首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Foraging behaviors of the piscivorous cornetfish Fistularia commersonii were observed at shallow reefs in Kuchierabu-jima Island, southern Japan. This fish foraged on two types of prey fishes: one was reef fish that typically dwell on or near substrata (e.g., Tripterygiidae and Labridae), and the other was pelagic fish that shoal in the water column (e.g., Clupeidae and Carangidae). The prey sizes, prey types and foraging behaviors changed as the predator size increased. Prey sizes were largely limited by gape size of the cornetfish, and small predators consumed small prey. The small cornetfish (10–30 cm in total length) fed only on reef fish captured after stalking (where the fish slowly approaches the prey and then suddenly attacks). The stalking was done either solitarily or in foraging association with conspecifics. Large fish (30–120 cm) fed on both types of fishes by stalking and/or chasing (where the fish chases the prey using its high mobility and attacks), either solitarily or in foraging association with con- or heterospecifics. Thus, chasing was only performed by the large cornetfish against pelagic prey fish in associative foraging with other con- and heterospecific predators. As their body sizes increased, F. commersonii began to show a diversification of foraging behaviors, which was strongly related not only to the habitat types and anti-predatory behaviors of the prey fishes but also to associative foraging with con- or heterospecifics, which improves their foraging success.  相似文献   

2.
We investigated the occurrence pattern of the pond-living endangered cyprinid, Pseudorasbora pumila, and also compared its habitat characteristics with those of the congeneric invasive species, Pseudorasbora parva, in the contact zone. Comparison of 16 environmental variables among the P. pumila habitats, P. parva habitats, and unoccupied ponds revealed that conductivity was a common limitation factor of distribution of both species. We found that emergent vegetation occupancy along the pond bank was the most important factor determining P. pumila occurrence and that ponds with steep banks may have a low probability of containing P. parva. We constructed a logistic regression model to predict the establishment risk of P. parva in ponds occupied by P. pumila. The model demonstrated that more than half of the ponds exhibited a high establishment risk of P. parva. Principal component analysis using six parameters selected from stepwise logistic regression analysis revealed that seven unoccupied ponds had the potential to sustain P. pumila, suggesting that our study site is capable of supporting more P. pumila populations and expanding the current range.  相似文献   

3.
We examined foraging behaviors of four insectivorous bird species (Great Tit Parus major, Varied Tit P. varius, Long-tailed Tit Aegithalos caudatus and Japanese White-eye Zosterops japonica) on the two oak species (Q. serrata and Q. variabilis) in relation to fine-scale foliage structures, abundance, and distribution of folivorous insects and physical and chemical characteristics of leaves. There was no difference in the mean number of insects for each oak species, but there was a significant difference in the mean biomass. The distance from twigs or branches to leaf tips or blade-petiole junctions showed that leaves of Q. variabilis were more dispersed than those of Q. serrata. The different size distribution of insects influenced insect sizes selected and foraging maneuvers used by each bird species. Parus major and P. varius fed on beetles (low energy gain) with perch-gleaning (the most energy-saving maneuver) from the upper side of leaves on Q. variabilis, whereas they fed on large lepidopteran larvae (high energy gain) from the lower side of leaves on Q. serrata using a variety of maneuvers (including energy-consuming ones). Both A. caudatus and Z. japonica fed on insects from the lower side of leaves by hang-gleaning and reach-gleaning, respectively. These species appeared to be morphologically adapted to the energy-consuming but more effective maneuvers used to take preys from the undersides of leaves. We hypothesize that differences in foliage structures between closely related species of trees have evolved as a balance between defense against folivorous insects and attraction of insectivorous birds.  相似文献   

4.
Loss of foraging opportunities and intraspecific competition for prey may be important costs of using refuges, because a hiding animal is unable to use or defend its foraging area from conspecific intrusions. Thus, animals should balance antipredator demands with other requirements in deciding when to come out from a refuge after a predators unsuccessful attack. Observations on foraging and social interactions of backswimmers Notonecta maculata suggest that foraging may be costly in terms of intraspecific agonistic interactions. When prey density is low, increasing the probability of finding a prey may require active exploration of a larger area, but this also increases the probability of encountering a competitor. After simulated exposure to predators, unfed bugs resumed feeding positions after a significantly shorter hiding period than recently fed bugs. We hypothesized that hiding time may also be reduced by recent interactions with conspecific competitors, due to an increased perceived need to defend feeding opportunities. Thus, when a predator attack occurred immediately after an agonistic conspecific interaction, backswimmers resumed feeding positions more quickly, and closer to the original position from which they were disturbed, suggesting short-term defense of particular positions. We conclude that when foraging, backswimmers balance the benefits of finding prey with the costs of predation risk and social interference in deciding their foraging strategy.Communicated by P.K. McGregor  相似文献   

