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1.
2.
Light-dependent magnetoreception in birds: the effect of intensity of 565-nm green light 总被引:1,自引:0,他引:1
In a previous study, Australian silvereyes tested in autumn under monochromatic 565-nm green light at intensities of 2.1
and 7.5 mW m–2 preferred their normal northerly migratory direction, whereas they showed a significantly different tendency towards northwest
at 15.0 mW m–2. Repeating these experiments in spring with silvereyes migrating southward, we again observed well-oriented tendencies in
the migratory direction at 2.1 and 7.5 mW m–2. At 15.0 mW m–2, however, the birds once more preferred northwesterly directions, i.e. their response under this condition proved to be independent
of the migratory direction. This contradicts the interpretation that monochromatic green light of this high intensity leads
to a rotation of compass information; instead, it appears to produce sensory input that causes birds to give up their migratory
direction in favor of a fixed direction of as yet unknown origin.
Received: 3 April 2000 / Accepted in revised form: 19 June 2000 相似文献
3.
Variation in melanin patterns among individuals, populations, and species is common in fishes of the genus Xiphophorus. In the variable platyfish, Xiphophorus variatus, variation in metabolic rate is associated with melanin coloration and the color morphs appear to be physiological specialists adapted to particular environmental conditions. This study investigates whether a melanin polymorphism in the green swordtail, Xiphophorus helleri, is likewise associated with variation in metabolic rate. We measured metabolic rate as oxygen consumption rate of both adult male and juvenile X. helleri in static respirometers. The oxygen consumption rate does not differ significantly between the spotted and nonspotted morphs in either group, suggesting that-unlike in X. variatus-selection on metabolic rate is not involved in maintaining the polymorphism in X. helleri. We suggest that explanations need to be sought for the evolution of melanophore diversity in Xiphophorus that are pertinent to each melanin pattern polymorphism or groups of similar polymorphisms. 相似文献
4.
Fisher CR MacDonald IR Sassen R Young CM Macko SA Hourdez S Carney RS Joye S McMullin E 《Die Naturwissenschaften》2000,87(4):184-187
During a research cruise in July 1997 in the Gulf of Mexico we discovered a gas hydrate approximately 1 m thick and over
2 m in diameter which had recently breached the sea floor at a depth of 540 m. The hydrate surface visible from the submarine
was considerably greater than that of any other reported hydrate. Two distinct color bands of hydrate were present in the
same mound, and the entire exposed surface of the hydrate was infested (2500 individuals/m2) with 2 to 4 cm-long worms, since described as a new species, Hesiocaeca
methanicola, in the polychaete family Hesionidae (Desbruyères and Toulmond 1998). H.
methanicola tissue stable isotope values are consistent with a chemoautotrophic food source. No evidence of chemoautotrophic symbionts
was detected, but geochemical data support the presence of abundant free living bacteria on the hydrate. The activities of
the polychaetes, grazing on the hydrate bacteria and supplying oxygen to their habitats, appears to contribute to the dissolution
of hydrates in surface sediments.
Received: 16 August 1999 / Accepted in revised form: 19 January 2000 相似文献
5.
A phylogenetic analysis of the Neotropical dart-poison frogs, genus Phyllobates, was performed based on mitochondrial cytochrome b sequences. Members of Phyllobates from South and Central America were found to form each an evolutionary lineage. Among the South American lineage, species
with uniform dorsal coloration as adults form a derived monophyletic clade.
Received: 26 June 2000 / Accepted in revised form: 8 November 2000 相似文献
6.
Hariyama T 《Die Naturwissenschaften》2000,87(7):327-330
This paper deals with the structure and function of the intracerebral ocelli in the caudal area of the brain of the Japanese
firefly. A pair of epilaterally placed specialized pigmented organs was found at the caudal ends of the brains of the fireflies
Luciola cruciata and L. lateralis. On the basis of light and transmission electron micrographs of both male and female individuals these organs seemed photoreceptive
in nature. Intracellular and extracellular recordings were obtained from the intracerebral ocelli of the fireflies with microelectrodes.
The physiological evidence revealed that the cells found in the brain were, indeed, photoreceptors.
Received: 7 April 2000 / Accepted in revised form: 16 June 2000 相似文献
7.
