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981.
982.
Pedro Daleo Tomás Luppi Agustina Mendez Casariego Mauricio Escapa Pablo Ribeiro Paola Silva Oscar Iribarne 《Marine Biology》2009,156(3):269-275
Size advantage in male–male competition over mates, combined with male preference over large females, is a common feature
that can drive to size assortative mating and, eventually, sexual selection. In crabs, appendage autotomy can affect assortative
mating and opportunity for sexual selection by affecting size advantage in mating contests. In this work, we evaluate the
effect of size and appendage autotomy in generating assortative mating in the mud crab Cyrtograpsus angulatus. Field observations of guarding pairs in two different populations show a positive correlation between carapace width of
males and females in both the populations. In one of the populations, incidence of appendage autotomy was low and the variability
in the size of reproductive males was lower than the variability in the size of randomly collected males (i.e. only larger
males were successful in getting a female), whereas there was no differences in the other population (i.e. most male sizes
were successful) where the incidence of appendage autotomy was very high, indicating that the importance of size is higher
when the incidence of autotomy is low. In this context, experiments (in both populations) show that, in contests for a female,
larger males outcompete smaller ones only when they had intact appendages. When males had missing chelipeds, winning or loosing
against smaller males was random. This may lead to a decrease in the importance of male size in populations with high incidence
of cheliped autotomy, affecting assortative mating and opportunity for selection and, thus, affecting selective pressures. 相似文献
983.
Positive plant–animal interactions are important in community ecology, but relatively little attention has been paid to their
effect on the production of mangroves, dominant halophytic trees in tropical coastal marshes. Here, the role of fiddler crab
(Uca spp.) burrowing on the growth and production of the white mangrove, Laguncularia racemosa (<2 years old), was examined in a restored marsh in Tampa Bay, Florida (27°41.65 N, 82°30.34 W) with manipulative experiments
from June 2006 to May 2007. Fiddler crab burrowing significantly increased mangrove height by 27%, trunk diameter by 25%,
and leaf production by 15%, compared to mangroves in crab exclusion enclosures. Additionally, the exclusion of fiddler crabs
significantly increased interstitial water salinity from 32.4 to 44.2, and decreased the oxidation–reduction potential of
the low organic sediments, but did not affect soil pH or sulfide concentration. Mangrove height, trunk diameter, and leaf
production along a transect that varied in crab burrow density were positively associated with the number of crab burrows.
Further, the density of sympatric Spartina alterniflora shoots was positively correlated with crab burrow density along the transect. As in temperate marshes, fiddler crabs can
have significant ecological effects on mangrove communities, serving as ecological engineers by modulating the amount of resources
available to marsh plants, and by altering the physical, chemical, and biological state of these soft sediment communities.
In restored coastal systems that typically have very poor sediment quality, techniques such as soil amendment could be used
to facilitate a more natural interaction between crabs and mangroves in ecosystem development. 相似文献
984.
Many benthic colonial invertebrates have the ability to fuse and form chimeras with compatible colonies. Botryllid ascidians
are model organisms for the study of the evolution of and molecular basis for allorecognition, and fusion rates have been
determined for different populations and species by random sampling and fusion testing between individuals. However, natural
fusion rates over time have not been documented. Nine settlement panels were deployed in Salem Harbor, Massachusetts, USA
and Botrylloides violaceus settlement, growth, and fusion monitored from July to mid-August 2007. Seventy-three percent of the recruits observed fused
with at least one other colony, while 4% neither fused nor were overgrown. Multifused colonies were not observed to grow faster
than single colonies when growth was calculated as increase in size beyond the summation of fused entities; however, they
were significantly larger. These results suggest that larvae settle in clumps of compatible individuals, and that large subtidal
colonies may be the result of high numbers of fusions between compatible colonies. 相似文献
985.