5.
The bionomics and conservation status of a threatened, endemic fish Puntius denisonii has been reported.  相似文献   

6.
7.
Schatz GS  McCauley E 《Oecologia》2007,153(4):1021-1030
Mismatches in the elemental composition of herbivores and their resources can impact herbivore growth and reproduction. In aquatic systems, the ratio of elements, such as C, P, and N, is used to characterize the food quality of algal prey. For example, large increases in the C:P ratio of edible algae can decrease rates of growth and reproduction in Daphnia. Current theory emphasizes that Daphnia utilize only assimilation and respiration processes to maintain an optimal elemental composition, yet studies of terrestrial herbivores implicate behavioral processes in coping with local variation in food quality. We tested the ability of juvenile and adult Daphnia to locate regions of high-quality food within a spatial gradient of algal prey differing in C:P ratio, while holding food density constant over space. Both juveniles and adults demonstrated similar behavior by quickly locating (i.e., <10 min) the region of high food quality. Foraging paths were centred on regions of high food quality and these differed significantly from paths of individuals exposed to a homogeneous environment of both food density and food quality. Ingestion rate experiments on algal prey of differing stoichiometric ratio show that individuals can adjust their intake rate over fast behavioral time-scales, and we use these data to examine how individuals choose foraging locations when presented with a spatial gradient that trades off food quality and food quantity. Daphnia reared under low food quality conditions chose to forage in regions of high food quality even though they could attain the same C ingestion rate elsewhere along a spatial gradient. We argue that these aspects of foraging behavior by Daphnia have important implications for how these herbivores manage their elemental composition and our understanding of the dynamics of these herbivore–plant systems in lakes and ponds where spatial variation in food quality is present. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

8.
Seagrasses are well known ecosystem engineers that can significantly influence local hydrodynamics and the abundance and biodiversity of macrobenthic organisms. This study focuses on the potential role of the seagrass canopy structure in altering the abundance of filter-feeding organisms by modifying the hydrodynamic driven food supply. We quantified the effect of two ecosystem engineers with contrasting canopy properties (i.e. Zostera noltii and Cymodocea nodosa) on the food intake rate of a suspension-feeding bivalve Cerastoderma edule living in these seagrass meadows. Field experiments were carried out in two seagrass beds (Z. noltii and C. nodosa) and bare sediment, located on sandflat characterised by a relatively high hydrodynamic energy from waves and currents. Results demonstrated that the filter-feeding rate was almost twofold increased when C. edule was inhabiting Z. noltii meadows (1.10 ± 0.24 μg Chl g Fresh Weight−1) when compared to cockles living on the bare sediment (0.65 ± 0.14 μg Chl g FW−1). Intermediate values were found within C. nodosa canopy (0.97 ± 0.24 μg Chl g FW−1), but filter feeding rate showed no significant differences with values for Z. noltii meadows. There were no apparent correlations between canopy properties and filter-feeding rates. Our results imply that food refreshment within the seagrass canopies was enough to avoid food depletion. We therefore expect that the ameliorated environmental conditions within vegetated areas (i.e. lower hydrodynamic conditions, higher sediment stability, lower predation pressure…) in combination with sufficient food supply to prevent depletion within both canopies are the main factors underlying our observations.  相似文献   

9.
Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.  相似文献   

10.
The loss of feeding areas may pose a threat to many wintering waders because increased competition arising from reduced foraging space may force birds either to emigrate or to die. This has been demonstrated to occur in northwest European estuaries, but virtually no studies have been performed in the estuaries of southern Europe, where the loss of supratidal habitats (salines and saltmarshes), rather than intertidal habitats, are currently the main threat to waders’ habitats. If these habitats are lost, waders may be forced to move to the intertidal mudflats, perhaps increasing competition between individuals and ultimately leading to starvation or emigration. We tested this hypothesis in the Mondego estuary, a small estuary on Portugal’s west coast, which is presently under heavy human pressure. We used indirect methods to test for the occurrence of both components of intra-specific competition: interference and prey depletion. We found no evidence that either interference or depletion competition was occurring at present, either on the mudflats or in the salines. Overall, the results suggest that the intertidal mudflats may still be able to accommodate birds displaced from the destroyed supratidal salines, but modelling is required to predict the effect that the combined loss of feeding area and foraging time that this would entail would have on their fitness, and thus numbers.  相似文献   

