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 46 毫秒
1.
Specimens of ocean skaters Halobates were collected off the south coast of Japan in the East China Sea in 1995, and from the Kumano‐nada Sea to the East China Sea in 1998 and 1999. Three species were identified: H. micans, H. germanus and H. sericeus. We found two species co‐occurring in comparable densities in different years, a phenomenon not hitherto reported in other regions of the ocean. We discuss distributions of the three Halobates species with special reference to the influence of the Kuroshio Current, temporal variations of sea‐surface temperature, and monsoonal winds.  相似文献   

2.
Species composition and food habits of four istiophorid billfishes were investigated and compared in three different tropical areas of the eastern North Pacific Ocean by longline operations from September to November 2004. Sailfish Istiophorus platypterus, shortbill spearfish Tetrapturus angustirostris and blue marlin Makaira nigricans had specific habitat preferences and mainly occurred in the near‐continent area (13–16° N; 103–107° W), the open‐ocean area (16–18° N; 118–134° W) and the near‐equator area (5° N; 104–120° W). Small (<140 cm in lower jaw–fork length) striped marlin Kajikia audax mainly occurred in the near‐continent area; however, large (≥140 cm) individuals occurred throughout all three areas. Prey compositions of large K. audax in the three areas were different from one other reflecting the prey availability in each area. In the open‐ocean area, molid fishes were dominant in mass for both large K. audax (49%) and T. angustirostris (73%), and large K. audax also fed on ostraciid (33%) and scombrid fishes (15%). In the near‐continent area, tetraodontid fishes were dominant for large and small I. platypterus (54, 57%), and both large and small K. audax also fed on tetraodontid fishes (3, 12%). Large K. audax in this area fed mainly on scombrid fishes (86%). These results indicate that large K. audax show overlaps but little segregations of its prey with other billfishes. In the near‐equator area, stomach contents of large K. audax and M. nigricans were few and billfish prey items were thought to be scarce.  相似文献   

3.
Two species of ocean skaters, Halobates germanus and Halobates micans, live in the tropical and subtropical waters of the Indian Ocean. From December 1992 to December 1993, Halobates was intensively sampled in the easternmost region of the South Indian Ocean (13–18.5°S, 114–121E°), from which there have been a small number of records of Halobates. No H. germanus was caught, but a total of 1190 H. micans were collected, with densities estimated at 13 900–28 100 individuals/km2. This suggests that H. micans lives in the study area at high densities comparable to those in the Atlantic and the Pacific Oceans. We also discuss the possible effects of ocean currents and winds on the geographic distributions of the two Halobates species in the eastern South Indian Ocean.  相似文献   

4.
Sexual differences in the distribution pattern, sex ratio and the gonad condition of four istiophorid billfishes were investigated in three different tropical areas of the eastern North Pacific Ocean from September to November 2004. Sex ratios of striped marlin Kajikia audax were equal (female : male = 11 : 11) in the open‐ocean area (16–18°N, 118–134°W), biased to males (32 : 62) in the near‐continental area (13–16°N, 103–107°W), and biased to females (19 : 6) in the near‐equatorial area (5°N, 104–120°W). Sex ratios of sailfish Istiophorus platypterus in the near‐continental area and shortbill spearfish Tetrapturus angustirostris in the open‐ocean area were not biased from 1 : 1 (43 : 36, 11 : 13), and that of blue marlin Makaira nigricans in the near‐equatorial area was biased to females (14 : 1). Reproductively active females were found for striped marlin, sailfish and shortbill spearfish. Striped marlin showed a specific spawning area (the near‐continental area), and sexual dimorphism in its temporal distribution pattern, which was presumably related to reproduction. On the other hand, the limited distribution with evidence from spawning of sailfish and shortbill spearfish imply that these species complete their life history within limited areas.  相似文献   

