sea-water temperature in spring,
and after the most successful feeding season, but comparing localities there was a clear temporal shift in the time of gametes
release, appearing well linked to the shift in sea-water temperature rising in spring in both sites at the depth where populations
are placed. Therefore, in this study the temperature appears as the main synchronizing factor of gonadal development within
these populations. Significant differences in gonadal volume per polyp were found in both species owing mainly to differences
in the number of gonads per polyp between populations, with Cape of Palos populations displaying higher values in both studied
species, suggesting that the exposition to different local conditions may be reverted in a different gonadal output. But the
observed patterns in lipid concentrations levels in gorgonians disable us to conclude that lipid concentration levels explain
the observed differences in gonadal output found in this study. 相似文献
2.
Gorgonian species may contribute to the three-dimensional seascape in soft bottom-gravel areas, but the information on their
biology and ecology is very scarce. The biometry and secondary production of the Mediterranean soft bottom-gravel passive
suspension feeder Leptogorgia sarmentosa (Cnidaria: Octocorallia) was studied using photographic monitoring of the primary branches from May 1998 to September 2000.
The primary branches observed had a high density of polyps (2.2 ± 0.2 SD polyps mm−1) and a high organic matter content (63.2 ± 9.1 SD %). During the two-year sampling period, there was a net negative growth
in 90% of the gorgonian population. The mean loss during the 27-month period was −2.9 ± 0.9 SD cm per branch (5.7 mg C branch−1). However, considering only the initial and final diameters and maximum height in the 27 months elapsed time, the gorgonians
showed positive growth, which meant that photographic sampling of single branches was a more appropriate method for gorgonian
secondary production monitoring. A water mass anomaly detected in 1999 in the north-western Mediterranean Sea may have been
the cause of the net negative growth in L. sarmentosa in the studied area. Partial mortality due to different factors, such as strong currents, predation, disease, etc., could
be a common strategy in sessile colonial benthic populations that would facilitate their maintenance even during very stressful
circumstances. 相似文献
3.
In a previous study on the kuruma shrimp Penaeus japonicus from the South China Sea, we detected high genetic divergence between two morphologically similar varieties (I and II) with
distinct color banding patterns on the carapace, indicating the occurrence of cryptic species. In the present study, we clarify
the geographical distribution of the two varieties in the western Pacific by investigating the genetic differentiation of
the shrimp from ten localities. Two Mediterranean populations are also included for comparison. Based on the mitochondrial
DNA sequence data, the shrimps are separated into two distinct clades representing the two varieties. Variety I comprises
populations from Japan and China (including Taiwan), while variety II consists of populations from Southeast Asia (Vietnam,
Singapore and the Philippines), Australia and the Mediterranean. Population differentiation is evident in variety II, as supported
by restriction profiles of two mitochondrial markers and analysis of two microsatellite loci. The Australian population is
genetically diverged from the others, whereas the Southeast Asian and Mediterranean populations show a close genetic relationship.
Variety I does not occur in these three localities, while a small proportion of variety II is found along the northern coast
of the South China Sea and Taiwan, which constitute the sympatric zone of the two varieties. The present study reveals high
genetic diversity of P. japonicus. Further studies on the genetic structure of this species complex, particularly the populations in the Indian Ocean and Mediterranean,
are needed not only to understand the evolutionary history of the shrimp, but also to improve the knowledge-based fishery
management and aquaculture development programs of this important biological resource. 相似文献
4.
Fine-scale movement patterns in penaeid prawns are rarely observed in situ, but are essential in understanding habitat use,
foraging, and anti-predator behaviour. Acoustic telemetry was applied to examine the activity, space utilization, and habitat
use of the eastern king prawn Penaeus (Melicertus) plebejus, at small temporal and spatial scales. Tracking of sub-adult P. plebejus (n = 9) in Wallagoot Lake (36.789°S, 149.959°E; 23 April–12 May 2009) and calculation of a minimum activity index (MAI) revealed high variation in activity rates across diel periods and in different habitats. Elevated activity rates and movement
indicated foraging in unvegetated habitats during the night. Areas within the 95 and 50% space utilization contours averaged
2,654.1 ± 502.0 and 379.9 ± 103.9 m2, respectively, and there was a significant negative relationship between these areas and prawn activity rates in unvegetated
habitats. This study provides the first estimates of prawn activity rates and space utilization in the field. Application
of acoustic telemetry can increase knowledge of prawn movements and their interactions with other marine species in different
habitats. 相似文献
5.
