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971.
Dirivultid copepods are among the most successful organisms at deep-sea hydrothermal vents, as this family includes 50 morphologically
described species. We studied COI diversity of some species in various geographical areas and vent fluid regimes, in order
to gain a better understanding of true species diversity, dispersal strategies, and evolution. DNA taxonomy revealed the same
entities as described with morphological characters. No cryptic species were detected. With the help of COI analyses, it was
possible to identify a new species and match the dimorphic sexes of another species. The geographical distance between vents,
as well as the extreme physico-chemical environment, are thought to affect the gene flow of fauna. We could not detect any
sequence differences within species among different geographical scales (up to 2,000 km) or different vent fluid regimes.
We suggest that Dirivultidae have relatively high gene flow between vents and are able to disperse relatively easy along ridges.
Further, they have a broad physiological tolerance and thus might not have undergone speciation in response to heterogeneity
caused by vent fluids. 相似文献
972.
Mie H. Sichlau Jørgen L. S. Hansen Thorbjørn J. Andersen Benni W. Hansen 《Marine Biology》2011,158(3):665-676
Distribution, abundance and age of diapause eggs from three species of calanoid copepods (in particular from Acartia spp. most likely Acartia tonsa, and Centropages hamatus and less numerous from Temora longicornis) were recorded in sediment profiles by enumerating hatched nauplii from incubated sediment samples. Phytoplankton pigments
and 210Pb and 137Cs analyses indicated that the sedimentation regimes were different between two southern and two northern stations of the
island Funen, Denmark. Significant variations in vertical distribution, abundance and mortality of diapause eggs were found
between the stations. Dating of the sediment cores suggested a ~70-year maximum age of viable eggs on the northernmost stations,
and ~28 year at the southernmost stations. The eggs exhibited a significantly higher mortality rate at the southernmost stations
compared with the northernmost, 0.35–0.53 year−1 vs. 0.07–0.08 year−1 with no systematic pattern among species. The differences in abundance, mortality and age of the diapause eggs are suggested
to be due to the sediment characteristics in which they are buried. 相似文献
973.
In 1977, Phidiana hiltoni (O’Donoghue in J. Entomol Zool (Pomona College, Claremont, California) 19:77–119, 1927) began spreading northward from Monterey, California. By 1992, it had reached Duxbury Reef (37° 53′ 23″ N, 122° 41′ 59″ W),
100 km to the north, where other nudibranchs subsequently appeared to decline. The role of P. hiltoni in this decline was investigated through diet analysis, feeding trials, and comparison of historical and recent abundance
data. In the wild, P. hiltoni preyed largely on hydroids, but also showed evidence of predation on nudibranchs. In the laboratory, P. hiltoni attacked most of the dendronotid and aeolid nudibranchs presented to it, ingesting small individuals whole. The pooled abundance
of nudibranchs vulnerable to attack by P. hiltoni declined an average of two-thirds at Duxbury Reef since its arrival, compared to (1) no change in the non-vulnerable species
and (2) no change in either group at two other sites where P. hiltoni was one to two orders of magnitude less abundant. Phidiana
hiltoni therefore appears to have caused this decline, likely through a combination of direct predation and competition for prey.
A brief larval period, combined with cyclonic re-circulation in the lee of Point Reyes, may be driving self-recruitment of
P. hiltoni at Duxbury Reef, as well as hindering further northward spread. 相似文献
974.
We tested joint effects of predator loss and increased resource availability on the grazers’ trophic level and the propagation
of trophic interactions in a benthic food web by excluding larger predatory fish from cages and manipulating nutrients in
the coastal zone of the Baltic Sea. The combination of nutrient enrichment and excluding larger predators induced an increase
in medium-sized predatory fish (three-spined stickleback). The meso-predator fish in turn did not change the total abundance
of the invertebrate herbivores, but did cause a substantial shift in their community composition towards the dominance of
gastropods by reducing amphipods by 40–60%, while gastropods were left unchanged. The shift in grazer composition generated
a 23 times higher producer biomass, but only under nutrient enrichment. Our results show that top-predator declines can substantially
shift the species composition at the grazers’ level, but that cascading effects on producers by a trophic cascade strongly
depend on resource availability. 相似文献
975.
Effects of oceanic and terrestrial sediment suspensions on the behavioral traits activity, colony expansion, and mucus formation
of the gorgonian octocoral Subergorgia suberosa (Pallas, 1766) were studied in the laboratory. Increased sediment concentration significantly changed the logits of activity
indices (as colony expansion) and was correlated with decreased activity. For both sources of sediments, the activity index
decreased as the concentration of sediment increased. The level of decrease was more significance for terrestrial sediments.
The activity index showed no clear time pattern for the control group, but a decrease over time occurred in both sediment
treatment groups. Activity change was linearly correlated with exposure time and concentration of terrestrial and ocean sediments.
