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1.
Summary. Tannins are plant defense compounds that exhibit antibiotic (e.g. toxic) and antixenotic (e.g. repellent) effects against
an array of plant pests. They are broadly divided into two major groups, hydrolysable tannins (gallotannins and ellagitannins)
and proanthocyanidins, each with an undetermined number of compounds. We investigated constitutive levels of hydrolysable
tannins and proanthocyanidins in the leaves and stems of American (Castanea dentata Marshall) (Fagales: Fagaceae) and Chinese (C. mollissima Blume) chestnut. American chestnut contained more proanthocyanidins in leaves and stems than Chinese chestnut, but Chinese
chestnut contained more foliar hydrolysable tannins. Regardless of these differences, gypsy moth (Lymantria dispar L, Lepidoptera: Lymantriidae) performance did not differ when fed American and Chinese chestnuts. We also investigated the
effects of jasmonic acid (JA) treatment on differential tannin induction in American and Chinese chestnut leaves and stems.
JA treatment increased proanthocyanidins in American chestnut stems and hydrolysable tannins in both tissue types of American
chestnut, but did not influence tannin concentrations in Chinese chestnut leaves or stems. HPLC-ESI-MS analysis of pooled
samples suggested that hydrolysable tannins in each tissue were qualitatively comprised primarily of ellagitannins, and JA
generally increased the number of hydrolysable tannins that could be detected by ESI-MS. Third, we investigated the performance
of gypsy moths on JA treated and untreated American and Chinese chestnut. Caterpillar relative growth was not influenced by
JA treatment on Chinese chestnut, but decreased in response to JA application on American chestnut. Our results indicate that
JA-dependent defenses differ between these chestnut species. This study improves our understanding of ecologically important
differences in tannin induction and herbivore susceptibility in Castanea, and has important implications in efforts for American chestnut restoration and commercial chestnut production. 相似文献
2.
Summary. Females of both species start their pheromone-releasing activity on the second day after emergence at the beginning of the
photophase. During the present work, a peak of calling activity with close to 100% of active Ph. nigrescentella females was registered 1.5 hour after the light had been put on. The high pheromone release behaviour with 50% active females
lasted for 3 hours. The calling activity of the group of females was about 6 h/day. The beginning of a photophase under laboratory
conditions or an early morning in nature is a common period for sex pheromone release in the genus Phyllonorycter. (8Z,10E)-tetradecadien-1-yl acetate (8Z,10E-14:Ac), (8Z,10E)-tetradecadien-1-ol (8Z,10E-14:OH) and (8E,10Z)-tetradecadien-1-yl acetate (8E,10Z-14:Ac) in the ratio 96:4:traces as well as 8Z,10E-14:Ac and 8Z,10E-14:OH in the ratio 88:12 collected by Solid Phase Micro Extraction (SPME) were found to be specific for the calling periods
of virgin Phyllonorycter insignitella and Ph. nigrescentella females respectively. Field trapping experiments demonstrated that all three compounds are important for the attraction of
Ph. insignitella males while only 8Z,10E-14:Ac is the essential sex pheromone component for Ph. nigrescentella. The pheromone activity of all three compounds is reported for the first time. Addition of either 8Z,10E-14:OH or 8E,10Z-14:Ac to 8Z,10E-14:Ac did not have a significant effect on the attraction of Ph. nigrescentella males, while the efficiency of the three component blend was 5 times lower as compared to that of 8Z,10E-14:Ac. Our data demonstrate that 8Z,10E-14:OH and 8E,10Z-14:Ac play a dual function, they are minor sex pheromone components of Ph. insignitella essential for attraction of conspecific males and show an allelochemical, antagonistic effect on Ph. nigrescentella males and, thus, ensuring specificity of the mate location signal in two related Phyllonorycter species. 相似文献
3.
