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1.
Carnivorous zooplankton is a key element to the energy transfer through the arctic food web, linking lipid rich herbivores to the top predators. We investigated the growth and lipid dynamic of the Arctic pelagic amphipod Themisto libellula in Kongsfjorden (Svalbard, 79°N) from May to October 2007. Additional samplings were performed in spring and summer 2006 and further north in Rijpfjorden (80°N), in September 2006 and 2007. In Kongsfjorden, the first free-swimming stages (3 mm) appeared early May and reached their adult length (25 mm), in October. During their first year, they grew according to a Von Bertalanffy model and most probably constituted a single cohort. Juveniles had the highest growth rate (0.19 mm day−1) and revealed relatively low total lipid (TL) content (about 2.5% wet weight (WW)) with phospholipids as the major lipid class. Sub-adults showed a distinct decrease of growth rates which coincided with the increase of neutral lipid storage, reflecting a switch in energy allocation, from somatic growth to lipid storage. Indeed wax esters (WE) increased up to 48.5% TL on average in adults in 2006 while triacylglycerols (TAG) remained almost constant below 25.2% TL. The absence of lipid accumulation (in disproportion of the weight) in 2007 could be explained by a higher metabolism of T. libellula or preys of lower quality. In Rijpfjorden, adults in their second year continued accumulating lipid (up to 10% WW) with high and similar proportions of both lipid classes, WE and TAG. We highlighted that T. libellula exhibited a variable lipid metabolism along its life cycle depending on its physiological needs and environmental conditions. 相似文献
2.
Life-history features of the sympatric amphipods Themisto pacifica and T. japonica in the western North Pacific were analyzed based on seasonal field samples collected from July 1996 through July 1998, and data from laboratory rearing experiments. T. pacfica occurred throughout the year, with populations peaking from spring to summer. In contrast, T. japonica were rare from autumn to early winter, but became abundant in late winter to spring. Mature T. pacifica females and juveniles occurred together throughout the year, indicating year-round reproduction. Mature T. japonica females were observed only in spring, and juveniles occurred irregularly in small numbers, suggesting limited, early-spring reproduction in this study area. Size composition analysis of T. pacifica identified a total of eight cohorts over the 2 years of the study. Due to the smaller sample size and rarity of mature females (>9.6 mm) and males (>7.1 mm), cohort analyses of T. japonica were not comparable. Laboratory rearing of specimens at 2°C, 5°C, 8°C and 12°C revealed that a linear equation best expressed body length growth by T. pacifica, while a logistic equation best expressed body length growth by T. japoncia. Combining these laboratory-derived growth patterns with maturity sizes of wild specimens, the minimum and maximum generation times of females at a temperature range of 2–12°C were computed as 32 days (12°C) and 224 days (2°C), respectively, for T. pacifica, and 66 days (12°C) and 358 days (2°C), respectively, for T. japonica. The numbers of eggs or juveniles in females marsupia increased with female body length and ranged from 23 to 64 for T. pacifica and from 152 to 601 for T. japonica. Taking into account the number of mature female instars, lifetime fecundities were estimated as 342 eggs for T. pacifica and 1195 eggs for T. japonica. Possible mechanisms for the coexistence of these two amphipods in the Oyashio region are also discussed.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
3.
Morphological and behavioural traits can serve as anti-predator defence either by reducing detection or recognition risks,
or by thwarting initiated attacks. The latter defence is secondary and often involves a ‘startle display’ comprising a sudden
release of signals targeting more than one sensory modality. A suggested candidate for employing a multimodal defence is the
peacock butterfly, Inachis io, which, by wing-flicking suddenly, produces sonic and ultrasonic sounds and displays four large eyespots when attacked. The
eyespots make small birds retreat, but whether the sounds produced thwart predator attacks is largely unknown. Peacocks hibernate
as adults in dark wintering sites and employ their secondary defence upon encounter with small rodent predators during this
period. In this study, we staged predator–prey encounters in complete darkness in the laboratory between wild mice, Apodemus flavicollis and Apodemus sylvaticus, and peacocks which had their sound production intact or disabled. Results show that mice were more likely to flee from sound-producing
butterflies than from butterflies which had their sound production disabled. Our study presents experimental evidence that
the peacock butterfly truly employs a multimodal defence with different traits targeting different predator groups; the eyespots
target birds and the sound production targets small rodent predators. 相似文献
4.
