Kim P. Bryceson

Image quality and acceptance angle in a reflecting superposition eye

Summary1.Intracellular recordings of acceptance angles were made at different adaptation states and at different times of day, from retinula cells in the central region of the reflecting superposition eye of the freshwater crayfish,Cherax destructor (Clark 1936). A number of cells were held for longer than 24 h.2.The acceptance angle is greater in the dark-adapted (DA) state than in the light-adapted (LA) state, but this difference is significantly smaller at night than during the day. Mean values were 5 ° (LA day and night), 19 ° (DA day) and 13 ° (DA night).3.The anatomy was studied with proper attention to the time of day. Light microscopy shows that there is an increase of 10–15% in the clear-zone width in the DA state at night compared to the other states. This is achieved by a proximal movement of the rhabdom layer.4.The position of the distal screening pigment depends on the ambient light level. It is around the distal cones in the dark and moves into the clear zone on light-adaptation. The proximal screening pigment, however, attains only the first stage of dark-adaptation (Frixione et al. 1979) during the day. Complete dark-adaptation (movement below the basement membrane) occurs only at night. The distal reflecting pigment remains around the cones at all times, and the proximal reflecting pigment forms a cup around the base of the rhabdom during both day and night.5.The smaller acceptance angle in the DA state at night, compared to that of the DA day state, indicates that the receptors lie closer to the best superposition focus in this state, when the animal is in air.6.The effect of the change in clear-zone width and the performance of the eye in air and under-water are examined using a model of the eye.

The use of Landsat MSS data to determine the locust eggbeds of locust eggbeds in the Riverina region of New South Wales, Australia

Abstract Processed Landsat multispectral data were used to determine areas in the Riverina region of New South Wales, Australia, in which eggs were likely to have been laid by swarms of the Australian plague locust ( Chortoicetes terminifera (Walker)), which invaded the region at the end of March 1987. A map was produced from the processed data with potential eggbed areas highlighted, which could be used for field survey purposes in the spring and summer when hatching started. The results showed that > 95 per cent of all nymphal band targets were in the areas defined by a normalized difference vegetation index as being those where vegetation growth had resulted from rain during March. Furthermore, a maximum-likelihood classification using a known eggbed location as a training area, produced an excellent correlation with locusts hatching in September/October 1987. The results are discussed in relation to the future operational use of such techniques by the Australian Plague Locust Commission.

An analysis of the 1984 locust plague in Australia using multitemporal landsat multispectral data and a simulation model of locust development

Abstract An analysis of the 1984 locust ( Chortoicetes terminifera (Walker)) plague in Australia was undertaken to determine its source region using a simulation model of locust development and whether using appropriately enhanced satellite data, the individual areas that were suitable for locust breeding could be detected within this region. The origin of the 1984 plague was found to be in the Channel Country of south west Queensland, and satellite data indicated that there were localised areas suitable for locust breeding at the appropriate time other than those detected by ground survey. It is concluded that it isfeasible to use satellite data on an operational basis to detect areas suitable for locust breeding by monitoring changes in vegetation condition. Using the locust simulation model, the course of breeding and possible plague development can then be forecast, and ground surveys directed to the areas of interest at the approximate time.

Diurnal changes in photoreceptor sensitivity in a reflecting superposition eye

Summary1.Intracellular recordings of intensity response functions (V/log I curves) were made at different adaptation states at different times during a 24th period, from single photoreceptors in the central region of the eye of the Australian crayfishCherax destructor (Clark 1936).2.The intensity that elicits a criterion response (50% of the maximum) is less at night than in the day in both the dark-adapted (DA) and lightadapted (LA) states.3.Within the first 30 s of light-adaptation there is an extremely fast initial decrease in sensitivity, while in the latter stages of dark-adaptation there is a slow but steady increase, neither of which can be correlated with the position of the screening pigments.4.The time courses for the movement of screening-pigment on lightor dark-adaptation during both day and night were measured using light microscopy. As found by de Bruin and Crisp (1957) in several species of prawn and Frixione et al. (1979) in the crayfishProcambarus, the proximal pigment migrates faster than the distal pigment on light-adaptation. On dark-adaptation, the distal pigment migrates faster than the proximal pigment, the latter only carrying out the first stage of dark-adaptation during the day.5.It is concluded that there are three variable systems affecting sensitivity in a reflecting superposition eye: (a) The effective rhabdom cross-sectional area as determined by the position of proximal pigment; (b) the blur circle diameter and intensity determined by the position of the distal pigments and the width of the clear zone, and (c) transduction gain.

Alignment of performance metrics in a multi-enterprise agribusiness: Achieving integrated autonomy?