Beata Szafranek Elżbieta Synak Danuta Waligóra Janusz Szafranek Jan Nawrot 《Chemoecology》2008,18(4):205-216
Summary. The sampling behavior of the Colorado potato beetle Leptinotarsa decemlineata Say (CPB) involves examination of the surface
of potato leaves. It has been suggested that leaf surface compounds (volatiles and cuticular waxes) may be involved in host-plant
recognition, acceptance or discrimination. Here we report on the effect of leaf surface extracts of six Polish commercial
potato varieties on CPB feeding. We tested the influence of potato leaf surface extracts on CPB adult and larval feeding,
then separated the extracts with HPLC, and finally tested the effect of the HPLC-separated fractions on CPB feeding. The bioassays
were performed using potato leaf discs deprived of their original surface compounds. Applied to test discs at concentrations
ten times higher than natural (10 leaf area equivalent), the extracts deterred CPB adults and larvae from feeding. HPLC-separated
fractions composed of alkanes, sesquiterpene hydrocarbons, wax esters, benzoic acid esters, fatty acid methyl, ethyl, isopropyl
and phenylethyl esters, aldehydes, ketones, methyl ketones, fatty acids, primary alcohols, β-amyrin and sterols did not affect
adult CPB feeding. Similarly, alkanes, sesquiterpene hydrocarbons, wax esters, methyl ketones, sesquiterpene alcohols and
secondary alcohols had no effect on larval CPB feeding. The sterol fraction (cholesterol, β-sitosterol and stigmasterol) acted
as a phagostimulant to CPB larvae. We isolated a fraction demonstrating a phagodeterrent effect on CPB adults and larvae.
The qualitative composition of the deterrent fraction was quite similar in all potato extracts, but there were quantitative
differences between the varieties. Much further work is needed to identify the compounds that can produce the deterrent effect. 相似文献
4.
Louis Hautier Jean-Claude Grégoire Jérôme de Schauwers Gilles San Martin Pierre Callier Jean-Pierre Jansen Jean-Christophe de Biseau 《Chemoecology》2008,18(3):191-196
Summary. Under laboratory conditions, the multicolored Asian lady beetle, Harmonia axyridis is well known as an intraguild predator of other ladybirds. However the real impact of this exotic species on native species
was poorly investigated in the field. Because many ladybird species produce alkaloids as defensive compounds, we propose here
a new method of intraguild predation monitoring in coccinellids based on alkaloid quantification by GC-MS. In laboratory experiments,
adaline was unambiguously detected in fourth instar larvae of H. axyridis having ingested one egg or one first instar larva of Adalia bipunctata. Although prey alkaloids in the predator decreased with time, traces were still detected in pupae, exuviae and imagines of
H. axyridis having ingested one prey when they were fourth instar larvae. Analysis of H. axyridis larvae collected in two potato fields shows for the first time in Europe the presence of exogenous alkaloids in 9 out of
28 individuals tested. This new method of intraguild predation detection could be used more widely to follow the interactions
between predators and potential chemically defended insect preys. 相似文献
5.
A. Mosleh Arany T. J. de Jong H. K. Kim N. M. van Dam Y. H. Choi R. Verpoorte E. van der Meijden 《Chemoecology》2008,18(2):65-71
Because many secondary metabolites in plants act as defense against herbivores it has been postulated that these compounds
have evolved under selective pressure by insect herbivores. One explanation for the within-species variation in metabolite
patterns in a particular species is that different populations are under selection by different herbivores. We tested this
hypothesis, using Arabidopsis thaliana plants that originated from dune and inland areas. We analyzed Arabidopsis thaliana leaves using NMR spectroscopy and multivariate data analysis. Major differences in chemical composition were found in water-methanol
fractions and were due to higher concentrations of sinigrin and fumaric acid in dune plants. Inland plants showed lower levels
of glucose. Quantitative analysis of glucosinolates was performed with HPLC. Individual plants and populations demonstrated
differences in glucosinolate composition and concentration. In growth chamber experiments, the generalist herbivore, Spodoptera exigua grew significantly better on the inland plants, while the specialist herbivore Plutella xylostella performed equally well on plants of both origins. Aliphatic glucosinolate as well as total glucosinolate concentrations negatively
correlated with larval mass of Spodoptera exigua. No significant correlations, however, were found between larval mass of Plutella xylostella and glucosinolates in the leaves. A specialist and a generalist herbivore were responding differently to plant secondary
chemistry, as was also found in several other studies. This is an important indication that differences in glucosinolate concentrations
among populations may result from differential selection by different guilds of herbivores. 相似文献
6.
