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941.
Bacterial isolates from multi-species biofilms were identified by 16S rDNA gene sequences and investigated for their inductive
effects as monospecific biofilms on larval metamorphosis of Mytilus galloprovincialis. Alteromonas sp. 1 biofilm was found to have inductive activity, which increased with increasing cell density. The cue(s) of Alteromonas sp. 1 biofilm responsible for inducing larval metamorphosis was further investigated. Treatment of the biofilm with formalin,
ethanol, heat or ultraviolet irradiation resulted in a significant reduction in the inductive activity of Alteromonas sp. 1, and the crude extract of surface-bound products of the biofilm showed no activity. These results indicated that if
the cue was a surface-bound chemical cue, it was unstable, or susceptible to the treatments or the extraction process. On
the other hand, the inductive activity of treated biofilms had a linear regression to the cell survival of bacteria, indicating
a metabolically active biofilm was a requirement for larval metamorphosis. Conditioned water of the biofilm did not induce
larvae to metamorphose. However, larval crawling behavior in the conditioned water was the same as that in the biofilm prior
to larval metamorphosis, and significantly different to larval behavior in seawater. This indicated that a potential or partial
waterborne cue existed, but remained inactive when alone. A synergistic effect of the conditioned water with formalin-fixed
Alteromonas sp. 1 biofilm resulted in a significant increase in larval metamorphosis. Heat treatment and fractionation of the conditioned
water demonstrated that the waterborne cue was heat-stable and <3,000 Da in molecular weight. Platinum-coating, Lentil Lectin
and Wheat Germ Agglutinin treatments of the formalin-fixed biofilm significantly reduced its synergistic effect with the conditioned
water, suggesting that a surface-bound cue was present on the biofilm and that the cue might be associated with the bacterial
exopolysaccharide or glycoprotein. Evidence presented here suggests that two chemical cues derived from bacteria act synergistically
on larval metamorphosis of Mytilus galloprovincialis. 相似文献
942.
To investigate copepod nauplii ingestion rates on phytoplankton, we have adapted the traditional gut fluorescence technique
as it can be used with lower gut pigment concentrations. With the improved technique, laboratory experiments were performed
to estimate functional responses for nauplii of Calanus helgolandicus and Centropages typicus. Nauplii were raised from eggs to copepodites and the experiments were performed with stages NIV-NV. Gut evacuation rates
and ingestion rates were measured on Isochrysis galbana at different concentrations. Specific ingestion rates ranged between 0.038–0.244 μg C μg−1 nauplii C d−1 for C. typicus and 0.041–1.412 μg C μg−1 nauplii C d−1 for C. helgolandicus. Both species showed a type III functional response, reaching a saturation concentration at around 600 μgC l−1 for C. typicus and 800 μgC l−1 for C. helgolandicus.
An erratum to this article can be found at 相似文献
943.
Peter J. Edmunds 《Marine Biology》2007,150(5):783-796
For clonal taxa, the reduced genetic variability associated with clonal proliferation is hypothesized to reduce the ability
to respond to variable conditions, unless a general-purpose genotype (GPG) confers success in multiple environments. In this
study, Corynactis californica (Carlgren 1936) from the subtidal of California was used as a model system to test the hypothesis that clones dampen fluctuations
in fitness through a GPG that facilitates phenotypic plasticity. To achieve this goal, tissue composition, respiration, excretion,
and growth were compared among clones of C.
californica at one site, and a reciprocal transplant experiment was used to test the response of clones to differing conditions at two
sites. All experiments were completed at Santa Catalina Island (N 33°25′, W 118°30′) between April and September 1991. Clones
at a single site differed significantly in multiple traits, varying as much as 1.6-fold in protein content, 3.4-fold in respiration,
and 3.5-fold in excretion. Interestingly, while tissue growth was the most labile trait (differing up to 35.4-fold among clones),
polyp fission rates were not significantly different among clones, in part because fission continued even though tissue growth
was unable to restore polyp size in between divisions. Partial energy budgets revealed that the majority (47–90%) of the daily
energy expenditure was accounted for by respiration, 13–47% by growth, and 0.3–14% by excretion. In the transplant experiment,
reaction norms revealed strong effects of the environment on some traits but not others, notably with growth differing between
sites in a pattern that differed among clones, and excretion differing between sites; neither respiration nor fission were
affected by transplantation. Partial energy budgets revealed that the energy allocation to respiration varied between sites
in a pattern that differed among clones, and a similar trend was evident for tissue growth. Together, these results demonstrate
that clones of C. californica have markedly different phenotypes and exploit phenotypic plasticity to maintain relatively constant fission rates, even
though tissue growth varies greatly among clones and between environments. While these findings support the GPG hypothesis
for clones of C. californica—at least based on relative fitness achieved through asexual proliferation—this conclusion depends on the extent to which
polyps are successful when they have low rates of tissue growth. 相似文献
944.
