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1.
Organisms in natural habitats participate in complex ecological interactions that include competition, predation, and foraging.
Under natural aquatic environmental conditions, amphibian larvae can simultaneously receive multiple signals from conspecifics,
predators, and prey, implying that predator-induced morphological defenses can occur in prey and that prey-induced offensive
morphological traits may develop in predators. Although multiple adaptive plasticity, such as inducible defenses and inducible
offensive traits, can be expected to have not only ecological but also evolutionary implications, few empirical studies report
on species having such plasticity. The broad-headed larval morph of Hynobius retardatus, which is induced by crowding with heterospecific anuran (Rana pirica) larvae, is a representative example of prey-induced polyphenism. The morph is one of two distinct morphs that have been
identified in this species; the other is the typical morph. In this paper, we report that typical larval morphs of Hynobius can respond rapidly to a predatory environment and show conspicuous predator-induced plasticity of larval tail depth, but
that broad-headed morphs cannot respond similarly to a predation threat. Our findings support the hypothesis that induction
or maintenance of adaptive plasticity (e.g., predator-induced polyphenism) trades off against other adaptive plastic responses
(e.g., prey-induced polyphenism). For a species to retain both an ability to forage for larger prey and an ability to more
effectively resist predation makes sense in light of the range of environments that many salamander larvae experience in nature.
Our results suggest that the salamander larvae clearly discriminate between cues from prey and those from predators and accurately
respond to each cue; that is, they adjust their phenotype to the current environment. 相似文献
2.
Summary The ontogeny of sibling recognition behavior was studied in the laboratory in tadpoles of the western toad (Bufo boreas boreas) to test the hypothesis that Bufo tadpoles associate with siblings and to compare this behavior with two species of anurans previously studied. Tadpoles reared exclusively with sibs demonstrated a preference to associate with sibs over non-sibs both early and late in development but tadpoles reared with sibs and non-sibs (mixed rearing groups) exhibited no preference. Larvae that developed a preference for sibs after being reared with them for 75 days lost this preference following exposure to a mixed group for 2 to 6 days. Additionally, larvae reared in a mixed group did not develop a preference for the familiar mixed group nor was a preference exhibited by individual larvae that were reared exclusively with 5 non-sibs. These results suggest that larvae learn by prior association to discriminate sibs from non-sibs and that preferences are rapidly modifiable following exposure to non-sibs. However, the latter two experiments suggest that social preferences are not totally labile and are not based entirely on familiarity. Field observations of larval activity, aggregation behavior, and dispersal patterns in B. boreas indicate that tadpoles mix with non-sibs from early larval stages throughout development. Because even short term exposure to nonsibs resulted in a loss of sib preference in our experiments, we suggest that a kin selection interpretation of B. boreas aggregation behavior is not parsimonious. Results differ with those of other studies of sib recognition in larval anurans. 相似文献
3.
ANDREW R. BLAUSTEIN§ JOHN M. ROMANSIC ERIN A. SCHEESSELE BARBARA A. HAN ALLAN P. PESSIER† JOYCE E. LONGCORE‡ 《Conservation biology》2005,19(5):1460-1468
Abstract: As part of an overall biodiversity crisis many amphibian populations are in decline throughout the world. Numerous causes have been invoked to explain these declines. These include habitat destruction, climate change, increasing levels of ultraviolet radiation, environmental contamination, and the introduction of non-native species and diseases. Several types of pathogens have been implicated in contributing to amphibian population declines: viruses, bacteria, oomycetes, and fungi. One particular fungus, the chytridiomycete Batrachochytrium dendrobatidis may have caused amphibian population declines in several regions. This pathogen causes chytridiomycosis, which is fatal to newly metamorphic and adult amphibians of certain species. We present experimental evidence that larval stages may also be susceptible to exposure to Batrachochytrium . There was, however, differential sensitivity to B. dendrobatidis in larvae we examined. In laboratory experiments, larval western toads ( Bufo boreas ) exposed to B. dendrobatidis experienced increased mortality and behaviors that suggested they were affected by exposure compared with unexposed control tadpoles. Larvae of Cascades frogs ( Rana cascadae ), bullfrogs ( R. catesbeiana ), and Pacific treefrogs ( Hyla regilla ) did not die after exposure to Batrachochytrium and appeared to behave normally. R. cascadae larvae exposed to B. dendrobatidis , however, showed an increase incidence in mouthpart abnormalities, a characteristic effect of chytridiomycosis, compared with unexposed controls. These results show that Batrachochytrium can negatively affect some species of amphibians at the larval stage and not others. The implications of interspecific variation in susceptibility to fungal infection are broad. 相似文献
4.