Andrea Gori Sergio Rossi Cristina Linares Elisa Berganzo Covadonga Orejas Mark RT Dale Josep-Maria Gili 《Marine Biology》2011,158(8):1721-1732
In the Western Mediterranean Sea, the gorgonian Eunicella singularis (Esper, 1794) is found at high densities on sublittoral bottoms at depths from 10 to 70 m. Shallow colonies have symbiotic
zooxanthellae that deeper colonies lack. While knowledge of the ecology of the shallow populations has increased during the
last decades, there is almost no information on the ecology of the deep sublittoral populations. In October and November 2004
at Cap de Creus (42°19′12″ N; 03°19′34″ E), an analysis of video transects made by a remotely operated vehicle showed that
shallow populations (10–25 m depth) were dominated by small, non-reproductive colonies, while deep sublittoral populations
(50–67 m depth) were dominated by medium-sized colonies. Average and maximum colony heights were greater in the deeper populations,
with these deeper populations also forming larger patch sizes and more extensive regions of continuous substrate coverage.
These results suggest that shallow habitats are suitable for E. singularis, as shown by the high recruitment rate, but perturbations may limit or delay the development of these populations into a
mature stage. This contrasts with the deep sublittoral habitats where higher environmental stability may allow the development
of mature populations dominated by larger, sexually mature colonies. 相似文献
6.
R. Allen Brooks Martha S. Nizinski Steve W. Ross Kenneth J. Sulak 《Marine Biology》2007,152(2):307-314
The occurrence and relative abundance of tissue (arm) regeneration in the ophiuroid, Ophiacantha bidentata (Retzius), was examined in individuals collected primarily among colonies of the deep-water coral Lophelia pertusa off the southeastern United States. Seven deep-water coral sites (384–756 m), located between Cape Lookout, NC, and Cape
Canaveral, FL, were sampled in June 2004 using a manned submersible. The presence of regenerative tissue was evaluated by
visual inspection of each individual ophiuroid, and the proportion of regenerating arms per individual was examined relative
to size of individual, geographic location, and depth of collection. Ophiacantha bidentata, the dominant brittle star collected, commonly displayed signs of sublethal injury with over 60% of individuals displaying
some evidence of regeneration. These levels of regeneration rival those reported for shallow-water ophiuroids. Larger individuals
(>6.5 mm disc size) had a higher incidence of regeneration than smaller individuals. Size of individual and percent of regeneration
were negatively correlated with depth. Although O. bidentata was significantly less abundant in southern versus northern sites, ophiuroid abundance did not appear to be influenced by
amount or density of coral substratum. Presence of dense aggregations of O. bidentata indicates that they are an important component of the invertebrate assemblage associated with deep-water coral habitat especially
in the northern part of the study area. Assuming that observed frequencies of injury and subsequent regeneration represent
predation events then dense ophiuroid aggregations in deep-water coral habitats represent an important renewable trophic resource
within these communities. 相似文献
7.
The euphausiids Thysanoessa inermis (Kroyer 1846), Thysanoessa spinifera (Holmes 1900), and Euphausia pacifica (Hansen 1911) are key pelagic grazers and also important prey for many commercial fish species in the Gulf of Alaska (GOA).
To understand the role of the euphausiids in material flows in this ecosystem their growth rates were examined using the instantaneous
growth rate (IGR) technique on the northern GOA shelf from March through October in 2001–2004. The highest mean molting increments
(over 5% of uropod length increase per molt) were observed during the phytoplankton bloom on the inner shelf in late spring
for coastal T. inermis, and on the outer shelf in summer for T. spinifera and more oceanic E. pacifica, suggesting tight coupling with food availability. The molting rates were higher in summer and lower in spring, for all species
and were strongly influenced by temperature. Mean inter-molt periods calculated from the molting rates, ranged from 11 days
at 5°C to 6 days at 8°C, and were in agreement with those measured directly during long-term laboratory incubations. Growth
rate estimates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm day−1 or 0.023 day−1 for T. inermis) and July (0.091 mm day−1 or 0.031 day−1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm day−1 (0.016 day−1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5°C) and ambient chlorophyll-a concentration fit a Michaelis–Menten curve (r
2 = 0.48) with food saturated growth rate of 0.032 day−1 with half saturation occurring at 1.65 mg chl-a m−3, but such relationships were not significant for T. spinifera or E. pacifica. 相似文献
8.