5.
Wild populations of the pustulose ark, Anadara tuberculosa (Bivalvia), an emblematic species of the East Pacific mangrove ecosystem declined in South American countries (Colombia, Ecuador, and Peru) mainly due to overharvesting and habitat loss or degradation. Understanding the genetic aspects of geographic variations and population structure of A. tuberculosa, currently unknown, appears as a priority to fishery authorities in order to elaborate integrated and collaborative conservation policies for fishery management, aquaculture, and stock enhancement programs. We used mtDNA sequence data to investigate haplotype diversity, genetic structure, and demography of A. tuberculosa. Results indicate genetic homogeneity of populations distributed north and south of the equator, respectively. However, statistically significant differentiation emerged between northern and southern populations with pairwise фST values ranging between 0.036 and 0.092. The oceanic current system acting in the area (Panama Current and Humboldt Current) might play a role in limiting the larval dispersal of the species, still poorly understood. Demography reconstruction supported recent population expansion, possibly started after last glacial maximum. Our results would suggest separate and independent management of populations north and south of the equator.  相似文献   

6.
  • 1 Xylosandrus germanus typically colonizes physiologically‐stressed deciduous hosts but it is increasingly being recognized as a key pest of ornamental nursery stock. We tested the attractiveness of common plant stress‐related volatiles to ambrosia beetles occupying the nursery agroecosystem, as well as their ability to induce attacks on selected trees. Experiments were conducted in Ohio, U.S.A.
  • 2 Stress volatile attractiveness was first assessed by positioning traps baited with acetaldehyde, acetone, ethanol and methanol in ornamental nurseries. Cumulative trap counts confirmed that ethanol was the most attractive stress‐related volatile to X. germanus. Methanol‐baited traps were slightly attractive to X. germanus, whereas traps baited with acetaldehyde and acetone were not attractive to any ambrosia beetle.
  • 3 A series of tree injection experiments were also conducted to determine the ability of these volatiles to induce attacks by ambrosia beetles under field conditions. Injection of ethanol into Magnolia virginiana induced the largest number of attacks, whereas injection of acetaldehyde induced more attacks than methanol or acetone. Xylosandrus germanus was the most predominant species emerging from M. virginiana injected with each of the stress‐related volatiles. No attacks by wood‐boring beetles were observed on water injected or uninjected control trees.
  • 4 Solid‐phase microextraction–gas chromatography–mass spectrometry confirmed the emission of acetaldehyde, acetone, ethanol and methanol after their injection into M. virginiana.
  • 5 Xylosandrus germanus has an efficient olfactory‐based mechanism for differentiating among host volatile cues. Injecting select trees with stress‐related volatiles, particularly ethanol, shows promise as a trap tree strategy for X. germanus and other ambrosia beetles.
  相似文献   

7.
Abstract The effect of four host plant species of the herbivore Maruca vitrata Fabricius (Lepidoptera: Crambidae) on development time, longevity, fecundity and sex ratio of the parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) was investigated under laboratory conditions. The larvae were parasitized when in the second instar. Maruca vitrata larvae were fed with flowers of four legumes, that is, Vigna unguiculata (cowpea), Sesbania rostrata, Lonchocarpus sericeus and Pterocarpus santalinoides, or an artificial diet both before and after parasitization. The parasitoid did not develop in hosts feeding on L. sericeus or V. unguiculata at 25°C, or on P. santalinoides at 25°C or 29°C. Apanteles taragamae had the shortest development time on artificial diet at both 25°C and 29°C while the longest development time was recorded on L. sericeus at 29°C. Female wasps took longer to develop compared to males at the two temperatures, regardless of the feeding substrate of their host. The longevity of the wasps at 25°C varied among feeding substrates, but not at 29°C. Survival rate of parasitized larvae depends on the feeding substrate. Moreover, infection of host larvae with Maruca vitrata multi‐nucleopolyhedrovirus (MaviMNPV) killed larger proportions of parasitized larvae at 25°C than at 29°C, which was likely caused by the difference in parasitoid developmental rate. The proportion of female parasitoids was lowest on L. sericeus. The daily fecundity showed a nonlinear trend regardless of the feeding substrate, indicating that A. taragamae is a pro‐ovigenic species. The data support the slow growth–high mortality hypothesis.  相似文献   

