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1.
For dioecious species, choosing a mate of the same sex can have reproductive costs. For sex-changing animals, however, a lack
of sex recognition may not carry a reproductive cost, as pairs that were initially same-sex can become opposite-sex pairs
as one partner changes sex. The strength of sex discrimination in sex changers, then, should depend on the duration of mating
associations and whether the time of sex change is influenced by social situation (“flexible” sex change). We studied two
species of marine snails that change sex from male to female, one with flexible sex change and long-term or permanent mating
associations (Crepidula fornicata) and one with short-term pairings and relatively fixed time of sex change (Crepidula convexa), to determine whether either species exhibits sex recognition and whether members of C. convexa show stronger sex discrimination. In laboratory experiments, small males, the choosing animals, were placed with either a
male or a female conspecific (no-choice experiments) or given a choice of a male or female (choice experiments). We controlled
for shell length in all experiments, as relative size may influence sex change or choice. Males of both species paired more
often with females than males, but, as predicted, males of C. convexa showed stronger discrimination: When given a choice, no C. convexa male paired with another male. In contrast, some C. fornicata males always chose other males even when given the choice of a female. These results suggest that sex recognition can be
adaptive even for sex changers but demonstrate that the level of sex recognition will depend on other aspects of reproductive
behavior. 相似文献
2.
Home range, activity and distribution patterns of a temperate rocky-reef fish, Cheilodactylus fuscus
Red morwong (Cheilodactylus fuscus; Cheilodactylidae: Perciformes), are large temperate rocky reef fish that are patchily distributed in local aggregations
of 3 to >100 fish. The home ranges and aggregating behaviour of red morwong were investigated using external tags (n = 114, over 35 mo) and ultrasonic transmitters (n = 9 over 20 d) at coastal and estuarine sites in south-east Australia. Adult red morwong had a mean home range during the
day of 1865 m2 (SE = 268). Night movement, determined by ultrasonic telemetry, indicated a significantly greater mean home range of 3639 m2 (SE = 416). Home range did not differ significantly with size or sex. Fish movements were greatest and aggregation sizes
varied most during the non-reproductive mid-summer period. Tagged fish (N = 20) displaced 200 to 900 m returned in 1 to 3 d to the point of capture, often traversing open sand habitat and other aggregations.
During the day, fish were commonly found on bouldered habitat. During the night, these site-specific aggregations fragmented
as fish dispersed over a variety of substrata, with crepuscular peaks in activity. Therefore, estimates of habitat-specificity
and feeding patterns collected only by day may give misleading results.
Received: 28 June 1996 / Accepted: 8 July 1998 相似文献
3.
The reproductive biology of the alfonsino Beryx splendens was studied by histological examinations, gonadosomatic index and macroscopic scales of maturation of a large sample of gonads.
Alfonsino is a gonochoric species. The size-frequency distribution of the sex ratio was bimodal and considered to be due to
size dimorphism. In New Caledonia, the breeding period of this species occurs during the southern summer, with a peak in December
to January. The spawning stage is attained at a minimum fork length of 28 cm for females and 33 cm for males. The size at
which 50% of the population attain sexual maturity (FL50) is 33.2 cm for females and 34.5 cm for males. Maximum potential fecundity is estimated to lie between 270 000 to 675 000
eggs for fish between 34 and 40 cm in fork length. It was possible to differentiate vegetative zones, in which juvenile alfonsino
grow until they reach maturity, from reproductive zones (fishing grounds) which are inhabited by mature individuals. The larvae
and juveniles could be carried from the reproductive zone to the vegetative zone by currents in an oceanic eddy system.
Received: 26 April 1996 / Accepted: 20 September 1996 相似文献
4.