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
5.
The genetic population structures of Atlantic northern bluefin tuna ( Thunnus thynnus thynnus) and albacore ( T. alalunga) were examined using allozyme analysis. A total of 822 Atlantic northern bluefin tuna from 18 different samples (16 Mediterranean, 1 East Atlantic, 1 West Atlantic) and 188 albacore from 5 samples (4 Mediterranean, 1 East Atlantic) were surveyed for genetic variation in 37 loci. Polymorphism and heterozygosity reveal a moderate level of genetic variability, with only two highly polymorphic loci in both Atlantic northern bluefin tuna ( FH* and SOD- 1*) and albacore ( GPI- 3* and XDH*). The level of population differentiation found for Atlantic northern bluefin tuna and albacore fits the pattern that has generally been observed in tunas, with genetic differences on a broad rather than a more local scale. For Atlantic northern bluefin tuna, no spatial or temporal genetic heterogeneity was observed within the Mediterranean Sea or between the East Atlantic and Mediterranean, indicating the existence of a single genetic grouping on the eastern side of the Atlantic Ocean. Very limited genetic differentiation was found between West Atlantic and East Atlantic/Mediterranean northern bluefin tuna, mainly due to an inversion of SOD- 1* allele frequencies. Regarding albacore, no genetic heterogeneity was observed within the Mediterranean Sea or between Mediterranean and Azores samples, suggesting the existence of a single gene pool in this area. 相似文献
6.
Bearded vultures (<Emphasis Type="Italic">Gypaetus barbatus</Emphasis>) prefer fatty bones 总被引:1,自引:0,他引:1
Antoni Margalida 《Behavioral ecology and sociobiology》2008,63(2):187-193
In animal species, prey processing and the provisioning of nutrients are subject to several constraints related with finding,
ingesting and processing food. In most bird species, these constraints are obvious as a consequence of food morphology. In
the case of the bearded vulture (Gypaetus barbatus), in comparison with other species, its behavioural and physiological adaptations apparently allow this vulture to ingest
bone remains irrespective of their morphology. Here, by comparing bones delivered to the nest to be consumed (selected) and
remains found at an experimental feeding station and at bone-breaking sites or ossuaries (rejected), I tested whether bearded
vultures are capable of choosing from among the various anatomical parts of an animal carcass in relation to their fatty acid
content (nutrient concentration hypothesis), their size (width-reduction hypothesis) or both. The results suggest that bearded
vultures prefer the fatty anatomical parts (with a high percentage of oleic acid) of an animal carcass regardless of bone
length, although bone morphology as a consequence of handling efficiency or the ingestion process may also play a secondary
role in food selection. The close association between the bones selected and their high fat value implies an optimisation
of foraging time and of the increased energy gained from the food. This is in line with selective foraging to redress specific
nutritional imbalances (nutrient concentration hypothesis) and, secondarily, the width-reduction hypothesis. 相似文献
7.