8.
Abstract. The interactive effects of temperature (20 °C or 25 °C) and photoperiod (LD 12 : 12 h or LD 15 : 9 h) on diapause induction and termination are investigated in the west‐Japan type yellow‐spotted longicorn beetle, Psacothea hilaris (Pascoe) (Coleoptera: Cerambycidae). Larval diapause of P. hilaris is induced under three diapause‐inducing conditions (20 °C–SD, 20 °C–LD and 25 °C–SD), and the diapause larvae are transferred to one of four conditions (20 °C–SD, 20 °C–LD, 25 °C–SD or 25 °C–LD) for observation of pupation, which indicates termination of diapause. The intensity of diapause induced under the three conditions increases in the order 20 °C–SD < 25 °C–SD < 20 °C–LD, when assessed by the time course of pupation after the transfer. On the other hand, the effectiveness of the temperature–photoperiod combinations to terminate diapause is in the order 25 °C–SD (ineffective) < < 20 °C–LD < 25 °C–LD < 20 °C–SD. Among the temperatures (5, 10, 15 and 20 °C) examined, 15 °C is the most effective in terminating diapause under the short day; diapause in most larvae appears to have been completed in 15 days.  相似文献   

9.
Aims: The potential effect of in‐premise plumbing temperatures (24, 32, 37 and 41°C) on the growth of five different Legionella pneumophila strains within free‐living amoebae (Acanthamoeba polyphaga, Hartmannella vermiformis and Naegleria fowleri) was examined. Methods and Results: Compared with controls that actively fed on Escherichia coli prey, when Leg. pneumophila was used as prey, strains Lp02 and Bloomington‐2 increased in growth at 30, 32 and 37°C while strains Philadelphia‐1 and Chicago 2 did not grow at any temperature within A. polyphaga. Strains Lp02, Bloomington‐2 and Dallas 1E did not proliferate in the presence of H. vermiformis nor did strain Philadelphia‐1 in the presence of N. fowleri. Yet, strain Bloomington‐2 grew at all temperatures examined within N. fowleri, while strain Lp02 proliferated at all temperatures except 41°C. More intriguing, strain Chicago 2 only grew at 32°C within H. vermiformis and N. fowleri suggesting a limited temperature growth range for this strain. Conclusions: Identifying the presence of pathogenic legionellae may require the use of multiple host amoebae and incubation temperatures. Significance and Impact of the Study: Temperature conditions and species of amoeba host supported in drinking water appear to be important for the selection of human‐pathogenic legionellae and point to future research required to better understand Legionella ecology.  相似文献   

10.
11.
Anoplophora chinensis (Forster) (Coleoptera: Cerambycidae) is an A1 class quarantine pest, native to China, Japan, and North Korea. The A. chinensis outbreak in China has severely affected the local environment and economic development. This study investigates potential areas in China with suitable climate for Achinensis using historical climate data (1971–2000) and future climate‐warming estimates generated by CLIMEX1.1. These future estimates are based on simulated climate data (2010–2039) provided by the Tyndall Centre for Climate Change Research (TYN SC 2.0). The results suggest that a wide area of China will have a climate suitable for Achinensis, and every province may contain some suitable areas for this pest. The predicted areas are distributed primarily in central and southern China, with an estimated distribution range of 18.2–49.5°N and 81.3–135.0°E. Using a global‐warming scenario and predictions based on historical climate data, the areas in China with a climate generally suitable for A. chinensis are predicted to decline, whereas the areas that are highly suitable for A. chinensis are predicted to expand particularly to the northeast and northwest. The estimated distribution range covered 18.2–49.1°N and 73.6–135.0°E. Anoplophora chinensis hosts grow in much of China; therefore, the pest could possibly establish this entire predicted area. These results support enhanced quarantine and control measures combined with stronger monitoring systems to prevent the spread and export of A. chinensis.  相似文献   