J. H. M. Kouwenberg H. I. Browman J. J. Cullen R. F. Davis J.-F. St-Pierre J. A. Runge 《Marine Biology》1999,134(2):269-284
In the Gulf of St. Lawrence, Canada, productivity-determining biophysical interactions occur in the upper 0 to 30 m of the
water column. The eggs and larvae of several commercially important marine invertebrates and fishes (e.g. Gadus morhua L.) are found in this layer. Measurements of the diffuse attenuation coefficients for ultraviolet-B radiation (280 to 320 nm,
UV-B) at various locations in this geographic region indicated maximum 10% depths (the depth to which 10% of the surface energy
penetrates at a given wavelength) of 3 to 4 m at a wavelength of 310 nm. This represents a significant percentage of the summer
mixed-layer water column: organisms residing in this layer are exposed to UV-B radiation. Laboratory experiments using a Xenon-arc-lamp
based solar simulator revealed that cod embryos exposed to UV-B exhibited high wavelength-dependent mortality. The strongest
effects occurred under exposures to wavelengths below 312 nm. This susceptibility was also dependent upon developmental stage;
mortality was particularly high during gastrulation. At the shorter wavelengths (<305 nm) UV-B-induced mortality was strongly
dose-dependent, and not significantly influenced by dose-rate. The biological weighting function (BWF) derived for UV-B-induced
mortality in cod eggs is similar to that reported for naked DNA – suggesting that the mortality is a direct result of DNA
damage. There was no evidence of a detrimental effect of ultraviolet-A radiation (320 to 400 nm). Calculations based upon
the BWF indicate that, under current noon surface irradiance, 50% of cod eggs located at or very near (within 10 cm) the ocean
surface will be dead after 42 h of exposure. Under solar spectral irradiance simulating a 20% decrease in ozone layer thickness,
this time drops to 32 h. These are first-order estimates based upon surface irradiance taken at a time of day during which
the values would be maximal. Nonetheless, they illustrate the relative changes in UV-B impacts that will result from ozone
layer depletions expected over the coming decades. It is also important to point out that variability in cloud cover, water
quality, and vertical distribution and displacement of cod eggs and larvae within the mixed layer, can all have a greater
effect on the flux of UV-B radiation to which fish eggs are exposed than will ozone layer depletion at these latitudes.
Received: 2 March 1998 / Accepted: 18 December 1998 相似文献
5.
Both sexes of the damselfish Stegastes nigricans hold individual territories in which they feed on filamentous algae. At dawn, females visit males' territories to spawn,
and the males guard the eggs until hatching. We examined how females' spawning behavior varied according to the distances
to their mates. Females usually mated with a single male per morning. The distance to the territory of a mate (0.7–12.8 m)
did not affect a female's total spawning time per morning, but affected the number of her spawning visits with that male.
Females made many repeated spawning visits when spawning with males at short distances, while they spawned the entire clutch
in one visit when spawning with males at long distances. This plasticity in female behavior appears to be related to two costs
during the spawning visits: (1) intrusions by other fish to feed on algae in the female's territory during her absence, which
may cause the female to return repeatedly to her territory for defense, and (2) attacks on the female by other territorial
fish, which increased with the distance to their mates' territories. To minimize the sum of both costs, females should change
the number of spawning visits depending on the distance to the males' territories.
Received: 30 September 1996 / Accepted after revision: 17 March 1997 相似文献
6.
Association patterns of sailfin mollies (Poecilia latipinna): alternative hypotheses 总被引:3,自引:0,他引:3
Caitlin Gabor 《Behavioral ecology and sociobiology》1999,46(5):333-340
Individuals may associate with each other due to a variety of selective forces, such as intra- and intersexual selection,
and conspecific recognition. Previous studies have concluded that mate choice governs association behavior in polygynous species
of fish. I examined whether mate choice underlies the preference for larger individuals by examining preference for association
(time spent in proximity to a fish) not only between opposite-sex individuals but also between same-sex individuals of the
live-bearing sailfin molly (Poecilia latipinna). Males and females from three size classes were tested with a large and a small object fish of the same and opposite sex.
Females preferred to associate with larger over smaller males. Males also preferred to associate with larger over smaller
females, as expected. The same female and male test fish also preferred to associate with larger over smaller fish of the
same sex. Moreover, females demonstrated no significant difference in their strength of preference (large–small) when offered
males or females. The same held true for males. When males and females were subsequently tested with one large male and one
large female, females tended to prefer large males while males showed no significant preference for association based on sex.
