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981.
The population of small copepod species (approximately <1 mm) were investigated during an annual cycle in Disko Bay, western
Greenland. The small species considered were Acartia longiremis, Pseudocalanus spp., Oithona spp., Oncaea spp., Microsetella spp., and Microcalanus spp. Most of the small species were present in the surface waters year round and numerically dominated the community, and
in biomass from late summer and throughout winter. Oithona spp. was numerically the main contributor, while Pseudocalanus spp. dominated in terms of biomass. In the uppermost 50 m, maximum abundance, biomass and secondary production were observed
in late September after the phytoplankton production practically had terminated and the winter initiated. The free spawning
Acartia longiremis showed a strong seasonal fluctuation in biomass and egg production, in contrast to the egg carrying species Pseudocalanus spp. and Oithona spp. These had a long spawning season and maintained a more stable biomass year round. Secondary production was estimated
by three different ways: (1) based on the obtained specific egg production rates, (2) a temperature dependent equation, and
(3) a multilinear regression taking temperature, body weight and chlorophyll into consideration. The contribution of the small
species was insignificant when compared to the large Calanus species during the spring- and post-bloom. However, during late summer and winter, where Calanus had left the upper water strata for hibernation, the small species played a crucial role in the pelagic carbon cycling. 相似文献
982.
The pelagic yellowtail kingfish Seriola lalandi has become a target species for aquaculture in Asia and Australasia. Australasian production is reliant on larviculture from
eggs of captive brood stock; however, knowledge regarding the nutritional requirements of larvae of this species is still
scarce, particularly in relation to lipids. As a first step in establishing these requirements, eggs and larvae from captive
S. lalandi brood stock were examined for differences in total protein, total lipid and lipid classes between individual spawning events,
over the spawning season, and during larval development from fertilisation to 15 days post hatch. Results indicate that total
protein egg−1 varied significantly between individual spawning events within a season, but neither total lipid nor total protein egg−1 varied significantly across the spawning season. Brood stock egg lipids were made up of approximately 60% phospholipid, 25%
wax and/or sterol esters (WE), 15% triacylglycerol (TAG), and small amounts of sterols and free fatty acids. During the early
larval period, both WE and TAG were utilised concurrently for energy. The larvae experienced very high mortality around 5–7 days
post hatch, which coincided with very low levels of all neutral lipid classes. Although many other factors may also influence
larval mortality, these results indicate that lipid provisioning may be an important factor in larval survival during the
critical period around first-feeding in this species. Examination of ratios of TAG:ST, often used as a condition index in
fish larvae, suggested that some of the larvae were suffering from starvation. However, as egg-derived WE appears to provide
a significant source of energy during the early larval period in S. lalandi, it is suggested that WE should be included in any index of larval nutritional state. 相似文献
983.
Kathleen S. Cole 《Marine Biology》2008,154(6):943-951
The Neotropical seven-spined gobies (tribe Gobiosomatini), including the Gobiosoma and Microgobius groups, constitute a speciose,
monophyletic gobiid taxon. In particular, member species of the Gobiosoma group exhibit a combination of behavioral diversification
and microhabitat specialization that may have played a major role in their collective rapid evolution and high rate of speciation.
Functional hermaphroditism, which is common among gobiids, can promote exploitation of patchily distributed micro-niches by
countering potential reductions in reproductive opportunities. However, the possible role of functional hermaphroditism in
the exploitation of microhabitats and rapid speciation in the Gobiosoma group is unknown. One member species, Tigrigobius multifasciatus, is a functional hermaphrodite. Two other Gobiosoma group species are functionally gonochoric (i.e., constant-sexed), but
exhibit transient hermaphroditic ovarian structure among immatures. In this study, ovarian morphology among immature and adult
females of several Gobiosoma group species was examined to see if hermaphroditic gonadal features are present. Although no
evidence of functional hermaphroditism in the form of precursive accessory gonadal structures (pAGS) associated with the adult
ovary was found among newly examined species, all species exhibited the transient expression of hermaphroditic gonadal features
associated with the immature ovary. In contrast, among six species of non-Gobiosomatini genera having no record of hermaphroditism,
none exhibited similar transient hermaphroditic features associated with the immature ovary. These findings suggest that hermaphroditism
may have been an ancestral trait which has been secondarily lost within some Gobiosoma group species. This study also shows
that ontogenetic and morphogenic processes within the gobiid reproductive system may provide new insights into the evolution
of life history traits and significantly further our understanding of the extraordinary evolutionary success of this group. 相似文献
984.