M. A. Iannotta F. P. Patti M. Ambrosino G. Procaccini M. C. Gambi 《Marine Biology》2007,150(6):1115-1126
The aim of this work was to define the phylogeographic patterns of the two species of polychaete Eunicidae, Lysidice ninetta Audouin and Milne Edwards and Lysidice collaris Grube, both associated as sheath borers to the Mediterranean seagrass Posidonia oceanica, and with reference to their different origin and their actual geographic distribution. L. ninetta is distributed in the Atlantic and in the Mediterranean Sea while L. collaris is a tropical species, whose introduction into the Mediterranean Sea through the Suez Canal (lessepsian migrant) has been
hypothesized in recent years. The two species have been often confused in the past, although they appear morphologically distinct.
They share the same microhabitat (Posidonia sheaths) and they co-exist along a broad bathymetric range (1–30 m). Several populations for both taxa were sampled all along
the coast of the Mediterranean basin. A variable no coding region of nuclear DNA (rDNA, ITS1) and a portion of a more conservative
coding region of mitochondrial DNA (sub-unit one of citochrome oxidase, COI) were used as molecular markers. Both markers
confirmed the separation between the two species. Low intraspecific polymorphism was present in L. collaris, together with absence of phylogeographic structure. In L. ninetta, instead, the presence of intraspecific cryptic lineages, sympatric in some sites, was recorded. Clustering of single populations
in the two main clades was not always consistent between markers. The mitochondrial COI region showed more resolution at the
given spatial scale. Our results suggest that Lysidice collaris could be recently introduced into the Mediterranean Sea from one or more separate events. On the other hand, for L. ninetta one could presume a re-colonization of the Mediterranean basin from the Atlantics, after the Messinian crisis (dry-out of
the Mediterranean Sea, 5.5 my) with the subsequent separation of intraspecific lineages. The phylogeographic patterns of both
Lysidice spp. are disjoined with respect to that of the host plant, P. oceanica. The obtained results suggest that environmental constraints and evolutionary history of these polychaetes and their host
plant act in different ways to determine their actual genetic spatial structure. 相似文献
9.
The venomous striped eel catfish Plotosus
lineatus was first recorded in the Mediterranean in 2002. Within 1–3 years, it has spread throughout the entire Israeli coast. We
have studied its spatiotemporal distribution patterns via trawl surveys in order to determine the scale and extent of this
invasion. Findings indicate that a population explosion has occurred, and the catfish now inhabits all sandy and muddy substrates
up to ca 80 m. P. lineatus was found to recruit in autumn in the Mediterranean and displays similar or improved growth patterns and condition factor
compared to those found in its native habitat. We discuss the possible ecological mechanisms responsible for its success:
Benthic invaders are among its main prey items, suggesting an invasional meltdown process. We also point to the decline of
indigenous species using its trophic and behavioral–ecological niche and hypothesize that they might be outcompeted and displaced
by the catfish. 相似文献
10.
Great scallop, Pecten maximus, and blue mussel, Mytilus edulis, clearance rate (CR) responses to low natural seston concentrations were investigated in the laboratory to study (1) short-term
CR variations in individual bivalves exposed to a single low seston diet, and (2) seasonal variations in average CR responses
of bivalve cohorts to natural environmental variations. On a short temporal scale, mean CR response of both species to 0.06 μg L−1 chlorophyll a (Chl a) and 0.23 mg L−1 suspended particulate matter (SPM) remained constant despite large intra-individual fluctuations in CR. In the seasonal study,
cohorts of each species were exposed to four seston treatments consisting of ambient and diluted natural seston that ranged
in mean concentration from 0.15 to 0.43 mg L−1 SPM, 0.01 to 0.88 μg L−1 Chl a, 36 to 131 μg L−1 particulate organic carbon and 0.019 to 0.330 mm3 L−1 particle volume. Although food abundance in all treatments was low, the nutritional quality of the seston was relatively
high (e.g., mean particulate organic content ranged from 68 to 75%). Under these low seston conditions, a high percentage
of P. maximus (81–98%) and M. edulis (67–97%) actively cleared particles at mean rates between 9 and 12 and between 4 and 6 L g−1 h−1, respectively. For both species, minimum mean CR values were obtained for animals exposed to the lowest seston concentrations.