In another experiment, females were tested with a large female and a small male, and significantly preferred the former. These
findings suggest that association patterns may have arisen under a variety of conditions, such as predation pressures, shoaling
behavior, and associative preference behavior. The assumption that association behavior is a uniformly sufficient predictor
of mate choice in fish needs to be re-examined for P. latipinna and other species.
Received: 6 November 1998 / Received in revised form: 12 May 1999 / Accepted: 12 May 1999 相似文献
7.
We studied sexual selection in the red bishop, Euplectes orix, a colonial, polygynous weaverbird widely distributed over sub-Saharan Africa. Male reproductive success measured in terms
of the number of nests accepted by females and the number of eggs and nestlings in all the nests on a male's territory varied
considerably. The standardized variance (variance/mean2) in male reproductive success ranged from 0.505 to 1.737 in different years, indicating a high potential for sexual selection
in this species. An analysis of genetic parentage for 432 nestlings by non-radioactive, multilocus DNA fingerprinting confirmed
that male reproductive success (number of young sired on the territory) in this species can be reliably estimated by the measures
introduced above. In all 4 study years there was a strong positive correlation between male mating success and the total number
of nests that males built in their territories. The number of nests built can be partitioned into the number of weeks a male
held a territory and his nest-building performance. Both factors exert a significant positive effect on male mating success
and in combination explained between 53.3 and 86.3% of the variation in male reproductive success. Male morphological characters
were found to be of no importance. Males that established a territory in the following season built more nests and held their
territories for longer than males that did not establish a territory in the following season, suggesting that these measures
might be indicators of male condition and quality. Male nest-building performance (number of nests built per week) seems to
be unrelated to male condition or quality.
Received: 8 January 1999 / Received in revised form: 7 June 1999 / Accepted: 13 June 1999 相似文献
8.
The talitrid amphipod Uhlorchestia spartinophila lives in close association with standing-dead leaves of the smooth cordgrass Spartina alterniflora Loisel in salt marshes along the Atlantic coast of North America. This study probed the strength of the trophic link between
the amphipod population and the decomposition process in this detrital-based ecosystem. We measured survival, growth and reproductive
output in groups of amphipods reared for 6 wk on five diets derived from sheath and blade portions of S. alterniflora leaves just prior to (senescent) and during (dead) decomposition. In unfed treatments, the daily specific mortality rate
was 0.391 and starved amphipods survived no longer than 11 d. Among the fed treatments, a diet of senescent sheaths resulted
in the lowest survival (20%) and yielded no offspring. Groups fed senescent blades, dead sheaths, dead blades and unwashed
dead sheaths had survival rates of 56 to 84% and produced 5.0 to 12.5 offspring replicate−1. Sex ratio usually favored females, but approached unity in treatments with high overall survival, suggesting that quality
of available food resources may influence sex ratio in this species. Mean specific growth rates (mm mm−1 d−1) ranged from 0.013 to 0.016, and matched previous estimates of growth from field populations. Overall ecological performance
(survival + growth + reproduction) was similar for all food treatments, except senescent sheaths, which yielded a final mean
(±SD) dry biomass (0.4 ± 0.42 mg replicate−1) of amphipods significantly lower than that of other diets (1.7 ± 0.81 to 2.6 ± 0.69 mg replicate−1). Natural diets derived from decomposing cordgrass leaves can fulfill the nutritional requirements of U. spartinophila populations, but variation in initial amounts of living fungal biomass among the five experimental diets only partially explained
the responses of amphipods in our experiment. Structural characteristics and variation in rates of fungal occupation within
different portions of cordgrass leaves may affect the amphipod's ability to access plant production made available by decomposers.
Received: 12 December 1996 / Accepted: 18 December 1996 相似文献
9.
