Olfaction in the Queensland fruit fly, Bactrocera tryoni. II: Response spectra and temporal encoding characteristics of the carbon dioxide receptors

Single-unit electrophysiology was used to record the nerve impulses from the carbon dioxide receptors of female Queensland fruit flies, Bactrocera tryoni. The receptors responded to stimulation in a phasic-tonic manner and also had a period of inhibition of the nerve impulses after the end of stimulation, at high stimulus intensities. The cell responding to carbon dioxide was presented with a range of environmental odorants and found to respond to methyl butyrate and 2-butanone. The coding characteristics of the carbon dioxide cell and the ability to detect other odorants are discussed, with particular reference to the known behavior of the fly.

Modelling the population dynamics of the Queensland fruit fly, Bactrocera (Dacus) tryoni: a cohort-based approach incorporating the effects of weather

Queensland fruit fly, Bactrocera (Dacus) tryoni (QFF) is arguably the most costly horticultural insect pest in Australia. Despite this, no model is available to describe its population dynamics and aid in its management. This paper describes a cohort-based model of the population dynamics of the Queensland fruit fly. The model is primarily driven by weather variables, and so can be used at any location where appropriate meteorological data are available. In the model, the life cycle is divided into a number of discreet stages to allow physiological processes to be defined as accurately as possible. Eggs develop and hatch into larvae, which develop into pupae, which emerge as either teneral females or males. Both females and males can enter reproductive and over-wintering life stages, and there is a trapped male life stage to allow model predictions to be compared with trap catch data. All development rates are temperature-dependent. Daily mortality rates are temperature-dependent, but may also be influenced by moisture, density of larvae in fruit, fruit suitability, and age. Eggs, larvae and pupae all have constant establishment mortalities, causing a defined proportion of individuals to die upon entering that life stage. Transfer from one immature stage to the next is based on physiological age. In the adult life stages, transfer between stages may require additional and/or alternative functions. Maximum fecundity is 1400 eggs per female per day, and maximum daily oviposition rate is 80 eggs/female per day. The actual number of eggs laid by a female on any given day is restricted by temperature, density of larva in fruit, suitability of fruit for oviposition, and female activity. Activity of reproductive females and males, which affects reproduction and trapping, decreases with rainfall. Trapping of reproductive males is determined by activity, temperature and the proportion of males in the active population. Limitations of the model are discussed. Despite these, the model provides a useful agreement with trap catch data, and allows key areas for future research to be identified. These critical gaps in the current state of knowledge exist despite over 50 years of research on this key pest. By explicitly attempting to model the population dynamics of this pest we have clearly identified the research areas that must be addressed before progress can be made in developing the model into an operational tool for the management of Queensland fruit fly. (C) 2003 Published by Elsevier B.V.

Detection of fruit and the selection of primate visual pigments for color vision

Primates have X chromosome genes for cone photopigments with sensitivity maxima from 535 to 562 nm. Old World monkeys and apes (catarrhines) and the New World ( platyrrhine) genus Alouatta have separate genes for 535-nm ( medium wavelength; M) and 562-nm ( long wavelength; L) pigments. These pigments, together with a 425-nm ( short wavelength) pigment, permit trichromatic color vision. Other platyrrhines and prosimians have a single X chromosome gene but often with alleles for two or three M/L photopigments. Consequently, heterozygote females are trichromats, but males and homozygote females are dichromats. The criteria that affect the evolution of M/L alleles and maintain genetic polymorphism remain a puzzle, but selection for finding food may be important. We compare different types of color vision for detecting more than 100 plant species consumed by tamarins ( Saguinus spp.) in Peru. There is evidence that both frequency-dependent selection on homozygotes and heterozygote advantage favor M/L polymorphism and that trichromatic color vision is most advantageous in dim light. Also, whereas the 562-nm allele is present in all species, the occurrence of 535- to 556-nm alleles varies between species. This variation probably arises because trichromatic color vision favors widely separated pigments and equal frequencies of 535/543- and 562-nm alleles, whereas in dichromats, long-wavelength pigment alleles are fitter.