The Mytilus species complex consists of three closely related mussel species: Mytilus trossulus, Mytilus edulis, and Mytilus galloprovincialis, which are found globally in temperate intertidal waters. Introduction of one or more of these species have occurred world-wide
via shipping and aquaculture. Stable hybrid zones have developed in areas where these species have come into contact, making
the invasion process complex. On the east coast of Vancouver Island (VI), British Columbia (BC), Canada, the native (M. trossulus) and introduced species (M. edulis and M. galloprovincialis), as well as their hybrid offspring, occur sympatrically. This study used a common environment experiment to quantify growth
and survival differences among native, introduced, and introgressed mussels on VI. Mussels were collected from an area of
known hybridization and reared in cages from May to August 2006. The cages were deployed at a local site as well as a remote
site (approximately 150 km apart), and the mussels were genotyped at two species-specific loci. Growth and survival, as fitness
measures, were monitored: native, introduced, and introgressed individuals were compared between and within sites to determine
whether growth and survival were independent of site and genotype. Overall, mussels reared at Quadra Island performed better
than locally-reared mussels at Ladysmith. Specifically, introgressed mussels reared at Quadra Island performed better than
all genotypes reared at Ladysmith, as well as better than native mussels reared at Quadra Island. Differences in survival
and growth among the native, introduced and introgressed mussels may serve to explain the complex hybridization patterns and
dynamics characteristic of the VI introgression zone. 相似文献
985.
Rapid tissue reduction and recovery in the sponge <Emphasis Type="Italic">Aplysinella</Emphasis> sp.
We observed a pronounced, yet reversible tissue reduction in the tropical sponge Aplysinella sp. under non-experimental conditions in its natural habitat, after transfer into seawater tanks, as well as after transplantation
from deep to shallow water in the field. Tissue reduction resulted in the formation of small “reduction bodies” tightly attached
to the sponge skeleton. Although volume loss and gain were substantial, both tissue reduction and regeneration were often
remarkably rapid, occurring within few hours. Microscopic analysis of the reduction bodies revealed morphological similarities
to previously described sponge primmorphs, with densely packed archaeocytes and spherulous cells enclosed by a thin layer
of epithelial-like cells. Denaturing gradient gel electrophoresis (DGGE) revealed pronounced changes in the sponge-associated
microbial community upon tissue reduction during laboratory and field experiments and following changes in ambient conditions
after transplantation in the field. Generally, the microbial community associated with this sponge proved less stable, less
abundant, and less diverse than those of other, previously investigated Verongid sponges. However, one single phylotype was
consistently present in DGGE profiles of Aplysinella sp. This phylotype clustered with γ-proteobacterial sequences found previously in other sponge species of different taxonomic
affiliations and geographic provenances, as well as in sponge larvae. No apparent changes in the total secondary metabolite
content (per dry weight) occurred in Aplysinella sp. upon tissue reduction; however, comparative analysis of intact and reduced tissue suggested changes in the concentrations
of two minor compounds. Besides being ecologically interesting, the tissue reduction phenomenon in Aplysinella sp. provides an experimentally manipulable system for studies on sponge/microbe symbioses. Moreover, it may prove useful
as a model system to investigate molecular mechanisms of basic Metazoan traits in vivo, complementing the in vitro sponge
primmorph system currently used in this context. 相似文献
986.
Chemical and colloidal analyses of natural seep water collected from the exploratory studies facility inside Yucca Mountain,Nevada, USA 总被引:1,自引:0,他引:1
Cizdziel JV Guo C Steinberg SM Yu Z Johannesson KH 《Environmental geochemistry and health》2008,30(1):31-44
Yucca Mountain is being considered as a geological repository for the USA’s spent nuclear fuel and high-level nuclear waste.
Numerous groundwater seeps appeared during March 2005 within the exploratory studies facility (ESF), a tunnel excavated in
the mountain. Because of the relevance to radionuclide transport and unsaturated zone-modeling studies, we analyzed the seep
samples for major anions and cations, rare earth elements, and colloids. Major ion species and elemental concentrations in
seep samples reflect interaction of the water with the volcanic rock and secondary calcites. Elemental fractograms from flow-injection
field-flow fractionation ICP–MS scans detected Br, Ca, Cl, Cu, Fe, I, Mg, Si, Sr, W, and U at void fractions, suggesting they
may be present in the form of dissolved anions. Colloids approximately 10 nm in hydrodynamic diameter, possibly calcite, were
also present in the seepage samples. Geochemical calculations indicate, however, these may be an artifact (not present in
the groundwater) which arose because of loss of CO2 during sample collection and storage. 相似文献
987.
