Flight responses of tsetse flies (Glossina) to octenol and acetone vapour in a wind-tunnel

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^-8mg1^-l for octenol and 10^-6mg1^-1 for acetone. Kinetic responses were unaffected by octenol at low concentrations, but flight speed was significantly reduced and sinuosity (^om^-1) and angular velocity (^os^-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).     

Upwind flight of tsetse (Glossina spp.) in response to natural and synthetic host odour in the field

Abstract. In Zimbabwe, studies were made of the flight responses of tsetse ( Glossina spp.) to synthetic and natural ox odour using arrangements of electric nets.Tsetse flying away from a target showed a significant upwind bias when a blend of carbon dioxide (2/1 min), acetone (500 mg/h), octenol (0.4 mg/h), 4-methylphenol (0.8 mg/h) and 3-n-propylphenol (0.1 ma) was dispensed 15 m upwind, with c. 35% flying upwind.Without carbon dioxide this percentage was significantly reduced to 15% which was not significantly different from that with no odour (8%).This pattern was not altered by reducing the doses of acetone, octenol and phenols by 10–100 times, to levels comparable to those produced by an ox.With natural ox odour or a synthetic equivalent of ox odour dispensed from a ventilated pit 8 m upwind of the target, c. 28% flew upwind.This was reduced significantly to 15% if carbon dioxide was removed.In studies using a 17 m line of nets arranged orthogonally across the prevailing wind line, c. 50% of the catch was caught on the downwind side in the absence of odour.This increased significantly to c.60% when acetone, octenol and phenols were dispensed 15 m upwind, with or without carbon dioxide.With a shorter line (9 m) or an incomplete one (16.5 m long with 5 times 1.5 m wide gaps along its length) there was no change in the proportion caught downwind.For all three lines, dispensing odour upwind increased the catch 2–5 times on both the up-and downwind sides of the nets.It is concluded that a stronger upwind response to host odour is elicited when carbon dioxide is present.It is suggested that in nature upwind flight is very imprecisely orientated, with tsetse making flights up and down an odour plume 'searching' for a host.     

The activation of resting tsetse flies (Glossina) in response to visual and olfactory stimuli in the field

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 4^o 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 (35–37^oC) than on cooler days (32–34.5^oC). 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.     

Extracellular release of photosynthetic products by freshwater phytoplankton populations, with special reference to the algal species involved

SUMMARY. Over three successive years, depth profiles of C-fixation and excretion, chlorophyll- a concentrations, phytoplankton species composition and bacterial numbers were determined in Lake Vechten, a slightly eutrophic lake in The Netherlands. Special attention was given to the method used to measure extracellular release.
Excretion of dissolved organic ¹⁴C depended largely upon the photo-synthetic activity of the phytoplankton, ranging from 0–2.5 mg m^-1 h^-1, representing a percentage extracellular release (PER) of 0–25%.
During a period in August, however, a subsurface chlorophyll- a maximum at 5–7 m depth coincided with high excretion rates of up to 10 mg Cm^-3 h^-1 (PER = 55%). Phytoplankton analysis revealed a stratification in numbers of Mallomonas caudata with a maximum at 5–7 m depth.
The results suggest that in these water layers bacterial populations grew at the expense of the dissolved organic carbon compounds excreted by Mallomonas caudata. This means that extracellular release can temporarily function as an important nutrient source for the heterotrophie community in addition to the more or less constant dissolved organic carbon pool.     

Wind as a factor influencing flower-visiting by Hadena bicruris (Noctuidae) and Deilephila elpenor (Sphingidae)

Abstract. 1. In a low-speed wind tunnel, male as well as female moths of Hadena bicruris responded to floral odours with positive anemotaxis. Hitherto, such orientation has only been demonstrated for male moths in response to pheromones.
2. H.bicruris had a maximum flight speed of 4.5–5.4ms^-1 and stopped its flower visiting at a wind speed of 2.5–2.8 m s^-1.
3. Deilephila elpenor had a similar maximum flight speed (4.5— 5.1 ms^-1), but it continued visiting flowers up to wind speeds of 3.0–5.0 ms^-1.
4. Apart from mechanical resistance during flight and flower visits, wind might have adverse effects on the energy budget and on evaporative water loss.     