Changes in the protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Octopus vulgaris and O. defilippi tissues (gonad, digestive gland and muscle) during sexual maturation (spermatogenesis and oogenesis) were investigated. Both species showed an increase of amino acids and protein content in the gonad throughout sexual maturation (namely in oogenesis), but allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids in the three tissues were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and alanine. With respect to carbon compounds, a significant increasing trend (P<0.05) in the lipid and fatty acid contents in the three tissues was observed, and, consequently, there was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production both Octopus species use energy directly from food, rather than from stored products. This direct acquisition model contrasts with the previous model for Octopus vulgaris proposed by ODor and Wells (1978: J Exp Biol 77:15–31). Most of saturated fatty acid content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid content as 18:1 and 20:1 and polyunsaturated fatty acid content as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). Though cholesterol is an important precursor of steroid hormones, this sterol content exhibited variations that do not seem to be related with the maturation process. Moreover, significant differences (P<0.05) were obtained between genders, suggesting that perhaps there is a greater physiological demand for cholesterol during spermatogenesis than oogenesis. If the component sterols of octopus are of a dietary origin, considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. The glycogen reserves increased significantly in the gonad and decreased significantly (P<0.05) in the digestive gland and muscle of O. vulgaris (these trends were not evident in O. defilippi). Glycogen may play an important role in the maturation process and embryogenesis of these organisms, because carbohydrates are precursors of metabolic intermediates in the production of energy. It was evident that sexual maturation had a significant effect upon the gonad energy content, but the non-significant energy variation (P>0.05) in the digestive gland and muscle revealed no evidence that storage reserves are transferred from tissue to tissue. The biochemical composition of digestive gland and muscle may not be influenced by sexual maturation, but rather by other biotic factors, such as feeding activity, food availability, spawning and brooding.Communicated by S.A. Poulet, Roscoff 相似文献
8.
10.
Among the diverse patterns of energy allocation to the offspring of gastropods, the presence of egg capsules to protect embryos
is common. Females of the edible snail Zidona
dufresnei attach egg capsules to hard substrates in shallow Argentine Patagonian waters (40°45′S, 64°56′W) during spring-summer. Embryonic
development takes about 30 days at 22°C. In this study, three likely capsule predator species and the marks left by each on
egg capsule walls were identified in laboratory experiments in February 2010. Abundances of predators and egg capsules with
evidence of predation were assessed in the field in the summers of 2010 and 2011. Under laboratory conditions (N = 10 replicates per treatment and control), the predation rate by the chiton Chaetopleura
isabellei was the highest (up to 90%), followed by the gastropod Tegula
patagonica and the crab Neohelice
granulata (~20% each). Nearly 60% of 41 capsules found in the field showed signs of predation. According to the marks identified in
the laboratory, C. isabellei was responsible for 79% of this predation, and T. patagonica for the rest. Predation appears to be important during the encapsulated early life and could be an agent for selecting for
resistant capsule walls and a relatively shorter development time. 相似文献
11.
The influence of abiotic factors on the establishment and success of invasive species is often difficult to determine for
most marine ecosystems. However, examining this relationship is critical for predicting the spread of invasive species and
predicting which habitats will be most vulnerable to invasion. Here we examine the mortality and physiological sensitivity
to salinity of adult colonies of the colonial ascidians Botryllus schlosseri and Botrylloides violaceus. Adult colonies of each species were exposed to abrupt changes in salinity (5, 10, 15, 20, 25, 30 psu) in the laboratory.
Salinity ranges used in the laboratory corresponded with those of the field distributions of B. violaceus and B. schlosseri in the Great Bay Estuary, NH. Heart rate was used as a proxy for health to assess the condition of individual colonies. Heart
rates were monitored daily for approximately 2 weeks. Results revealed that both species experienced 100% mortality after
1 day at 5 psu and that their heart rates declined with decreasing salinity. Heart rates of B. schlosseri remained consistent between 15 and 30 psu and slowed at 10 psu. Heart rates of B. violaceus remained constant between 20 and 30 psu, but slowed at 15 psu. These laboratory results corresponded to the distribution
of these species in estuaries, indicating salinity is a key factor in the distribution and dominance of B. schlosseri and B. violaceus among coastal and estuarine sites. Furthermore, physiological differences to salinity were found between colonies of B. schlosseri in the Venetian Lagoon and colonies in Portsmouth Harbor, suggesting adaptation to environmental variables. 相似文献
12.