Within treatments, P. maximus showed a greater degree of seasonality in CR than M. edulis, which fed at a relatively constant rate despite seasonal changes in food and temperature. P. maximus showed a non-linear CR response to increasing Chl a levels, with rates increasing to a maximum at approximately 0.4 μg L−1 Chl a and then decreasing as food quantity continued to increase. Mean CR of M. edulis also peaked at a similar concentration, but remained high and stable as the food supply continued to increase and as temperatures
varied between 4.6 and 19.6°C. The results show that P. maximus and M. edulis from a low seston environment, do not stop suspension-feeding at very low seston quantities; a result that contradicts previous
conclusions on the suspension-feeding behavior of bivalve mollusks and which is pertinent to interpreting the biogeographic
distribution of bivalve mollusks and site suitability for aquaculture. 相似文献
11.
Nicole M. Phillips Jennifer A. Chaplin David L. Morgan Stirling C. Peverell 《Marine Biology》2011,158(4):903-915
Northern Australia is considered to be one of the last strongholds for three critically endangered sawfishes, Pristis zijsron, Pristis clavata, and Pristis microdon, making these populations of global significance. Population structure and levels of genetic diversity were assessed for
each species across northern Australia using a portion of the mitochondrial control region. Statistically significant genetic
structure was detected in all three species, although it was higher in P. microdon (F
ST = 0.811; N = 149) than in either P. clavata (F
ST = 0.419; N = 73) or P. zijsron (F
ST = 0.202; N = 49), possibly due to a much higher and/or localized level of female philopatry in P. microdon. The overall levels of haplotype diversity in P. zijsron (h = 0.555), P. clavata (h = 0.489), and P. microdon (h = 0.650) were moderate, although it appears to be reduced in the assemblages of P. zijsron and P. clavata in the Gulf of Carpentaria (h = 0.342 and h = 0.083, respectively). Since female migration (replenishment) between regions is unlikely, conservation plans should strive
to maintain current levels of diversity and abundances in the regional assemblages of each species. 相似文献
12.
Red coral (Corallium rubrum) is an important component of the Mediterranean coralligenous habitat. The present study analyzes the relationship between
energy storage molecule concentration (i.e. tissue balance of protein–carbohydrate–lipid levels) and the gonadal output in
two populations located at different depths (16–18 m and 40–45 m depth) through a seasonal cycle (2002–2003). In June 2003,
another six populations have been sampled to compare medium-scale geographical variation. The colonies sampled were less than
6 cm high, thus representing the majority of the population in the studied area. There was no clear relationship between energy
storage (i.e. carbohydrate and lipid levels) and gonadal output, nor in the seasonal cycle or the spatial variation. A clear-cut
seasonal trend of energy storage was detected only in the shallower population. The water temperature was warmer at 20 m depth
and the water transparency (Secchi disk) was also higher (lower seston concentration) in 2003 when the same periods in 2002
and 2003 were compared (May–August). Carbohydrates seemed to be more sensitive to food constraints than lipids. The partial
mortality detected in summer 2003 in the sampling area appeared to be recorded in the carbohydrate and lipid levels of this
species, especially in the shallow population. The biochemical levels prove to be a useful tool to detect unusual environmental
conditions that may cause partial or total mortality in benthic suspension feeders. 相似文献
13.
Most research on biological invasions to date has focused on the population dynamics of very successful and disruptive introduced
species; however, additional knowledge of the biology of the native species is essential for understanding interactions between
the two and may reveal factors that limit invasion success. The invasive bryozoan Membranipora membranacea interacts with native Electra pilosa on two substrates in northwest Atlantic subtidal habitats: highly dynamic and fast-growing kelps; and smaller, more stable,
and slow-growing fucoid algae. We quantified the relative abundance and evaluated encounter outcomes in different seasons
of these two bryozoans on kelp and Fucus at four sites in Nova Scotia. We also examined the effects of substrate (kelp, Fucus), temperature (7, 10, 13°C), and food (limited, unlimited) on growth rates of E.