Hiroe Yasui Toshiharu Akino Midori Fukaya Sadao Wakamura Hiroshi Ono 《Chemoecology》2008,18(4):233-242
Summary. We conducted a series of experiments with the white-spotted longicorn beetle Anoplophora malasiaca (Thomson), and its host plant, Citrus unshiu, to examine the origin of the sesquiterpene hydrocarbons (SHCs; including β-elemene, β-caryophyllene, α-humulene, α-farnesene,
and several unidentified compounds) that are contained in the elytra of the beetles and act as an attractant. In the laboratory,
mechanically wounded citrus branches, as well as those fed upon by A. malasiaca, attracted males more frequently than intact branches. Solid phase microextraction (SPME) and subsequent analyses by gas
chromatography (GC) analyses detected measurable SHCs from the air around both mechanically wounded and beetle-infested branches,
as well as trace amounts from intact branches. The SHCs were also detected for a certain time from beetles that had fed on
the citrus branches, but the amounts decreased rapidly after they were removed from the host. This decrease generally corresponded
with a reduction of attractiveness of the beetles in a behavioural assay. Isolated females acquired the SHCs after exposure
to, but not upon contact with, other females that had fed on C. unshiu branches. We hypothesize that the citrus SHCs are adsorbed in, retained on, and released from the wax layer of the beetle
elytra. Since these compounds are released from branches when beetles feed, they may indirectly signal the presence of beetles
to others in the field. The high response rate to SHCs by males is likely representing mate searching behavior. The SHCs act
as kairomones with a releaser effect in the communication system of A. malasiaca.
Hiroe Yasui, Toshiharu Akino, Midori Fukaya: These authors contributed equally to this article. 相似文献
7.
Summary. The leaf beetle Ophraella communa infests
almost exclusively Ambrosia artemisiifolia in the fields of
Japan, even though it normally feeds on several Asteraceous
plants. A filter paper bioassay showed that the feeding of
O. communa is strongly stimulated by methanolic extracts of
A. artemisiifolia. The feeding stimulants for O. communa have
been isolated from methanolic extracts of A. artemisiifolia.
-Amyrin acetate, -amyrin acetate, 5-caffeoylquinic acid
(chlorogenic acid) and 3,5-dicaffeoylquinic acid from
A. artemisiifolia have been identified as feeding stimulants
for O. communa. Triterpenoid derivatives
(-amyrin acetate or -amyrin acetate) and caffeic acid derivatives (3,
5-dicaffoylquinic acid or 5-caffeoylquinic acid) showed
feeding stimulant activity when mixed together. 相似文献
8.
Summary. In earlier investigations on host plant discrimination of leaf beetles glucosinolates were described as feeding stimulants
for the Brassicaceae specialist Phaedon cochleariae F. (Coleoptera: Chrysomelidae). However, since these findings could not be confirmed in later studies offering 2-propenylglucosinolate
in concentrations corresponding to those detected in host plant leaf material, the identification of feeding stimulants of
this leaf beetle species remained unclear. In order to investigate which compounds of the host plant Sinapis alba (Brassicaceae) are involved in feeding stimulation, leaf extracts of different polarities were tested in bioassays with adults
of P. cochleariae. Number of feeding beetles and net consumption rates were highest on pea leaves painted with methanol extracts of S. alba, whereas weak feeding responses were also detectable for hexane extracts. In subsequent bioassay-guided fractionations of
methanol extracts with semi-preparative high performance liquid chromatography, two distinct fractions, one containing glucosinolates
and another containing flavonoids, were found to stimulate beetles to feed to variable degrees. Other collected fractions
had zero activity. The combination of both active fractions evoked significantly higher consumption rates and stimulated more
beetles to feed than fractions tested individually. At least one compound of each fraction, among these the main glucosinolate
of S. alba, 4-hydroxybenzylglucosinolate, act additively. Effects of two different naturally-occurring ratios of glucosinolates and
flavonoids on the strength of feeding responses were investigated by use of extracts of two sets of host plants differently
exposed to radiation. One set was outdoors-exposed, whereas the second set was kept in the greenhouse. However, the feeding
behaviour of P. cochleariae was not affected by the significantly different relative compositions of both compound classes in the host material. In conclusion,
mustard leaf beetles need a combination of distinct plant metabolites acting in concert for feeding stimulation, whereby the
mere presence of these stimulants, but probably not the ratio of involved compounds, determines their feeding response. 相似文献
9.