Alan M. Piggot Bruce W. Fouke Mayandi Sivaguru Robert A. Sanford H. Rex Gaskins 《Marine Biology》2009,156(11):2379-2389
Results from controlled in situ experimentation conducted on the leeward reef tract of Curaçao, Netherlands Antilles, indicate that the coral Montastraea annularis exhibits a complex, yet consistent, cellular response to increasing sea surface temperature (SST) and decreasing irradiance. This was determined by simultaneously quantifying and tracking the tissue density of zooxanthellae and mucocytes using a novel technique that integrates the lectin histochemical stain wheat germ agglutinin (WGA) with high-resolution (200 nm) optical epifluorescence microscopy. Coral colonies growing at 6-m water depth (WD) and an irradiance of 100.2 ± 6.5 μmol m?2 s?1 were treated with a shading experiment for 11 days that reduced irradiance to 34.9 ± 6.6, 72.0 ± 7.0 and 90.1 ± 4.2 μmol m?2 s?1, respectively. While a significant decrease in the density of both zooxanthellae and mucocytes were observed at all shade levels, the largest reduction occurred between the natural non-shaded control (44,298 ± 3,242 zooxanthellae cm?2; 4,853 ± 346 mucocytes cm?2) and the highest shading level (13,982 ± 1,961 zooxanthallae cm?2; 2,544 ± 372.9 mucocytes cm?2). Colonies were also sampled during a seasonal increase in SST of 1.5°C, where the density of zooxanthellae was significantly lower (from 54,710 ± 1,755 to 34,322 ± 2,894 cells cm?2) and the density of mucocytes was significantly higher (from 6,100 ± 304 to 29,658 ± 3,937 cells cm?2). These observations of coral cellular response to environmental change provide evidence to support new hypotheses for coral survival and the complex role played by mucus in feeding, microbial associations and resilience to increasing SST. 相似文献
986.
Herbivory has a strong impact on algal distribution, abundance and community structure and may influence the establishment
and spread of introduced seaweed species. In this study, we assess the potential regulating role of herbivory on one of the
most invasive brown seaweeds: Sargassum muticum. Multiple choice feeding experiments were conducted with 13 native seaweeds, S. muticum and 5 herbivore species from the Northwest, Southwest and South of Portugal. S. muticum was always the least or among the least preferred seaweeds and attained one of the highest growth rates of the tested seaweeds,
with and without herbivores. The addition of herbivores increased the number of cases by 40% in which the invader had higher
growth rates. Our results suggest that low grazing pressure on S. muticum by the recipient herbivore community may give the invader a competitive advantage over at least part of the native seaweed
community, thereby contributing to the invasiveness of S. muticum along the Portuguese coast. 相似文献
987.
988.
At specific locations within the Baltic Sea, thermoclines and haloclines can create rapid spatial and temporal changes in
temperature (T) and salinity (S) exceeding 10°C and 9 psu with seasonal ranges in temperature exceeding 20°C. These wide ranges in abiotic factors affect
the distribution and abundance of Baltic Sea copepods via species-specific, physiological-based impacts on vital rates. In
this laboratory study, we characterized the influence of T and S on aspects of reproductive success and naupliar survival of a southwestern Baltic population of Temora longicornis (Copepoda: Calanoida). First, using ad libitum feeding conditions, we measured egg production (EP, no. of eggs female−1 day−1) at 12 different temperatures between 2.5 and 24°C, observing the highest mean EP at 16.9°C (12 eggs female−1 day−1). Next, the effect of S on EP and hatching success (HS, %) was quantified at 12°C for cohorts that had been acclimated to either 8, 14, 20 or 26 psu
and tested at each of five salinities (8, 14, 20, 26 and 32 psu). The mean EP was highest for (and maximum EP similar among)
14, 20 and 26 psu cohorts when tested at their acclimation salinity whereas EP was lower at other salinities. For adults reared
at 8 psu, a commonly encountered salinity in Baltic surface waters, EP was relatively low at all test salinities—a pattern
indicative of osmotic stress. When incubated at 12°C and 15 different salinities between 0 and 34 psu, HS increased asymptotically
with increasing S and was maximal (82.6–84.3%) between 24 and 26 psu. However, HS did depend upon the adult acclimation salinity. Finally,
the 48-h survival of nauplii hatched and reared at 14 psu at one of six different temperatures (10, 12, 14, 16, 18 and 20°C)
was measured after exposure to a novel salinity (either 7 or 20 psu). Upon exposure to 7 psu, 48-h naupliar mortality increased
with increasing temperature, ranging from 26.7% at 10°C to 63.2% at 20°C. In contrast, after exposure to 20 psu, mortality
was relatively low at all temperatures (1.7% at 10°C and ≤26.7% for all other temperatures). An intra-specific comparison
of EP for three different T. longicornis populations revealed markedly different temperature optima and clearly demonstrated the negative impact of brackish (Baltic)
salinities. Our results provide estimates of reproductive success and early survival of T. longicornis to the wide ranges of temperatures and salinities that will aid ongoing biophysical modeling examining climate impacts on
this species within the Baltic Sea. 相似文献
989.