pilosa in laboratory experiments and using field manipulations. We compared our findings on factors affecting the growth of E. pilosa to those on M. membranacea obtained in similar and thus directly comparable experiments from a previous study. The proportional abundance of M.
membranacea was greater than that of E. pilosa on kelps, but the opposite was observed on Fucus. Competitive standoffs between the two bryozoans were more frequent than expected, with no differences recorded between substrates;
most encounters were won by M. membranacea. Growth of E.
pilosa was faster on Fucus than kelp, decreased with increasing temperature only on Fucus, and was not affected by food. Growth rate of E. pilosa in all treatments was slower than that previously measured for M.
membranacea. Faster growth and strong overgrowth abilities likely interact on kelps to ensure success of the invasive bryozoan. Success
can be limited by low space availability, which in turn restricts growth rate, and consequently, colony size, such as on fucoid
substrates. The incorporation of alternative contexts into invasion research can reveal factors involved in the resilience
of native communities. 相似文献
14.
Bivalves are important in shallow marine habitats, not at least being the major food resource for seaducks such as the common
scoter (Melanitta nigra), thousands of which are wintering on the Western Coastal Banks, near the Belgian-French border (North Sea). Next to this
ecological importance, fishable stocks of one of these bivalves, Spisula subtruncata, occur in the area. This study aimed at investigating S. subtruncata’s spatial distribution, population dynamics and productivity and its implications for a sustainable Spisula fishery in seaduck wintering areas. The spatial distribution of S. subtruncata was studied in 1994 and 1997 in two areas of the Belgian Western Coastal Banks. The population dynamics and production were
investigated by monthly sampling of two stations between April 1995 and April 1996 and a seasonal sampling between April 1996
and April 1998. Spisula subtruncata had a patchy distribution in the deeper (6 m), fine sandy (200 ± 20 μm) sediments of the Abra alba community, mainly found in the western most part of the Western Coastal Banks. In August 1995, an overwhelming and successful
recruitment was observed in this area: local densities were as high as 150,000 ind m−2. Minor, non-successful recruitments were detected in August 1996 and 1997. Due to space limitation, high densities of S. subtruncata are hypothesized to be responsible for the occurrence of aberrant shapes as observed from August 1996 onwards. Growth was
described by a seasonally oscillating version of the von Bertalanffy growth function (VBGF): a growth stop was observed from
late autumn till early spring. The VBGF parameters K (growth constant) and L
∞ (asymptotic length) were estimated at 0.7–0.9 and 31–33 mm. A combination of length and individual biomass increment showed:
(1) a faster length increment of smaller individuals during the second growing period (catching-up phenomenon), (2) a constant
length combined with a decreasing individual biomass during the suboptimal winter periods (except for the first winter, when
the individual biomass slightly increased), (3) a positive relationship between the individual biomass decrease and the seawater
temperature during the winter periods, and (4) a strong increase of the individual biomass in early spring (April 1997 and
1998) because of gametogenesis, followed by a decrease because of spawning (August 1997). The extremely high total production
of the 1995 year class in the tidal gully (Potje) during the study period was estimated at approximately 1,500 g ash-free
dry weight (ADW) m−2 or 600 g ADW m−2 on average per year. Shellfisheries for S. subtruncata within seaduck wintering areas, such as the Western Coastal Banks, should be carefully deliberated since (1) an important
food resource for the seaducks will decrease, (2) the ecologically most diverse and rich macrobenthic A. alba community will be heavily affected, and (3) the recovery of Spisula populations after depletion is expected to be erratic. 相似文献
15.
Fernando Gómez 《Marine Biology》2007,151(5):1899-1906
The morphology and distribution of the diatoms Chaetoceros tetrastichon and Ch. dadayi as epiphytes on the loricae of the tintinnids Eutintinnus apertus and E. pinguis investigated in the open waters of the Pacific Ocean. The Eutintinnus–Chaetoceros consortia was encountered in 38 of the 52 sampling stations from 34°N to 33°S, and together were among represented the most
wide-spread species. The abundance was low with a maximum of 32 consortia l−1 and E. apertus was often the most abundant species of the genus. The free-living Eutintinnus congeneric species showed a wider vertical distribution, whereas E. apertus–Chaetoceros tended to be near the surface. The success of E. apertus in consortium with Chaetoceros may be due to increase of the clearance rate and/or the lower susceptibility to predation. Chaetoceros modifies its morphology to adapt the epiphytic life, especially Ch. dadayi. The shorter curved setae may facilitate the transfer to the lorica of the daughter tintinnid after the cell division. The
free-living Ch. tetrastichon and Ch. dadayi are very rare and Chaetoceros remained attached to empty loricae or encysted tintinnid cells. This suggests that the Eutintinnus–Chaetoceros consortium is obligate for the success of the diatom and renders the tintinnid more competitive versus congeneric species. 相似文献
16.
