共查询到20条相似文献,搜索用时 15 毫秒
1.
Zoë A. Doubleday 《Journal of experimental marine biology and ecology》2011,397(1):8-12
Stylet increment analysis (SIA) is the key method to age octopus, however, currently it is not reliable for all species. The suitability of the age-pigment lipofuscin as an alternative ageing method for octopus was examined. To determine the relationship between age and lipofuscin known-age octopus (Octopus pallidus) were reared in the laboratory from hatching to eight months old. Twenty-eight individuals at three different ages (3, 6 and 8 months old) were collected for lipofuscin analysis. The first two age groups (n = 5 each) were reared under ambient temperatures, while the oldest group (n = 18) was reared under three different controlled temperature regimes (n = 6 per treatment). For comparison, five wild O. pallidus were also collected for lipofuscin analysis and aged using SIA. Lipofuscin was analysed in the brain tissue and quantified at a commercial ageing centre using standard histological methods. Lipofuscin granules were clearly discernable in the brain tissue, and there was a strong exponential relationship between age and lipofuscin (R2 = 0.86). Lipofuscin concentration was not related to sex, temperature or body weight in same-age individuals. Except for one individual, the predicted age of the wild animals, based on the relationship between lipofuscin and age, was close to the age determined using SIA. This study is the first to report lipofuscin in an octopus species and shows that lipofuscin has excellent potential as an alternative ageing method for octopus. This research will have important applications for species which cannot be reliably aged using current ageing methods. 相似文献
2.
The importance of spatial pattern in ecosystems has long been recognized. However, incorporating patchiness into our understanding of forces regulating ecosystems has proved challenging. We used a combination of continuously sampling moored sensors, complemented by shipboard sampling, to measure the temporal variation, abundance and vertical distribution of four trophic levels in Hawaii's near shore pelagic ecosystem. Using an analysis approach from trophic dynamics, we found that the frequency and intensity of spatial aggregations-rather than total biomass-in each step of a food chain involving phytoplankton, copepods, mesopelagic micronekton and spinner dolphins (Stenella longirostris) were the most significant predictors of variation in adjacent trophic levels. Patches of organisms had impacts disproportionate to the biomass of organisms within them. Our results are in accordance with resource limitation-mediated by patch dynamics-regulating structure at each trophic step in this ecosystem, as well as the foraging behaviour of the top predator. Because of their high degree of heterogeneity, ecosystem-level effects of patchiness such as this may be common in many pelagic marine systems. 相似文献
3.
Karla Martins Yuri Niella Fernanda Albuquerque Leandro Nolé Eduardo Paulo Oliveira Paulo Travassos 《Journal of fish biology》2024,104(4):1112-1121
The yellowfin tuna is a very abundant tropical tuna species in the western equatorial Atlantic Ocean and an important fishery resource for the Brazilian tuna fleet. In this study we performed stable isotope analysis to better understand the spatial trophodynamics and dietary changes in yellowfin tuna around two insular marine protected areas in Brazil. A total of 65 yellowfin tuna specimens measuring between 47 and 138 cm LT (total length) were sampled around the archipelagos of Fernando de Noronha (FNA; n = 34) and Saint Peter and Saint Paul (SPSPA; n = 31) between July 2018 and September 2019. Bayesian mixing models and generalized additive models were used to investigate the contributions of four different prey items (zooplankton, cephalopods, fish larvae, and flying fish) to yellowfin tuna diet in each area and their potential changes in relation to predator growth. The four prey items were found to have different overall contributions between the two studied areas, with zooplankton being the most important prey in FNA, whereas flying fish was the most relevant prey to the species' diet in SPSPA. Significant changes in the species diet by size were also found, with fish smaller than 90 cm (TL) having a more generalist diet and larger animals relying more on consuming larger and more nutritious prey (i.e., flying fish). Our results suggest that these two marine protected areas play an important role in ocean dynamics, providing important and different foraging grounds for the development of this predator species. 相似文献
4.