A. S. Grutter 《Marine Biology》1999,135(3):545-552
The dynamics of infestation by parasitic juveniles of gnathiid isopods were investigated at Lizard Island in the summer of
1997/1998 to determine when, and at what rate, they infest fishes. Variation in gnathiid abundance on wild-caught fish (Hemigymnus melapterus) between dawn and sunset was examined, and unparasitized H. melapterus in cages were exposed to gnathiids in the field for 4 h (8 h for fish sampled at 06:00 h) at five different times of the
day and night (10:00, 14:00, 18:00, 22:00, 06:00 hrs) on three reefs. To control for any potential effect of the cleaner-fish
Labroides dimidiatus, which consumes large numbers of gnathiids each day, sampling was carried out on reefs from which all cleaner-fish had been
removed. Gnathiid abundance decreased during the day. Standardized abundance per wild-caught fish was 1.9 times higher at
dawn than at sunset. Gnathiids successfully infested fish in cages. Sixty-one percent of the fish in cages were infested with
≥1 gnathiids, with 51% of the fish having between 1 and 4 gnathiids after 4 h exposure. Gnathiids infested fish both day and
night. The log10 (abundance +1) of gnathiids per caged fish varied significantly between time periods, with higher gnathiid numbers on fish
sampled at 18:00, 22:00, and 06:00 hrs than on fish sampled at 10:00 and 14:00 hrs. In contrast to gnathiid abundance on wild-caught
fish, the number of gnathiids on caged fish sampled at sunset was as high as that at dawn. The estimated mean (SE) cumulative
number of gnathiids per caged fish [mean size = 13.7 cm (±0.25)] per day was 7.8 (1.1); this is similar to the estimated mean
number of 7.3 gnathiids on similar-sized wild-caught fish at 6:00 hrs. The high infestation rate of gnathiids on caged fish
in the late afternoon contrasted with the low numbers on wild-caught fish at this time, suggesting that factors other than
infestation behaviour may be responsible for the low numbers of gnathiids on wild-caught fish in the afternoon.
Received: 19 August 1998 / Accepted: 1 June 1999 相似文献
10.
Predation on Euphausia pacifica by demersal fishes: predation impact and influence of physical variability 总被引:2,自引:0,他引:2
The importance of Euphausia pacifica Hansen to the demersal fish community off Sendai Bay, northern Japan, was studied based on a total of 256 trawl samples collected
during May, October and November, from 1989 to 1992. The samples were classified into 16 assemblages according to year, month
and depth. The importance of E. pacifica to the total diet of each of the assemblages was measured using an index considering both fish diet and species composition.
A total of 24 fish species out of 87 were found to ingest E. pacifica. Of these, Gadus macrocephaus and Theragra chalcogramma had the highest predation impact due to their dominance in the fish assemblages and the high proportion of E. pacifica in their diets. The contribution of E. pacifica to the total diet of the fish assemblage was highest in the shallow (≤300 m) regions during May, accounting for an average
of 38.5% for the 4 years. However, during May 1990, when the warm Kuroshio Extension prevailed, the contribution was higher
in the deep (>300 m; 22.6%) region, reflecting active and/or passive movements of E. pacifica. The average predation impact was maximal in the May/shallow assemblage (mean ± SE; 4.6 ± 1.4 kg wet wt km2 d−1) and was minimal in the November/shallow assemblage (0.4 ± 0.3). Annual estimates of consumption by demersal fish fishes
ranged from 43 to 128 metric tons, representing 15 to 64% of the annual commercial catch of E. pacifica by local fisheries. It is therefore suggested that the fisheries on E. pacifica have the potential to considerably impact the demersal fish assemblages.
Received: 3 December 1997 / Accepted: 10 June 1998 相似文献
11.