Purpose – The purpose of this paper is to examine the disconnect that can develop between corporate goals and those of individual intra‐organisational business units arranged as an internal supply chain within a large vertically integrated agribusiness. It also aims to explore and discuss the development of a holistic performance metrics system that facilitates internal supply chain coordination and cohesion, while allowing synergies to develop across the company.Design/methodology/approach – A case study approach involving a participative action research component was used to examine the disconnect between internal business unit (operational) goals and overall corporate (strategic) goals and to develop a conceptual performance assessment model addressing both operational and strategic contexts.Findings – The findings show that appropriate performance indicators and measures can be created that relate directly to logical operational outcomes, thus encouraging a more tightly integrated internal supply chai...

Digitally processed satellite data as a tool in detecting potential Australian plague locust outbreak areas

Abstract This paper presents an investigation into the use of digital satellite data as a tool in identifying potential Australian plague locust (Chortoicetes terminifera (Walker)) outbreak areas at an early stage in semi-arid areas of south west Queensland. The results show that standard processing techniques of the digital data allow areas of green vegetation to be discriminated from soil background information (a problem encountered in an earlier investigation using commercially produced false colour imagery of the same data), thus enabling the detection of potential outbreak areas. The results are discussed in relation to future applications of satellite data in the Australian Plague Locust Commission.

The development of the 1983 outbreak of the common armyworm, Mythimna convecta, in eastern Australia.

A large outbreak of common arymworm began in spring 1983, 6 months after the conclusion of a nation-wide drought, and occurred throughout the major cereal-growing regions of E Australia. Probable source areas were in the extensive grasslands of inland Australia, particularly SW and C Queensland. Population increase appeared to follow a complex sequence of overlapping, complementary generations. Although some generations were initiated directly by the drought-breaking rains, others appeared to arise from isolated thunderstorms which preceded them by several weeks in late summer. Moth emergence occurred in early April, late May, late July, and from late August to November. In each case, except late May, it was hypothesized that there were both local and long-range movements of adults on the synoptic airflows, resulting in moths spreading progressively from several isolated sources into the flourishing grasslands of E Australia. Multitemporal satellite data were used to identify areas of potential armyworm habitat in an inland source area of SW Queensland. Very small patches of suitable habitat were identified during the drought whilst, after the drought broke, 36% of the area comprised green grasses ideal for colonization. The subtropical grasses dried off by late winter and emigration by newly emerged moths on prefrontal airflows enabled the spring populations to colonize the temperate grass regions of inland New South Wales.

Likely locust infestation areas in western New South Wales, Australia, located by satellite

Abstract A retrospective investigation was undertaken of the area around Broken Hill in the Western region of New South Wales, where Australian plague locust (Chortoicetes terminifera) nymphal band control took place during September ‐ November (spring) of 1987. Processed Landsat‐5 multispectralscanner data for March 1987 (autumn) were used to locate the likely spring/summer locust infestation areas using habitat type, condition and soil type as the delineating parameters. The results show that a vegetation index (indicating the degree of vegetation greeness in an area) is useful for predicting where locusts are most likely to aggregate, a classification of vegetation types is needed for determining likely breeding sites, and that there is an additional relationship between soils/geology and the location of locust infestations. These results are discussed in relation to the future operational use of the techniques in the Australian Plague Locust Commission.

Water balance and the mantle cavity fluid of Nucella lapillus(L.) (Mollusca: Prosobranchia)

When uncovered by the tide Nucella lapillus (L.) retains fluid in the mantle cavity which accounts for ≈ 39% of the total water content of the attached animal. This extra-corporeal fluid reservoir retained in the mantle cavity has been investigated in relation to desiccation. Volume changes of mantle cavity fluid (m.c.f.) and concentration changes in Cl−, Na+ and total osmotic pressure of m.c.f. and blood, suggest that the m.c.f. reduces the full effects of desiccation on the animal by restricting those effects to the external compartment. The blood of Nucella living in normal sea water was found to be hypo-osmotic and an hypothesis is presented which links this to the role of the m.c.f. during desiccation.

Acquisition and use of low-cost meteorological satellite data in the Australian Plague Locust Commission

Abstract Recent studies have shown that satellite data can be used in the detection and monitoring of potential outbreak areas of the Australian plague locust. However, the routine monitoring of such areas using Landsat MSS data is precluded by the high cost of the data, although it is still used selectively for forecasting. An alternative approach has been to make use of lower-cost meteorological satellite data with lower spatial resolution, for example that of the NOAA and GMS satellites, which provide an acceptable compromise between frequency of monitoring, relevant data and cost. This paper describes the acquisition of GMS LRFAX and NOAA APT data and other relevant meteorological data at the Australian Plague Locust Commission (APLC) Headquarters in Canberra and the use of the data in the APLC.