Annika Bengtson Arne A. Anderberg Per Ola Karis 《Botanical journal of the Linnean Society. Linnean Society of London》2014,174(2):173-198
Metalasia is a genus in tribe Gnaphalieae (Asteraceae), endemic to South Africa and with its main distribution in the Cape Floristic Region. The genus comprises 57 species and, with a number of closely related genera, it constitutes the ‘Metalasia clade’. A species‐level phylogenetic analysis is presented, based on DNA sequences from two nuclear (internal and external transcribed spacer: ITS, ETS) and two plastid (psbA‐trnH, trnL‐trnF) regions together with morphological data. Analyses combining molecular and morphological data attempt not only to resolve species interrelationships, but also to detect patterns in character evolution. Phylogenetic analyses corroborate our earlier study and demonstrate that Metalasia is formed of two equally sized, well‐supported sister groups, one of which is characterized by papillose cypselas. The results differ greatly from earlier hypotheses based on morphology alone, as few morphological characters support the phylogenetic patterns obtained. The two clades of Metalasia do, however, appear to differ in distribution, corresponding to the different rainfall regimes of South Africa. Analyses show a few taxa to be problematic; one example is the widely distributed M. densa which appears to be an intricate species complex. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 173–198. 相似文献
5.
KRYSTAL A. TOLLEY ATHERTON L. DE VILLIERS MICHAEL I. CHERRY G. JOHN MEASEY 《Biological journal of the Linnean Society. Linnean Society of London》2010,100(4):822-834
Traditional models of amphibian dispersal and gene flow point to low dispersal and high philopatry. In recent years, this traditional view has been challenged and it appears that no general model holds across taxa. Conservation of amphibians cannot be addressed on an over‐arching scale, but must come on a case‐by‐case basis, especially for range‐restricted species where information on gene flow and migration must be incorporated into conservation efforts. The only two members of the genus Capensibufo Grandison, 1980 (Anura: Bufonidae) are range restricted small bufonids, with distributions limited to montane areas in South Africa. Using a Bayesian analysis of two mitochondrial markers (16S and ND2), we examined the genetic patterns in Capensibufo rosei and Capensibufo tradouwi in order to understand both taxonomic and geographic boundaries. These species were not monophyletic, and demonstrate no clear taxonomic boundaries. Instead, the genus is extremely diverse genetically, with distinct lineages confined to isolated mountains that represent geographic boundaries. In addition, bioclimatic modelling using MAXENT and scenarios of climatic conditions at both the present and last glacial maximum suggest multiple bioclimatic and physical barriers to gene flow at present and in the past. We conclude that members of the genus have very low vagility, that current taxonomic boundaries are inadequate, and that strong geographic structuring has undoubtedly contributed to genetic diversity at the species level, rather than the population level. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 822–834. 相似文献
6.
Meshack N. Dludlu Samson B. M. Chimphango Charles H. Stirton A. Muthama Muasya 《Journal of Plant Ecology》2018,11(4):632
Aims The Cape Peninsula is a small area (471 km 2) situated on the south-westernmost tip of the Core Cape Subregion (CCR) of South Africa. Within the Cape Peninsula, Fabaceae are the third most species-rich plant family (162 species) and they have the second highest number of endemic species after the Ericaceae. However, legumes are not the dominant taxa in the vegetation. They tend to show patchy distributions within the landscape and different species assemblages usually occupy particular niches at any given locality. The present study undertook to establish if edaphic factors influence legume species distribution in the Cape Peninsula and to determine the key indicator species for the different assemblages.Methods Soils from 27 legume sites, spanning all major geological substrates of the Cape Peninsula, were analysed for 31 chemical and physical properties. Legume species present at each site were recorded and a presence/absence matrix was generated. Cluster analysis and discriminant function analysis (DFA) were run to group the sites based on overall similarity in edaphic characteristics and to identify the soil parameters contributing towards discriminating the groups. Canonical correspondence analysis (CCA) was used to test for a correlation between legume species compositions and edaphic factors. The strength of the association between legume species and site groupings based on edaphic properties was assessed using indicator species analysis.Important findings Based on similarity in overall soil characteristics, the sites formed three clusters: one comprising sites of sandstone geology, one with dune sand sites and the third cluster comprising sites of both shale and granite geologies (hereafter referred to as soil types). The DFA confirmed the distinctness of these clusters and the CCA showed a significant correlation between legume species composition and edaphic factors. The key edaphic parameters were clay content, iron (Fe), potassium (K), sulphur (S) and zinc (Zn). These findings reveal that the Cape Peninsula is edaphically heterogeneous and edaphically distinct habitats contain discrete legume species assemblages that can be distinguished by unique indicator species. Furthermore, multiple soil parameters, rather than a single parameter, are involved. Therefore, edaphic factors play a significant role in driving the distribution of legume species in the Cape Peninsula and discrete legume species assemblages occupy distinct habitats. 相似文献
7.
