Nik Fadzly

Ontogenetic colour changes in an insular tree species: signalling to extinct browsing birds?

* Animals often use colours to hide from predators (crypsis) or advertise defences (aposematism), but there is little evidence for colour-based defence in plants. * Here, we test whether ontogenetic changes in leaf colour of lancewood (Pseudopanax crassifolius) may have been part of a defensive strategy against flightless browsing birds called moa, which were once the only large herbivores in New Zealand. We tested this hypothesis by conducting spectrographic measurements on different-sized plants grown in a common garden. We also compared these results with observations on a closely related, derived species that evolved in the absence of moa on the Chatham Islands. * Spectrographic analyses showed that birds would have difficulty distinguishing seedling leaves against a background of leaf litter. Conversely, brightly coloured tissues flanking spines on sapling leaves are highly conspicuous to birds. Once above the reach of the tallest known moa, adults produce leaves that are typical in appearance to adult leaves. The Chatham Island species lacks ontogenetic colour changes entirely. * Overall, the results indicate that P. crassifolius goes through a remarkable series of colour changes during development, from cryptically coloured seedlings to aposematically coloured saplings, which may have formed a defensive strategy to protect against giant browsing birds.

Colonized Aedes albopictus and its sexual performance in the wild: implications for SIT technology and containment

BackgroundMating is a physiological process of crucial importance underlying the size and maintenance of mosquito populations. In sterile and incompatible insect technologies (SIT and IIT), mating is essential for mass production, persistence, and success of released individuals, and is a central parameter for judging the effectiveness of SIT/IIT programs. Some mosquitoes have an enormous reproductive potential for both themselves and pathogens and mating may contribute to persistence of infection in nature. As Aedes albopictus can transmit flaviviruses both sexually and horizontally, and as infected insects are usually derived from laboratory colonies, we investigated the implications of mating between a long-term laboratory colony of Ae. albopictus and wild populations.MethodsThrough a series of mating experiments, we examined the reproductive outcomes of sexual cross-affinity between laboratory-raised and wild adults of Ae. albopictus.ResultsThe results indicated appreciable mating compatibility between laboratory-reared and wild adults, and equivalent levels of egg production among reciprocal crosses. We also observed comparable larval eclosion in lab females mated with wild males, and increased adult longevity in female offspring from wild females|×|laboratory males crosses.ConclusionsTaken together, these data suggest that Ae. albopictus can preserve its reproductive fitness over a long period of time in the laboratory environment and has valuable attributes for SIT application. These observations together with the ability to successfully inseminate heterospecific females indicate the potential of Ae. albopictus to act as an ecological barrier if non-sterilized males are massively released in areas occupied by Aedes aegypti. The observed substantial reproductive fitness combined with the capability to reproduce both, itself and viruses illustrates the potential of Ae. albopictus to pose a serious threat if infected and released accidentally.

HIDING FROM THE GHOST OF HERBIVORY PAST: EVIDENCE FOR CRYPSIS IN AN INSULAR TREE SPECIES

The color of many animals matches that of their preferred habitats, making them difficult for predators to locate. However, quantitative examples of crypsis in plants are comparatively rare. We conducted morphometric and spectrographic analyses of a heteroblastic tree species that is endemic to New Zealand (Elaeocarpus hookerianus Raoul) to test whether it is cryptic in appearance from the perspective of birds, who were once dominant browsers in New Zealand. The leaves of smaller, juvenile plants are highly variable in size and shape and are mottled brown in color from the perspective of birds, which would make them difficult for herbivorous birds to locate against a background of leaf litter. However, once plants grow to above 3 m in height, beyond the reach of the largest herbivorous bird known to inhabit New Zealand, plants suddenly produce leaves that are ordinary in size, shape, and color. Results provide quantitative support for the hypothesis that E. hookerianus is cryptically colored when within reach of flightless browsing birds.

