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901.
We examined the mating behaviour of the New Zealand ocypodid crab Macrophthalmus hirtipes in the laboratory between February and June 1998. This species has a discrete breeding season. Mating and moulting were not
linked and only intermoult females with mobile gonopore opercula were attractive to males. Allometry and compatibility of
gonopods and gonopores of different-sized crabs was investigated. Under laboratory conditions, the opercula of intermoult
females remained mobile on average for 11.4 d, but the duration of receptivity did not appear to be under female control.
The operational sex ratio in the laboratory fluctuated greatly, but was always male-dominated. During the period of opercular
mobility, females mated many times with several different males. Matings in the absence of burrows were relatively short (mean
duration = 23 min, max. = 122 min) and the mating behaviour of M. hirtipes lacked courtship and mate-guarding. Males used a search-intercept method to acquire mates, with very low levels of intrasexual
competition. There was no evidence of mate preference in M. hirtipes, and males spent just as long mating with ovigerous females as with non-ovigerous ones. Although M. hirtipes has ventral-type spermathecae, as do several other ocypodid crabs, it is unclear whether this promotes last-male sperm precedence.
The role of burrows in modifying the mating behaviour of M. hirtipes in the field remains to be established.
Received: 7 January 2000 / Accepted: 5 June 2000 相似文献
902.
The Chilean intertidal Lottiidae limpet fauna consists of at least nine species, grouped into the monophyletic taxon Scurria and a single taxon preliminarily designated as `Lottia' orbignyi (Dall). Within the Scurria clade, the most basal species are Scurria variabilis (Sowerby), S. viridula (Lamarck), and S.zebrina (Lesson), and among the most crown groups are S. ceciliana (Orbigny) and S. araucana (Orbigny). This phylogenetic information, obtained by the analysis of molecular characters (16S mtDNA), provides a framework
for a comparative study of behavioral characters. In this study, we analyze the escape responses of two basal limpet species
(`L.' orbignyi and S. viridula) and two derived limpet species (S. araucana and S. ceciliana) in the presence of the limpet predatory seastar Heliaster helianthus (Lamarck) and the limpet non-predatory seastars Stichaster striatus Muller and Troschel and Patiria chilensis Lutken. Neither P.chilensis nor Stichaster striatus induced escape responses such as those observed with the predatory H. helianthus. Moreover, in the presence of H. helianthus, basal and derived limpet species differed significantly in the percentage of individuals responding, reaction time, and
duration of the response. The basal species `L.' orbignyi and Scurriaviridula exhibited instantaneous and vigorous locomotor responses, whereas the derived species S. araucana and S. ceciliana displayed no locomotor responses. The same pattern was found in responses to H. helianthus homogenates. The results strongly suggest a correlation between phylogeny and anti-predator escape responses to the seastar
H. helianthus. Alternative escape responses have evolved for basal and derived species within the Chilean clade.
Received: 27 April 2000 / Accepted: 16 August 2000 相似文献
903.
The isopod Munnopsurus atlanticus occupies bathyal depths in both the Bay of Biscay (NE Atlantic; between 383 and 1022 m) and in the Catalan Sea (Northwestern
Mediterranean; between 389 and 1859 m). The species was dominant in both assemblages, reaching bathymetric peaks of abundance
on the upper part of the continental slope (400 m depth) in the Bay of Biscay and at ˜600 m in the Catalan Sea. Both the Atlantic
and the Mediterranean populations are bivoltines. Demographic analysis of the Bay of Biscay population revealed the production
of two generations per year with different potential longevity (5 mo for G1 and 11 mo for G2). The mean cohort-production interval (CPI) was estimated at 8 mo, and results of the demographic analysis were also used
to estimate production for the Catalan Sea populations. Mean annual density (D) and biomass (B) were higher in the Bay of
Biscay (D = 356.7 individuals 100 m−2; B = 0.803 mg dry wt m−2 yr−1) than in the Mediterranean (D = 16.3 individuals 100 m−2; B = 0.078 mg dry wt m−2 yr−1). Also, mean annual production was an order of magnitude higher in the Atlantic (between 4.063 and 4.812 mg dry wt 100 m−2 yr−1 depending on the method used) than in the Catalan Sea (between 0.346 and 0.519 mg dry wt 100 m−2 yr−1). M. atlanticus feeds on a wide variety of benthic and pelagic food sources. In both study areas, phytodetritus was not important in the
diet of M. atlanticus. In contrast, gut-content data suggested an indirect coupling with phytoplankton production in both areas via foraminiferans.
