Expression of Cysteine Proteinases by Metacyclic Promastigotes of Leishmania mexicana

ABSTRACT. The expression of cysteine proteinases by metacyclic promastigotes of Leishmania mexicana was investigated using gelatin polyacrylamide gel electrophoresis. Two prominent bands were detected which distinguished metacyclics from multiplicative promastigotes, lacking detectable cysteine proteinase activity, and amastigotes, with a distinct banding pattern composed of multiple enzymes. A correlation between relative activity of the metacyclic-specific bands and the prevalence of metacyclics was found both during the growth cycle in vitro as metacyclogenesis occurred, and by comparison of stationary phase populations from consecutive subpassages in vitro. Irreversible inhibition of the metacyclic activities using N-benzyloxycarbonyl-phenylalanyl-alanyl diazomethane did not inhibit metacyclic to amastigote transformation in vitro. These activities provide a useful biochemical marker for the metacyclic promastigotes of L. mexicana .     

Seasonal pattern of abundance of honeyeaters and their resources in heathland areas near Sydney

Abundances of honeyeaters, flowers and flying insects, the daily nectar-energy production per flower and the average size of flying insects were estimated every three weeks for circles of radius 20 m located in three heathland areas near Sydney. Seasonal fluctuations in honeyeater density showed no apparent relationship with seasonal fluctuations in nectar-energy productivity or in biomass of flying insects. Variation between circles in honeyeater density was also unrelated to spatial variation in energy productivity and insect biomass. The relatively low incidence of nectar-feeding and high incidence of flying exhibited by birds observed during troughs in nectar-energy production suggest that many of these birds are transient and that their density may consequently be unrelated to local conditions.     

Heterochronic evolution in the Heliolites interstinctus-decipiens lineage of the Chaleur Bay region, eastern Canada

A study of the Heliolites interstinctus-decipiens lineage from the Silurian of the Chalcur Bay region, eastern Canada, indicates that most morphological characters of this lineage, including tabularium diameter, coenenchymal tubule diameter and corallite spacing, remain relatively invariate through a Llandovery to Pridoli interval of about 20 million years. In contrast, septal development and corallite wall erenulation show pronounced evolutionary changes due to heterochrony, as shown by comparison of astogenies throughout the lineage. The reduction of septa and the replacement of crenulate corallites by smooth ones in the 'decipiens' type descendent appear to have been by paedomorphosis from the 'interstinctus' type ancestor. The problems of speciation in this lineage are discussed including the alternative hypotheses of a speciation event in the early Ludlow or a phyletic trend within a single species whose longevity is due in part to the stabilization processes of niche separation.     

Phenotypic plasticity in hoverflies: the relationship between colour pattern and season in Episyrphus balteatus and other Syrphidae

1. The abdominal colour patterns of some multivoltine species of hoverfly are phenotypically plastic and change through the flying season.
2. It was predicted how the abdominal colour pattern of one species, Episyrphus balteatus , should change in the field with season based on a hypothesis that the pattern influences the thermoregulatory capabilities of the animal. The colour patterns were quantified using image analysis. The observed changes in the colour pattern through the year supported the thermoregulation hypothesis.
3. A further three Metasyrphus species were analysed similarly to allow a comparative study of the forms of the plasticities of the above four species and four Eristalis species from a previous study.
4. Whilst it was clear that the abdominal colour patterns of many of the species were plastic, it was also apparent that not all species used the same developmental pathway to control the seasonal colour pattern changes. This suggests convergent evolution towards a general type of plasticity and that abdominal colour pattern plasticity in hoverflies is functional.