A new ant species of Megalomyrmex conducts mass raids to usurp gardens of the fungus-growing ant Cyphomyrmex longiscapus, then lives in the gardens and consumes the cultivated fungus. Unlike attine ants, however, Megalomyrmex sp. does not forage for substrate to manure the gardens; therefore, when gardens become depleted, Megalomyrmex sp. must locate and usurp new gardens. Megalomyrmex sp. workers feed their larvae with attine brood, but only after removing the fungal mycelium that covers the attine larval integument,
suggesting that this fungal coat may provide partial protection against other predators. Unlike other known Megalomyrmex species, which coexist as social parasites in attine colonies, Megalomyrmex sp. expels its attine hosts during the garden raids. Megalomyrmex sp. thus maintains a unique agro-predatory lifestyle that is described here for the first time.
Received: 18 August 2000 / Accepted in revised form: 1 November 2000 相似文献
8.
Flavonoid wing pigments increase attractiveness of female common blue (Polyommatus icarus) butterflies to mate-searching males 总被引:1,自引:0,他引:1
Common blue butterflies (Polyommatus icarus) sequester flavonoids from their larval host plants and allocate these UV-absorbing pigments to the wings. In field experiments
using dummies constructed from female butterflies, mate-searching males inspected flavonoid-rich dummies more intensively
than those with little or no flavonoids. Flavonoid content as signalled by UV-wing pattern may indicate ontogenetically determined
female quality or enhance detectability to males.
Received: 21 March 2000 / Accepted in revised form: 17 May 2000 相似文献
9.
In a population exhibiting partial migration (i.e. migration and residency tactics occur in the same population), the mechanisms
underlying the tactical choice are still unclear. Empirical studies have highlighted a variety of factors that could influence
the coexistence of resident and migratory individuals, with growth and body size considered to be key factors in the decision
to migrate. Most studies suffer from at least one of the two following caveats: (1) survival and capture probabilities are
not taken into account in the data analysis, and (2) body size is often used as a proxy for individual growth. We performed
a capture–mark–recapture experiment to study partial migration among juvenile brown trout Salmo trutta at the end of their first year, when a portion of the population emigrate from the natal stream while others choose residency
tactic. Bayesian multistate capture–recapture models accounting for survival and recaptures probabilities were used to investigate
the relative role of body size and individual growth on survival and migration probabilities. Our results show that, despite
an apparent effect of both size and growth on migration, growth is the better integrative parameter and acts directly on migration
probability whereas body size acts more strongly on survival. Consequently, we recommend caution if size is used as a proxy
for growth when studying the factors that drive partial migration in juvenile salmonid species. 相似文献
10.
We investigated thermal characteristics of aggregations of social, tent-building caterpillars of the small eggar moth Eriogaster lanestris (Lepidoptera: Lasiocampidae). The highly synchronous behavior of individuals of the colony has important consequences for
their thermal ecology. Air temperature in the tent fluctuates according to the caterpillars' activity: air temperature slowly
rises about 2.5–3 °C above the surroundings when caterpillars aggregate in the tent after feeding and decreases rapidly when
the larvae leave the tent. Thermal energy can be stored for a few hours when ambient temperature drops. Experiments show that
metabolic heat production sufficiently explains this effect. As even minor additional heat gain may reduce developmental time,
aggregating in the tent may thus confer selective advantages under overcast weather or at night, when behavioral thermoregulation
through basking is not possible.
Received: 24 November 1999 / Accepted in revised form: 26 January 2000 相似文献
11.
The bone-eating marine annelid Osedax consumes mainly whale bones on the deep-sea floor, but recent colonization experiments with cow bones and molecular age estimates
suggesting a possible Cretaceous origin of Osedax indicate that this worm might be able grow on a wider range of substrates. The suggested Cretaceous origin was thought to
imply that Osedax could colonize marine reptile or fish bones, but there is currently no evidence that Osedax consumes bones other than those of mammals. We provide the first evidence that Osedax was, and most likely still is, able to consume non-mammalian bones, namely bird bones. Borings resembling those produced
by living Osedax were found in bones of early Oligocene marine flightless diving birds (family Plotopteridae). The species that produced these
boreholes had a branching filiform root that grew to a length of at least 3 mm, and lived in densities of up to 40 individuals
per square centimeter. The inclusion of bird bones into the diet of Osedax has interesting implications for the recent suggestion of a Cretaceous origin of this worm because marine birds have existed
continuously since the Cretaceous. Bird bones could have enabled this worm to survive times in the Earth’s history when large
marine vertebrates other than fish were rare, specifically after the disappearance of large marine reptiles at the end-Cretaceous
mass extinction event and before the rise of whales in the Eocene. 相似文献
12.