The life history and the recorded production are considered in respect to both the dynamics and levels of primary production
and the total mass flux in the respective study areas. Differences in the secondary production of both populations seemed
to be more consistently explained by differences in total mass flux than by differences in the primary production levels;
this is also consistent with the variety of food sources exploited by M. atlanticus.
Received: 22 February 1999 / Accepted: 3 February 2000 相似文献
904.
The benthic response to a plume front was studied in two areas of the northern Adriatic (Mediterranean Sea) differently influenced
by the Po River freshwater input. Sediment samples were collected in June 1996 and February 1997 from 12 stations. The adopted
sampling strategy was able to identify the front line in real time by satellite images and to locate sampling stations along
an inner–outer plume gradient in order to cover the benthic area beneath the river plume, where enhanced biological production
was expected, and open-sea sediments not directly influenced by freshwater inputs. Meiofaunal parameters were compared to
the physical conditions and to phytodetritus inputs, organic matter accumulation and bacterial secondary production. The sediments
of the Adriatic Sea were characterised by high concentrations of phytopigments (0.6 to 13.9 μg g−1 for chlorophyll a and 1.2 to 17.7 μg g−1 for phaeopigments) and biopolymeric organic carbon (0.15 to 3.02 mg g−1). The plume system extended for a large sector of the northern Adriatic. In the northern area, a large and highly dynamic
plume area was coupled with a sediment organic matter concentration significantly higher than in open-sea sediments. In the
southern sector, where the plume area and the front line did not change markedly during the year, plume–benthic coupling was
evident only in the sediments beneath the front, and corresponded to phaeopigment accumulation. Bacterial parameters and secondary
production were high and significantly higher in the frontal area than at open-sea stations. Meiofauna density (1342 to 8541
ind. 10 cm−2) did not change either by season or between areas and was significantly correlated with phaeopigments and bacterial secondary
production. Meiofauna displayed different responses to plume inputs in the two sampling areas. In the northern sector, meiofauna
density was coupled with organic matter distribution and displayed highest values beneath the plume. In the southern sector,
the densities of copepods, turbellarians and kinorhynchs displayed highest values under the front in summer, and the same
applied to total meiofauna density in winter. Juvenile decapods and copepod nauplii significantly increased their densities
in sediments beneath the front. Data presented in the present study suggest that plume inputs and frontal systems, enhancing
phytodetritus accumulation and benthic bacterial response, might influence density, composition and distribution of meiofaunal
assemblages. As river plumes are highly variable systems affecting the trophic characteristics of the sediments underneath,
their dynamics should be considered when analysing mesoscale spatial changes of meiofaunal assemblages.
Received: 30 November 1999 / Accepted: 24 May 2000 相似文献
905.