We conducted grazing experiments with the three marine cladoceran genera Penilia, Podon and Evadne, with Penilia avirostris feeding on plankton communities from Blanes Bay (NW Mediterranean, Spain), covering a wide range of food concentrations (0.02–8.8 mm3 l–1, plankton assemblages grown in mesocosms at different nutrient levels), and with Podon intermedius and Evadne nordmanni feeding on the plankton community found in summer in Hopavågen Fjord (NE Atlantic, Norway, 0.4 mm3 l–1). P. avirostris and P. intermedius showed bell-shaped grazing spectra. Both species reached highest grazing coefficients at similar food sizes, i.e. when the food organisms ranged between 15 and 70 µm and between 7.5 and 70 µm at their longest linear extensions, respectively. E. nordmanni preferred organisms of around 125 µm, but also showed high grazing coefficients for particles of around 10 µm, while grazing coefficients for intermediate food sizes were low. Lower size limits were >2.5 µm, for all cladocerans. P. avirostris showed upper food size limits of 100 µm length (longest linear extension) and of 37.5 µm particle width. Upper size limits for P. intermedius were 135 µm long and 60 µm wide; those for E. nordmanni were 210 µm long and 60 µm wide. Effective food concentration (EFC) followed a domed curve with increasing nutrient enrichment for P. avirostris; maximum values were at intermediate enrichment levels. The EFC was significantly higher for P. intermedius than for E. nordmanni. With increasing food concentrations, the clearance rates of P. avirostris showed a curvilinear response, with a narrow modal range; ingestion rates indicated a rectilinear functional response. Mean clearance rates of P. avirostris, P. intermedius and E. nordmanni were 25.5, 18.0 and 19.3 ml ind.–1 day–1, respectively. Ingestion rates at similar food concentrations (0.4 mm3 l–1) were 0.6, 0.8 and 0.9 g C ind.–1 day–1.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
13.
Previous research on gametic incompatibility in marine invertebrates suggests that for highly dispersive marine invertebrate species, barriers to fertilization among closely related taxa are often incomplete and sometimes asymmetric. The nature of these barriers can dramatically affect the patterns of gene flow and genetic differentiation between species, and thus speciation. Blue mussels, in the genus Mytilus, are genetically distinct in allopatry yet hybrids are present wherever any two species within the group co-occur. The present study sampled M. edulis (L.) and M. trossulus (Gould) in May and June 2001 from the East Bay section of Cobscook Bay, Maine, USA (latitude 44°56′30″N; longitude 67°07′50″W), where the two species are sympatric. Gamete incompatibility was investigated in a series of laboratory fertilizations carried out in July 2001. The proportion of fertilized eggs typically exceeded 80% at sperm concentrations of 103–104 ml?1 among intraspecific matings (n=18), but was <30% even at sperm concentrations in excess of 105–106 ml?1 for interspecific matings (n=13). Further analysis indicated that approximately 100- to 700-fold higher sperm concentrations were required to achieve 20% fertilization in interspecific matings relative to intraspecific matings, indicating strong barriers to interspecific fertilization. The proportion of fertilized eggs did not follow this general pattern in all matings, however. The eggs from two (out of five) M. edulis females were almost as receptive to M. trossulus sperm as they were to M. edulis sperm. In contrast, the eggs from all M. trossulus females (n=3) were unreceptive to M. edulis sperm, suggesting that fertilization barriers between these species may be asymmetric. Given the experimental design employed in this study, the results are also consistent with a strong maternal or egg effect on the level of interspecific gamete compatibility in M. edulis. 相似文献
14.