Summary. The major component of the trail pheromone of
the myrmicine ant Crematogaster castanea
has been identified as (R)-2-dodecanol from
the tibial glands of the hind legs. The substance gave activity comparable to the
contents of 8 tibial glands at a concentration of 1 pg per 32 cm trail. 相似文献
10.
The aim of this study was to examine the effects of chemical nonylphenols (NPs) on the antioxidant system of Microcystis aeruginosa strains. The degradation and sorption of NPs by M. aeruginosa were also evaluated. High concentrations of NPs (1 and 2 mg/l) were found to cause increases in superoxidase dismutase (SOD)
and glutathione-S-transferase (GST) activities and in glutathione (GSH) levels. These results suggest that toxic stress manifested by elevated
SOD and GST levels and GSH contents may be responsible for the toxicity of NPs to M. aeruginosa and that the algal cells could improve their antioxidant and detoxification ability through the enhancement of enzymatic
and nonenzymatic prevention substances. The observed elevations in GSH levels and GST activities were relatively higher than
those in SOD activities, indicating that GSH and GST contributed more in eliminating toxic effects than SOD. Low concentrations
of NPs (0.05–0.2 mg/l) enhanced cell growth and decreased GST activity in algal cells of M. aeruginosa, suggesting that NPs may have acted as a protecting factor, such as an antioxidant. The larger portion of the NPs (>60%)
disappeared after 12 days of incubation, indicating the strong ability of M. aeruginosa to degrade the moderate persistent NP compounds. The sorption ratio of M. aeruginosa after a 12-day exposure to low nominal concentrations of NPs (0.02–0.5 mg/l) was relatively high (>30%). The fact that M. aeruginosa effectively resisted the toxic effects of NPs and strongly degraded these pollutants indicate that M. aeruginosa cells have a strong ability to adapt to variations in environmental conditions and that low and moderate concentrations of
organic compounds may favor its survival. Further studies are needed to provide detailed information on the fate of persistent
organic pollutants and the survival of algae and to determine the possible role of organic pollutants in the occurrence of
water blooms in eutrophic lakes. 相似文献
11.
Many animals show seasonal shifts in behaviors that coincide with breeding, migration, or hibernation. These behavioral shifts provide ideal opportunities to study the regulation of behavior. The red-sided garter snake (Thamnophis sirtalis parietalis) spends 8 months of the year inactive in underground hibernacula, 1 month breeding, and 3 months feeding to build up enough energy stores to survive the following winter. Although they emerge from 8 months of hibernation with severely depleted energy reserves, they do not feed until weeks later, after the breeding season. We tested the hypothesis that this lack of feeding during the breeding season is due to a shift in behavior rather than the distribution of food and potential mates. Male garter snakes were given a series of choices between pursuing a breeding or feeding opportunity. The proportion of tests in which males selected feeding over breeding gradually increased throughout the study period, reaching almost 100% in the final tests. Males also were given opportunities to feed and court at the beginning and end of the study. Males initially refused food and courted females, but when retested at the end of the study they fed and did not court females. Thus aphagia during the breeding season is due at least in part to an endogenous shift in behavior.Communicated by P. Weatherhead 相似文献
12.