Western sandpiper (Calidris mauri) predation was examined by concurrent experiments and direct observations of foraging behaviour on high intertidal mudflats
of the Fraser River estuary, British Columbia. Western sandpipers foraged by either “pecking” on the surface (64% of observational
time) or probing into sediment (29%). The first experiment (probe-mark method) consisted of collecting small-volume cores
(21.2 cm3) of probed (experimental) and non-probed (control) sediment on the tidal flat, following a 22.5-min feeding period. The second
experiment (exclosure method) involved deploying exclosures immediately prior to the feeding period and subsequent collection
of cores from inside (control) and outside (experimental) the exclosures. Sediment cores were analysed for both macrofaunal
and meiofaunal size fractions. Comparisons between macro- and meiofaunal invertebrate densities in experimental and control
sediments revealed significant differences, attributed to shorebird predation, for both experiments. The probe-mark experiment
detected the removal of large infaunal polychaetes (∼ 20 mm), while the exclosure experiment showed depletion of epifaunal
harpacticoid copepods (0.063–0.5 mm). Predation on macrofaunal cumaceans was detected in both experiments. Invertebrates selected
by western sandpipers neither fell within traditional infaunal size classifications (macro- vs. meiofauna; 500 μm delineation)
nor corresponded to the highest densities of taxa. Rather, inference from experimental results and observations is that western
sandpipers forage in two modes, by: (1) surface gleaning of epibenthic copepods and cumaceans in the macro- and meiofaunal
size ranges and (2) selective probing for larger infauna, such as polychaetes. These findings were facilitated by the combination
of methodologies employed.
Received: 29 December 1999 / Accepted: 11 September 2000 相似文献
906.
Maternal investment in rhesus macaques (Macaca mulatta): reproductive costs and consequences of raising sons 总被引:1,自引:0,他引:1
Maternal investment in offspring is expected to vary according to offspring sex when the reproductive success of the progeny
is a function of differential levels of parental expenditure. We conducted a longitudinal investigation of rhesus macaques
to determine whether variation in male progeny production, measured with both DNA fingerprinting and short tandem repeat marker
typing, could be traced back to patterns of maternal investment. Males weigh significantly more than females at birth, despite
an absence of sex differences in gestation length. Size dimorphism increases during infancy, with maternal rank associated
with son’s, but not daughter’s, weight at the end of the period of maternal investment. Son’s, but not daughter’s, weight
at 1 year of age is significantly correlated with adult weight, and male, but not female, weight accounts for a portion of
the variance in reproductive success. Variance in annual offspring output was three- to fourfold higher in males than in females.
We suggest that energetic costs of rearing sons could be buffered by fetal delivery of testosterone to the mother, which is
aromatized to estrogen and fosters fat accumulation during gestation. We conclude that maternal investment is only slightly
greater in sons than in daughters, with mothers endowing sons with extra resources because son, but not daughter, mass has
ramifications for offspring sirehood. However, male reproductive tactics supersede maternal investment patterns as fundamental
regulators of male fitness.
Received: 23 July 1999 / Received in revised form: 23 February 2000 / Accepted: 13 March 2000 相似文献
907.
Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive
rate (PRR) of the choosing sex relative to that of the chosen sex, and the variation in quality of potential mates. This experimental
study tested how these factors affected choosiness in male and female sand gobies, Pomatoschistus minutus. We manipulated relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or
female was offered a choice between two mates with either a small or a large difference in body length representing a small
or a large variation in mate quality. Choosiness was measured as (1) preference for the larger mate, and (2) as whether or
not spawning occurred with the smaller mate, while the larger mate was visible but screened off. We found that females preferred
large males, and that their level of choosiness was affected by variation in male quality, but not by their own relative PRR.
Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with
their provided partner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative
PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one
important factor explaining the observed sex difference in choosiness.
Received: 17 April 2000 / Revised: 24 June 2000 / Accepted: 17 July 2000 相似文献
908.