J. D. Salierno J. D. Shields A. Z. Murphy G. E. Hoffman A. S. Kane 《Marine Biology》2007,152(4):835-843
To better understand sublethal effects of harmful algal blooms (HABs) on fish, mummichog, Fundulus heteroclitus (L.), were exposed in the laboratory to varying, environmentally relevant densities of Pfiesteria shumwayae (Glasgow et Burkholder, CCMP 2089, dinoflagellate) and Chaetoceros concavicornis (Mangin, CCMP 169, diatom). Two experiments were conducted during the spring of 2003 and 2004 to quantitatively examine the
effects of acute (2 h) P. shumwayae and C. concavicornis algal exposure on mummichog brain activity using c-Fos expression as a marker of altered neuronal activity. Brains from HAB-exposed
fish were removed, sectioned, and stained using immunocytochemistry prior to quantifying neuronal c-Fos expression. Fish exposed
to P. shumwayae and C. concavicornis showed increased c-Fos expression compared to unexposed control fish. A significant dose-response relationship was observed,
with increased labeling in brains of fish exposed to higher cell densities for both HAB species tested (P ≤ 0.01). Increased labeling was found in the telencephalon, optic lobes, midbrain, and portions of the medulla. The greatest
increases in expression were observed in the telencephalon of P. shumwayae-exposed fish, and in the telencephalon and optic lobes of C. concavicornis-exposed fish (P ≤ 0.01). These increases in c-Fos expression are consistent with other physical and chemical stress exposures observed in
fish. Neuronal stress, evidenced by c-Fos expression, demonstrates a sublethal effect of exposure and changes in brain activity
in fish exposed to HAB species. 相似文献
17.
Lotfi Rabaoui Sabiha Tlig Zouari Stelios Katsanevakis Oum Kalthoum Ben Hassine 《Marine Biology》2007,152(3):537-548
The variability in absolute and relative growth of Pinna nobilis along the Tunisian coastline was investigated. Five populations of P. nobilis were sampled, three from northern and two from eastern Tunisia. The specimens were aged and ten morphometric characters were
measured on each individual. To test if differences existed in absolute and relative growth patterns among the different populations
an information theory approach was followed. For absolute growth, von Bertalanffy, Gompertz, the logistic and the power models
were fitted in combination with three assumptions regarding inter-population differences in absolute growth patterns: no differences,
differences among all five populations or just between northern and eastern populations. The assumption of common absolute
growth parameters among all five populations had the greatest support by the data, whereas the assumption of different growth
patterns among all five populations had no support. Von Bertalanffy growth model and the power model were both equally supported
by the data (while Gompertz had considerably less support and the logistic model had no support), and thus it may not be definitely
concluded whether P. nobilis grows asymptotically or not. The P. nobilis populations of the Tunisian coastline had a slow growth and up to an age of ∼ 9 years their shells were smaller than from
all other reported populations in the Mediterranean. For relative growth, apart from the classical allometric model Y = aX
b
, relating the size of a part of a body Y to another reference dimension X, more complicated models were used in combination with the three abovementioned assumptions regarding inter-population differences.
Those models, of the form logY = f (logX), either assumed breakpoints in the relative growth trajectories or non-linearities. For most morphometric characters, the
classical allometric model had no support by the data and more complicated models were necessary. In most cases, different
relative growth either among all five populations or between the northern and eastern population groups was supported by the
data. Further investigation is needed to relate the morphological differences observed among different populations of P. nobilis to environmental factors. 相似文献
18.