Bryaninops, Gobiodon, Paragobiodon and Pleurosicya are the most abundant genera of coral-associated gobies. These genera are adapted to live among coral, while other small
reef gobies (e.g., the genus Eviota) show no obligate association with this living substrate. Thirteen coral-associated species and two Eviota species were sampled from different regions of the Red Sea, along with four populations/species of Gobiodon from the Indian and western Pacific Oceans. A molecular phylogenetic analysis was performed using partial sequences of 12S
rRNA, 16S rRNA and cytochrome b mitochondrial genes, 1,199 base pairs in total. Several clades were consistently resolved in neighbor joining-, maximum parsimony-,
maximum likelihood and Bayesian analyses. While each of the four genera Gobiodon, Paragobiodon, Bryaninops and Pleurosicya proved to be monophyletic, their relative position in the phylogeny did not support an emergence of coral-associated gobiids
as a monophyletic assemblage. Instead, two separate monophyletic sub-groups were discovered, the first comprising Gobiodon and Paragobiodon, and the second Bryaninops and Pleurosicya. Our molecular phylogenetic examinations also revealed one unassigned species of Gobiodon from the Maldives as a distinct species and confirmed three putative and yet unassigned species from the Red Sea. Moreover,
the uniformly black colored species of Gobiodon are not monophyletic but have evolved independently within two distinct species groups. Genetic distances were large in particular
within Pleurosicya and Eviota. Estimated divergence times suggest that coral-associated gobies have diversified in parallel to their preferred host corals.
In particular, divergence times of Gobiodon species closely match those estimated for their typical host coral genus Acropora. 相似文献
990.
We investigated the constraints on sulfide uptake by bacterial ectosymbionts on the marine peritrich ciliate Zoothamnium niveum by a combination of experimental and numerical methods. Protists with symbionts were collected on large blocks of mangrove-peat.
The blocks were placed in a flow cell with flow adjusted to in situ velocity. The water motion around the colonies was then
characterized by particle tracking velocimetry. This shows that the feather-shaped colony of Z. niveum generates a unidirectional flow of seawater through the colony with no recirculation. The source of the feeding current was
the free-flowing water although the size of the colonies suggests that they live partly submerged in the diffusive boundary
layer. We showed that the filtered volume allows Z. niveum to assimilate sufficient sulfide to sustain the symbiosis at a few micromoles per liter in ambient concentration. Numerical
modeling shows that sulfide oxidizing bacteria on the surfaces of Z. niveum can sustain 100-times higher sulfide uptake than bacteria on flat surfaces, such as microbial mats. The study demonstrates
that the filter feeding zooids of Z. niveum are preadapted to be prime habitats for sulfide oxidizing bacteria due to Z. niveum’s habitat preference and due to the feeding current. Z. niveum is capable of exploiting low concentrations of sulfide in near norm-oxic seawater. This links its otherwise dissimilar habitats
and makes it functionally similar to invertebrates with thiotrophic symbionts in filtering organs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献