共查询到20条相似文献,搜索用时 15 毫秒
1.
In the central region of the Great Barrier Reef, Acanthaster planci eats its own disk area of coral each day. At the southern end of the reef lagoon populations of A. planci eat substantially less than this amount of coral per day. Branching and plate corals are preferred food species and massive and encrusting forms are rejected while the preferred food species are available. Only when branching and plate forms on a reef have been consumed will A. planci attack massive and encrusting species. On Australian reefs preferred food species form between 70–99% of the coral cover.
On the Great Barrier Reef A. planci spawns in January and juveniles settle in the top 3 m of water on the windward edge of reefs or on isolated patch reefs behind the main reef. Intolerance of wave attack forces the growing starfish to migrate into deeper water. Lateral movements, probably induced by shortage of living coral in deep water, bring the starfish around the ends of the reef to the leeward side. Here they destroy most of the living coral.
It is suggested that the visual impact of A. planci on reefs of the Indo-Pacific region is related to the composition of the coral fauna. Reefs with a high proportion of preferred food species will be severely damaged while those with faunas composed mainly of massive and encrusting forms will not be altered greatly by starfish predation.
Work on larval development of A. planci carried out by Henderson & Lucas, 1971 showed that metamorphosis took place only at water temperatures of 28o -29o C. This suggests that the A. planci plague on the Great Barrier Reef will not spread south of latitude 20o S (29o C isotherm in January). 相似文献
On the Great Barrier Reef A. planci spawns in January and juveniles settle in the top 3 m of water on the windward edge of reefs or on isolated patch reefs behind the main reef. Intolerance of wave attack forces the growing starfish to migrate into deeper water. Lateral movements, probably induced by shortage of living coral in deep water, bring the starfish around the ends of the reef to the leeward side. Here they destroy most of the living coral.
It is suggested that the visual impact of A. planci on reefs of the Indo-Pacific region is related to the composition of the coral fauna. Reefs with a high proportion of preferred food species will be severely damaged while those with faunas composed mainly of massive and encrusting forms will not be altered greatly by starfish predation.
Work on larval development of A. planci carried out by Henderson & Lucas, 1971 showed that metamorphosis took place only at water temperatures of 28
2.
The influence of environmental parameters on the bacterial populations of thermal springs in West Bengal, India 总被引:2,自引:0,他引:2
The physico-chemical characteristics and the bacterial populations of three thermal springs in West Bengal have been examined. The springs range in temperature from 42o C (Saubhagya Kund) to 65o C (Agni Kur.d). The levels of carbonate and bicarbonate alkalinity, total hardness and the ppm of chloride, phosphate and silicate as well of dissolved oxygen were measured at monthly intervals. Estimates of the bacterial populations were obtained from cultures. Water samples incubated at 37o C for enumeration of mesophilic microbes, at 50o C for thermo-tolerant bacteria and at 60o for strict thermophiles. Tests for coliform organisms were carried out at 37o C and at 50o C.
All three springs show seasonal variation in their physico-chemical characteristics and in their bacterial populations. The cooler springs have large populations of mesophilic and thermotolerant bacteria but fewer thermophilic types. In the two hot springs (Saubhagya Kund and Swetganga), the differences of mean bacterial populations observed between 37o and 50"C and between 50o and 60o C are highly significant ( P < 0.01), in the third (Agni Kund) the differences are also significant ( P < 0.01) but the population showed a rising trend with the temperature. Of the biotic and abiotic factors which could be involved in the observed seasonal variation in the bacterial populations, only the fluctuations in the phosphate levels were found to show a significant correlation (0.001 < P < 0.01). 相似文献
All three springs show seasonal variation in their physico-chemical characteristics and in their bacterial populations. The cooler springs have large populations of mesophilic and thermotolerant bacteria but fewer thermophilic types. In the two hot springs (Saubhagya Kund and Swetganga), the differences of mean bacterial populations observed between 37
3.