J. H. M. Kouwenberg H. I. Browman J. A. Runge J. J. Cullen R. F. Davis J.-F. St-Pierre 《Marine Biology》1999,134(2):285-293
The copepod Calanus finmarchicus Gunnerus is a key component of the planktonic food web in the Gulf of St. Lawrence, Canada. In this region, productivity-determining
biophysical interactions occur in the upper 0 to 30 m of the water column. The eggs and nauplii of C. finmarchicus are found in this layer. Measurements of the diffuse attenuation coefficients for solar ultraviolet-B radiation (280 to 320 nm,
UV-B) at various locations in this region indicated maximum 10% depths (the depth to which 10% of the surface energy penetrates)
of 3 to 4 m at a wavelength of 310 nm. This represents a significant percentage of the summer mixed-layer water column: organisms
residing in this layer are exposed to UV-B radiation. Laboratory experiments using a Xenon-arc-lamp based solar simulator
revealed that C. finmarchicus embryos exposed to UV-B exhibited high wavelength-dependent mortality. The strongest effects occurred under exposures to
wavelengths below 312 nm. A significant percentage of nauplii hatched from eggs exposed to these wavelengths exhibited malformations
indicative of errors in pattern formation during embryogenesis. At the shorter wavelengths (<305 nm), UV-B-induced mortality
was strongly dependent on cumulative exposure. The biological weighting function (BWF) derived for UV-B-induced mortality
in C. finmarchicus eggs is similar to that reported for naked DNA. This suggests that the UV-B-induced mortality effect on C. finmarchicus embryos is a direct result of DNA damage. There was no evidence of a detrimental effect of ultraviolet-A radiation (320 to
400 nm). Calculations based upon the BWF indicate that, under current noon surface irradiance, 50% of C. finmarchicus eggs located at or very near (within 10 cm) the ocean surface will be dead after 2.5 h of exposure. Under solar spectral
irradiance simulating a 20% decrease in ozone layer thickness, this time drops to 2.2 h. These are first-order estimates based
upon irradiance taken at a time of day during which the values would be maximal. Nonetheless, they illustrate the relative
changes in UV-B effects that will result from ozone layer depletions expected over the coming decades. It is also important
to point out that variability in cloud cover, water quality, and vertical distribution and displacement within the mixed layer,
can all have a greater effect on the flux of UV-B radiation to which C. finmarchicus eggs are exposed than will ozone layer depletion at these latitudes.
Received: 2 March 1998 / Accepted: 18 December 1998 相似文献
12.
K. A. Tricklebank 《Marine Biology》2000,136(2):337-348
Parma microlepis (Günther) were collected from Malabar, an urban location close to the centre of Sydney, Australia, and from Jervis Bay, a
reference location 170 km south of the city centre. At each location, fish were collected from two sites separated by 100
to 200 m. The ultrastructure of normal liver tissue is described based on 20 female fish collected from Jervis Bay, where
fish are known to be exposed to low levels of organochlorine contaminants. Alterations in the endoplasmic reticulum, mitochondria,
lysosomes and nuclei of hepatocytes were identified and quantified in the liver tissue of fish from this location and compared
to alterations in 20 female fish collected from Malabar, where fish are exposed to higher concentrations of organochlorine
pesticides such as DDT compounds. There were significant differences in the percentage of hepatocytes with swollen mitochondria
(F = 124.025, df = 2, 2, P = 0.008) and atypical nuclei (F = 22.198, df = 2, 2, P = 0.043) between sites (100 to 200 m apart), but there were no clear differences between the percentage of structural alterations
in the hepatocytes of P. microlepis from Jervis Bay and Malabar. Associations between liver morphology and the organochlorines aldrin, dieldrin, DDE and chlordane
were examined using a Pearson correlation matrix. Significant correlations were detected between the percentage of hepatocytes
with dilated endoplasmic reticulum and the concentrations of the pesticide aldrin (r = 0.600, df = 11, r
crit(α = 0.05) = 0.553). Significant associations were also detected between the percentage of hepatocytes with disorganised endoplasmic
reticulum and the concentrations of dieldrin and DDE residues in fish (r = 0.576, r = 0.567, respectively, df = 13, r
crit (α = 0.05) = 0.514). However, there was little evidence that ultrastructural alterations in fish responded to increasing concentrations
of these pesticides in a consistent dose-response manner.
Received: 20 October 1998 / Accepted: 24 November 1999 相似文献
13.
Population biology and antipredator defenses of the shallow-water Antarctic nudibranch Tritoniella belli 总被引:1,自引:0,他引:1
The circumpolar nudibranch Tritoniella belli Eliot occurs in abundance in shallow-water benthic communities of McMurdo Sound, Antarctica. Density estimates based on belt
transects averaged collectively 0.46 individuals m−2 at three study sites between depths of 6 and 30 m in November 1996. At two of the sites, population densities increased linearly
between 18 and 30 m depth (up to 0.7 and 1.15 individuals m−2 at 30 m depth). Individuals at all sites were rare or absent at depths shallower than 12 m. Size frequencies of individuals
at the sites were similar, and a pooled analysis revealed a unimodal distribution skewed highly towards juvenile size classes.