Behavioral ecologists are often faced with a situation where they need to compare the central tendencies of two samples. The
standard tools of the t test and Mann–Whitney U test (equivalent to the Wilcoxon rank-sum test) are unreliable when the variances of the groups are different. The problem
is particularly severe when sample sizes are different between groups. The unequal-variance t test (Welch test) may not be suitable for nonnormal data. Here, we propose the use of Brunner and Munzel’s generalized Wilcoxon
test followed by randomization to allow for small sample sizes. This tests whether the probability of an individual from one
population being bigger than an individual from the other deviates from random expectation. This probability may sometimes
be a more clear and informative measure of difference between the groups than a difference in more commonly used measures
of central tendency (such as the mean). We provide a recipe for carrying out a statistical test of the null hypothesis that
this probability is 50% and demonstrate the effectiveness of this technique for sample sizes typical in behavioral ecology.
Although the test is not available in any commercial software package, it is relatively straightforward to implement for anyone
with some programming ability. Furthermore, implementations in R and SAS are freely available on the internet. 相似文献
988.
Sergio Castellano Valentina Marconi Valeria Zanollo Giulia Berto 《Behavioral ecology and sociobiology》2009,63(8):1109-1118
As in many lekking anurans, Italian treefrog males use two mating tactics: they can attract females by calling vigorously
or be satellites, that is, they can remain silent in proximity of a calling male and try to intercept females attracted by
their neighbour. We investigated the factors that affected the expression of this mating tactic. Consistent with the conditional
mating tactic hypothesis, satellites were smaller than average and smaller than their parasitised calling males. They spent
a larger-than-average number of nights at the breeding site, where most of them were also observed calling. Moreover, satellites
showed lower call rates and lower mating success than those of males they parasitise but not lower than those of males they
did not parasitise. Overall, these results, together with those derived from the analyses of the seasonal and spatial distribution
of males, provide evidence for a non-random association between satellites and calling males and are consistent with the hypothesis
that satellites have spectral and temporal acoustic preferences that parallel those of females. By adopting the less-successful
satellite mating tactic, competitively inferior males can nevertheless maximise their potential reproductive fitness by sexually
parasitising the most attractive chorusing males. 相似文献
989.
Oliver Behr Mirjam Knörnschild Otto von Helversen 《Behavioral ecology and sociobiology》2009,63(3):433-442
In many animal species, individuals compete for resources but avoid escalated conflicts by threat displays, i.e. a mutual
signalling behaviour that enables the opponents to predict the outcome of the conflict without the necessity of actual fighting.
For example, territory holders may use acoustic signals to communicate not only their own identity and the borders of their
territory but also their competitive quality, fighting ability and motivation. Here, we show that male sac-winged bats, Saccopteryx bilineata, adjust their vocal territorial displays according to the fundamental frequency of territorial songs of their opponents.
In playback experiments with territorial males, low-frequency stimuli elicited a higher territorial song rate and length than
high-frequency stimuli. Male S. bilineata that sing more often and with lower fundamental frequencies have been shown to sire more offspring than their competitors.
Fundamental frequency of territorial songs, hence, may reveal male quality and, consequently, the resulting threat posed to
competing males. We argue that this is reflected in the increased response of competitors to low-frequency territorial songs
shown here. Such competitive signalling behaviour has been shown in a few mammal species like red deer and baboons but, thus
far, not in bats.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
990.
A common explanation for hunting in groups is that doing so yields a greater per capita caloric benefit than hunting solitarily.
This is logical for social carnivores, which rely exclusively on meat for energy, but arguably not for omnivores, which obtain
calories from either plant or animal matter. The common chimpanzee, Pan troglodytes, is one of the few true omnivores that regularly hunts in groups. Studies to date have yielded conflicting data regarding
the payoffs of group hunting in chimpanzees. Here, we interpret chimpanzee hunting patterns using a new approach. In contrast
to the classical assumption that hunting with others maximizes per capita caloric intake, we propose that group hunting is
favored because it maximizes an individual’s likelihood of obtaining important micronutrients that may be found in small quantities
of meat. We describe a mathematical model demonstrating that group hunting may evolve when individuals can obtain micronutrients
more frequently by hunting in groups than by hunting solitarily, provided that group size is below a certain threshold. Twenty
five years of data from Gombe National Park, Tanzania are consistent with this prediction. We propose that our ‘meat-scrap’
hypothesis is a unifying approach that may explain group hunting by chimpanzees and other social omnivores. 相似文献