11.
The aim of this paper is to detail a control programme of the invasive Asian cyprinid fish Pseudorasbora parva in the UK that was initiated in March 2005. Described as Europe’s most invasive fish, P. parva presents a risk to native fishes through the transmission of a novel pathogen and undesirable impacts arising from processes including increased inter-specific competition. Populations have been recorded in 32 UK waters since their first recording outside of aquaculture in 1996; the majority are lakes <5 ha used for recreational angling in England. The aims of the control programme were to develop a basic evaluation framework that assesses populations by risk (high, medium and low), determine commensurate management actions according to that risk and then execute those actions. For populations assessed as ‘high-risk’, for example those that could result in P. parva dispersal into a river catchment, eradication was determined as the commensurate management action and six operations have since been completed, principally using rotenone, and all have been successful to date. For P. parva populations in sites evaluated as lower risk, techniques such as biomanipulation were determined as more appropriate actions and have been used to successfully reduce their abundance by >99%. To date, the total direct cost of this programme of sustained and on-going P. parva control is approximately £190,000.  相似文献   

12.
13.
 Two biological types of Japanese dark chub, so-called types A and B of Zacco temminckii, were taxonomically inspected. A comparison of types A and B with the lectotypes of Leuciscus sieboldii and L. temminckii in Siebold's collection revealed that type A is identical to L. sieboldii, whereas type B matches L. temminckii. Hence, Zacco sieboldii and Z. temminckii were redescribed on the basis of the lectotype and additional specimens from Japan. Zacco sieboldii is distinguishable from Z. temminckii by having a narrower band on the anterior portion of both body sides, nine branched rays of anal fin (10 in Z. temminckii), lateral line scales not less than 53 (not more than 52 in Z. temminckii), and scales above lateral line not less than 13 (not more than 11 in Z. temmincki). A key to the species of Japanese Zacco is also provided. Received: August 15, 1999 / Revised: July 25, 2002 / Accepted: August 19, 2002 Acknowledgments We express our cordial thanks to all the following investigators: Dr. M.J.P. Van Oijen (RMNH) for the specimen loan of von Siebold's collection; Professor San-Rin Jeon, Sang-Myung University (formerly, Seoul) for providing several papers on Korean Zacco congeners; Dr. Harumi Sakai, National Fisheries University; Dr. Tetsuo Furukawa-Tanaka, Museum of Nature and Human Activities, Hyogo; Dr. Seishi Kimura, Mie University; Dr. Akihisa Iwata, Kyoto University; Dr. Osamu Katano, National Research Institute of Fisheries Sciences; Mr. Kazuo Hoshino, Oita Marine Palace; and Dr. Kouichi Kawamura, National Research Institute of Aquaculture, for the valuable comments and information on the ecological aspects of both species of the Japanese dark chub. Correspondence to:Kazumi Hosoya  相似文献   

14.
A genetic transformation system has been developed for callus cells of Crataegus aronia using Agrobacterium tumefaciens. Callus culture was established from internodal stem segments incubated on Murashige and Skoog (MS) medium supplemented with 5 mg l−1 Indole-3-butyric acid (IBA) and 0.5 mg l−1 6-benzyladenine (BA). In order to optimize the callus culture system with respect to callus growth and coloration, different types and concentrations of plant growth regulators were tested. Results indicated that the best average fresh weight of red colored callus was obtained on MS medium supplemented with 2 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.5 mg l−1 kinetin (Kin) (callus maintenance medium). Callus cells were co-cultivated with Agrobacterium harboring the binary plasmid pCAMBIA1302 carrying the mgfp5 and hygromycin phosphotransferase (hptII) genes conferring green fluorescent protein (GFP) activity and hygromycin resistance, respectively. Putative transgenic calli were obtained 4 weeks after incubation of the co-cultivated explants onto maintenance medium supplemented with 50 mg l−1 hygromycin. Molecular analysis confirmed the integration of the transgenes in transformed callus. To our knowledge, this is the first time to report an Agrobacterium-mediated transformation system in Crataegus aronia.  相似文献   