The genetic structure and phylogeography of the brown seaweed Sargassum horneri/filicinum complex in Japan were studied based on the mitochondrial cox3 haplotype. The cox3 haplotypes found were divided into three clades in a statistical parsimony network, among which there were large numbers
of steps. Contrary to the reported large amount of drifting S. horneri along the Japanese coast, the three clades were dividedly distributed on the Japanese coast: the northern Pacific, the central
Pacific, and western Japan. The western Japan S. horneri had haplotypes that were phylogenetically closer to those of S. filicinum than to the northern and central Pacific S. horneri populations. The S. filicinum populations were included within the western Japan clade and grouped together with the S. horneri samples from western Japan. Taken together with the unstable morphological diagnosis, this result suggests that S. filicinum should be reduced into a synonymy of S. horneri. The TMRCA analysis suggested that the divergence time of each clade may go back to the last interglacial period and a skyline
plot suggested that the last glacial maximum had only a small effect on the population size of S. horneri. The geographic subdivision of the three groups, in spite of a large amount of drifting mats, suggests a limited contribution
of drifting mats to gene flow on a large geographic scale. On a small geographic scale, a small number of haplotypes were
shared between S. horneri-type and S. filicinum-type populations. This result suggests that populations of these two types are partially, though not completely, isolated
from each other, possibly by selfing in S. filicinum-type populations or by a difference in peak reproduction. 相似文献
15.
Resting stages (cysts) of Artemia franciscana, Hexarthra fennica and Fabrea salina were exposed for two periods (acute and chronic exposures) to different concentrations of five aquaculture disinfectants (formalin, sodium hypochlorite, potassium permanganate, organic iodine, copper sulphate). The effects of chemical treatments were ranked according to their action on cyst hatching: total inhibition (no cyst hatching), heavy inhibition (significant decrease of cyst hatching), alteration of hatching synchrony, and occurrence of anomalous hatching (death of emerging individuals or birth of malformed organisms). Resting-stage viability was not completely impaired by disinfectant exposures at the ordinary doses used in aquaculture, so that usual treatments are possibly ineffective against the protist and metazoan cysts potentially present in breeding systems. On the other hand, the high resistance shown by cysts suggests the possibility of using these chemicals in live-feed disinfection. 相似文献
16.
Luciana Möller Fernanda Pedone Valdez Simon Allen Kerstin Bilgmann Shannon Corrigan Luciano B. Beheregaray 《Marine Biology》2011,158(1):113-126
Oceanographic processes play a significant role in shaping the genetic structure of marine populations, but it is less clear
whether they affect genetic differentiation of highly mobile vertebrates. We used microsatellite markers and mtDNA control
region sequences to investigate the spatial genetic structure of short-beaked common dolphins (Delphinus delphis) in southeastern Australia, a region characterised by complex oceanographic conditions associated with the East Australian
Current (EAC). A total of 115 biopsy samples of dolphins were collected from six localities spanning approximately 1,000 km
of the New South Wales (NSW) coastline. We found evidence for contrasting genetic diversity and fine-scale genetic structure,
characterised by three genetically differentiated populations with varying levels of admixture. Spatial genetic structure
was not explained by a model of isolation by distance, instead it coincides with main patterns of oceanographic variation
along the EAC. We propose that common dolphins along the EAC may be adapted to three water masses recently characterised in
this region. 相似文献
17.
Joana Isabel Robalo C. Sousa-Santos H. Cabral R. Castilho V. C. Almada 《Marine Biology》2009,156(8):1733-1737
Fish belonging to the genus Macroramphosus are distributed throughout the Atlantic, Indian and Pacific oceans. Some authors consider this genus monotypic, Macroramphosus scolopax being the only valid species. Other authors consider (based on several morphological and ecological characters) that another
species (Macroramphosus gracilis) exists and occurs frequently in sympatry with the first one. Intermediate forms are also reported in literature. In this
paper, using the mitochondrial control region and the nuclear first S7 intron markers, we failed to find genetic differences
between individuals considered to belong to both species as well as the intermediate forms. Our results suggest that in the
northeastern Atlantic, Macroramphosus is represented by a single species, M. scolopax, with different morphotypes interbreeding in the sampling areas. 相似文献
18.