Volatiles from leaves or bark of nonhost birch (Betula pendula) and Norway spruce (Picea abies) dramatically reduced the attraction of the bark beetle, Pityogenes bidentatus (Coleoptera: Scolytidae), to their aggregation pheromone components (cis-verbenol and grandisol) in the field. In addition, odors from both the needles and bark of the host Scots pine (Pinus sylvestris) similarly inhibited attraction. Monoterpenes of pine and spruce (α-pinene, β-pinene, terpinolene, and 3-carene) as well
as ethanol, chalcogran and some nonhost green leaf alcohols [(Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, and 1-hexanol], also reduced catches. Collections of volatiles from the field-tested plant tissues indicated
they released monoterpenes in amounts similar to the synthetics that inhibited responses. The various plant and insect sources
of these inhibitory compounds indicate that P. bidentatus bark beetles have evolved several strategies to increase their fitness by avoiding nonhost and unsuitable host trees in a
complex olfactory landscape.
Received: 6 June 2000 / Accepted in revised form: 25 September 2000 相似文献
13.
Burrows play an important role for many species, providing them with shelter and access to food resources. For subterranean
rodents, living underground imposes constraints on morphology and physiology. The convergence in burrow architecture among
subterranean rodents has been related to the energy demands imposed by the cost of constructing an entire system. The low
frequency of tunnels with downward angles steeper than 40° appears to be a common feature in burrow design. In the subterranean
habitat, movements through the soil are expensive and gravity can exert important restrictions on digging energetics when
individuals push out the soil removed in steeper digging angles. The aim of this study was to determine the effect of digging
angle on digging energetics in Ctenomys talarum. The mass of the removed soil and burrowing speed were similar while digging metabolic rate and net cost of transport were
higher in individuals digging in tunnels with angles >40° than in those digging tunnels with angles <40°. The cost of constructing
a burrow in the horizontal plane differed by 20% from others in which the natural representation of tunnels >40° was considered.
Even given that tunnels >40° represented only 6% of the total burrow length, burrow architecture appears to be constrained
by the high energetic cost of constructing in steeper angles. 相似文献
14.
Queenless workers of the Cape honeybee (Apis mellifera capensis) can develop into reproductives termed pseudoqueens. Although they morphologically remain workers they become physiologically
queenlike, produce offspring, and secrete mandibular gland pheromones similar to those of true queens. However, after queen
loss only very few workers gain pseudoqueen status. A strong intracolonial selection governs which workers start oviposition
and which remain sterile. The “queen substance”, 9-keto-2(E)-decenoic acid (9-ODA), the dominant compound of the queen's mandibular
gland pheromones, suppresses the secretion of queenlike mandibular gland pheromones in workers. It may act as an important
signal in pseudoqueen selection. By analysing the mandibular gland pheromones of workers kept in pairs, we found that A. m. capensis workers compete to produce the strongest queen-like signal.
Received: 2 July 2000 / Accepted in revised form: 28 July 2000 相似文献
15.
Stano Pekár Onřej Šedo Eva Líznarová Stanislav Korenko Zdeněk Zdráhal 《Die Naturwissenschaften》2014,101(7):533-540
It is rare to find a true predator that repeatedly and routinely kills prey larger than itself. A solitary specialised ant-eating spider of the genus Zodarion can capture a relatively giant prey. We studied the trophic niche of this spider species and investigated its adaptations (behavioural and venomic) that are used to capture ants. We found that the spider captures mainly polymorphic Messor arenarius ants. Adult female spiders captured large morphs while tiny juveniles captured smaller morphs, yet in both cases ants were giant in comparison with spider size. All specimens used an effective prey capture strategy that protected them from ant retaliation. Juvenile and adult spiders were able to paralyse their prey using a single bite. The venom glands of adults were more than 50 times larger than those of juvenile spiders, but the paralysis latency of juveniles was 1.5 times longer. This suggests that this spider species possesses very potent venom already at the juvenile stage. Comparison of the venom composition between juvenile and adult spiders did not reveal significant differences. We discovered here that specialised capture combined with very effective venom enables the capture of giant prey. 相似文献
16.
The behavioral response of the obligate bamboo-nesting ant Cataulacus muticus to nest flooding was studied in a perhumid tropical rainforest in Malaysia and in the laboratory. The hollow internodes of
giant bamboo, in which C. muticus exclusively nests, are prone to flooding by heavy rains. The ants showed a two-graded response to flooding. During heavy
rain workers block the nest entrances with their heads to reduce water influx. However, rainwater may still intrude into the
nest chamber. The ants respond by drinking the water, leaving the nest and excreting water droplets on the outer stem surface.