Paula A. White 《Behavioral ecology and sociobiology》2008,62(3):377-361
Among spotted hyenas, Crocuta crocuta, neonatal aggression in twins is a well-known phenomenon and serves to establish intra-litter dominance soon after birth.
As the stronger more aggressive cub presumably attains dominance over its twin, intra-litter dominance presents mothers with
an ideal opportunity to assess individual cub fitness and, thereafter, to selectively favor one cub over the other. This study
quantified maternal response to sibling conflict in 26 sets of twins born to 16 wild-living females to determine whether mothers
of different social ranks exhibited favoritism towards sons or daughters, or in the case of same-sex twins, the dominant or
subordinate cub. Maternal response to sibling conflict did not vary with litter sex composition, suggesting that mothers do
not favor offspring of one sex over the other. All mothers intervened when their cubs fought and sometimes punished their
cubs. Higher-ranking mothers more often punished both cubs, while lower-ranking mothers were more selective and punished the
dominant cub. Where sibling aggression was most extreme, rather than favor the dominant sibling, mothers of all ranks made
concessions to the subordinate cub that included procuring private nursing bouts for the subordinate and temporarily housing
twins in separate dens, presumably to decrease sibling conflict. These findings represent a complex example of parent–offspring
conflict and support both the insurance cub hypothesis and resource tracking hypothesis that mothers endeavor to keep all
offspring alive for as long as possible in the event that the dominant sibling dies or that resources provide for the rearing
of twins.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献
13.
Summary. Myrmecophytic plants use obligate ant mutualists as a constitutive
indirect defence mechanism. These plants often produce cellular food bodies (FBs) to
nourish their resident ants. Lipids, proteins, and even highly specialised compounds
such as glycogen have been reported from FBs, but detailed chemical analyses of FB
composition have so far been presented only for Southeast Asian Macaranga
and Central American Piper myrmecophytes. Here we
report the chemical composition of FBs of five myrmecophytic Acacia
(Fabaceae) species from Mexico using HPLC (carbohydrates and proteins) and GC-MS
(lipids). Feeding experiments revealed no hints on any use of external food sources
by the inhabiting Pseudomyrmex ants. These ants
obviously rely completely on FBs and extrafloral nectar provided by their hosts.
The total content of nutrients in Acacia FBs was 15-25% of FB
dry mass, being much lower than in Macaranga or
Piper FBs. Proteins were dominating (8-14 % dm)
in Acacia FBs and thus were present in higher amounts than in
Macaranga FBs, yet in lower amounts than in
Piper. Lipids contributed 1-9 %
of dry mass, showing a lower proportion than in FBs of Macaranga
or Piper. Carbohydrates made up 3-11 % dm, reaching
in most Acacia species the same range as observed in
Macaranga and in Piper FBs.
Water content was 18-24 % of FB fresh mass, and structural tissue obviously made up
a much higher proportion in Acacia FBs than in
Macaranga or Piper
FBs. Both characters might represent an adaptation to producing FBs unprotected at
the leaf tips under dry conditions. Acacia FBs
contain all amino acids and all fatty acids that are considered essential for
insects, and their contents of lipids and proteins are higher than in the leaves
from which they are ontogenetically derived. This indicates a putatively adaptive
enrichment of nutritionally valuable compounds in structures functioning as ant-food. 相似文献
14.