Carotenoid content of pandanus fruit cultivars and other foods of the Republic of Kiribati

Background: Kiribati, a remote atoll island country of the Pacific, has serious problems of vitamin A deficiency (VAD). Thus, it is important to identify locally grown acceptable foods that might be promoted to alleviate this problem. Pandanus fruit (Pandanus tectorius) is a well-liked indigenous Kiribati food with many cultivars that have orange/yellow flesh, indicative of carotenoid content. Few have been previously analysed. Aim: This study was conducted to identify cultivars of pandanus and other foods that could be promoted to alleviate VAD in Kiribati. Method: Ethnography was used to select foods and assess acceptability factors. Pandanus and other foods were analysed for beta- and alpha-carotene, beta-cryptoxanthin, lutein, zeaxanthin, lycopene and total carotenoids using high-performance liquid chromatography. Results: Of the nine pandanus cultivars investigated there was a great range of provitamin A carotenoid levels (from 62 to 19 086 mu g beta-carotene/100 g), generally with higher levels in those more deeply coloured. Seven pandanus cultivars, one giant swamp taro (Cyrtosperma chamissonis) cultivar and native fig (Ficus tinctoria) had significant provitamin A carotenoid content, meeting all or half of estimated daily vitamin A requirements within normal consumption patterns. Analyses in different laboratories confirmed high carotenoid levels in pandanus but showed that there are still questions as to how high the levels might be, owing to variation arising from different handling/preparation/analytical techniques. Conclusions: These carotenoid-rich acceptable foods should be promoted for alleviating VAD in Kiribati and possibly other Pacific contexts where these foods are important. Further research in the Pacific is needed to identify additional indigenous foods with potential health benefits.

Numerous gene rearrangements in the mitochondrial genome of the wallaby louse, Heterodoxus macropus (Phthiraptera)

The complete arrangement of genes in the mitochondrial (mt) genome is known for 12 species of insects, and part of the gene arrangement in the mt genome is known for over 300 other species of insects. The arrangement of genes in the mt genome is very conserved in insects studied, since all of the protein-coding and rRNA genes and most of the tRNA genes are arranged in the same way. We sequenced the entire mt genome of the wallaby louse, Heterodoxus macropus, which is 14,670 bp long and has the 37 genes typical of animals and some noncoding regions. The largest noncoding region is 73 bp long (93% A+T), and the second largest is 47 bp long (92% AST). Both of these noncoding regions seem to be able to form stem-loop structures. The arrangement of genes in the mt genome of this louse is unlike that of any other animal studied. All tRNA genes have moved and/or inverted relative to the ancestral gene arrangement of insects, which is present in the fruit fly Drosophila yakuba. At least nine protein-coding genes (atp6, atp8, cox2, cob, nad1-nad3, nad5, and nad6) have moved; moreover, four of these genes (atp6, atp8, nad1, and nad3) have inverted. The large number of gene rearrangements in the mt genome of H. macropus is unprecedented for an arthropod.

Improved germination of the Australian natives: Hibbertia commutata, Hibbertia amplexicaulis (Dilleniaceae), Chameascilla corymbosa (Liliaceae) and Leucopogon nutans (Epacridaceae)

Hibbertia commutata (Steudel), H. amplexicaulis (Steudel), Chameascilla corymbosa [(R.Br.) F.Muell. Ex Benth.] and Leucopogon nutans (E. Pritzel) are four Australian species that are difficult to germinate during mine-site rehabilitation. Laboratory germination trails were conducted to identify dormancy mechanisms and to improve germination response. Treatments applied to all species included scarification and scarification followed by soaking seeds in smoke water (1, 5 or 10%) or gibberellic-acid solution (50, 200 or 1000 muM). Additional treatments with kinetin solution (50, 200 or 1000 muM) and smoke water (50 or 100%) were applied to scarified or unscarified seeds of C. corymbosa. Thermal-shock treatment was applied to L. nutans fruit, some of which were subsequently scarified and subjected to both smoke water (10%) and gibberellic-acid solution (1000 muM). Significant germination increases were obtained by using dormancy-breaking treatments on H. commutata ( from 12.8 to 76.0%), H. amplexicaulis (from 6.8 to 55.1%) and C. corymbosa (from 48.5 to 86.4%). Scarification alone increased germination of both Hibbertia species, suggesting that these species display a physical seed coat-imposed dormancy mechanism. Germination of H. amplexicaulis was further increased by the application of gibberellic-acid solution, indicating a possible embryo-imposed dormancy mechanism. Scarification followed by the application of smoke water produced the highest germination response for C. corymbosa seeds. Scarification alone did not significantly increase germination, inferring the existence of a smoke-responsive embryo dormancy mechanism. Seeds of L. nutans, although viable, failed to germinate and are thought to display complex seed coat- and embryo-imposed dormancy mechanisms.

Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris: a comparison of two age-assigning techniques

We compared growth rates of the lemon shark, Negaprion brevirostris, from Bimini, Bahamas and the Marquesas Keys (MK), Florida using data obtained in a multi-year annual census. We marked new neonate and juvenile sharks with unique electronic identity tags in Bimini and in the MK we tagged neonate and juvenile sharks. Sharks were tagged with tiny, subcutaneous transponders, a type of tagging thought to cause little, if any disruption to normal growth patterns when compared to conventional external tagging. Within the first 2 years of this project, no age data were recorded for sharks caught for the first time in Bimini. Therefore, we applied and tested two methods of age analysis: ( 1) a modified 'minimum convex polygon' method and ( 2) a new age-assigning method, the 'cut-off technique'. The cut-off technique proved to be the more suitable one, enabling us to identify the age of 134 of the 642 previously unknown aged sharks. This maximised the usable growth data included in our analysis. Annual absolute growth rates of juvenile, nursery-bound lemon sharks were almost constant for the two Bimini nurseries and can be best described by a simple linear model ( growth data was only available for age-0 sharks in the MK). Annual absolute growth for age-0 sharks was much greater in the MK than in either the North Sound (NS) and Shark Land (SL) at Bimini. Growth of SL sharks was significantly faster during the first 2 years of life than of the sharks in the NS population. However, in MK, only growth in the first year was considered to be reliably estimated due to low recapture rates. Analyses indicated no significant differences in growth rates between males and females for any area.

Silencing of the ACC synthase gene ACACS2 causes delayed flowering in pineapple [Ananas comosus (L.) Merr.]

Flowering is a crucial developmental stage in the plant life cycle. A number of different factors, from environmental to chemical, can trigger flowering. In pineapple, and other bromeliads, it has been proposed that flowering is triggered by a small burst of ethylene production in the meristem in response to environmental cues. A 1-amino-cyclopropane-1-carboxylate synthase (ACC synthase) gene has been cloned from pineapple (ACACS2), which is induced in the meristem under the same environmental conditions that induce flowering. Two transgenic pineapple lines have been produced containing co-suppression constructs designed to down-regulate the expression of the ACACS2 gene. Northern analysis revealed that the ACACS2 gene was silenced in a number of transgenic plants in both lines. Southern hybridization revealed clear differences in the methylation status of silenced versus non-silenced plants by the inability of a methylation-sensitive enzyme to digest within the ACACS2 DNA extracted from silenced plants, indicating that methylation is the cause of the observed co-suppression of the ACACS2 gene. Flowering characteristics of the transgenic plants were studied under field conditions in South East Queensland, Australia. Flowering dynamics studies revealed significant differences in flowering behaviour, with transgenic plants exhibiting silencing showing a marked delay in flowering when compared with non-silenced transgenic plants and control non-transformed plants. It is argued that the ACACS2 gene is one of the key contributors towards triggering 'natural flowering' in mature pineapples under commercial field conditions.

Evaluation of the effectiveness of enrichment for a group of captive squirrel monkeys (Saimiri sciureus) using time-lapse recording and instantaneous scan sampling

One aim of providing enrichment to captive animals is to promote the expression of behavioural patterns similar to their wild conspecifics. We evaluated the effectiveness of four types of simple feeding enrichment, using surveillance cameras to record the behaviour of 11 captive squirrel monkeys housed in a single enclosure at Alma Park Zoo in Brisbane, Australia. The enrichment involved differences in presentation (whole/chopped) and distribution (localised/scattered) of fruit and vegetables that were part of the normal diet of these animals. Distinguishing between individual squirrel monkeys was not possible from the videos, so Instantaneous Scan Sampling was used to record the numbers of animals performing particular behaviours every 15 minutes over the 24 hour period as well as every 5 minutes for the hour following provision of enrichment. This provided an estimation of the percentage of time spent by the group in various activities. As a result of the enrichment, the activity budget of the group more closely approximated that of wild squirrel monkeys. However on a number of occasions where the enrichment required the squirrel monkeys to work to obtain their food (whole fruit and vegetables), a number of individuals became aggressive towards the zookeepers. This result highlights the variation in responses of individual animals towards enrichment and indicates that in enclosures with large numbers of animals, the response of each individual should be evaluated in addition to the overall benefit of the enrichment for the group. Furthermore, this variation also suggests that it may be beneficial to provide the animals with choices of enrichment as opposed to providing single forms of enrichment that may only be effective for a proportion of the animals in the enclosure, and may even result in undesirable responses from some individuals.