The activity indices of polyps were negatively correlated with the formation of mucus sheets (correlation = −0.536, p = 0.048). For both sources of sediments, the frequency of mucus sheet formation (MSF) increased with sediment concentration.
Increases in terrestrial sediment loads resulted in more striking effects. The probability for MSF under different sediment
groups at different concentrations over time was modeled by regressions. Frequency of polyp activity is suggested as a suitable
biomarker to monitor the effects of sedimentation stress. 相似文献
976.
Rosemary E. Golding Donald J. Colgan Guy Nelmes Tina Reutelshöfer 《Marine Biology》2011,158(6):1259-1269
DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene were collected from estuarine snails in the genus
Phallomedusa to examine the effects of estuarine isolation on population structure and gene flow. Three clades were recovered, one corresponding
to Phallomedusa austrina and two others with the morphology of Phallomedusa solida. The haplotype diversity in all three clades indicated recent population expansion. Phallomedusa austrina was restricted to the west of a previous land bridge in the Bass Strait between mainland Australia and Tasmania, and P. solida to its east and to northern Tasmania. Phylogeographic analysis of P. austrina and P. solida shows strong geographic separation of species, but no local genetic structure indicative of regional or estuarine isolation.
The clades of P. solida exhibit substantial genetic divergence and were sympatric across their entire distribution in eastern Tasmania and mainland
Australia. Such a situation, which has not previously been observed in phylogeographic studies of southeast Australia, suggests
that P. solida has had a complex refugial history during periods of environmental challenge. 相似文献
977.
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
978.
The present study addresses the effect of maternal diet on hatching success and condition of embryos and larvae of Antarctic
krill Euphausia superba. Lipid and fatty acid content and composition were determined in field and laboratory samples. Developmental stages analyzed
in embryos included: multiple-cell, gastrula, and limb-bud stages. Larval stages analyzed included: nauplius I, nauplius II,
and metanauplius. Laboratory-reared embryos were spawned by gravid females incubated under three feeding groups: (1) phytoplankton
mixture, (2) phytoplankton mixture and minced clam, and (3) phytoplankton mixture, minced clam, and commercial larval food.
Hatching success was highest in group 3 (100%), lowest in group 1 (0%), and highly variable in field samples (0–48%). Lipid
decreased slightly in embryos during embryonic development, while large decreases in lipid were found during nauplius development.
High levels of 18:2(n-6), 20:4(n-6), and 22:6(n-3) observed with group 3 samples coincided with high hatching success in krill
embryos. The ratio of 22:6(n-3)/20:5(n-3) also correlated to hatching success of embryos. The fatty acid profile of embryos
in group 3 was similar to that of the field-collected embryos, reflecting the contribution of the commercial larval food in
the maternal diet. In our study, the maternal diet was found to influence the fatty acid composition of embryos and in turn
affects the hatching success of krill. Specific polyunsaturated fatty acids appeared to play important roles in embryogenesis
in krill. 相似文献
979.
M. Koopmans P. van Rijswijk D. Martens T. A. Egorova-Zachernyuk J. J. Middelburg R. H. Wijffels 《Marine Biology》2011,158(1):9-20
The carbon metabolism of two marine sponges, Haliclona oculata and Dysidea avara, has been studied using a 13C isotope pulse-chase approach. The sponges were fed 13C-labeled diatoms (Skeletonema costatum) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total 13C enrichment, and fatty acid (FA) composition and 13C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased
until none was left 10 days after enrichment. The sponge-specific FAs incorporated 13C label already during the first day and the amount of 13C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during
the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are
able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of
fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with 13C isotope–labeled diatom (Pheaodactylum tricornutum) either after or before damaging and tracing back the 13C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The
rate of respiration in H. oculata reduced immediately after damage, but returned to its initial level after 6 h. The 13C data revealed that H. oculata has a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate
is increased after damage of the tissue. For D. avara, no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after
damage. 相似文献
980.
Prevailing oceanographic processes, pelagic larvae, adult mobility, and large populations of many marine species often leads
to the assumption of wide-ranging populations. Applying this assumption to more localized populations can lead to inappropriate
conservation measures. The Pacific ocean perch (Sebastes alutus, POP) is economically and ecologically valuable, but little is known about its population structure and life history in Alaskan
waters. Fourteen microsatellite loci were used to characterize geographic structure and connectivity of POP collections (1999–2005)
sampled along the continental shelf break from Dixon Entrance to the Bering Sea. Despite opportunities for dispersal, there
was significant, geographically related genetic structure (F
ST = 0.0123, P < 10−5). Adults appear to belong to neighborhoods at geographic scales less than 400 km, and possibly as small as 70 km, which indicates
limited dispersal throughout their lives. The population structure observed has a finer geographic scale than current management,
which suggests that measures for POP fisheries conservation should be revisited. 相似文献