This cooperative 'peeing' behavior is a new survival mechanism adaptive to the ants' nesting ecology. Laboratory experiments
conducted with two other Cataulacus species, C. catuvolcus colonizing small dead twigs and C. horridus inhabiting rotten wood, did not reveal any form of water-bailing behavior.
Received: 3 August 2000 / Accepted in revised form: 6 November 2000 相似文献
17.
We determined chitinase activity in leaves of four myrmecophytic and four non-myrmecophytic leguminous species at the plants'
natural growing sites in Mexico. Myrmecophytic plants (or 'ant plants') have obligate mutualisms with ants protecting them
against herbivores and pathogenic fungi. Plant chitinases can be considered a reliable measure of plant resistance to pathogenic
fungi. The myrmecophytic Acacia species, which were colonised by mutualistic ants, exhibited at least six-fold lower levels of chitinase activity compared
with the non-myrmecophytic Acacia farnesiana and three other non-myrmecophytes. Though belonging to different phylogenetic groups, the myrmecophytic Acacia species formed one distinct group in the data set, which was clearly separated from the non-myrmecophytic species. These
findings allowed for comparison between two recent hypotheses that attempt to explain low chitinase activity in ant plants.
Most probably, chitinases are reduced in myrmecophytic plant species because these are effectively defended indirectly due
to their symbiosis with mutualistic ants.
Received: 16 August 2000 / Accepted in revised form: 28 October 2000 相似文献
18.
The myrmicine ant Mayriella overbecki lays recruitment trails during foraging and nest emigrations. The trail pheromone originates from the poison gland. From
ten identified components of the poison gland secretions only methyl 6-methylsalicylate 1 elicited trail following behavior.
Received: 6 April 2000 / Accepted in revised form: 6 June 2000 相似文献
19.
Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active
individuals. In contrast, the widely held view is that daily torpor reduces energy expenditure usually by about 30%, is employed
for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on
laboratory studies, whereas knowledge on daily torpor in the field is scant. We used temperature telemetry to quantify thermal
biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily torpor is a crucial survival strategy of this species in winter.
All individuals entered torpor daily with the exception of a single male that remained normothermic for a single day (torpor
on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T
a) ranging from approximately −1°C to 36°C. Dunnarts usually entered torpor during the night and aroused at midday with the
daily increase of T
a. Torpor was on average about twice as long (mean 11.0 ± 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally
omitted activity for several days in sequence. Consequently, we estimate that daily torpor in this species can reduce daily
energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily torpor is an essential mechanism
for overcoming energetic challenges during winter and that torpor data obtained in the laboratory can substantially underestimate
the ecological significance of daily torpor in the wild. 相似文献
20.
M. Tchebakova Nadezda E. Rehfeldt Gerald I. Parfenova Elena 《Mitigation and Adaptation Strategies for Global Change》2006,11(4):861-882
Inter- and intraspecific effects of climate change were assessed for the dominant conifers of Siberia (60–140∘E and 48–75∘N): Larix spp. (L. sibirica, L. dahurica, and L. sukaczewii) and Pinus sylvestris
. The approach employed a tri-variate (degree-days above 5 ∘C, degree-days below 0 ∘C, and a moisture index) estimate of the climatic envelope within which exists the actual ecological distribution of a species
and their constituent climatypes (genotypes physiologically attuned to similar environments). Limits of the actual ecological
distribution were approximated by reducing the climatic envelope according to effects of permafrost and interspecific competition.
Climatypes were mapped within the climatic envelope according to the climatic interval that must separate populations for
reasonable assurance of genetic differentiation. This interval was calculated from response functions that related 13-year
growth and survival of a species to the difference in climate between the provenance of a climatype and the climate of numerous
test sites distributed across Russia. Mapping species' distributions and their climatypes was done for the contemporary climate
and for future climates predicted by the HadCM3GGa1 scenario of Hadley Centre.
The results showed that if the forests of the future are to reflect the adaptedness of today, the distribution of species
will shift and genotypes within species will be redistributed. Some contemporary climatypes are projected to disappear from
Siberia while others common elsewhere would evolve. To mitigate these effects, climatypes should be transferred today to the
expected future location of their climatic optima, a distance that is likely to approach 700–1200 km for these species. 相似文献