Morten Frederiksen Tycho Anker‐Nilssen Grégory Beaugrand Sarah Wanless 《Global Change Biology》2013,19(2):364-372
The boreal Northeast Atlantic is strongly affected by current climate change, and large shifts in abundance and distribution of many organisms have been observed, including the dominant copepod Calanus finmarchicus, which supports the grazing food web and thus many fish populations. At the same time, large‐scale declines have been observed in many piscivorous seabirds, which depend on abundant small pelagic fish. Here, we combine predictions from a niche model of C. finmarchicus with long‐term data on seabird breeding success to link trophic levels. The niche model shows that environmental suitability for C. finmarchicus has declined in southern areas with large breeding seabird populations (e.g. the North Sea), and predicts that this decline is likely to spread northwards during the 21st century to affect populations in Iceland and the Faroes. In a North Sea colony, breeding success of three common piscivorous seabird species [black‐legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge) and Atlantic puffin (Fratercula arctica)] was strongly positively correlated with local environmental suitability for C. finmarchicus, whereas this was not the case at a more northerly colony in west Norway. Large seabird populations seem only to occur where C. finmarchicus is abundant, and northward distributional shifts of common boreal seabirds are therefore expected over the coming decades. Whether or not population size can be maintained depends on the dispersal ability and inclination of these colonial breeders, and on the carrying capacity of more northerly areas in a warmer climate. 相似文献
8.
The configuration, slipping and rotation of self-interstitial atoms cluster along <111> crystal orientation with different sizes in a tungsten are investigated systematically with molecular dynamics. It is found that (I) the SIA clusters with high symmetry are always favoured; (II) the SIA clusters can undergo one-dimensional fast migration along <111> direction, and their migration barriers are no more than 0.07?eV, which is expected due to the strong interaction in the SIA clusters; (III) the rotation energy barriers of the SIA clusters are rather high and they are basically positively correlated with the size of the cluster. For example, the reorientation barrier is 0.66?eV for 1 SIA, 1.2–1.8?eV for SIAn (2?≤?n?≤?5) clusters and over 2.7?eV for SIAn (6?≤?n?≤?7) clusters. Compared with slipping of SIA clusters, is an infrequent event, especially for larger SIAs cluster, the vast majority SIAs cluster would have already recombination with vacancies or annihilates at surface and grain boundary through slipping before rotation, which explained that there are very low density of SIAs cluster found in the experiment. 相似文献
9.
O. R. Anderson 《The Journal of eukaryotic microbiology》2012,59(6):564-570
Effects of glucose‐carbon supplementation on soil respiration and bacterial and protist biomass were investigated in laboratory studies of three soil samples from Alaskan tundra: spring tussock sample 1 (thin surface moss), spring tussock sample 2 (thick surface moss), and a summer tundra open field sample. Addition of 1% (w/v) glucose solution produced an immediate, pronounced two to three fold increase in respiration above basal rate, which declined over 4 h to baseline levels. Less than 1% (w/w) of glucose‐C supplement was respired during the respiratory spike, relative to the 89 μg/g added. A more substantial amount of the glucose‐C became incorporated in microbial biomass. The total difference in microbial carbon (μg/g) between the experimental treatments and controls without glucose after 1 wk was as follows: spring sample 1 (8), spring sample 2 (31), and summer sample (70). The percent (w/w) of glucose‐C incorporated was: spring sample 1 (5%), spring sample 2 (17%), and summer sample (39%), most attributed to biomass of bacteria and heterotrophic nanoflagellates. Although respiratory response to pulsed glucose‐C was minimal, the overall mean basal rate after 1 wk ranged between 4 and 6 nmol/min/g soil, indicating a significant assimilation and respiration of constituent soil organic carbon. 相似文献
10.