15.
The foraging behaviour variability of three striped red mullet (Mullus surmuletus L. 1758) populations with respect to the vegetation cover was examined along the French Mediterranean coasts. We tested both the carrying capacity of different habitats and the hypothesis of a food segregation by the invasive alga Caulerpa taxifolia (Vahl) C. Agardh, on the functioning of benthic fish populations. The results indicated a significant site effect on M. surmuletus foraging behaviour and movements. The vegetation cover may play an important role in modifying the striped red mullet cost of foraging (sampling effort) and thus its strategy of prey capture. As long as the cover of marine phanerogams and/or macrophyte algae (Caulerpaceae) increases, the foraging budget and the distances covered in search of prey decrease significantly. Similarly, the striped red mullet increases the prospected sample periods to augment its foraging success, swimming above the bottom. These changes are related to the development of a dense superficial network of plagiotropic rhizomes and stolons, and to the reduction of space between fronds that limits the accessibility to resources and may increase intra-specific food competition. The role of C. taxifolia does not differ from that of other marine phanerogams but induces significant changes in the structure of Mullidae populations at the local level. The rapid expansion of Caulerpaceae in the Mediterranean Sea could constitute a real threat for the balance of the marine coastal biodiversity and the ecology of M. surmuletus, which is considered a flagship species for coastal Mediterranean demersal fisheries.  相似文献   

16.
New combinations are proposed in anticipation of the Polygonaceae treatment in the forthcoming volume of Intermountain Flora: Polygonum kelloggii var. esotericum, P. kelloggii var. watsonii , Rumex densiflorus var. pycnanthus , R. salicifolius var. utahensis, and R. occidentalis var. tomentellus. Typifications are proposed to facilitate ongoing studies in Polygonaceae and to maintain current usage.  相似文献   

17.
The phylogenetic relationships of two cavefish, Phreatichthys andruzzii and Garra barreimiae, belonging to the family Cyprinidae, were investigated by sequencing the mitochondrial cytochrome b gene. These cavefish species are native to Somalia (eastern Africa) and Oman (southeastern Arabian peninsula), respectively, and so far no molecular support to their taxonomy and phylogenetic position was ever provided. The analysis of cytochrome b sequences showed that the species are monophyletic taxa, closely related to each other and to other species of the genus Garra. Molecular clock calculations allowed to date the origin of these hypogaean species back to the Plio-Pleistocene and support the hypothesis that African cyprinids originated from Miocenic immigrations of Asian ancestors.  相似文献   

18.
It was shown that stimulation by food odor (aquatic extract of food organisms, 10?2 and 10?3 g/l) does not cause shifts in gustatory preferences in carp Cyprinus carpio and cod Gadus morhua but modifies gustatory behavior. The level of consumption by carp of control granules and granules with attractive, by taste, L-proline (0.1 M) or deterrent L-lysine (0.1 M) (item by item presentation of granules) and by cod of control granules and granules with indifferent, to it, L-asparagine (0.1 M) (presentation of 10 granules simultaneously) is similar prior to and during olfactory stimulation. In the presence of food odor, the duration of taste testing for most types of granules, as well as the number of repeated graspings of granules with an attractive taste do not change in fish. At the same time, granules with indifferent or repulsive gustatory properties are rejected and repeatedly grasped by fish against the background of food odor more frequently than in water without odor. Olfactory stimulation leads to a considerable increase in the average number of graspings per one grasped granule with an indifferent or repulsive taste. Such behavior manifested by fish in the presence of food odor in response to granules with unattractive gustatory properties is apparently caused by the contradiction between the information coming via different chemosensory canals—olfactory and gustatory. The obtained results indicate that food stimulation caused by food odor in nature can lead to an increase in the actual consumption of only those accessible food items that have an attractive taste for fish.  相似文献   

19.
Studying Pneumocystis has proven to be a challenge from the perspective of propagating a significant amount of the pathogen in a facile manner. The study of several fungal pathogens has been aided by the use of invertebrate model hosts. Our efforts to infect the invertebrate larvae Galleria mellonella with Pneumocystis proved futile since P. murina neither caused disease nor was able to proliferate within G. mellonella. It did, however, show that the pathogen could be rapidly cleared from the host.  相似文献   

20.
A revision of Penstemon sect. Saccanthera subsect. Serrulati includes a new species (P. salmonensis), a new variety (P. triphyllus var. infernalis), and the elevation of a subspecies to species (P. curtiflorus), bringing the total number of species to eight, which are keyed and described, complete with nomenclature and type citations.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号