Climate change is expected to increase the frequency and severity of drought and wildfire. Aquatic and moisture‐sensitive species, such as amphibians, may be particularly vulnerable to these modified disturbance regimes because large wildfires often occur during extended droughts and thus may compound environmental threats. However, understanding of the effects of wildfires on amphibians in forests with long fire‐return intervals is limited. Numerous stand‐replacing wildfires have occurred since 1988 in Glacier National Park (Montana, U.S.A.), where we have conducted long‐term monitoring of amphibians. We measured responses of 3 amphibian species to fires of different sizes, severity, and age in a small geographic area with uniform management. We used data from wetlands associated with 6 wildfires that burned between 1988 and 2003 to evaluate whether burn extent and severity and interactions between wildfire and wetland isolation affected the distribution of breeding populations. We measured responses with models that accounted for imperfect detection to estimate occupancy during prefire (0–4 years) and different postfire recovery periods. For the long‐toed salamander (Ambystoma macrodactylum) and Columbia spotted frog (Rana luteiventris), occupancy was not affected for 6 years after wildfire. But 7–21 years after wildfire, occupancy for both species decreased ≥25% in areas where >50% of the forest within 500 m of wetlands burned. In contrast, occupancy of the boreal toad (Anaxyrus boreas) tripled in the 3 years after low‐elevation forests burned. This increase in occupancy was followed by a gradual decline. Our results show that accounting for magnitude of change and time lags is critical to understanding population dynamics of amphibians after large disturbances. Our results also inform understanding of the potential threat of increases in wildfire frequency or severity to amphibians in the region. Incrementos Rápidos y Declinaciones Desfasadas en la Ocupación de Anfibios Después de un Incendio 相似文献
5.
Francesca Porri Gerardo I. Zardi Christopher D. McQuaid Sarah Radloff 《Marine Biology》2007,152(3):631-637
Settlement is a major determinant of intertidal populations. However, the energy costs of lost larvae are very high. Accordingly,
arrival and attachment on suitable substrata are essential requirements for species’ survival. On the intertidal, the presence
of cues left by adult or juvenile conspecifics could be vital for the successful establishment of larvae arriving on the shore.
Two mussel species, the indigenous Perna perna and the invasive Mytilus galloprovincialis, co-occur on the lower eulittoral zone on the south coast of South Africa. P.
perna dominates the low and M. galloprovincialis the high mussel zones, with co-existence in the mid mussel zone. This study tested the hypothesis of settlement selectivity
for conspecifics in these two mussel species, to understand whether the final adult distribution of mussels on the shores
is determined by active behavioural and chemical mechanisms. Preferential selection by larvae for conspecifics was tested
in the field during the peak settlement period in 2004 in natural mussel beds across zones and through manipulative experiments
in the mid-zone where the species co-exist. On natural beds, settlement was determined by counts of settlers attached over
48 h onto artificial collectors. Collectors were placed on beds of P. perna and M. galloprovincialis present at both high- and low-adult densities, as well as in mixed beds. On such natural beds, settlers of both species consistently
favored low-zone P. perna beds. Settlement patterns over 24 h onto experimentally created mussel patches consisting of P.
perna, M. galloprovincialis or the two species combined beds, set in the mixed zone, did not conform with the results of the natural beds study: settlers
of both species settled with no discrimination among different patches. The results indicate that mussels, which are sedentary,
lack attraction to conspecifics at settlement. This highlights the importance of tidal height in setting settlement rates,
and of post-settlement events in shaping populations of these broadcast spawners. 相似文献
6.