Jason S. Link Bernard A. Megrey Thomas J. Miller Tim Essington Jennifer Boldt Alida Bundy Erlend Moksness Ken F. Drinkwater R. Ian Perry 《Biology letters》2010,6(6):723-726
Understanding the drivers that dictate the productivity of marine ecosystems continues to be a globally important issue. A vast literature identifies three main processes that regulate the production dynamics of such ecosystems: biophysical, exploitative and trophodynamic. Exploring the prominence among this ‘triad’ of drivers, through a synthetic analysis, is critical for understanding how marine ecosystems function and subsequently produce fisheries resources of interest to humans. To explore this topic further, an international workshop was held on 10–14 May 2010, at the National Academy of Science''s Jonsson Center in Woods Hole, MA, USA. The workshop compiled the data required to develop production models at different hierarchical levels (e.g. species, guild, ecosystem) for many of the major Northern Hemisphere marine ecosystems that have supported notable fisheries. Analyses focused on comparable total system biomass production, functionally equivalent species production, or simulation studies for 11 different marine fishery ecosystems. Workshop activities also led to new analytical tools. Preliminary results suggested common patterns driving overall fisheries production in these ecosystems, but also highlighted variation in the relative importance of each among ecosystems. 相似文献
11.
J. Tyler Faith 《Diversity & distributions》2012,18(5):438-447
Aim Promoting population growth of genetically distinct subpopulations of Cape mountain zebra (Equus zebra zebra) is crucial to the survival of the subspecies. Several important Cape mountain zebra reserves are dominated by fynbos vegetation, and population growth is limited by a lack of grassland habitat. A fossil ungulate sequence spanning the last c. 18,000 years is examined to understand the long‐term history of this conservation challenge. Location Boomplaas Cave (BPA), South Africa. Methods The fossil sequence from BPA is examined to reconstruct ungulate community dynamics in relation to climate and vegetation change over the last 18,000 years. Results Ungulates from 18,000 to 12,000 years ago suggest an expansion of open grasslands that supported a grazing ecosystem dominated by an extinct caprine antelope and equid remains attributed to E. zebra and E. quagga. At the onset of the Holocene, the grazing ungulate community disappears and small browsers and mixed feeders dominate the assemblage, indicating the loss of open grassland vegetation. Several open‐habitat grazers go extinct at this time, and Equus persists at much lower abundances. This shift can be explained by global climate change across the Pleistocene–Holocene transition. Main conclusions The fossil sequence supports contemporary observations indicating that access to open grassland is crucial to maintaining large Cape mountain zebra subpopulations. Although fynbos is abundant throughout the historic range of the Cape mountain zebra, fossil evidence suggests that such vegetation is unlikely to support dense populations. It has been suggested that the acquisition of agricultural lands that were historically converted to open grasslands for livestock could promote Cape mountain zebra population growth. Results presented here support this management option, as the open grasslands in these converted landscapes likely approximate the vegetation structure during latest Pleistocene, when grasslands were widespread and grazing ungulates abundant. 相似文献
12.
The hypothesis that the elements of the modern species-rich flora of the Cape Floristic Region (CFR), South Africa, originated more or less simultaneously at the Miocene/Pliocene boundary, in response to the development of a mediterranean climate, has been challenged by numerous molecular dating estimates of Cape floral clades. These studies reveal a more gradual emergence, with the oldest clades originating in the Eocene, but others appearing later, some as recently as the Pliocene. That there are factors which might affect the dates recovered, such as choice of calibration point, analysis method, sampling density and the delimitation of Cape floral clades, suggests a need for further critical evaluation of the age estimates presented to date. In this study, the dates of origin of two Cape floral clades (the legume Crotalarieae p.p. and Podalyrieae) are estimated, constrained by a shared calibration point in a single analysis using an rDNA ITS phylogeny in which 633 taxa are sampled. The results indicate that these two clades arose contemporaneously 44-46 mya, not at the Miocene/Pliocene boundary as had been previously supposed. The contemporaneous origin of these Cape floral clades suggests that additional more inclusive analyses are needed before rejecting the hypothesis that a single environmental trigger explains the establishment of Cape floral clades. 相似文献
13.