Drinking rate, uptake of bacteria and microalgae in turbot larvae

The drinking rate of turbot larvae increased from 14 to 120 nl larva^-1 h^-1 from day 2 to 11 after hatching, which gave a slightly increased specific drinking rate (calculated per biomass) from day 2 to 7 (0·8–1·9 nl μg carbon^-1 h^-1. The clearance rate of both algae and bacteria was 10–100 times higher than the drinking rate, which indicated that the larvae had an active uptake of both algae and bacteria. On day 2 and 4 after hatching highest clearance rate was observed for Tetraselmis sp. On day 6 about the same clearance rate was observed for bacteria, Isochrysis galbana and Tetraselmis sp. Until day 4 the turbot larvae had a higher ingestion rate of Tetraselmis sp. than of I. galbana , whereas on day 6 the rates were similar (28–41 ng carbon larvae^-1 h^-1). The assimilation efficiency was somewhat higher for I. galbana than for Tetraselmis sp., and on day 6 the assimilated algae constituted 1·5 and 0·9% of the larval biomass for I. galbana and Tetraselmis sp., respectively.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).     

Effects of carbon dioxide, acetone and 1-octen-3-ol on the activity of the stable fly, Stomoxys calcitmns

Abstract. The responses of Stomoxys calcitrans (L.) to carbon dioxide, acetone and 1-octen-3-ol were assessed using flight activity as a measure of activation. Carbon dioxide and acetone caused significant increases in activity, with thresholds at -0.006% and -0.01 μg 1^-l, respectively. For l-octen-3-ol, flight activity decreased at 2 μg 1^-1 for males, and at 0.2 μg 1^-1 for females. Variation in activity was also manifest as differences in the time elapsed between landing and subsequent take-off: CO₂ (7.1 s) and acetone (12.2s) had lower times than the corresponding no-odour controls (16.6 and 23.2s), whereas 1-octen-3-ol (25 s) had a higher time than the control (21.5 s). The proportion of the total number of flights landing on a black target was higher in CO₂(0.16) and acetone (0.11) than in clear air (c. 0.07), but was lower for l-octen-3-ol.     

Effects of carbon dioxide, acetone and 1-octen-3-ol on the flight responses of the stable fly, Stomoxys calcitrans, in a wind tunnel

Abstract. The flight behaviour of Stomoxys calcitrans (L.) in odour plumes containing carbon dioxide, acetone or l-octen-3-ol was assessed from video recordings. A downwind bias was evident in clean air, whereas all three test chemicals elicited upwind anemotaxis. Response thresholds were ∼0.006% for CO2, between 0.001 and 0.01 μg/l for acetone, and ∼0.0002 u.g/1 for l-octen-3-ol. Sinuosity (° cm^-1) and angular velocity (° s^-1) increased with C0₂ concentration, but velocity (cm s"¹) decreased. Similar, but less clear effects were observed for acetone and l-octen-3-ol.     

Foraging energetics of Grey-headed Albatrosses Diotnedea chrysostoma at Bird Island, South Georgia

At-sea metabolism (CO₂ production) and water turnover of six breeding Grey-headed Albatrosses Diomedea chrysostoma were measured, using the doubly labelled water method, at Bird Island, South Georgia, Mean food consumption (estimated from a water influx rate of 1.01 1 d^-1 and data on dietary composition) was 1200gd^-1 or 50.4 W. At-sea metabolism (derived from a rate of CO₂ production of 3.98 1 h^-1) was 27.7 W, 2.5 times the estimated basal metabolic rate (BMR). On average the birds ingested nearly twice as much food energy as they expended to obtain it. The metabolic rate during flight (estimated from at-sea metabolism and activity budget data) was 36.3 W (range 34.7–39.0 W) or 3.2 (range 3.0–3.4) times the predicted BMR. This is the lowest cost of flight yet measured, but consistent with the highly developed adaptations for economic flight shown by albatrosses. These results are briefly compared with data for other polar vertebrates (penguins, fur seals) exploiting similar prey.     

Differential responses of Aedes and Culex mosquitoes to octenol or light in combination with carbon dioxide in Queensland, Australia

Abstract. Field studies were conducted with EVS (encephalitis vector surveillance) traps in south-eastern Queensland, Australia, to determine the relative response rates of mosquitoes to three levels (0.1, 4.5 and 30mg/h) of 1-octen-3-ol (octenol) in combination with a standard bait of 2200 g carbon dioxide (CO₂), compared with CO₂ alone or CO₂ with light from a 6V incandescent bulb. Compared to CO₂ alone, Aedes vigilax collections increased significantly when CO₂ was supplemented by all three octenol emission levels, but not by the addition of light. Furthermore, the 4.5 and 30 mg/h release rate of octenol gave a significant increase in numbers of Ae.vigilax relative to that from CO₂+ light. In contrast, collections of Culex annulirostris and Culex sitiens were not enhanced significantly by either the addition of light or octenol at all three levels. Fewer Cx sitiens were collected with octenol released at 4.5 mg/h in comparison to CO₂ alone. These differential sampling rates should be taken into account when using EVS traps.     