Jürgen Liebig Dorit Eliyahu Colin S. Brent 《Behavioral ecology and sociobiology》2009,63(12):1799-1807
Reproductive division of labor in social insects is accompanied by the reliable communication of individual fertility status.
A central question is whether there exists a general mechanism underlying this communication system across species. The best
way to produce reliable information is through physiological markers tightly associated with reproductive status. Cuticular
hydrocarbons exhibit this link to individual fertility in several species of ants, bees, and wasps, and we present the first
evidence for such a system in a non-Hymenopteran eusocial species. In the termite Zootermopsis nevadensis, we identified four polyunsaturated alkenes, which only occur in significant amounts on reproductives that are actively producing
gametes. These compounds are either absent or only occur in small amounts in soldiers, worker-like larvae, and secondary reproductives
with inactive gonads. In contrast to Hymenopteran social insects, both sexes express the reproductive peaks. The reproductive-specific
hydrocarbons may promote tending behavior by worker-like larvae or act as a primer pheromone, inhibiting the reproductive
development of immature conspecifics. 相似文献
7.
Most marine fishes undergo a pelagic larval phase, the early life history stage that is often associated with a high rate
of mortality due to starvation and predation. We present the first study that examines the effects of prey swimming behavior
on prey-capture kinematics in marine fish larvae. Using a digital high-speed video camera, we recorded the swimming velocity
of zooplankton prey (Artemia franciscana, Brachionus rotundiformis, a ciliate species, and two species of copepods) and the feeding behavior of red drum (Sciaenops ocellatus) larvae. From the video recordings we measured: (1) zooplankton swimming velocity in the absence of a red drum larva; (2)
zooplankton swimming velocity in the presence of a red drum larva; and (3) the excursion and timing of key kinematic events
during prey capture in red drum larvae. Two-way ANOVA revealed that: (1) swimming velocity varied among zooplankton prey;
and (2) all zooplankton prey, except rotifers and ciliates, increased their swimming velocity in the presence of a red drum
larva. The kinematics of prey capture differed between two developmental stages in S. ocellatus larvae. Hyoid-stage larvae (3–14 days old) fed on slow swimming B. rotundiformis (rotifers) while hyoid-opercular stage larvae (15 days and older) ate fast moving A. franciscana. Hyoid-opercular stage red drum larvae had a larger gape, hyoid depression and lower jaw angle, and a longer gape cycle duration
relative to their hyoid-stage conspecifics. Interestingly, the feeding repertoire within either stage of red drum development
was not affected by prey type. Knowledge of the direct relationship between fish larvae and their prey aids in our understanding
of optimal foraging strategies and of the sources of mortality in marine fish larvae. 相似文献
8.
Hirofumi Michimae 《Behavioral ecology and sociobiology》2006,60(2):205-211
Alternative phenotypes in natural populations can arise from either genetic polymorphism or an environmentally induced phenotype, that is, polyphenism. Evolutionary models of polyphenism developed by theoretical studies predict that polyphenism is favored when there are environment-dependent fitness trade-offs between alternatives and that the threshold frequency for a facultative switch between alternative phenotypes is adjusted in accordance with different selection regimes. The broad-headed (alternative) larval morph of Hynobius retardatus, which is induced by crowding with conspecifics or heterospecific anuran (Rana pirica) larvae, is a representative example of cannibalistic polyphenism. Morph induction by such proximate factors must reflect evolutionary (conditional frequency-dependent) processes. To clarify the role of frequency-dependent processes in polyphenism, I investigated the occurrence rate of the broad-headed morph under experimental crowding conditions (low conspecific, high conspecific, and high heterospecific densities) using larvae from eight natural populations with different larval densities of conspecifics and heterospecifics, and found interpopulational differences in the expression of the morph. Thus, there is a larval density-dependent equilibrium frequency of the morph in each pond, suggesting that the local switch point for morph induction was modified by selection to produce evolved differences between ponds. The evolution of such interpond differences has three necessary conditions: (1) There are pond-dependent fitness trade-offs between alternatives, (2) The maintenance of the morph is costly, and (3) The presence of conspecific or, especially, heterospecific larvae provides a reliable cue to the receiver. 相似文献
9.