Maud C. O. Ferrari François Messier Douglas P. Chivers 《Behavioral ecology and sociobiology》2008,62(7):1079-1083
A prerequisite for prey to show adaptive behavioural responses to predators is that the prey has the ability to recognise
predators as threats. While predator recognition can be innate in many situations, learning is often essential. For many aquatic
species, one common way to learn about predators is through the pairing of a novel predator odour with alarm cues released
from injured conspecifics. One study with fish demonstrated that this mode of learning not only allows the prey to recognise
the predatory cues as a threat, but also mediates the level of threat associated with the predator cues (i.e. threat-sensitive
learning). When the prey is exposed to the novel predator with a high concentration of alarm cues, they subsequently show
a high intensity of antipredator response to the predator cues alone. When exposed to the predator with a low concentration
of alarm cues, they subsequently show a low-intensity response to the predator cues. Here, we investigated whether larval
mosquitoes Culex restuans have the ability to learn to recognise salamanders as a threat through a single pairing of alarm cues and salamander odour
and also whether they would learn to respond to salamander cues in a threat-sensitive manner. We conditioned individual mosquitoes
with water or a low, medium or high concentration of crushed conspecific cues (alarm cues) paired with salamander odour. Mosquitoes
exposed to salamander odour paired with alarm cues and subsequently exposed to salamander odour alone responded to the salamander
as a threat. Moreover, the intensity of antipredator response displayed during the conditioning phase matched the response
intensity during the testing phase. This is the first demonstration of threat-sensitive learning in an aquatic invertebrate. 相似文献
15.
In bumblebees all species of the subgenus Psithyrus are social parasites in the nests of their Bombus hosts. In the bumblebee B. terrestris we investigated how colony size influences survival rates of nest entering females of the social parasite Psithyrus vestalis. Furthermore, we studied whether the host worker’s dominance status and age are reflected in its individual scent and whether
Psithyrus females use volatiles to selectively kill host workers. The survival rate of Psithyrus vestalis females drops from 100%, when entering colonies with five workers, to 0% for colonies containing 50 host workers. Older host
workers, born before the nest invasion, were selectively killed when Psithyrus females entered the nest. In contrast, all workers born after the nest invasion survived. The host workers’ dominance status
and age are reflected by their individual odours: newly emerged workers produced a significantly lower total amount of secretions
than 4-day-old workers. In chemical analyses of female groups we identified saturated and unsaturated hydrocarbons, aldehydes,
and unsaturated wax-type esters of fatty acids. In a discriminant function analysis different worker groups were mainly separated
by their bouquets of hydrocarbons. Killed workers release significantly more scent and of a different chemical composition,
than survivors. Survivors alter scent production and increase it beyond the level of the killed workers within 1 day of the
invasion. The Psithyrus female clearly maintains reproductive dominance utilizing these differences in the odour bouquets as criteria for killing
workers that compete for reproduction. 相似文献
16.
We examine vigilance within a mixed-species troop of saddleback (Saguinus fuscicollis) and moustached (S. mystax) tamarins over a complete year. Saddleback tamarins were consistently more vigilant than moustached tamarins. This may be linked to their preference for lower strata. In accordance with previous studies of other primates, vigilant tamarins of both species were significantly further away from their nearest neighbours, and were also at lower heights in the forest than non-vigilant individuals. There was no observed sex difference in the amount of time spent vigilant. In terms of modes of scanning, the saddleback tamarins looked up significantly more frequently than the moustached tamarins, whereas there was no difference between the species in the frequency of side sweeps. There were no differences between the sexes in the frequencies of either type of vigilant behaviour. The proportion of time spent vigilant was higher than average immediately prior to entering a sleeping site for saddleback tamarins, but not for moustached tamarins. Both species were more vigilant immediately after exiting a sleeping site than at other times of the day. There was significant variation in the amount of time devoted to vigilance over the course of the year. These findings are discussed with respect to the social structure, ecology and main predator threats facing these species.Communicated by D. Watts 相似文献
17.
Summary. The harvestman Mitopus morio (Phalangidae) is
a generalist predator. It is known to prey on larvae of the
chrysomelid leaf beetle Oreina cacaliae defended by plant
acquired pyrrolizidine alkaloids (PAs). Tracer feeding
experiments were performed to determine how harvestmen
tolerate protoxic PAs. Minced meat containing either
[14C]senecionine or [14C]senecionine N-oxide was fed to
M. morio and subsequently feces and bodies were analyzed.
Labeled alkaloid N-oxide remained stable and was eliminated
almost unaltered with the feces; only 10% was recovered
as tertiary PA. In contrast, approximately 80% of
labeled tertiary alkaloid (senecionine) ingested with the diet
was N-oxidized and eliminated; the remaining 20% consisted
of unchanged senecionine and a polar metabolite
of unknown structure. Harvestmen process their diet by
excreting digestive juice, indicated by bleaching of the meat
color. Analysis of the processed diet revealed some N-oxidation
of [14C]senecionine, suggesting the gut as the site of Noxidation.