W. T. CATTON 《Physiological Entomology》1988,13(2):147-152
The spike discharges of the descending contralateral movement detector (DCMD) neurone, and of some smaller visual interneurones (S-units), were recorded in the ventral nerve cord of adult Schistocerca gregaria Forsk., in response to a stationary disc (25o ) or a small spot (0.2o ) stimulus. The discharge rate of each neurone was plotted over a period of 5 s exposure; the total number of spikes in this period was also noted. The DCMD response to the 25o disc was a high-frequency burst falling off quickly to a low rate; the 0.2o spot evoked a prolonged discharge with an early peak in rate. In S-units the discharge was prolonged with both targets; the rate rose to an early peak in each case, with a much higher rate for the larger disc. For the DCMD the total number of spikes per stimulus (5 s) was greater for the 0.2o spot; for S-units it was greater for the 25o disc. Thus an increase of about 30-fold in the number of ommatidia stimulated resulted in a fall in the total DCMD response to about one-quarter; a similar increase evoked a rise of about 6-fold in the S-unit response. When the 25o disc was presented at progressively reduced intensities the total spike response of the DCMD rose steadily to a maximum at about 2.9 μ W m-2 ; using the same procedure the spike output of S-units, initially high, declined monotonically. The role of inhibition in these results is discussed. 相似文献
4.
Abstract The visual acuity of two species of tsetse flies, Glossina morsitans morsitans Westw. and Glossina pallidipes Aust., was investigated. Male G. morsitans eyes have an acute zone in the forward region, with large hexagonal lenses (mean minimum diameter, D=33, SE±0.7 μm), relatively small interommatidial angle (Δ(φ=1.08o ) and angular receptive field of individual ommatidia (Δp) of not less than 1.14o . A narrow band of square lenses, with intermediate diameter and Δφ, merges with smaller hexagonal lenses in the periphery (24±0.7 μm), with relatively large interommatidial angle (Δφ=3.7o ) and small angular receptive field (Δp = c. 1.6o ). G.pallidipes eyes are similar, except that the lenses in the acute zone are larger than those of G.morsitans , in proportion to their larger body size. Female eyes are not significantly different from male eyes, except that they have a narrower region of binocular overlap (maximum for males = 24o , for females = 18o ). The eye parameter (p=DΔφ) in the acute zone of male G.morsitans = 0.62, and in the peripheral zone = 1.56. These relatively high values are consistent with fast flight, visual detection of drift due to low wind speeds, mating chases and discrimination of cryptic host animals at high light intensities. The extended region of binocular overlap in males may serve as an early warning system of the approach of potential females. From our estimates, tsetse flies ought to be able to detect small objects against the sky c. 30 min before sunrise and after sunset, and to use their peripheral vision perhaps 15 min earlier and later than this. 相似文献
5.
The species of coliform bacterium predominant on fresh grass was found to be a capsulated type growing well at 30o C. but unable to grow at 37o C. For this reason it will not be detected by the presumptive test in bile salt-lactose broth at 37o C. The name Bacillus (Aerebacter) aerogenes graminis is proposed for this species.
It is possible that conforms of the above type contribute to a small extent to the initial fermentation of the silage. Those coliforms giving the presumptive test at 37o C. were found in such small numbers in the silage investigated that their influence was concluded to be negligible.
This work forms part of some research carried out under grant from the Research Council of Imperial Chemical Industries, Ltd., to whom the authors wish to make due acknowledgement. Valuable help was also received from Dr S. J. Watson, who supplied samples of grass and silage- 相似文献
It is possible that conforms of the above type contribute to a small extent to the initial fermentation of the silage. Those coliforms giving the presumptive test at 37
This work forms part of some research carried out under grant from the Research Council of Imperial Chemical Industries, Ltd., to whom the authors wish to make due acknowledgement. Valuable help was also received from Dr S. J. Watson, who supplied samples of grass and silage- 相似文献
6.
CLIFFORD RAY JOHNSON 《Zoological Journal of the Linnean Society》1977,60(4):381-390
Mean thermal preferenda for the head and body were found to be similar in Egernia whitei, E. cunninghami, and E. bungana (range in TH = 33.6o -33.8o C; range in TB = 34.0o -35.3o C). However, those for E. majors were significantly lower (TH = 31.1o C, TB =32.9o C). Significant differences were found between mean head and body preferred temperatures in E. cunninghami and E. major. Higher temperatures were tolerated by the body than the head in all four species. Gaping was not observed to occur prior to cessation of respiration in any of the four species during radiant or solar heating. Based upon thermal preferenda and critical thermal maxima data, thermal safety margins for body temperature were calculated for E. whitei and E. cunninghami Postural orientation to the sun's rays increased and decreased heat gain. The seeking of shade was the most effective method employed by all four species for reducing head and body temperature. 相似文献
7.
