Michael Kokkinn

Modelling the ecology of the coastal mosquitoes Aedes vigilax and Aedes camptorhynchus at Port Pirie, South Australia

Abstract Two mosquito species, Aedes camptorhynchus (Thomson) and Aedes vigilax (Skuse) (Diptera: Culicidae) are responsible for significant nuisance biting and disease transmission in southern coastal Australia. Mosquito abundance, tide height, temperature and rainfall data were collected over three summer seasons (2002, 2003, 2004) at Port Pirie, South Australia and subjected to statistical analysis to develop ecological models for predicting problem mosquito outbreaks. A logistic regression model for Ae. camptorhynchus gave a predictive R2 of 0.30 using mean air temperature, whereas, for Ae. vigilax, tide height, mean air temperature and day length yielded a regression with an R2 of 0.68. These models identify significant environmental drivers for both species and may be useful in the prediction of future outbreaks, particularly of Ae. vigilax.

Intraspecific Variation in Odor-Mediated Host Preference of the Mosquito Culex annulirostris

The preference of two allopatric populations of Culex annulirostris mosquitoes in South Australia (SA) for guinea pigs and chickens was investigated using host-baited traps in the field and in a flight tunnel for laboratory assays. Mosquitoes from the Riverland of SA preferred guinea pigs, those from northeast SA preferred chickens. In the field, 2184 Cx. annulirostris were captured during four experiments in each region. The proportion choosing chicken was 0.5393 in northeast SA and 0.4348 in the Riverland. In the laboratory, replicate trials utilizing 15 mosquitoes at a time yielded results concordant with field assays. This study demonstrates variation in Cx. annulirostris host preference throughout this species geographic range. Semiochemical analysis of the two host species was performed on solvent extractions and volatile trapping samples from fur and feathers, respectively. This revealed differences that are likely to be the basis for host discrimination by Cx. annulirostris.

Environmental and entomological factors determining Ross River virus activity in the River Murray Valley of South Australia

Objectives: 1) To determine whether environmental and mosquito abundance variables could be used to explain fluctuations in the activity of Ross River (RR) virus, in the River Murray Valley of South Australia (SA). 2) To develop models at the local government spatial scale to understand local variability in RR activity factors.

Larval crowding effects on the mosquito Culex quinquefasciatus: physical or chemical?

Culex quinquefasciatus Say (Diptera: Culicidae) is an abundant urban mosquito that is the vector of filariasis. Breeding in septic tanks, where there are very high levels of bacterial food, it is likely to have a different reaction to crowding compared with other mosquitoes. To test for the presence and type of crowding effects, four larval densities of C. quinquefasciatus varying from 0.4 to 3.2 larvae ml−1 of water were reared in tubes. Mortality was found to greatly increase at densities above 0.8 larvae, whereas larval duration increased even above 0.4 larvae ml−1. Changing the water in the tubes daily gave a small (but significant) response in reducing mortality and larval duration. However, when larvae kept at a low density shared the same water with larvae at high density, there was no chemical influence on their growth rate and mortality. The effect of crowding was primarily due to physical disturbances between larvae. When larvae were kept at a high density in the same volume of water, but in shallow trays with a large surface area and therefore much less contact between them, mortality was the same as for the lowest density. There was still, however, a significant increase in larval duration from 8.6 days at 0.4 larvae ml−1 to 12.1 days at 3.2 larvae ml−1. It is therefore concluded that the larvae respond to physical rather than chemical factors by prolonging larval development and having some increase in mortality.

The Effect of Sampling Methods on the Apparent Constituents of Ink from the Squid Sepioteuthis australis

Results of experiments conducted on ink recovered from the squid Sepioteuthis australis indicate that there is no epinephrine or protein naturally present in the ink as it would be ejected in vivo. Protein content was effectively zero when ink was syringed from the duct end of the ink sac of freshly killed animals. By contrast, there were proteins in samples collected from dead specimens where ink was collected by a stripping method. From these samples, a single large molecular weight protein was identified as having tyrosinase activity. Digestion of syringed ink did not yield signs of melanin-bound proteins. Analysis of supernatants after centrifugation of squid ink consistently revealed the presence of DOPA, dopamine, and taurine, whereas epinephrine and nor-epinephrine were recorded from what was believed to be contaminated ink. Histological investigations of the ink sac revealed a compartmentalised glandular structure distal to the duct end. Closer observation of the glandular tissue showed that compartments increased in size as they matured and moved further into the lumen. It was concluded that the presence of epinephrine and tyrosinase (or a related protein) in the ink of S. australis could be attributed to rupturing of basal glandular compartments or contamination from other sources during the extraction process.

Mosquitoes (Diptera: Culicidae) of the spencer gulf coast of South Australia.

Abstract Mosquitoes are responsible for both nuisance biting and arbovirus transmission along the Spencer Gulf coast of South Australia. Mosquito community sampling, comprising both adult and immature stage collections, was performed at Port Broughton, Port Pirie, Cowell and Whyalla from 1997–2008. Eleven species were represented in the nearly 24,000 mosquitoes collected in these studies, with the saline water breeding Aedes camptorhynchus Thomson and Aedes vigilax (Skuse) predominant. The most likely vectors of arboviruses and sources of mosquito nuisance in the region have been identified as salt marsh breeding species, thereby providing the focus for future mosquito control efforts.

Flowering timing prediction in Australian native understorey species (Acrotriche R.Br Ericaceae) using meteorological data

The aim of this study was to determine the climatic influences on floral development for five members of the Australian native plant genus Acrotriche R. Br (Ericaceae). An observed period of summer floral dormancy suggests temperature is involved in flowering regulation in these species. Models were developed to determine temperature requirements associated with the likelihood of flowering occurring on any one day. To this end, the timing of flowering and meteorological data were collated for several sites, and multivariate logistic regressions performed to identify variables with a significant influence on flowering timing. The resultant models described a large amount of variation in flowering presence/absence, with r2 values ranging from 0.72 to 0.79. Temperature was identified as influential on both floral development and flowering timing in each of the study species. The positive influence of short photoperiods on flowering in three of the winter flowering species was not surprising. However, the reporting here of a significant association between interdiurnal temperature and flowering in one species is novel. The predictive power of the models was validated through a jackknife sequential recalculation approach, revealing strong positive and negative predictive ability for flowering for four of the five species. Applications of the models include assisting in determination of the suitability of areas for vegetation restoration and identifying the possible effects of climate change on flowering in the study species.

Pollen tetrad segregation and pollen ovule ratios in six species of Acrotriche (Styphelioideae: Ericaceae)

Pollen morphology can be useful in the determination of phylogeny and mating systems of plants. Pollen ovule ratios can give an indication of the mating system of plant species, and there are a number of theories as to reductions in response to pollination strategies. Pollen tetrad segregation occurs when a number of pollen grains within a tetrad abort; this process has evolved a number of times in the family Ericaceae. Pollen ovule ratios along with the total number of tetrads, number of viable grains and proportions of each of the tetrad types were investigated in six species of Acrotriche (Styphelioideae: Ericaceae). Pollen ovule ratios were used in comparison with related species to give indications of mating systems and to examine theories regarding reductions in pollen production. The study species can be arranged into distinct groupings based on the proportions of tetrad types that correlate with floral morphology and may be indicative of phylogentic associations.