12.
13.
The effect of temperature on the distributions of ectothermic vertebrates is well documented. Despite the increase of 6°C expected in the next 60 years in South America, numerous vertebrates are still considered as ‘Least Concern’ species by the IUCN due to their large distribution, insufficient widespread threats and insignificant population decline. One example is the lizard Tropidurus torquatus (Squamata: Tropiduridae), commonly found thermoregulating in anthropic environments throughout the Brazilian Cerrado, but restricted to gallery forests in the equator‐ward localities. The urban areas in this warmer region have been colonised by other closely related congeners (e.g. Tropidurus oreadicus). This study aimed to understand this divergence of habitat selection by these tropirudids that may explain some of the species responses to past and future climate warming. We collected body temperatures (Tb), micro‐environmental temperatures (Ta) and operative (Te) temperatures in four sites along a latitudinal gradient: a pole‐ward and two central sites where T. torquatus inhabit urban areas and one equator‐ward site where T. torquatus and T. oreadicus occur in the gallery forest and in urban microhabitats, respectively. All three populations of T. torquatus present similar Tb (35.5–36°C) and shared microhabitats with a similar Ta (34–37.3°C). The Te in the equator‐ward urban site was considerably higher than in the gallery forest. Tropidurus oreadicus Tb was 38.2 °C (30.1–41.3°C) and was active at a Ta of 30.5–42.3°C. The overlap between the genus Tb, Ta and Te highlights a decrease in the hours of activity that lizards would experience under climate warming. The reduction of hours of activity together with the devastation of natural habitats represents threats and an alarming scenario especially for the equator‐ward populations.  相似文献   

14.
  • 1 Xylosandrus germanus (Blandford) is a key pest of ornamental nursery trees. Ethanol is the most attractive semiochemical known for X. germanus, and its emission from trees represents a primary host‐selection cue. Ethanol production is induced by a variety of abiotic and biotic stressors, which could thereby predispose trees to attack by ethanol‐responsive ambrosia beetles.
  • 2 To better understand X. germanus host‐selection behaviour within ornamental nurseries, a series of experiments examined the influence of flood‐stress on the attractiveness and susceptibility of flowering dogwood Cornus florida L. Under field conditions, more X. germanus were attracted to experimentally flood‐stressed dogwoods than neighbouring nonflooded controls in 2009, 2010 and 2011. Flood‐stressed dogwoods were also preferentially attacked in 2009–2011, although no attacks occurred on any of the neighbouring nonflooded trees.
  • 3 Solid‐phase microextraction‐gas chromatography‐mass spectrometry detected ethanol in stem tissue from flooded dogwoods but not nonflooded trees. Acetaldehyde, acetic acid and ethanol were also emitted from the outer bark of flooded dogwoods but not nonflooded trees.
  • 4 These results demonstrate that X. germanus preferentially lands on and attacks physiologically‐stressed hosts, and further support the role of ethanol in mediating this interaction.
  • 5 Attacks by X. germanus have previously been suspected to occur on trees viewed as ‘apparently‐healthy’, although the possibility of such trees being in apparently‐stressed at the time of attack cannot be ruled out given the results obtained in the present study. Minimizing the impact of stressors known to induce the production of ethanol should be the primary foundation of a management plan for X. germanus and other ethanol‐responsive ambrosia beetles.
  相似文献   

15.
Estimates of sea-surface temperatures based on foraminiferal faunal species suggest that the Eastern Equatorial Pacific Ocean was 3–5°C cooler during the Last Glacial Maximum (LGM) than at present. Analysis of new cores from the Southeast Pacific reveals a likely source of ice-age cooling in variations of the Peru Current. Off southern Peru, LGM ocean temperatures were 6–8°C cooler than at present, consistent with substantial cooling on land inferred from regional glacier advances and ice-core data. In the Southeast Pacific, ice-age foraminiferal assemblages have good modern analogs, and transfer functions that define assemblages based on ancient samples yield results similar to those based on coretop samples. During the LGM, subpolar species dominate the Eastern Boundary Current off Peru and extend to the equator. In contrast, the range of the equatorial upwelling species remains roughly constant. We infer from these data and a heat budget model that equatorward advection of cool water, more than equatorial upwelling, drove LGM cooling of the Eastern Tropical Pacific Ocean.  相似文献   