Lauren M. Mathews 《Marine Biology》2007,152(3):645-655
Despite the apparent absence of geographic barriers, connectivity among marine populations may be restricted by, for example,
ecological or behavioral mechanisms. In such cases, populations may show genetic differentiation even over relatively small
spatial scales. Here, mitochondrial sequence data from the cytochrome oxidase I (COI) gene and seven polymorphic microsatellite
markers were used to investigate fine geographic scale population genetic structure in the snapping shrimp Alpheus angulosus, a member of the A. armillatus species complex, from collections in Florida, Jamaica, and Puerto Rico carried out from 1999 to 2005. The COI data showed
a deep divergence that separated these samples into two mitochondrial clades, but this divergence was not supported by the
microsatellite data. The COI data reflect past population divergence not reflected in extant population structure on the whole
genome level. The microsatellite data also revealed evidence for moderate population structure between populations as close
as ∼10 km, and no evidence for isolation by distance, as divergences between near populations were at least as strong as those
between more broadly separated populations. Overall, these data suggest a role for restricted gene flow between populations,
though the mechanisms that reduce gene flow in this taxon remain unknown. 相似文献
945.
A few species of the weakly electric snoutfish, the African freshwater family Mormyridae, have been reported to vocalise. However, allopatric populations of a single species were never compared. Members of three allopatric Marcusenius macrolepidotus populations, originating from the Upper Zambezi River in Namibia, the Buzi River (Mozambique), and the Incomati River system in South Africa, vocalised with pulsatile growl- and tonal hoot sounds in dyadic confrontation experiments. A high rate of growling accompanied territorial and agonistic interactions and also non-threatening interactions between males and females, which in one pair appeared to be courtship. Growl sound characteristics of M. macrolepidotus from the Incomati system differed from those of the Upper Zambezi in a significantly higher frequency of the first harmonic (mean, 355 Hz vs 266 Hz). The two vocalising males from the Buzi River generated growls about twice as long as the other fish. Furthermore, the growl pulse period was about 4 ms in M. macrolepidotus from the Upper Zambezi River and from the Incomati system, but 6 ms in M. macrolepidotus from the Buzi River. Hoots were only observed in agonistic encounters. Hoot oscillograms showed a sinusoidal waveform, and the mean duration of this sound was similar in Incomati system fish (mean, 161 ms), Upper Zambezi fish (172 ms) and Buzi fish (103 and 145 ms for the two vocalising individuals). The mean frequency of the first hoot harmonic was higher in Incomati system fish (326 Hz) than in Upper Zambezi fish (245 Hz). Both growl and hoot occurred only in the presence of conspecifics, probably signalling the presence and condition of an opponent, territory owner or potential mate. This is the first evidence for (1) sound production and acoustical communication in another species and genus, M. macrolepidotus, from southern Africa to be (2) geographically differentiated. 相似文献
946.
André Chiaradia Yan Ropert-Coudert Akiko Kato Thomas Mattern Julija Yorke 《Marine Biology》2007,151(4):1535-1542
Little Penguins, Eudyptula minor, breed in several small colonies in New Zealand and Australia. In this study, we compare the birds’ diving performances at
different sites situated throughout their breeding range. Environmental conditions and breeding success vary drastically amongst
colonies, but all birds feed on similar types of prey and face similar limitations on their foraging range. We examined several
diving parameters and calculated the proportion of foraging zone available during breeding to examine whether oceanographic
and geographic factors in the foraging zone can explain variations in diving behaviour and fledging success among the different
colonies. In colonies with high fledging success, Penguin Island and Oamaru, penguins made shallow dives <50 m depth and had
lower diving effort. More than 90% of the foraging zone was in waters <50 m depth in these colonies. Motuara Island also has
shallow waters with 95% <50 m depth, but the fledging success was low. Phillip Island has only 42% of waters <50 m and comparatively
low fledging success. Thus, penguins dived deeper and showed a higher diving effort in colonies with lower fledging success
(Motuara Island and Phillip Island), indicating that they were disadvantaged compared to conspecifics from other colonies
that dived shallower and with a lesser diving effort. We concluded that bathymetry is an important factor, but not the only
one, which influences fledging success. 相似文献
947.
Kaspar Delhey Anne Peters Arild Johnsen Bart Kempenaers 《Behavioral ecology and sociobiology》2007,61(6):853-862
Sex-allocation theory predicts that females paired to attractive males should bias the brood sex ratio towards male offspring,
as these would inherit the attractiveness of their father. We studied sex allocation based on male ornamentation in blue tits.