MANUEL E. ORTIZ‐SANTALIESTRA MATTHEW C. FISHER SAIOA FERNÁNDEZ‐BEASKOETXEA MARÍA J. FERNÁNDEZ‐BENÉITEZ JAIME BOSCH 《Conservation biology》2011,25(5):975-982
Abstract: Chytridiomycosis, the emerging disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) is responsible for declines and extirpations of amphibian populations worldwide. Environmental covariates modify the host‐Bd interaction and thus affect the ongoing spread of the pathogen. One such covariate may be the intensity of ultraviolet B (UV‐B) radiation. In a field experiment conducted in Laguna Grande de Peñalara (central Spain), a mountainous region where the presence of Bd has been documented since 1997, we analyzed the potential effect of environmental UV‐B (daily maximum 2.5–3.9 W/m2) on the susceptibility of larvae of the common toad (Bufo bufo) to Bd. The proportion of infected individuals increased as tadpoles developed. The prevalence of Bd was significantly lower in tadpoles exposed to environmental UV‐B intensities (2.94%) than in tadpoles not exposed to the radiation (9.72%). This finding mirrors that seen for a second amphibian species, the European midwife toad (Alytes obstetricans), for which conditional prevalence (i.e., prevalence of infection conditioned on the probability of a site being infected) across the Iberian Peninsula was inversely correlated with the intensity of UV‐B. 相似文献
10.
KAREN L. POPE 《Conservation biology》2008,22(6):1572-1581
Abstract: Sport‐fish introductions are now recognized as an important cause of amphibian decline, but few researchers have quantified the demographic responses of amphibians to current options in fisheries management designed to minimize effects on sensitive amphibians. Demographic analyses with mark–recapture data allow researchers to assess the relative importance of survival, local recruitment, and migration to changes in population densities. I conducted a 4‐year, replicated whole‐lake experiment in the Klamath Mountains of northern California (U.S.A.) to quantify changes in population density, survival, population growth rate, and recruitment of the Cascades frog (Rana cascadae) in response to manipulations of non‐native fish populations. I compared responses of the frogs in lakes where fish were removed, in lakes in their naturally fish‐free state, and in lakes where fish remained that were either stocked annually or no longer being stocked. Within 3 years of fish removals from 3 lakes, frog densities increased by a factor of 13.6. The survival of young adult frogs increased from 59% to 94%, and realized population growth and recruitment rates at the fish‐removal lakes were more than twice as high as the rates for fish‐free reference lakes and lakes that contained fish. Population growth in the fish‐removal lakes was likely due to better on‐site recruitment of frogs to later life stages rather than increased immigration. The effects on R. cascadae of suspending stocking were ambiguous and suggested no direct benefit to amphibians. With amphibians declining worldwide, these results show that active restoration can slow or reverse the decline of species affected by fish stocking within a short time frame. 相似文献
11.
One of the great mysteries of coral-reef fish ecology is how larvae locate the relatively rare patches of coral-reef habitat on which they settle. The present study aimed to estimate, by experiments in aquaria, the sensory modalities of coral-reef fish larvae for senses used in searching for their species settlement habitat. Larval recognition of settlement habitat can be based on the detection of conspecifics and/or of characteristics of coral habitat using visual, chemical and mechanical cues. For this study, larvae were captured with crest nets and were then introduced into experimental tanks that allowed testing of each type of cue separately (visual, chemical or mechanical cues). Among the 18 species studied, 13 chose their settlement habitat due to the presence of conspecifics and not based on the characteristics of coral habitat, and 5 species did not move toward their settlement habitat (e.g. Scorpaenodes parvipinnis, Apogon novemfasciatus). Among the different sensory cues tested, two species used the three types of cues (Parupeneus barberinus and Ctenochaetus striatus: visual, chemical and mechanical cues), six used two types (e.g. Myripristis pralinia: visual and chemical cues; Naso unicornis: visual and mechanical cues), and five used one type (e.g. Chrysiptera leucopoma: visual cues; Pomacentrus pavo: chemical cues). These results demonstrate that many coral-reef fish larvae could in practice use sensory cues for effective habitat selection at settlement, and have the ability to discriminate species-specific sensory cues.Communicated by J. Krause 相似文献
12.