Steffen Heelemann Veronika Bäuerlein Cornelia B. Krug Karen J. Esler Peter Poschlod Christoph Reisch 《African Journal of Ecology》2015,53(4):447-453
We tested the effects of life‐history traits on genetic variation and conducted a comparative analysis of two plant species with differing life‐history traits co‐occurring in the highly endangered renosterveld of South Africa. We selected eighteen renosterveld remnants with varying degrees of size and isolation where populations of the herbaceous, annual and insect‐pollinated Hemimeris racemosa and the shrubby perennial and both wind‐ and insect‐pollinated Eriocephalus africanus occurred. We postulated a lower genetic variation within populations and increased genetic variation between populations in the annual than in the perennial species. Genetic variation was lower within populations of H. racemosa than within E. africanus, as is typical for annual compared to perennial species. Variation within populations was, however, not correlated with fragment size or distance in either of the two species and genetic variation between populations of the two species was comparable (ΦST = 0.10, 0.09). 相似文献
14.
M. E. Castro-e-Almeida M. A. Gama-Antunes Vitor M. R. Marques 《International Journal of Anthropology》1991,6(3):197-205
The authors have studied the data relating to a 24 hours pilot inquiry carried out at 49 rural families from the Administrative Community of Praia, Santiago Island. Cape Verde. Their aims were: 1) to know about the consum-ed food; 2) to search out, in quality and quantity, the consumption in calories, proteins and other nutrients; 3) to define the level of satisfaction of the nutritional needs of the mentioned group. The discussion of the results stated the main conclusions: the group of nutriments mostly consumed was the fourth one which is composed by foods rich in carbohydrates and proteins of low valua. In this group the four most important nutriments are: maize, wheat, rice and bean, which represent around 66% of the total weight of them. An acceptable level of satisfaction of the individual average needs per family is achieved for proteins (although the consumption of proteins of vegetable origin is much more important than the consumption of animal proteins), for vitamins B1 and C and iron. Considering calories and other nutrients (vitamins A, B2 and PP, and calcium) there are some shortages. The individual average values per family obtained and those recommended by FAO/OMS showed significant differences for calories and nutrients (test ≪t≫ of Student). 相似文献
15.
Evidence is provided from stable isotope analysis that aggregations of small ocean sunfish Mola mola (total length <1 m) feed broadly within coastal food webs and their classification as obligate predators of gelatinous zooplankton requires revision. 相似文献
16.
G. ERIC E. MOODIE PATRICIA F. MOODIE THOMAS E. REIMCHEN 《Biological journal of the Linnean Society. Linnean Society of London》2007,92(4):617-623
Fluctuating asymmetry (FA) is often, but controversially, viewed as an indicator of fitness and a target of selection. In the brook stickleback, Culaea inconstans (Kirtland), FA of the pectoral fins, which are the main source of propulsion, is inversely correlated with fecundity. We examined the hypothesis that asymmetry of the pectoral fins could affect locomotion in such a way as to influence foraging and niche use in prereproductive brook stickleback. Nitrogen and carbon stable isotope analysis showed the diet of symmetric and asymmetric males diverged with increasing body size. Larger symmetric males fed at higher trophic levels and had a diet based on carbon emanating from a more pelagic source than their asymmetric counterparts. Such effects were not observed in females or smaller males. The number of chironomid larvae found in the gut was greater on average in asymmetric than symmetric fish. The results from this study strongly suggest FA of pectoral fins affects the foraging behaviour of C. inconstans and that stable isotope analyses of individual phenotypes provides a useful tool for assessing the ecological consequences of FA. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 617–623. 相似文献
17.