The ability of an invasive species to spread in a new locality depends on its interaction with the indigenous community and
on variation in time and space in the environment. The Mediterranean mussel Mytilus galloprovincialis invaded the South African coast 30 years ago and it now competes and coexists with the indigenous mussel Perna perna. The two species show different tolerances to wave and sand stress, two of the main environmental factors affecting this
intertidal community. P. perna is more resistant to hydrodynamic stress than M. galloprovincialis, while the invasive species is less vulnerable to sand action. Our results show that mortality rates of the two species over
a period of 6 months had different timing. The indigenous species had higher mortality than M. galloprovincialis during periods of high sand accumulation in mussel beds, while the pattern reversed during winter, when wave action was high.
A negative correlation between sand accumulation and attachment strength of the two mussels showed that sand not only affects
mussel mortality through scouring and burial, but also weakens their attachment strength, subjecting them to a higher risk
of dislodgement. Here we underline the importance of variations in time and space of environmental stress in regulating the
interaction between invasive and indigenous species, and how these variations can create new competitive balances. 相似文献
19.
The pattern of genetic variability of two species of Mediterranean gobiids was compared, with reference to their different
life history traits (Aphia minuta paedomorphic and pelagic; Gobius
niger metamorphosed and benthic). The aim was to evaluate how different life histories can affect the genetic structure in these
marine teleosts. The study was carried out on populations of both species sampled in the western Mediterranean and in the
Adriatic Sea. Seven restriction endonucleases were used for the RFLP analysis of a mitochondrial DNA segment comprising the
NADH dehydrogenase subunits 3, 4L and 4. The results highlighted two different patterns of genetic variation, a weak genetic
structure in A. minuta and population subdivision in G. niger. These observations may be explained not only in terms of the different dispersal capabilities of these species, but also
considering that A. minuta is an abbreviate iteroparous spawner while G. niger is a protracted iteroparous spawner. Because abbreviate iteroparity is a reproductive strategy selected in stable environments
with high resource availability, Pliocene and Pleistocene climate oscillations may have represented factors that negatively
influenced the reproductive success of A. minuta, producing demographic fluctuations and bottlenecks, as suggested by the mismatch distribution analysis. The weak genetic
structure of A. minuta populations seems to be therefore due to a more recent re-colonization of the Mediterranean basin after a severe population
decline, rather than to the high vagility of this pelagic goby. 相似文献
20.
Mangrove trees planted for restoration or rehabilitation often fail to show satisfactory survivals. Although it is generally
assumed that barnacle fouling is a factor in mangrove mortality, the sub-lethal response of mangroves to this fouling is not
known. In the present study, we compare the leaf morphology (stomata density, leaf thickness, percentage thickness of palisade
layer and number of hypodermal layers), lenticel density and the plant fitness (number of flowers or droppers per tree) between
mangroves fouled by the acorn barnacle Fistulobalanus albicostatus (the fouled group, number of barnacles ~ 120 individuals per tree) and non-fouled mangroves (the control group). We observed
55 Kandelia obovata from three locations, two in Hong Kong (n = 35, fouled 25 and control 10) and one location in Taiwan (n = 20, fouled 10 and control 10). Aegiceras corniculatum (n = 45) was observed from two sites in Hong Kong, one on the east coast (n = 20, 10/10) and one on the west coast (n = 25, 10/15). In seedlings (K. obovata
n = 10, 5/5), fouling density did not affect leaf morphology. In mature trees, however, leaves from fouled trees had significantly
higher density of stomata and stem lenticel, a lower percentage thickness of leaf palisade layer and more layers of lower
hypodermis in the leaves, probably for compensating the impeded gaseous exchange functions of the lenticels. The number of
droppers and flowers on fouled mangroves was significantly lower. It is possible that after compensating for respiratory stress,
the plant had less energy available for reproduction. Although there was no obvious barnacle-induced mortality in this study,
barnacles appear to be related to a reduction in plant fitness. This may induce sufficient stress that over time fouled mangroves
cannot sustain viable populations. 相似文献