This suggests both recent recruitment and constant rates of mortality across size classes. The relationship between foot length
and wet weight best fits an exponential growth equation, indicative of an allometric growth pattern. Distribution of T. belli in the field suggests that it is a habitat and diet generalist. Potential invertebrate predators include sea anemones and
seastars, both of which co-occur in abundance in McMurdo Sound. Laboratory experiments indicate that the sea anemone Isotealia antarctica can capture and ingest T. belli. However, 70% of T. belli that are captured escape from the tentacles or, following ingestion, are rejected from the gastrovascular cavity. The seastars
Odontaster validus, Perknaster fuscus, and Acodontaster conspicuus, avoid contact with T. belli, but if forced into contact with mantle tissues, retract their tube-feet. Mucus secreted from the mantle tissues, coated
on to the tips of glass rods, and presented to seastar tube-feet, causes significantly longer tube-foot retraction times than
control rods. Moreover, pieces of freeze-dried krill coated with mantle mucus are consumed significantly less often than untreated
control pieces of krill by a benthic scavenging fish (Pseudotrematomas bernacchi). Employing seastar tube-foot retractions as a bioassay, we found the bioactive compound(s) are soluble in ethyl acetate,
indicating they are lipophilic or moderately hydrophilic in nature. Chemical defenses in the mucus of T. belli probably contribute to its high abundance in Antarctic benthic communities.
Received: 6 October 1997 / Accepted: 24 March 1998 相似文献
14.
Parental investment, potential reproductive rates, and mating system in the strawberry dart-poison frog, Dendrobates pumilio 总被引:1,自引:0,他引:1
We studied the effect of relative parental investment on potential reproductive rates (PRRs) to explain sex differences in
selectivity and competition in the dart-poison frog Dendrobates pumilio. We recorded the reproductive behavior of this species in a Costa Rican lowland rainforest for almost 6 months. Females spent
more time on parental care than males, and `time out' estimates suggest that PRRs of males are much higher than than those
of females, rendering females the limiting sex in the mating process. Males defended territories that provide suitable calling
sites, space for courtship and oviposition, and prevent interference by competitors. Male mating success was highly variable,
from 0 to 12 matings, and was significantly correlated with calling activity and average perch height, but was independent
of body size and weight. Estimates of opportunity for sexual selection and variation in male mating success are given. The
mating system is polygamous: males and females mated several times with different mates. Females were more selective than
males and may sample males between matings. The discrepancy in PRRs between the sexes due to differences in parental investment
and the prolonged breeding season is sufficient to explain the observed mating pattern i.e., selective females, high variance
in male mating success, and the considerable opportunity for sexual selection.
Received: 9 June 1998 / Received in revised form: 27 March 1999 / Accepted: 3 April 1999 相似文献
15.
Bi-directional sex change in a coral-dwelling goby 总被引:1,自引:0,他引:1
Philip L. Munday M. Julian Caley Geoffrey P. Jones 《Behavioral ecology and sociobiology》1998,43(6):371-377
Bi-directional sex change has recently been reported among obligate coral-dwelling gobies of the genus Gobiodon. However, neither the functional role of this pattern of sex change nor the frequency of sex change in either direction in
natural populations is known. We investigated the social structure and pattern of sex change of Gobiodon histrio at Lizard Island on the Great Barrier Reef. The social structure of G. histrio within coral colonies usually consisted of a single juvenile or a heterosexual adult pair. The size of adult social groups
was not constrained by coral colony size. In contrast to expectations for pair-forming species, G.␣histrio was primarily a protogynous hermaphrodite. All immature G. histrio were females and sex change from female to male occurred readily when two mature females were placed in a coral colony. In
addition, male G. histrio were able to change back to females when two mature males were placed in a coral. Sex change from female to male, however,
occurred with over twice the frequency of sex change from male to female. Where two males were placed in a coral colony, heterosexual
pairs were most frequently re-established by immigration of females from outside the treatment population. This pattern might
be predicted if sex change from male to female is more expensive than sex change from female to male for G. histrio. Where sex change is expensive, movement may be favoured over sex change, particularly where coral densities are high and
movement among corals incurs little mortality risk.