Oxygen consumption of East Siberian cod: no support for the metabolic cold adaptation theory

Standard metabolic rate ( R _s) at 2°C of eight East Siberian cod Arctogadus borisovi , caught in West Greenland, body mass of 601.5 ± 147.6 g (mean ± s.D.), was 40.9 ± 5.9 mg O₂ kg^-1 h^-1 and 59.0 ± 6.6mg O₂ kg^-1 h^-1 when extrapolated to a standardized 100 g fish. R _s was compared with three other Gadidae, to test the theory of metabolic cold adaptation (MCA). There was no evidence of MCA in the family.     

A developmental study of Glycine max cell and protoplast isolation in relation to leaf age and photosynthetic competence

Leaf mesophyll cells were isolated from developing first trifoliate leaves of Glycine max (L.) Merr cv. Fiskeby V using a mechanical isolation procedure combined with low speed centrifugation. Cell yields of 17 ± 1.7% were routinely obtained with 55–75% intactness, as assessed by staining techniques, fluorescence transients and the ability of cells to convert to protoplasts after enzyme treatment. Rates of leaf photosynthesis were maximal in 27-day-old plants [280 μmol O₂ evolved (mg chlorophyll)^-1h^-1], from which isolated cells and protoplasts gave rates of up to 140 μmol O₂ evolved (mg chlorophyll)^-1 h^-1. Results are discussed in relation to leaf development and cell status during the attainment of photosynthetic competence.     

Photosynthesis and carbohydrate partitioning in sweet cherry: Fruiting effects

The effect of fruiting on carbon fixation and retention in leaves was monitored by measuring net photosynthesis (Pn) and total non-structural carbohydrates (TNC) on a seasonal basis on mature fruiting and non-fruiting sweet cherry trees ( Prunus avium L. cv. Bing). Pn was also measured diurnally during stages II and III of fruit development. Pn rates increased to between 18 and 20 mg CO₂ dm^-2 h^-1 during stage II of fruit development and were maintained until harvest. Diurnally, Pn increased in the morning to 20 mg CO₂ dm^-2 h^-1 and this rate continued until sunset. Leaf carbohydrate levels decreased in both fruiting and non-fruiting trees beginning at the equivalent of stage II of fruit growth. Carbohydrates were lower in leaves and woody portions of current, 1- and 2-year-old shoots of fruiting trees. Although differences were found in levels of non-structural carbohydrates, no differences in Pn were found in fruiting vs non-fruiting plants on either a seasonal or a diurnal basis. Pn rates in swet cherry in the field were primarily affected by ontogeny and environment and not by sink strength.     

Kinetic and metabolic effects of nitrogen, magnesium and sulphur restriction in Xanthomonas campestris batch cultures

By reducing the concentration of nitrogen (from 5.0 to 2.5 mmol 1^-1), batch cultures of Xanthomonas campestris induced the enzyme UDP-glucose dehydrogenase and stimulated the Entner-Doudoroff pathway enzyme glucose-6-P dehydrogenase. The surplus energy generation was directed to xanthan biosynthesis resulting in a 10% polysaccharide increase. The nitrogen restriction led to a higher consumption of nitrogen (93%) whereas glucose consumption did not surpass 75% utilization. Low concentrations of both magnesium and sulphur exerted a negative effect on xanthan formation. Both restrictions reduced the phosphomannose isomerase enzyme activity by 10-fold turning the mannose transference presumably into the rate-limiting step for xanthan biosynthesis. Conversely, the rate of synthesis of glucuronic acid residues did not affect the rate of xanthan biosynthesis. Polysaccharide synthesis in magnesium and sulphur cultures was negatively affected in comparison with cell formation as the cell volumetric production rate increased from 0.037 to 0.091 g 1^-1 h^-1 and the xanthan volumetric production rate dropped from 0.133 g 1^-1 h^-1 to the minimum obtained at 0.083 g 1^-1 h^-1. The efficiency of the carbon substrate conversion was also greatly changed.     

Respiration and energetics of the bumblebee Bombus terrestris queen

Carbon dioxide production by the Bombus terrestris queen was measured at different temperatures (10–30°C) and during different activities of the bumblebee. During flight the CO₂ production averaged 50 ml g⁻¹ (fresh weight) h⁻¹ and was only slightly affected by temperature. During rest (with a readiness to fly) and incubation the respiration rate clearly increased with decreasing temperature (5–40 and 13–56 ml g⁻¹ h⁻¹, respectively), whilst during torpor it increased with temperature (0.1–1.7 ml g⁻¹ h⁻¹ at temperatures from 10 to 30°C).
The expenditure of energy as calculated from the continuous respiration measurements agreed well with the amount of energy obtained from food (discrepancy 6–19%). The energy budget of an incubating queen was correctly predicted using the measured respiratory functions, prevailing temperatures, and the behaviour of the queen. The number of flower visits needed to fulfil the daily energy requirements of an incubating queen is discussed.     