16.
This study is the first large‐scale genetic population study of a widespread climax species of seagrass, Thalassia hemprichii, in the Western Indian Ocean (WIO). The aim was to understand genetic population structure and connectivity of T. hemprichii in relation to hydrodynamic features. We genotyped 205 individual seagrass shoots from 11 sites across the WIO, spanning over a distance of ~2,700 km, with twelve microsatellite markers. Seagrass shoots were sampled in Kenya, Tanzania (mainland and Zanzibar), Mozambique, and Madagascar: 4–26°S and 33–48°E. We assessed clonality and visualized genetic diversity and genetic population differentiation. We used Bayesian clustering approaches (TESS) to trace spatial ancestry of populations and used directional migration rates (DivMigrate) to identify sources of gene flow. We identified four genetically differentiated groups: (a) samples from the Zanzibar channel; (b) Mozambique; (c) Madagascar; and (d) the east coast of Zanzibar and Kenya. Significant pairwise population genetic differentiation was found among many sites. Isolation by distance was detected for the estimated magnitude of divergence (DEST), but the three predominant ocean current systems (i.e., East African Coastal Current, North East Madagascar Current, and the South Equatorial Current) also determine genetic connectivity and genetic structure. Directional migration rates indicate that Madagascar acts as an important source population. Overall, clonality was moderate to high with large differences among sampling sites, indicating relatively low, but spatially variable sexual reproduction rates. The strongest genetic break was identified for three sites in the Zanzibar channel. Although isolation by distance is present, this study suggests that the three regionally predominant ocean current systems (i.e., East African Coastal Current, North East Madagascar Current, and the South Equatorial Current) rather than distance determine genetic connectivity and structure of T. hemprichii in the WIO. If the goal is to maintain genetic connectivity of T. hemprichii within the WIO, conservation planning and implementation of marine protection should be considered at the regional scale—across national borders.  相似文献   

17.
This study clarifies the location, size and age at the onset of metamorphosis in Japanese eels Anguilla japonica through oceanic surveys, rearing experiments and analyses of the morphology and otoliths of leptocephali and glass eels. Twenty‐eight metamorphosing leptocephali were collected in the mesoscale eddy region to the east of Taiwan during research expeditions in 2004. Rearing experiments showed that the total length (LT) of leptocephali decreased by an average of 12·5% during metamorphosis and 13·9% during the 2–12 h after death. Thus, the mean back‐calculated LT at the onset of metamorphosis for 630 glass eels from Taiwan and Japan was estimated at 67·8 ± 2·7 mm (mean ± S.D.). The estimated mean ante‐mortem size of the fully grown pre‐metamorphic leptocephali collected in 2004 was 64·6 ± 3·4 mm, which was consistent with the LT estimate for glass eels. Otolith analysis showed that the mean age at the onset of metamorphosis was 137 ± 15 days and indicated that Japanese eels may have a recruitment route through the mesoscale eddies to the east of Taiwan in addition to the direct transfer route from the North Equatorial Current to the Kuroshio Current.  相似文献   