Brood sex ratios varied with male UV coloration in an age-dependent manner. For juvenile males, the proportion of sons increased
with increasing UV ornamentation, which is in agreement with previous findings from a Swedish population. However, the relationship
between UV ornamentation and brood sex ratio was reversed for adult males, with females paired to less UV-ornamented adult
males producing more sons. This pattern fits with the observation that, in our population, less UV-ornamented adult males
sire the majority of extra-pair young. To test the causality of the association between brood sex ratio and male coloration,
we experimentally manipulated crown colour largely within the natural range. We created two groups of males: one with higher
and one with lower UV reflectance, UV(+) and UV(−), respectively. Contrary to our expectations, there was no significant treatment
effect. However, in UV(−), but not UV(+) males, the proportion of sons was negatively correlated with male coloration before
manipulation. This suggests that the UV(−) treatment caused males that were more UV ornamented to decline more in attractiveness,
as shown in a similar experiment in Sweden. However, given that correlational patterns differ between these populations, similarities
in experimental results should not be taken as evidence for consistent patterns of adaptive sex allocation in this species. 相似文献
948.
Summary. In amphibians and fishes, evidence is increasing that chemical cues from injured conspecifics can play a role in the chemical
labelling and learned recognition of unfamiliar predators. In this laboratory study, we tested the prediction that prior chemical
exposure to a non-native predator feeding on conspecific tadpoles will subsequently allow tadpoles of the common toad (Bufo bufo) to recognize the chemical cues specifically released by this starved predator. Furthermore, we investigated the vulnerability
of this chemically-mediated process to herbicide contamination. With these aims in view, groups of tadpoles were kept either
unexposed or exposed for ten days to chemical cues from Turkish crayfish (Astacus leptodactylus) previously fed on tadpoles, both in uncontaminated water and in the presence of four sublethal concentrations of amitrole
(0.01, 0.1, 1 and 10 mg.l−1). We then assessed the effects of the six conditioning treatments on general activity and behavioural response to chemical
cues from starved crayfish. Larval treatments did not affect the general activity of the tadpoles. By contrast, the treatments
had significant effects on the behavioural response to the test solution prepared form starved crayfish. The only tadpoles
to show an antipredator behavioural response to the chemical stimulation from starved crayfish belonged to the groups derived
from chemical exposure to tadpole-fed crayfish in uncontaminated water and in contaminated water with the lowest concentration
of amitrole (0.01 mg.l−1). Conversely, this chemical stimulation produced no behavioural change in the control group or in the groups derived from
exposure to tadpole-fed crayfish in contaminated water containing 0.1, 1 and 10 mg.l−1 of amitrole. This study demonstrates that chemical cues released during the predator’s feeding activity can subsequently
be used by common toad tadpoles in the recognition of an unfamiliar predator. In addition, our results show that the presence
of sublethal amitrole concentrations can impair this recognition process. Such a pesticide effect might be especially detrimental
for amphibian populations threatened by invasive predators. 相似文献
949.
Lucia Fanini Giovanni Maria Marchetti Felicita Scapini Omar Defeo 《Marine Biology》2007,152(5):1169-1179
950.
Gilberto Pasinelli Mathis Müller Michael Schaub Lukas Jenni 《Behavioral ecology and sociobiology》2007,61(7):1061-1074
Studies of animal breeding dispersal have often focused on possible causes, whereas its adaptive significance has received
less attention. Using an information-theoretic approach, we assessed predictions of four hypotheses relating to causes and
consequences of breeding dispersal in a migratory passerine, the red-backed shrike Lanius collurio. As predicted by the reproductive performance hypothesis, probability of breeding dispersal in females (though not in males)
decreased with increasing annual average number of fledglings produced in the past year, but there was no association with
conspecific reproductive performance in either sex. The site choice hypothesis, stating that individuals disperse to improve
breeding site quality, received support in males only, as dispersal probability was positively associated to a measure indicating
low territory quality. The social constraints hypothesis, referring to dispersal in relation to intraspecific interactions,
received little support in either sex. The predation risk hypothesis was hardly supported either. Consequences of dispersal
were marginal in both sexes because neither fledgling production in females, nor territory quality in males improved after
dispersal. In addition, males settled on territories closer to the forest edge than those occupied predispersal, which is
opposite to the prediction of the predation risk hypothesis. We conclude that own reproductive success was the major factor
determining dispersal behavior in females, whereas territory quality and possibly predation risk were most important in males.
Overall, breeding dispersal appeared not to be adaptive in this dense population inhabiting an optimal habitat. 相似文献