CHRISTOPHER P. SANFORD FLS 《Zoological Journal of the Linnean Society》2001,132(2):259-275
Osteoglossomorph fishes are unique in possessing a specialized feeding mechanism, the tongue-bite apparatus (TBA) involving the hyoid apparatus. The TBA is associated with two unique behaviour patterns - raking and open-mouth chewing - used to disable and macerate prey. The kinematics of these two behaviours was compared in two species of knifefishes (family Notopteridae): Xenomystus nigri (Gunther, 1868) and Chitala ornata (Gray, 1831) using high-speed video (250 frames s"1 ). Both univariate and multivariate analyses indicated that there were significant interspecific differences in both raking and open-mouth chewing. Raking can be divided into three stages; the preparatory phase, power stroke, and recovery phase. During the power stroke posterior motion of the pectoral girdle and neurocranial elevation both appear to play a major role in prey reduction. In Xenomystus the power stroke involves significantly greater levels of neurocranial elevation (35o ) and pectoral girdle motion (38% of head length; 9.5o ) than that found in Chitala (neurocranial elevation 11o ; pectoral girdle motion 11% of head length and 5o ). Indeed, Xenomystus represents the most extreme raking behaviour of any osteoglossomorph thus far studied. Temporal displacement variables demonstrated that the power stroke in Xenomystus is significantly faster than in Chitala. Although some of the interspecific differences might be size related, these data suggest that a greater degree of difference exists in these highly specialized behaviours than previous work has demonstrated. These findings support the notion that biomechanical duplication (an additional ligament found in osteoglossomorphs) could be linked to increased functional versatility. 相似文献
8.
S.J. TORR 《Physiological Entomology》1988,13(3):315-325
ABSTRACT Studies were conducted in Zimbabwe of the responses of Glossina morsitans morsitans Westwood and Glossina pallidipes Austen resting in a refuge to various host stimuli. Tsetse took off in response to 100% ox odour, 0.08% carbon dioxide or a visual stimulus consisting of a 0.75 × 0.75 m black target placed c . 5 m from the refuge moving at 4o s-1 , but the level of response was low with only 35%, 19% and 29% responding, respectively. Tsetse did not take off in response to any one of 25% ox odour, 0.8% carbon dioxide, acetone (3 μg 1-1 ) or octenol (0.03 μg 1-1 ). In the absence of any host stimuli, flies emerged from the refuge later on hotter days (35–37o C) than on cooler days (32–34.5o C). Male G.pallidipes emerging later in the afternoon contained significantly more haematin than those emerging relatively earlier. There were no significant differences between the responses of G.m. morsitans and G.pallidipes. It is suggested that the initial activation of resting flies is primarily mediated through endogenous, rather than host, stimuli. 相似文献
9.
Flying mate detection and chasing by tsetse flies (Glossina) 总被引:1,自引:0,他引:1
JOHN BRADY 《Physiological Entomology》1991,16(2):153-161
Abstract Male tsetse flies, probably Glossina morsitans morsitans Westw., were video-recorded in the field as they took off and chased other tsetse flies. Chasers responded (took off) to a target fly at a maximum distance of c. 55 cm, when it subtended c. 1.6o to their eye (–1 foveal ommatidial subtense). Chased targets were always within this range (mean subtense at take-off = 3.2o ) and approaching the chaser. The most significant difference between chased and non-chased targets was in the rate of approach of the target fly in terms of the increase in its image size immediately before the chaser took off ( 21o s−1 ), especially as its relative increase (690% s-1 P< 0.005). No feature of the target's translational velocity, nor any relationship between that and the image size approached this level of significance. Chasers seemed to 'slipstream' their target at c. 20 cm directly behind it, perhaps suggesting target identification by speed matching. Chases were apparently abandoned when the target image shrank from covering at least two of the chaser's foveal ommatidia to covering only one. Parallax-free measurements of flight speeds indicated a preferred, stable mean groundspeed of 4.8±0.1 m s_1 (SE), at a mean wing-beat frequency of 209±3 Hz. 相似文献
10.