Analysis of the bodies of harvestmen 80 hours
after the tracer feeding pulse revealed only trace amounts of
the polar metabolite. Neither senecionine nor its N-oxide
could be detected in the body extracts. The results are discussed
in relation to the strategies of PA adapted insects to
avoid accumulation of tertiary PAs in living tissues. 相似文献
18.
Matthias Bandilla Teija Hakalahti-Sirén E. Tellervo Valtonen 《Behavioral ecology and sociobiology》2008,62(6):975-982
Mating is essential for sexually reproducing species to pass on their genes. For sexual parasites, this implies a need to
switch the host in the search for a mate when potential partners are not available on the same host, although host switching
includes risks like starvation and predation. Studies of mate-searching behavior predict that commonly only one sex searches
for mating partners while the other remains stationary. In the present work, we experimentally infected rainbow trout (Oncorhynchus mykiss) with the fish ectoparasite Argulus coregoni and determined whether the sex, age and the presence of mating partners influenced the host switching activity. Our results
show that increased host switching by A. coregoni occurred only after the parasite reached the adult stage and a difference between the sexes was also recorded. Host switching
by mature males was enhanced when no mating partners were present on the same host, whereas females remained mainly stationary
on their host regardless of male presence or absence. Our data therefore support the hypothesis that there is a strategic
difference in reproductive behavior between males and females; males invest energy in mate searching while females are rather
stationary and invest into body size and hence increased fecundity. Our data also showed that leaving the host to find a mate
is potentially costly in terms of predation since a substantial number of free-swimming parasites were eaten by fish. 相似文献
19.
Behavioural variation is known to occur between individuals of the same population competing for resources. Individuals also vary with respect to their boldness or shyness. An individuals position along the shy-bold axis may be defined as the extent to which it is willing to trade off potentially increased predation risks for possible gains in resources. Similarly, group living may be interpreted as a trade-off between anti-predatory tactics and foraging efficiency. The responses of three-spined sticklebacks (Gasterosteus aculeatus) were tested across four social contexts to assess relative boldness or shyness and to further examine whether their behaviour would be consistent within and between contexts. Individuals displayed consistent responses within and between the first two contexts: those individuals which resumed foraging rapidly after a simulated aerial predator attack also displayed low shoaling tendencies. Such fish were deemed to be bold, whilst those which displayed the converse behaviour, slow resumption of foraging and a high shoaling tendency, were deemed to be shy. In a third context, bold individuals out-competed shy conspecifics for food. Boldness was also positively correlated with growth over a 6-week period. The position adopted by an individual within a group is usually interpreted as a trade-off between predation risk and foraging efficiency—both are greater at the front of a mobile group. Bold individuals showed significantly stronger tendencies towards front positions than shy conspecifics. The results suggest that, contrary to some previous studies on other animals, bold or shy behaviour in sticklebacks is consistent between contexts.Communicated by T. Czeschlik 相似文献
20.
This study devised a staging system for, and monitored, the gonad development of the limpet species Patella vulgata and Patella ulyssiponensis on the South West coast of Ireland using histological techniques. Maturation began in the males of both species in January
and in the females it began in March. There was no statistical difference in gonad development between sexes and between species.
Spawning in the male P. vulgata occurred from September to December 2003 and in September and October 2004. In female P. vulgata spawning occurred from October to December 2003, no spawning of females was observed in 2004. In male P. ulyssiponensis spawning occurred in November and December 2003 and from September 2004 to December 2004. Spawning was observed from November
2003 to January 2004 and in September 2004 in female P. ulyssiponensis. Sex ratios also varied between the species and between months sampled. Nevertheless more males were observed in both species. 相似文献