Factors affecting Grey‐headed Flying‐fox (Pteropus poliocephalus: Pteropodidae) foraging in the Melbourne metropolitan area,Australia

Abstract Factors affecting the foraging of mobile native fauna in highly fragmented urban landscapes have seldom been quantified at large spatial scales. We investigated factors affecting foraging by Grey‐headed Flying‐foxes (Pteropus poliocephalus; ‘flying‐foxes’) in the greater Melbourne metropolitan area. Flying‐foxes established a continuously occupied colony site in the Royal Botanic Gardens Melbourne in 1986, and the size of the colony has subsequently increased greatly. We used a stratified‐random sampling design to examine the importance of six variables on the detection of foraging flying‐foxes: (i) distance from the colony site (0–10, 10–20 and 20–30 km); (ii) distance from the Yarra River (0–5 and 5–20 km); (iii) the relative tree density of the municipality; (iv) whether the site was a park or street; (v) whether there was a relatively high or low density of trees at the site; and (vi) whether food was or was not detected at the site. We surveyed 240 sites within a 30‐km radius of the colony site for foraging flying‐foxes in both May and October 2002. The probability of detecting a foraging flying‐fox declined with increasing distance from the colony site, but increased with increasing tree cover, and was higher for parks compared with streets and when food was present. Flying‐foxes were observed foraging in a number of plant genera that have no species that naturally occur in the Melbourne area. Flying‐foxes in Melbourne thus forage on planted resources that are widely distributed within a fragmented landscape, and are an example of a positive response by a native species to the process of urbanization.     

Impacts of changed fire regimes on tropical riparian vegetation invaded by an exotic vine

Abstract Riparian habitats are highly important ecosystems for tropical biodiversity, and highly threatened ecosystems through changing disturbance regimes and weed invasion. An experimental study was conducted to assess the ecosystem impacts of fire regimes introduced for the removal of the exotic woody vine, Cryptostegia grandiflora, in tropical north‐eastern Australian woodlands. Experimental sites in subcatchments of the Burdekin River, northern Queensland, Australia, were subjected to combinations of early wet‐season and dry‐season fires, and single and repeated fires, with an unburnt control. Woody vegetation was sampled using permanent quadrats to record and monitor plants species, number and size‐class. Sampling was conducted pre‐fire in 1999 and post‐fire in 2002. All fire regimes were effective in reducing the number and biomass of C. grandiflora shrubs and vines. Few woodland or riparian species were found to be fire‐sensitive and community composition did not change markedly under any fire regime. The more intense dry‐season fires impacted the structure of non‐target vegetation, with large reductions in the number of sapling trees (<5 cm d.b.h.) and reductions in the largest tree size‐class and total tree basal area. Unexpectedly, medium‐sized canopy trees (10–30 cm d.b.h.) appear to have been significantly benefited by fires, with decreases in number of trees of this size‐class in the absence of fire. Although the presence of C. grandiflora as a vine in riparian forest canopies changed the nature and intensity of crown combustion patterns, this did not lead to the initiation of a self‐perpetuating weed–fire cycle, as invaders were unable to take advantage of gaps caused by fire. Low intensity, early wet‐season burning, or early dry‐season burning, is recommended for control of C. grandiflora in order to minimize the fire intensity and risk of the loss of large habitat trees in riparian habitats.     

The circadian flight activity of Aedes aegypti parasitized with the filarial nematode Brugia pahangi

ABSTRACT. The circadian flight activity of Aedes aegypti L. infected with the filarial parasite Brugia pahangi was recorded for 16 consecutive days using an acoustic actograph. The flight activity of uninfected control mosquitoes in a LD 12:12h regime rose to a maximum 3 days after bloodfeeding, then decreased slightly and remained steady for the duration of the experiment. The flight activity of parasitized mosquitoes was temporarily depressed for 2 days after feeding on a microfilariaemic cat; this was probably caused by the parasites migrating from the midgut to the flight muscles. As parasitic larvae grew within the flight muscles during days 3—6, the daily activity of all mosquitoes returned to control levels. On days 7—8 the activity of mosquitoes parasitized with thirteen or more larvae fell dramatically to approximately 10% of that of the controls; this change coincided with the emergence of the highly-active infective stage larvae from the flight muscles. The presence of fewer larvae did not impair flight. Because of their reduced flight capability, heavily-infected mosquitoes probably play little if any part in the transmission of filariasis.     

Caryocyst-Like Host Cell Formation by Caryospora duszynskii (Apicomplexa: Eimeriidae) in Human Fetal Lung Cell Cultures1

ABSTRACT. Sporozoites of the coccidium, Caryospora duszynskii, penetrated human fetal lung cell cultures but did not undergo asexual or sexual multiplication during a 29-day observation period. Beginning three days postinoculation (PI), infected host cells lost their normal elongated fibroblast-like shape and became ellipsoidal in appearance and resembled caryocysts. These caryocyst-like infected cells were observed from 3 through 29 days PI. Sporozoites remained viable throughout the study as evidenced by motility of extracellular sporozoites in infected human fetal lung cell cultures. Results of this in vitro study suggest that some species of Caryospora may form caryocysts in secondary hosts without undergoing asexual or sexual multiplication in these hosts.     

The Structural Organization of Ribonucleic Acid Associated with Soybean Microsomes

The microsomal fraction of soybean (Glycine max) hypocotylswas characterized using analytical and electron microscope techniques.Two microsomal sub-fractions (smooth and rough vesicles) wereseparated by untracentrifugation. Analysis showed that the ribonucleicacid (RNA) of the microsomal fraction cannot be completely accountedfor by the ribosomes, and that some of the RNA is associatedwith the membranes in a non-ribosomal form. A similar conclusionwas reached by using ethylenediaminetetra-acetic acid (EDTA)to disperse the ribosomal material. Although no visible robosomesremained after the treatment with EDTA, the microsomal fractionretained a quarter of its RNA. Ribonuclease removed all themocrosomal RNA without visibly altering the membrane structureexamined in cross section. When hypocotyl tissue sections wereincubated with ¹⁴C amino-acids, the microsomes incorporatedthe radioactive label more rapidly than any other subcellularfraction. This was especially true in the rapidly growing zoneof the hypocotyl. Smooth microsomes were 75 per cent as activeas rough microsomes. These observations are discussed with referenceto the structural organization of the microsomal RNA and itsrole in protein synthesis.