Cold shock and heat shock: a comparison of the protection generated by brief pretreatment at less severe temperatures 总被引:1,自引:0,他引:1
Abstract Brief exposure to low (0o C) or high (40o C) temperature elicits a protective response that prevents injury when the flesh fly, Sarcophaga crassipalpis Macquart, is subjected to more severe cold (-10o C) or heat (45o C). Both the low and high temperature responses were found in all developmental stages of the fly, but were most pronounced in the pupal and pharate adult stages. The protective responses generated by brief exposure to 0 or 40o C appear similar in that both result in a rapid acquisition of cold or heat tolerance and a loss of protection after the flies are returned to 25o C. The protection generated by chilling is obvious within 10 min of exposure to 0o C while a 30 min exposure to 40o C is required to induce the high temperature protection. High temperature protects against cold shock injury within a narrow range (around 36o C) but we have no evidence that low temperature can protect against heat injury. We previously demonstrated that the rapid increase in cold tolerance correlates with concomitant increases in glycerol concentration, but in this study we found no significant elevation in glycerol in heat-shocked flies. Thus the physiological and biochemical bases for the rapid responses to cold and heat appear to be different. 相似文献
11.
BRADLEY A. MULLENS WALTER J. TABACHNICK FREDERICK R. HOLBROOK LEE H. THOMPSON 《Medical and veterinary entomology》1995,9(1):71-76
Abstract. Culicoides variipennis sonorensis females were fed bluetongue virus serotype 11 mixed in sheep blood and were held at constant temperatures of 32, 27, 21 and 15o C. Virogenesis, as measured by enzyme-linked immunosorbent assay (ELISA), proceeded significantly faster at higher temperatures. Based on ELISA absorbance ≥0.2, some flies first were categorized as infected after 1 day, 2 days and 4 days at 32, 27 and 21o C, respectively. Peak levels of virus antigen were seen after 5–7, 7–13 and 18–22 days for flies held at 32, 27 and 21o C, respectively. There was no significant virus replication in flies held at 15o C for 22 days, but latent virus replicated and was detected easily (44% infection) 4–10 days after these flies were transferred to 27o C. The implications for temperature effects on bluetongue epizootiology are discussed. 相似文献
12.
Development rates of some pre-adult stages in blowflies with reference to low temperatures 总被引:2,自引:0,他引:2
Abstract. Duration of some pre-adult stages of Calliphora vicina Robineau-Desvoidy, C.alpina Zett., C.vomitoria Linn., Phormia terraenovae R.-D. and Lucilia sericata Meig. were determined at 3.5–26o C, in the context of use of these insects in forensic estimates of post-mortem intervals. Egg development in C. vicina occurs down to at least 3.5o C, larval growth to 4o C and puparial formation, development and perfect adult emergence to 5o C. Growth curves by successive weighing of individual larvae showed specific differences in rates of development of the above species at constant temperatures. Alternating temperatures for 12 h periods (such as 10o C and 20o C) to simulate diurnal changes, usually, but not at all temperature pairs tested, caused acceleration of growth relative to the corresponding constant temperature (15o C in the above case), in C.vomitoria, P.terraenovae and L.sericata , but usually caused retardation of larval growth in C.vicina. In this species, larvae as single individuals on beef liver in small tubes grew on average at the same rates as those (50–100 larvae) growing communally. All species showed variation in larval growth between individuals, more marked in C.vicina , and slower-growing larvae showed increased unexplained mortality. Because of this and to avoid complication by fast-growing larvae from later laid egg batches on a carcass, growth curves given are those of mean weights of the heaviest 25% (upper quartile) of groups of 40–90 feeding larvae. Variation in growth rates, and acceleration or retardation of growth in different species under alternating temperatures, thus affect suggested procedures in obtaining estimates of post-mortem intervals using these insects. 相似文献
13.