D. Hedgecock S. Launey A. I. Pudovkin Y. Naciri S. Lapègue F. Bonhomme 《Marine Biology》2007,150(6):1173-1182
The great fecundity and very high larval mortality of most marine invertebrates and fish make possible substantial variance
in the number of offspring contributed by adults to subsequent generations. The reproductive success of such organisms may
thus resemble a sweepstakes lottery, in which a minority of progenitors succeeds in replacing an entire population, while
the majority fails to procreate. One specific prediction of this hypothesis, that genetic diversity of newly settled cohorts
should be less than that of the adult population, is tested in the present study. Microsatellite DNA markers were examined
in naturally spawned juvenile European flat oysters Ostrea edulis (L.), collected over a 12-day period in 1993 from the western Mediterranean Sea, near Sète, France (43°32′N, 3°56′E) and
grown out for a period of up to 10 months. Variation in these juveniles was compared to that in a pooled sample of adults
collected in 1994 from two locations (Thau Lagoon and Port St. Louis) that had statistically homogeneous allelic frequencies.
Though nearly twice as large as the pooled adult sample, the juvenile sample had only 60% of the adult allelic diversity.
Analyses of linkage disequilibrium and kinship, as well as estimation of the effective number of parents, suggested that 10–20
adults produced this juvenile cohort. This observation supports the hypothesis of sweepstakes reproductive success and suggests
that partial inbreeding may occur even in species with large populations and dispersing planktonic larvae.
Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
19.
Susanna Andersson 《Chemoecology》2003,13(1):13-20
Summary. To better understand the biological role of floral scents for
butterflies, electrophysiological responses to floral scents were
investigated using combined gas chromatography and electroantennographic
detection (GC-EAD). The antennal responses of three butterfly species,
Aglais urticae L. (Nymphalidae), Inachis io L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae) to floral scent compounds from both
natural and synthetic mixtures were examined. Floral scents were
collected from the butterfly nectar plants Cirsium arvense (L.)
(Asteraceae), and Buddleja davidii Franchet cv. (Loganicaeae) with
dynamic head-space methods on Tenax-GR and eluted with pentane. These
eluates, composed of natural floral scent blends, represent an array of
compounds in their natural state. In the GC-EAD analyses eleven
compounds were identified from C. arvense with the benzenoid compound
phenylacetaldehyde in highest abundance. Seventeen compounds were
identified from B. davidii with the irregular terpene oxoisophorone in
highest abundance. Thirty-nine synthetic floral scent compounds were
mixed in pentane, in equal amounts; about 35 ng were allowed to reach
the antennae. The butterflies showed antennal responses to most of the
floral scent compounds from both natural and synthetic blends except to
the highly volatile monoterpene alkenes. Certain benzenoid compounds
such as phenylacetaldehyde, monoterpenes such as linalool, and irregular
terpenes such as oxoisophorone, were emitted in relatively large amounts
from C. arvense and B. davidii, and elicited the strongest antennal
responses. These compounds also elicited strong antennal responses when
present in the synthetic scent blends. Thus, the butterflies seem to
have many and /or sensitive antennal receptors for these compounds,
which points to their biological importance. Moreover, these compounds
are exclusively of floral scent origin. For B. davidii, which depends
highly on butterflies for pollination, the exclusive floral scent
compounds emitted in high abundance could be the result of an adaptive
pressure to attract butterflies.
Received 2 Septemter 2001; accepted 9 September 2002. 相似文献
20.
Parvulastra exigua, a species that lacks a dispersive larva, is paradoxically one of the most widely distributed and abundant sea stars in Australia.
The potential that self-fertilization and successful development of self-generated progeny might contribute to population
maintenance in this species was investigated through induction of spawning in isolated individuals collected from five populations
near Sydney, New South Wales (34°S, 151°E), during the spawning period (August–October 2010, 2011). Evidence of selfing differed
significantly among the five populations but the level of selfing within individual egg masses did not. Overall, there was
a mean of 8.9% fertilization in egg masses with embryos. Some clutches developed to the juvenile stage while others arrested
development before hatching. The presence of miniscule testis tissue in gonads that appeared to be ovaries indicated that
hermaphroditism may be more common in some populations than indicated by anatomy. Mixed mating (selfing + outcrossing), pseudocopulation
during egg laying and developmental success of self-fertilized embryos may contribute to the ecological success of P. exigua. These might influence population genetic structure and would facilitate establishment of founder populations by a small
number of migrants. 相似文献