The flight and landing of tsetse (Glossina) in response to components of host odour in the field

ABSTRACT. Studies were conducted in Zimbabwe of the responses of Glossina morsitans morsitans Westwood and Glossina pallidipes Austen to various host odours using either arrangements of electrocuting nets or visual observations. Tsetse flying upwind in a plume of carbon dioxide, acetone and octenol turned downwind upon flying into a plume of acetone or octenol, but did not turn upon flying into a plume of carbon dioxide. They also turned in response to a transient decline in odour concentration. Tsetse landed on the ground in the vicinity of a source of natural odour or artificial odour containing carbon dioxide but not at sources of acetone or octenol only. The proportion of female G.pallidipes caught at a source of natural odour (37%) was significantly different from that caught at a source of synthetic odour (17%). Resting tsetse stimulated by natural odour took off sooner than non-stimulated flies and had a strong upwind bias in the direction of take off. Tsetse stimulated with artificial odour did not take off sooner than non-stimulated flies. It is suggested that there is an unidentified components) of ox odour that activates resting tsetse.     

Oxygen uptake and heart rate in young Green turtles (Chelonia mydas)

Oxygen uptake. heart rate and breathing frequencies were monitored in yearling Green turtles. Routine fed animals used about 100μ O₂ g live turtle^-1 h^-1 at 25C; this value was not significantly affected by size or short term food deprivation. Starved turtle showed a doubling of oxygen uptake after a satiation meal and heightened uptake persisted for five days. Between 15 and 30C oxygen consumption increased with rising temperature; below 15C there was falling temperature. Vigorous activity increased oxygen uptake to two or three times thr routine fed levels.
Turtles swimming gently at 25C exhibited a heart rate of around 46–48 beats min^-1; this rose to 64–68 beats min^-1 during vigorous and continuous activity. Contrary to expectations profound bradycardia was not seen during diving; even during 10 min dives a rate of 25–28 beats min^-1 was sustained. Significantly lower heart rates were only seen in turtles which were apparently asleep.     

Photosynthesis and photoassimilation of glucose during photomixotrophic growth of Marchantia polymorpha cells in suspension culture

Even in the presence of glucose the growth of Marchantia polymorpha L. (cell line HYH-2F) requires light, and growth is more sensitive to 10⁻⁶ M 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea than to 10⁻⁴ Antimycin A. The inability of the cells to grow in the dark is due to the low level of respiration. The respiration rate under light increased to four times the dark value. The values of the compensation ratio (the photosyntehtic rate/the respiration rate) for the oxygen exchange were below 1.0 daring the growth period, although oxygen evolution was found. At the early exponential phase, oxygen evolution was 0.373 μmol (mg cell dry weight)⁻¹ h⁻¹ [61.7 μmol (mg chlorophyll)⁻¹ h⁻¹]. M. polymorpha cells are unable to grow anaerobically in the light without a supply of carbon dioxide. When 1% carbon dioxide in nitrogen is supplied, photochemically produced oxygen and energy are sufficient for sustained growth although at significantly reduced yields in both cell dry weight and chlorophyll. Photosyntehtic CO₂ assimilation rate was 0.13 μmol (mg cell dry weight)⁻¹ h⁻¹[11.3 μmol (mg chlorophyll)⁻¹ h⁻¹]. At least one-third of the carbon atoms in cellular constituents seem to be derived from atmospheric carbon dioxide, which indicates that M. polymorpha cells grow photomixotrophicaily.     

Response properties of CO2-sensitive receptors in tsetse flies (Diptera: Glossina Palpalis)

Abstract. Extracellular single cell recordings of CO₂-sensitive receptors in tsetse flies revealed a steep dose response over a range of stimuli of two to three orders of magnitude and a maximum response of approximately 70 impulses/s after exposure to a high, but naturally feasible, C0₂ concentration of 5%. These receptor neurones are slightly sensitive to C0₂ levels occurring in air (-0.03%); the sensitivity to CO² above that level may be used to locate potential hosts. The C0₂-sensitive neurones did not respond to some other biologically relevant odours such as octenol, butanone or p-cresol; however, other receptor cells, some in the same sensillum, are sensitive to some of these odours.
A striking feature of the C0₂ receptors is that they appear not to adapt in their response frequencies. The spike numbers of the phasic-tonic response remain constant in the tonic portion during continuous (or repetitively pulsed) long-term stimulation (1 min). This unusual physiological ability would allow continuous monitoring of C0₂ values as well as detecting potential hosts that exhale CO₂. These electrophysiological results are compared to the behavioural findings in tsetse flies and to the physiological data on C0₂ receptors of other, non-bloodsucking insects.