ROGER M. EVANS 《Ibis》1995,137(3):340-344
Gannets (Sulidae) and some other pelecaniforms incubate their eggs under the webs of their totipalmate feet. These species have a wide latitudinal distribution from tropics to subarctic, but little is known of the incubation temperatures attained. I measured egg temperatures of the Australasian Gannet Morns serrator at Cape Kidnappers, New Zealand, employing a data logger to obtain records every 15 min for day-long sample periods at undisturbed nests. Egg surface temperatures were relatively stable and little affected by ambient temperature. Mean surface temperature of natural eggs was 34.9o C for samples taken during the first 4 days of incubation, but this then increased and stabilized at 36.5o C. Internal temperature of pipped eggs was about 1o C higher, attributable to embryonic heat production. Upper surface temperature of eggs kept in a fixed position was about 2o C below deep adult body temperature (40.3o C), suggesting heat is transferred directly from the body through the feet. Clutch size does not appear to be limited by an inability to warm two eggs. These results are in general agreement with measurements from other web incubators and are well within the range for species with conventional brood patch incubation. 相似文献
14.
Properties of lucerne transient streak virus, and evidence of its affinity to southern bean mosaic virus 总被引:1,自引:0,他引:1
A virus obtained from naturally infected lucerne ( Medicago sativa ) in New Zealand reacted with antiserum to an Australian isolate of lucerne transient streak virus (LTSV). Some plants infected with New Zealand isolates showed yellow flecks along lateral veins of leaves; symptoms were transient in some lucerne plants but persistent in others. A New Zealand isolate (LTSV-NZ) infected 14 of 39 plant species tested by mechanical inoculation, but was not transmitted by five aphid species. In sap of Nicotiana clevelandii , LTSV-NZ was infective after storage for 4 wk at 20 o C, diluting to 10-5 , or heating for 10 min at 70 o C. Purified virus preparations contained a single electrophoretic component and a single sedimenting component (s20w = 112 S ) which formed a single buoyant density component in CsCl (1.37 g cm-3 ) but two density components in Cs2 SO4 (1.26 and 1.32 g cm-3 ). LTSV-NZ particles were stable in 10 ITIM EDTA at pH 5, but not at pH 8, being degraded into two sedimenting components of 105 S and 92 S. Particles contained c. 18% RNA in the form of one single-stranded RNA molecule of mol. wt 1–4 times 106 , and a polypeptide of mol. wt c. 32 400. LTSV-NZ was serologically unrelated to 24 other isometric plant viruses. However, its properties are similar to those of southern bean mosaic virus and allied viruses. The present cryptogram of LTSV is R/l: 1–4/(18):S/S:S/*. 相似文献
15.
G. J. PERSLEY 《The Annals of applied biology》1979,93(2):159-166
Cassava seed which had been stored at 5 o C and 60% r.h. for 2–51 months was assayed for the presence of Xanthomonas manihotis by a leaf-infiltration technique, using as inoculum the supernatant from seeds soaked in sterile water at 30 o C for 2–4 h. The threshold of sensitivity of the assay method was 105 cells/ml. Twenty out of 50 samples yielded the pathogen. The infested seed had been in storage for 2–18 months. Bacteria reisolated from infiltrated leaves were identical to X. manihotis in cultural characteristics, phage type and pathogenicity. Surface sterilisation or hot air treatment for 24 h at 65o C or lower did not eliminate the pathogen from infested seed. Soaking of infested seed in hot water at 60 o C for 20 min reduced the number of bacteria to less than the minimum detectable level without appreciably reducing germination. Cassava bacterial blight was observed in 8-wk-old seedlings which had been planted during the dry season at a site where infection from outside sources was unlikely. It is postulated that a low percentage of successful seed transmissions of X. manihotis can occur under favourable environmental conditions. 相似文献
16.