Herring (Clupea harengus pallasi) spawning sites in Puget Sound, Washington overlap spatially and temporally with blooms of Alexandrium catenella, a toxic dinoflagellate species responsible for paralytic shellfish poisoning. Consequently, newly hatched herring larvae
may be regularly exposed to the suite of dissolved paralytic shellfish toxins that are released into the water column from
toxic cells during blooms. To date, virtually nothing is known about the impacts of these neurotoxins on early developmental
stages of marine fish. In the present study, herring larvae at three ages, 0 days post hatch (dph), 4 dph, and 11 dph, were
exposed to dissolved saxitoxin (STX) in 24-h and multi-day exposures. All larvae were examined for sensorimotor function (i.e.
spontaneous swimming behavior and touch response). Significant reductions in spontaneous and touch-activated swimming behavior
occurred within 1 h of exposure. EC50s at 1 h of exposure were 1,500, 840, and 700 μg STX equiv. l−1 for larvae introduced to STX at 0, 4, and 11 dph, respectively. This progressive age-specific increase in STX-induced paralysis
suggests that older larvae were more sensitive to the toxin than younger larvae. Interestingly, herring larvae at all ages
exhibited a significant degree of neurobehavioral recovery within 4–24 h of continuous exposure relative to the 1-h time point.
This recovery of normal motor behaviors was not observed in previous studies with freshwater zebrafish (Danio rerio) larvae under the same continuous exposure conditions, suggesting that an adaptive detoxification or toxin sequestration
mechanism may have evolved in some species of marine fish larvae. Our data reveal that (1) dissolved STX is bioavailable to
marine finfish larvae, (2) the toxin is a paralytic agent with potencies that differ between developmental stages, and (3)
STX-induced sensorimotor inhibition occurs rapidly but is transient in marine larvae. Collectively, these results suggest
that dissolved algal toxins may have important sublethal effects on marine fish populations. 相似文献
13.
Globally, many commercial bivalve populations have declined in recent decades. In addition to overharvesting and habitat loss,
the increasing frequency and intensity of harmful algal blooms (HABs) are likely to contribute to bivalve losses, particularly
in cases where blooms negatively impact larval stages. This paper reports on the lethal effects of clonal cultures and blooms
of Cochlodinium polykrikoides from the US Atlantic coast on the larvae of three species of commercially and ecologically valuable bivalves: the Eastern
oyster (Crassostrea virginica), the bay scallop (Argopecten irradians), and the Northern quahog (hard clam; Mercenaria mercenaria). Both cultures and blooms of C. polykrikoides were highly toxic to all three species of bivalve larvae causing 80–100% mortality during 24- to 72-h exposures at concentrations
of 1–2 × 103 cells ml−1. Toxicity was dependent on cell densities, growth stage of C. polykrikoides (i.e. cultures in exponential stage growth were more toxic than later stages), exposure time of larvae to cells (i.e. longer
exposure caused higher mortality), the age of larvae (i.e. younger larvae were more sensitive), and the relative abundance
of C. polykrikoides (i.e. the presence of other microalgae decreased toxicity). Free radical-scavenging enzymes (peroxidase and catalase) and
the removal of C. polykrikoides cells (i.e. culture filtrate) significantly increased larval survival suggesting toxicity is maximized by contact with live
cells and may involve labile toxins bound by these compounds including e.g. reactive oxygen species. The toxicity of C. polykrikoides to bivalve larvae was generally more severe than other HAB species (e.g. Karenia brevis, Karlodinium veneficum, Alexandrium tamarense, Prorocentrum minimum). Since the bivalves in this study spawn in the months when C. polykrikoides blooms on the east coast of North America, these results suggest that these blooms may have detrimental effects on efforts
to restore these already diminished populations. 相似文献
14.
15.