Received: 10 November 1997 / Accepted after revision: 16 May 1998 相似文献
16.
Seasonal variation in the relationship between cellular immune response and badge size in male house sparrows (Passer domesticus) 总被引:7,自引:2,他引:5
Guillermo Gonzalez Gabriele Sorci Florentino de Lope 《Behavioral ecology and sociobiology》1999,46(2):117-122
The immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signals of male quality because
steroid hormones (such as corticosteroids and sex steroids), which are supposed to favor the development of secondary sexual
traits, may also have immunosuppressive effects. Certain secondary sexual traits are not only used as mate choice signals
but also play a role as badges of status. In the house sparrow (Passer domesticus), males have a bib of black feathers which is used both as a signal of social status in male-male interactions and by females
when choosing a mate. We investigated the relationships between bib size and cellular immune response in male house sparrows
during and outside the reproductive season. Males with large badges were found to have lower levels of immunocompetence, as
assessed using a T-cell-mediated immunity assay, during the reproductive season, as predicted by the immunocompetence handicap
hypothesis. Conversely, in November, the correlation between badge size and cellular immune response was positive, possibly
reflecting the better access to trophic resources of large-badged dominant males in winter flocks.
Received: 24 September 1998 / Received in revised form: 2 February 1999 / Accepted: 14 February 1999 相似文献
17.
The genetic relationships among South-East Asian populations of the scad mackerels Decapterus macarellus, D. macrosoma and D. russelli (Pisces: Carangidae) were investigated. In 1995 and 1996, 216 fish were sampled in seven localities spanning the seas of
Indonesia and were examined for restriction-site polymorphisms using ten restriction enzymes for the mitochondrial (mt) DNA
control region, amplified by the polymerase chain-reaction. The inferred phylogeny of haplotypes led to the recognition of
three distinct mitochondrial lineages or phylads consistent with the distinctions of current taxonomy. All 15 mtDNA haplotypes
found in D. macarellus and all 9 haplotypes found in D. macrosoma were arranged as star-like clusters, suggesting recent evolutionary history. In contrast, the phylad formed by 6 haplotypes
in D. russelli from the Sulawesi Sea exhibited diffuse topology, suggesting that ancestral lineages of this species have been retained to
the present. Average nucleotide-divergence estimates between haplotypes of different phylads were between 0.042 and 0.135,
suggesting ancient separation, in consistency with published allozyme data. High levels of haplotype diversity, but no geographical
heterogeneity, was detected within D. macarellus from the Molucca Sea and the Banda Sea. Populations of D. macrosoma exhibited both significant differences between adjacent regions (Sunda Strait and Java Sea), and broadscale genetic homogeneity
from the South China Sea to the Sulawesi Sea via the Java Sea and Makassar Strait. The geographic isolation of the D. macrosoma population sampled in the Sunda Strait suggests that this region constitute a sharp transition zone between the Indian Ocean
and the Sunda Shelf. Near-monomorphism of haplotypes and low nucleotide diversity (d
X) were observed in the samples of D. macrosoma from the continental shelf (haplotype-diversity estimates, h, = 0.00 to 0.25 ± 0.08 and d
X = 0.000 to 0.002). This was in contrast to the comparatively high haplotype and nucleotide diversities observed in other
pelagic fish species including D. macarellus (h = 0.82 ± 0.05, d
X = 0.012 to 0.015) and D. russelli (h = 0.63 ± 0.12, d
X = 0.016), and in the oceanic D. macrosoma population sampled in the Sunda Strait (h = 0.67 ± 0.31, d
X = 0.005). We hypothesise that this may be the consequence of recent and perhaps repeated bottleneck events that have affected
the D. macrosoma population sampled on the continental shelf.
Received: 29 September 1997 / Accepted: 3 September 1999 相似文献
18.