RAVI PARKASH DEV KARAN ASHOK K. MUNJAL 《Biological journal of the Linnean Society. Linnean Society of London》1999,66(2):205-214
Indian geographical populations of Drosophila melanogaster, collected at latitude 10–32.3 o N, longitude 76.1–80.1 o E and altitude 16–2050 m, were analysed for changes in Adh 1 frequency and utilization potential of diverse alcoholic resources. Until now, there have been limited data on climatic association of correlated changes on these aspects in continental populations of D. melanogaster. Indian populations demonstrate an increase in Adh F frequency by 0.04 per degree latitude and significantly higher utilization of ethanol (9.0–15.2%), acetic acid (8.1–12.5%), n-propanol (2.55-4.25%), 2-propanol (1.5-3.5%), n-butanol (2.15 3.5%) and 2-butanol (0.68-1.2%). Data also revealed significant correlation with latitude as well as altitude. Regression analysis of climatic data from collection sites confirmed the observed clinal variation of Adh F as well as alcoholic utilization in D. melanogaster. On the Indian subcontinent, variation in Adh F frequency and alcoholic resource utilization along increasing latitude as well as altitude are due to climatic selection factors such as temperature and rainfall. 相似文献
17.
G.-J.E. NYCHAS AND C.C. TASSOU. 1996. The effect of vacuum and modified atomosphere packaging on the growth/survival of Samonella entertidis on fresh poultry and fish (Boops boos) is described. Salmonella enteritidis survived but did not grow significantly in all samples (poultry or fish) at 3o C. At 10o C the numbers of Salm. enteritidis increased rapidly in vacuum-packed samples and in samples flushed with 100% N2 , 20%, CO2 /80% O2 of both types of proteinaceous food. Growth was also evident in fish and poultry flushed with 100% CO2 ; however the rate of growth was greater in fish samples rather than in poultry. 相似文献
18.
Abstract. Female Glossina morsitans morsitans Westwood were video-recorded in a wind-tunnel as they entered, in crosswind flight, a broad plume of either octenol or acetone (two components of ox odour). Both odours produced upwind turning responses (in-flight anemotaxis) to a range of concentrations, with thresholds at around 10-8 mg1-l for octenol and 10-6 mg1-1 for acetone. Kinetic responses were unaffected by octenol at low concentrations, but flight speed was significantly reduced and sinuosity (o m-1 ) and angular velocity (o s-1 ) significantly increased by concentrations at or above those in ox breath; for acetone, these effects were apparent but inconsistently related to concentration. It is concluded that octenol and acetone vapour are used by tsetse flies to locate hosts by upwind anemotaxis, probably combined with kinetic responses. The behavioural basis for the 'repellency' of high octenol concentrations in the field is discussed in the context of the virtual loss of upwind anemotaxis to octenol at the highest concentration tested in the tunnel (30 × ox breath). 相似文献
19.
Flight behaviour of tsetse flies in host odour plumes: the initial response to leaving or entering odour 总被引:2,自引:0,他引:2
ABSTRACT. Free-flying, wild male and female Glossina pallidipes Aust. and G. m. morsitans Westw. were video-recorded in the field in Zimbabwe as they entered or left the side of a host-odour plume in cross-wind flight, or as they overshot a source of host odour in upwind flight (camera 2.5 m up looking down at a 3 times 2.5 m field of view at ground level). 80% of cross-wind odour leavers turned sharply ( turns 95o ), but without regard to wind direction (overshooters behaved essentially the same except that nearly 100% turned). Many fewer flies entering a plume cross wind turned ( c . 60%), and when they did they made much smaller turns ( 58o ); these turns were, however, significantly biassed upwind ( c . 70%). All three classes of fly had similar groundspeeds ( 5.5–6.5 m s_1 ) and angular velocities ( 350–400o s-1 ). Clear evidence was obtained of in-flight sensitivity to wind direction: significantly more flies entering odour turned upwind than downwind, and odour losers turning upwind made significantly larger turns than average. The main basis for the different sizes of turn was the different durations of the turning flight, rather than changes in angular velocity or speed. No evidence was found of flies landing after losing contact with odour. 相似文献
20.
ABSTRACT. From a Japanese population of Chymomyza costata which has been known to have a photoperiodic larval diapause, we selected a mutant strain which did not respond to photoperiod. However, about 70% of the individuals of this strain entered diapause at 11o C irrespective of photoperiod, and about the same percentage of those of the photoperiod-sensitive strain also did so in continuous illumination at 11o C. This indicates that low temperature induces diapause independently of photoperiod. On the other hand, a temperature drop from 18 or 25o C to 15o C and chilling at 4o C did not induce diapause. 相似文献