E. C. Ashworth M. Depczynski T. H. Holmes S. K. Wilson 《Journal of fish biology》2014,84(4):1031-1045
The diets of four common mesopredator fishes were examined in the back‐reef habitat of a subtropical fringing reef system during the summer months. Quantitative gut content analyses revealed that crustaceans, represented >60% of ingested prey (% mass) by the latticed sand‐perch Parapercis clathrata, brown dottyback Pseudochromis fuscus and half‐moon grouper Epinephelus rivulatus. Dietary analyses also provided insights into ontogenetic shifts. Juvenile P. fuscus ingested large numbers of crustaceans (amphipods and isopods); these small prey were rarely found in larger individuals (<1% of ingested mass). Fishes also made an important contribution to the diets of all three species representing 10–30% of ingested mass. Conversely, the sand lizardfish Synodus dermatogenys fed exclusively on fishes including clupeids, gobies and labrids. Differences in the gut contents of the four species recorded were not apparent using stable isotope analysis of muscle tissues. The similarity of δ13C values in muscle tissues suggested that carbon within prey was derived from primary producers, with comparable carbon isotope signatures to corals and macroalgae, whilst similarities in δ15N values indicated that all four species belonged to the same trophic level. Thus, interspecific differences between mesopredator diets were undetectable when using stable isotope analysis which suggests that detailed elucidation of trophic pathways requires gut content analyses. 相似文献
18.
J. A. Ledger 《Ostrich》2013,84(3):191-194
At Dyer Island, South Africa, observations of predation of seabirds by Cape Fur Seals Arctocephalus pusillus pusillus were made during 2004 and 2006/07. It was estimated that seals killed about 7% of adult African Penguins Spheniscus demersus annually. This may have contributed to the penguin colony not increasing in spite of food becoming more available in its vicinity during an eastward shift of epipelagic fish resources off South Africa at the start of the twenty-first century. Adult penguins were most susceptible to mortality in the breeding season as they returned to feed chicks in the evening. Seals also killed substantial numbers (3–9%) of Cape Cormorant Phalacrocorax capensis fledglings as they left the island, mostly in the morning. The losses of Cape Cormorant fledglings accounted for about 95% of the overall mortality of seabirds attributable to seals. Mortality inflicted by seals on adults of four species of cormorant was negligible and no predation by seals on gulls and terns was observed. 相似文献
19.
《Journal of bryology》2013,35(4):257-263
AbstractSouth African populations of Bryobartramia have been treated as B. novae-valesiae, a species otherwise restricted to Australia. However, material from the two regions differs in a number of traits, and the African populations are here described as a new species, B. schelpei. The Cape species differs most obviously from B. novae-valesiae in the markedly prorate-papillose, narrow, thick-walled cells of the calyptra. Nested analysis of variance reveals further morphometric differences, including the relatively narrower, more cylindrical, calyptra with a longer rostrum, and the smaller leaf cells and spores. Bryobartramia schelpii is known only from arid portions of the winter rainfall region in the Northern and Western Cape Provinces of South Africa. 相似文献
20.
J. Rey L. Fernandez‐Peralta L. F. Quintanilla M. Hidalgo C. Presas F. Salmeron M. A. Puerto 《Journal of fish biology》2015,86(3):1078-1097
This study investigated the somatic growth and energy allocation strategy of two sympatric hake species (Merluccius polli and Merluccius senegalensis), coexisting under the strong influence of the Mauritanian upwelling. The results revealed that ontogeny, bathymetry, geography and reproduction shaped the differences found between the condition dynamics of the two species. Aside from species‐specific differences, individuals were observed in better condition in the northernmost area (more influenced by the permanent upwelling) and in the deepest waters, probably the most favourable habitat for Merluccius spp. Both species also displayed contrasting trade‐offs in energy allocation probably due to the dissimilarity of their habitats, which favours the existence of divergent adaptive strategies in response to different ontogenic requirements. It was hypothesized that M. polli invests in mass and energy reserves while sacrificing growth, as larger sizes may not provide an ecological advantage in a deeper and more stable environment. Moreover, M. senegalensis capitalizes on a steady growth without major disruptions, enabling earlier spawning at the expense of a lower somatic mass, which is fitting to a less stable shallower environment. This study sheds new light on differences in the biological traits and life strategies of Merluccius spp., which permit their overlap in a complex upwelling system and may contribute to the long‐lasting scientific‐based management of these species. 相似文献