In the meerkat (Suricata suricatta), a cooperative mongoose, pups follow potential feeders while the group is foraging and emit incessant calls when soliciting
food from them. In contrast to a ’stationary’ brood of chicks, in which nestlings are fed at a fixed location, meerkat pups
are ’mobile’ and become spread out. The question arises whether meerkat pups that experience different constraints to those
facing chicks have evolved similar begging strategies. This paper describes the vocalisations that meerkat pups emit in the
context of begging and investigates the influence of these calls on food allocation by older group members and on the behaviour
of littermates. Meerkat pups use two types of calls when soliciting food from a potential feeder. The most common is a ’repeat’
call, which pups emit continuously when following an older forager over several hours a day. In addition, when a potential
feeder finds a prey item, the pups next to it emit a bout of calls with increased calling rate, amplitude and fundamental
frequency, termed ’high-pitched’ calls. Observations, together with playback experiments, showed that more prey was allocated
to pups that called longer and more intensely. The pup closest to a feeder was almost always fed. The probability of emitting
high-pitched calls did not depend on the time since a pup had received food, and the change from repeat to high-pitched calls
occurred suddenly. The main function of the high-pitched call, therefore, does not appear to be to signal a pup’s hunger state.
More likely, the two calls, in the context of begging, may be an adaptation to energetic constraints in a mobile feeding system.
Pups, which are dispersed during foraging, may emit repeat calls over long periods to prevent potential feeders from eating
all the prey themselves. At the moment a potential feeder finds prey, pups may give the more intense high-pitched calls to
direct feeders to bring the food item to them and not to a littermate. Therefore, unlike the stationary feeding system where
chicks emit one type of begging call when the feeder approaches the nest, meerkats, with a mobile feeding system, have evolved
two discrete types of vocalisations in the context of begging.
Received: 22 November 1999 / Revised: 1 July 2000 / Accepted: 17 July 2000 相似文献
909.
Weather-mediated natural selection on arrival time in cliff swallows (Petrochelidon pyrrhonota) 总被引:2,自引:0,他引:2
An unusually long period of cold weather in May 1996 caused extensive mortality among insectivorous cliff swallows (Petrochelidon pyrrhonota) in the northern and central Great Plains. We analyzed how viability selection affected spring arrival time in a migratory
Nebraska population by comparing capture histories of survivors with those of birds known to have died and by documenting
how arrival time changed in the year following the selection event. Surviving birds had significantly later first-capture
dates (an index of arrival time) in the years prior to selection than those that died; a significant selection differential
suggested directional selection for birds that arrived later. Colony sites were occupied significantly later following the
selection event, and the distribution of first-capture dates in the season after selection was significantly shifted toward
later arrivals. Offspring of the survivors tended to arrive later than birds of the same age prior to the selection event.
While major weather-caused mortality events of this magnitude are rare in the study area, spells of cold weather severe enough
to cause limited mortality are frequent in April and early May. At least 25 probable mortality events of varying severity
were identified in the last 50 years based on climatological data. Periodic weather-mediated selection against early arrival
constrains the cliff swallow’s breeding season and may partly prevent directional selection for earlier nesting.
Received: 19 October 1999 / Received in revised form: 15 January 2000 / Accepted: 24 January 2000 相似文献
910.
Male willow warblers have song repertoires which vary in complexity along several dimensions. We examined whether female choice,
as measured by date of pairing, was based on these song characteristics in 4 different years. Pairing date was negatively
correlated with song repertoire size in 1 year, and with song versatility in another year, but there was no consistent effect
of any song characteristic on pairing throughout the years or in the pooled sample. The variable that best explained how soon
a male pairs is male arrival date (only males that had settled territories before the first female arrived were considered
in the analysis). This correlation is consistently significant in all years. This is most parsimoniously interpreted as females
choosing some habitat characteristic in the same way that males do. A small percentage of males (8.3%) attracted and paired
with a second female. The likelihood of becoming polygynous was not explained by any measured song characteristic, but it
was related to arrival date: early males were more likely to pair with two females. Males with large repertoires fledged more
young in their primary nests, and there was a trend for the offspring of these males to have a greater probability of being
recruited into the population. In conclusion, the results show that in most years there is no sexual selection by female preference
on song characteristics, although the data on reproductive success is consistent with the idea of repertoire size being an
indicator of male quality.
Received: 4 June 1999 / Received in revised form: 1 December 1999 / Accepted: 31 December 1999 相似文献