ALESSANDRO CATENAZZI EDGAR LEHR LILY O. RODRIGUEZ VANCE T. VREDENBURG 《Conservation biology》2011,25(2):382-391
Abstract: Amphibians are declining worldwide, but these declines have been particularly dramatic in tropical mountains, where high endemism and vulnerability to an introduced fungal pathogen, Batrachochytrium dendrobatidis (Bd), is associated with amphibian extinctions. We surveyed frogs in the Peruvian Andes in montane forests along a steep elevational gradient (1200–3700 m). We used visual encounter surveys to sample stream‐dwelling and arboreal species and leaf‐litter plots to sample terrestrial‐breeding species. We compared species richness and abundance among the wet seasons of 1999, 2008, and 2009. Despite similar sampling effort among years, the number of species (46 in 1999) declined by 47% between 1999 and 2008 and by 38% between 1999 and 2009. When we combined the number of species we found in 2008 and 2009, the decline from 1999 was 36%. Declines of stream‐dwelling and arboreal species (a reduction in species richness of 55%) were much greater than declines of terrestrial‐breeding species (reduction of 20% in 2008 and 24% in 2009). Similarly, abundances of stream‐dwelling and arboreal frogs were lower in the combined 2008–2009 period than in 1999, whereas densities of frogs in leaf‐litter plots did not differ among survey years. These declines may be associated with the infection of frogs with Bd. B. dendrobatidis prevalence correlated significantly with the proportion of species that were absent from the 2008 and 2009 surveys along the elevational gradient. Our results suggest Bd may have arrived at the site between 1999 and 2007, which is consistent with the hypothesis that this pathogen is spreading in epidemic waves along the Andean cordilleras. Our results also indicate a rapid decline of frog species richness and abundance in our study area, a national park that contains many endemic amphibian species and is high in amphibian species richness. 相似文献
16.
Influence of UV radiation on the survival of larvae from broadcast-spawning reef corals 总被引:2,自引:2,他引:0
Effects of ambient ultraviolet light on the survivorship of eggs and planulae larvae was investigated for three species of broadcast-spawning reef corals, Acropora palmata, Montastraea annularis, and M. franksi. Eggs and larvae from these corals contain high concentrations of lipids (60–70% by weight) and float in surface waters for 3–4 days following spawning. Larvae originating from colonies living at deeper sites on the reef exhibited significantly lower survivorship than conspecifics originating from parents in shallow water when experimentally exposed for up to 4 days to ambient surface levels of ultraviolet radiation (UVR). Concentrations of the UVR-protective compounds correlated positively with survival and matched concentrations found in parent colonies, implying that higher concentrations of ultraviolet B protective compounds are responsible for greater survival of eggs and larvae from shallow compared to deeper-dwelling parents. Ultraviolet B appears to be responsible for most of the observed differences in larval survivorship with ultraviolet A playing a minor or insignificant role. Data presented here indicate that coral recruits on Caribbean reefs and elsewhere may originate primarily from adult colonies dwelling in shallow water.Communicated by P.W. Sammarco, Chauvin 相似文献
17.
C. L. SEARLE S. S. GERVASI J. HUA J. I. HAMMOND R. A. RELYEA D. H. OLSON A. R. BLAUSTEIN 《Conservation biology》2011,25(5):965-974
Abstract: The amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd) has received considerable attention due to its role in amphibian population declines worldwide. Although many amphibian species appear to be affected by Bd, there is little information on species‐specific differences in susceptibility to this pathogen. We used a comparative experimental approach to examine Bd susceptibility in 6 amphibian species from the United States. We exposed postmetamorphic animals to Bd for 30 days and monitored mortality, feeding rates, and infection levels. In all species tested, Bd‐exposed animals had higher rates of mortality than unexposed (control) animals. However, we found differences in mortality rates among species even though the amount of Bd detected on the different species’ bodies did not differ. Of the species tested, southern toads (Anaxyrus terrestris) and wood frogs (Lithobates sylvaticus) had the highest rates of Bd‐related mortality. Within species, we detected lower levels of Bd on individuals that survived longer and found that the relationship between body size and infection levels differed among species. Our results indicate that, even under identical conditions, amphibian species differ in susceptibility to Bd. This study represents a step toward identifying and understanding species variation in disease susceptibility, which can be used to optimize conservation strategies. 相似文献
18.