Alternative male mating tactics in a cichlid, Pelvicachromis pulcher: a comparison of reproductive effort and success 总被引:2,自引:0,他引:2
Pelvicachromis pulcher is a small African cichlid which breeds in holes. Males may either reproduce monogamously (pair males), polygynously (harem
males), or be tolerated as helpers in a harem territory (satellite males). These helpers share in defence of the territory
against conspecifics, heterospecific competitors and predators. There are two male colour morphs that are fixed for life and
are apparently genetically determined. These differ in their potential mating strategy. Red morph males may become harem owners,
while yellow morph males may become satellite males, and males of both morphs may alternatively pair up monogamously. We compared
the reproductive effort and success of these three male reproductive strategies. Effort was measured as attack rates, time
expenditure and the risk of being injured or killed when attacking competitors or predators of three sympatric fish species.
Reproductive success was measured by observing how many eggs were fertilized by each male when this was possible, and by using
genetic markers. The number of fry surviving to independence of parental care was used as a criterion of success. The reproductive
success of harem males was 3.3 times higher than that of pair males and 7 times higher than that of the average satellite
male. Dominant satellite males, however, were as successful as monogamous pair males, using the measure of fertilized eggs.
To our knowledge, this has not been found previously in any fish species. Both harem and pair males had lower parental defence
costs per sired offspring, however, than males using the alternative satellite tactic. Defence effort was significantly related
to the risk of injury.
Received: 17 January 1996 / Accepted after revision: 9 June 1997 相似文献
19.
Between June 1994 and September 1996, a mark–recapture study was conducted in the Hinchinbrook Channel area of tropical northeastern
Australia to investigate the movements of the sparid fish Acanthopagrus berda. A total of 962 A. berda were tagged, 922 within a single estuary system, Deluge Inlet. No movements among estuaries were detected. Of the fish tagged
in Deluge Inlet, 12.9% were recaptured. Two movement regimes were detected: local movements (mostly <500 m) during non-spawning
times, and longer migrations (up to 3.12 km) during spawning seasons, to and from a spawning site at the estuary mouth. Although
there appeared to be a major spawning aggregation in the mouth of Deluge Inlet, ripe female A. berda were present in upstream sites, indicating that spawning probably occurs there also. This contrasts to the situation in South
Africa, where A. berda is reported to spawn only close to estuary mouths. Differences such as this highlight our limited knowledge of variations
in the reproductive biology of widespread species such as A. berda.
Received: 25 November 1997 / Accepted: 10 September 1998 相似文献
20.
Vermilion snapper (Rhomboplites aurorubens) were collected from four sites off the Atlantic coast of the USA and one site in the Gulf of Mexico to evaluate effective
population size and genetic stock structure. Previous studies had suggested geographic variation in the ratio of males to
females, so this population characteristic was explored in conjunction with the genetic analysis. Sex ratio varied greatly
among the five sample sites; males comprised 57% of samples in the Gulf of Mexico, while within the South Atlantic Bight they
comprised between 36% (Morehead City, North Carolina) and 53% (Carolina Beach, North Carolina) of samples. No clear geographic
trends in the sex ratio emerged; instead, it was found to vary with fish length, the percentage of males decreasing with increasing
size. Allelic variation assessed at seven dinucleotide microsatellite loci was large; gene diversities ranged from 0.43 to
0.95 and allelic counts from 7 to 39. Estimates of the effective population size ranged from 24 500 (based on the infinite-alleles
model) to 150 500 (based on the stepwise-mutation model). There was evidence for excess homozygosity within samples: estimates
of F
IS
(the correlation of alleles within individuals) ranged from 0.01 to 0.03 among the seven loci, and three estimates were significantly
greater than zero. Differentiation among localities was very weak, as estimates of F
ST
(the correlation of alleles within populations) were on the order of 0.001 to 0.002 and genetic distance estimates between
localities were not related to geographic distances. This suggested that vermilion snapper in the South Atlantic Bight (Cape
Hatteras, North Carolina to Cape Canaveral, Florida) and Gulf of Mexico are likely to consist of one genetic stock. Despite
the overall homogeneity, there were indications of a temporally dynamic local structure that would bear further examination.
Received: 6 July 1998 / Accepted: 9 February 1999 相似文献