18.
Crystals of 5‐fluorouridine (5FUrd) have unit cell dimensions a = 7.716(1), b = 5.861(2), c = 13.041(1)Å, α = γ = 90°, β = 96.70° (1), space group P21, Z = 2, ρobs = 1.56 gm/c.c and ρcalc = 1574 gm/c.c The crystal structure was determined with diffractometric data and refined to a final reliability index of 0.042 for the observed 2205 reflections (I ≥ 3σ). The nucleoside has the anti conformation [χ = 53.1(4)°] with the furanose ring in the favorite C2′–endo conformation. The conformation across the sugar exocyclic bond is g+, with values of 49.1(4) and ? 69.3(4)° for Φθc and Φ respectively. The pseudorotational amplitude τm is 34.5 (2) with a phase angle of 171.6(4)°. The crystal structure is stabilized by a network of N–H…O and O–H…O involving the N3 of the uracil base and the sugar O3′ and O2′ as donors and the O2 and O4 of the uracil base and O3′ oxygen as acceptors respectively. Fluorine is neither involved in the hydrogen bonding nor in the stacking interactions. Our studies of several 5‐fluorinated nucleosides show the following preferred conformational features: 1) the most favored anti conformation for the nucleoside [χ varies from ? 20 to + 60°] 2) an inverse correlation between the glycosyl bond distance and the χ angle 3) a wide variation of conformations of the sugar ranging froni C2′–endo through C3′–endo to C4′–exo 4) the preferred g+ across the exocyclic C4′–C5′ bond and 5) no role for the fluorine atom in the hydrogen bonding or base stacking interactions.  相似文献   

19.
Aim This paper aims at determining how different floristic elements (e.g. cosmopolitan, tropical, and temperate) change with latitude and major climate factors, and how latitude affects the floristic relationships between East Asia and the other parts of the world. Location East Asia from the Arctic to tropical regions, an area crossing over 50° of latitudes and covering the eastern part of China, Korea, Japan and the eastern part of Russia. Methods East Asia is divided into forty‐five geographical regions. Based on the similarity of their world‐wide distributional patterns, a total of 2808 indigenous genera of seed plants found in East Asia were grouped into fourteen geographical elements, belonging to three major categories (cosmopolitan, tropical and temperate). The 50°‐long latitudinal gradient of East Asia was divided into five latitudinal zones, each of c. 10°. Phytogeographical relationships of East Asia to latitude and climatic variables were examined based on the forty‐five regional floras. Results Among all geographical and climatic variables considered, latitude showed the strongest relationship to phytogeographical composition. Tropical genera (with pantropical, amphi‐Pacific tropical, palaeotropical, tropical Asia–tropical Australia, tropical Asia–tropical Africa and tropical Asia geographical elements combined) accounted for c. 80% of the total genera at latitude 20°N and for c. 0% at latitude 55–60°N. In contrast, temperate genera (including holarctic, eastern Asia–North America, temperate Eurasia, temperate Asia, Mediterranean, western Asia to central Asia, central Asia and eastern Asia geographical elements) accounted for 15.5% in the southernmost latitude and for 80% at 55–60°N, from where northward the percentage tended to level off. The proportion of cosmopolitan genera increased gradually with latitude from 5% at the southernmost latitude to 21% at 55–60°N, where it levelled off northward. In general, the genera present in a more northerly flora are a subset of the genera present in a more southerly flora. Main conclusions The large‐scale patterns of phytogeography in East Asia are strongly related to latitude, which covaries with several climatic variables such as temperature. Evolutionary processes such as the adaptation of plants to cold climates and current and past land connections are likely responsible for the observed latitudinal patterns.  相似文献   

20.
Maesopsis eminii is referred to as one of the most widely distributed African tree species. However, its occurrence in Africa has never been mapped and little is known as to how this species can sustain in different environments. To gain insight into Maesopsis’ ecology, we (i) made a synthesis of its functional trait data from the literature, (ii) investigated phenological patterns using data on four M. eminii trees from Yangambi, DR Congo, (iii) assessed an empirical provenance trial from Uganda on 600 Maesopsis trees and (iv) synthesized geo‐referenced point location maps of Maesopsis entailing WorldClim precipitation and temperature and FAO soils, rainfall and ecological zones for Africa. We found M. eminii to straddle the equator equidistantly in terms of latitude (10.97°N and 10.98°S) covering five forest types where twenty soil types and variable rainfall regimes support complex plant biodiversity. Maesopsis eminii was, however, largely concentrated in the tropical rainforest ecosystem which contains fertile Orthic Ferralsol soils. More than 97% of the point locations were found where annual precipitation was >1000 mm, and 82% occurred where average annual temperature was 22–28°C. Its functional traits, phenology and provenance trial findings explained its occurrence in Africa.  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