Summary. We tested the hypothesis that aggregation behaviour of the
firebrat, Thermobia domestica (Packard) (Thysanura: Lepismatidae), an
inhabitant of enclosed microhabitats, is mediated, at least in part, by
a pheromone. Individual insects were released into the central chamber
of a 3-chambered olfactometer and test stimuli were placed in lateral
chambers. Paper discs previously exposed for 3 days to 10 female, male,
or juvenile T. domestica were all preferred by female, male, or juvenile
T. domestica over unexposed paper discs, indicating the presence of an
aggregation/arrestment pheromone. In additional experiments, frass and
scales from female T. domestica, tested singly and in combination,
proved not to be the source of the pheromone. Physical contact was
required for pheromone recognition, indicating that the pheromone
arrests rather than attracts conspecifics. Arrestment by the
long-tailed silverfish, Ctenolepisma longicaudata Escherich
(Thysanura: Lepismatidae), but not by the common silverfish, Lepisma
saccharina L. (Thysanura: Lepismatidae), to T. domestica exposed
paper discs suggests closer phylogenetic relatedness between C.
longicaudata and T. domestica, than between C.
longicaudata and L. saccharina. Whether C.
longicaudata or L. saccharina produce an aggregation
signal, and whether T. domestica respond to this signal is unknown.
Received 10 June 2002; accepted 30 September 2002. 相似文献
19.
Residency status of individuals in populations may be an important determinant of the outcomes of interspecific competition
between native and introduced species. We examined direct behavioral interactions between two similarly sized rodents, the
alien Rattus rattus and native Rattus fuscipes when they were respective residents and intruders in a small enclosure. Resident individuals were dominant in their behaviors
toward intruders irrespective of the species that was resident. In contrast, interactive behaviors between conspecifics were
often neutral or amicable, supporting suggestions that R. rattus and R. fuscipes are social animals. We then tested whether rodent species use heterospecific odors to avoid aggressive competitive interactions
and partition space in the field. Neither R. fuscipes nor R. rattus responded to traps scented with the odors of male or female heterospecifics. If R. fuscipes does not recognize the odor of introduced R. rattus, then odors will not be cues to the presence or territorial space of competing heterospecifics. Rather, findings from both
enclosure and field trials suggest that direct aggressive interactions between individual R. rattus and R. fuscipes probably facilitate segregation of space between these two species in wild populations, where resident animals may typically
be the winners and exclude heterospecific intruders. These findings have implications for the invasion success of introduced
rodents such as R. rattus into intact forests, where native populations may have competitive advantage because of their residency status. 相似文献
20.
Britta Grote Wilhelm Hagen Marek R. Lipinski Hans M. Verheye Erling K. Stenevik Werner Ekau 《Marine Biology》2011,158(5):1005-1017
Cape hakes, Merluccius paradoxus and M. capensis, are important gadoid fish that are commercially harvested in the Benguela Current system off Namibia and South Africa. The
aim of this study was to elucidate the nutritional condition and feeding preferences of their larvae. Hake eggs and larvae
were sampled in austral spring of two consecutive years, 2007 and 2008, off the west coast of South Africa. They were identified
to species using genetics, and total lipid content and fatty acid (FA) composition were analysed for each individual egg and
larva to compare the condition of different early life stages of both hake species. Higher abundances of M. paradoxus eggs and larvae were consistently found compared to M. capensis. In both species, eggs contained wax esters (WE) and had significantly higher lipid content per dry mass than larvae. Lipid
content as well as FA composition changed with the developmental stage of larvae. Quantities of essential fatty acid (EFA)
increased with feeding of larvae due to dietary lipid incorporation. In 2007, yolk-sac larvae contained significantly lower
total lipids than in 2008. It is argued that this was due to reduced lipid transfer by the spawning females to the eggs. These
findings indicate that maternal effects are important in determining condition of hake larvae and that this may have an effect
on their survival and subsequent recruitment. 相似文献