What weta want: colour preferences of a frugivorous insect

Plants use colours as signals to attract mutualists and repel antagonists. Fleshy-fruits are often conspicuously coloured to signal different types of information including fruit maturity and spatial location. Previous work on fruit colour selection focus on large diurnal vertebrates, yet fruit colours are perceived differently by frugivores with different types of visual systems. Here, we tested whether a nocturnal, frugivorous, seed-dispersing insect selects fruits based on their pigmentation and whether different lighting conditions affect fruit colour selection. We captured 20 Wellington tree weta (Hemideina crassidens) from a forest reserve on the North Island of New Zealand and brought them into laboratory conditions to test their fruit colour preferences. The fruits of Coprosma acerosa, a native shrub species that naturally produces translucent, blue-streaked fruits, were dyed either red or blue. Fruits were then offered to weta in a binary (y-maze) choice test in two light conditions, either at night during a full moon or under artificial light conditions in the lab. Weta preferred unmanipulated, naturally blue-streaked fruits and artificially-blue coloured fruits over those dyed red. Furthermore, their colour preferences were unaffected by light environment. Our results therefore suggest that weta can discriminate between colours (using colour vision) in both light and dark light environments. Their consistent preferences for colours other than red indicate that weta might be responsible for the unusual colours of fleshy-fruits in New Zealand.

Indirect effects of cigarette butt waste on the dengue vector Aedes aegypti (Diptera: Culicidae).

Despite major insecticide-based vector control programs, dengue continues to be a major threat to public health in urban areas. The reasons for this failure include the emergence of insecticide resistance and the narrowing of the spectrum of efficient products. Cigarette butts (CBs), the most commonly discarded piece of waste, also represent a major health hazard to human and animal life. CBs are impregnated with thousands of chemical compounds, many of which are highly toxic and none of which has history of resistance in mosquitoes. This study was performed to examine whether exposure to CB alters various biological parameters of parents and their progeny. We examined whether the mosquito changes its ovipositional behaviors, egg hatching, reproductive capacity, longevity and fecundity in response to CB exposure at three different concentrations. Females tended to prefer microcosms containing CBs for egg deposition than those with water only. There were equivalent rates of eclosion success among larvae from eggs that matured in CB and water environments. We also observed decreased life span among adults that survived CB exposure. Extracts of CB waste have detrimental effects on the fecundity and longevity of its offspring, while being attractive to its gravid females. These results altogether indicate that CB waste indirectly affect key adult life traits of Aedes aegypti and could conceivably be developed as a novel dengue vector control strategy, referring to previously documented direct toxicity on the larval stage. But this will require further research on CB waste effects on non-target organisms including humans.

DISCARDED CIGARETTE BUTTS ATTRACT FEMALES AND KILL THE PROGENY OF AEDES ALBOPICTUS

Abstract Discarded cigarette butts (DCB) waste occurs worldwide, pollutes landscapes, is unsightly, and results in added debris removal costs. There is, therefore, a great deal of current interest in making use of DCBs in beneficial ways. Despite evidence that DCBs are harmful to water fleas (Daphnia magna), which breed in aquatic environments as do mosquito larvae, their impact on dengue vectors is unknown. We examined whether Aedes albopictus alters its ovipositional responses, larval eclosion, and development in response to presence of DCBs in its habitats. We found oviposition activity in DCB-treated water similar to that of control water and that ovipositional activity in DCB solutions steadily increased over time as those solutions aged to 10 days. Larval eclosion was initially suppressed on day 1 in DCB solution, but increased thereafter to levels similar to control larval eclosion rates. The DCB–water solutions produced significantly higher mortality in both 1st and 2nd instars over control larvae for several days after initial exposure. Mortality rates decreased sharply 3 to 5 days postexposure as DCBs continued to decompose. We found increased survival rates during late development, but daily input of fresh DCBs prevented most young larvae from completing development. Taken together, these observations suggest that decomposing did not deter gravid Ae. albopictus females from ovipositing in treated containers and that DCB solutions had larvicidal effects on early instars. Our results are discussed in the context of DCB use to control container-breeding Ae. albopictus, a competent dengue vector in Asia and other parts of the world.

Risky behaviors: effects of Toxorhynchites splendens (Diptera: Culicidae) predator on the behavior of three mosquito species.

Viable biocontrol agents for mosquito control are quite rare, therefore improving the efficacy of existing biological agents is an important study. We need to have a better understanding of the predation-risk behavioral responses toward prey. This research examined prey choices by Toxorhynchites splendens by monitoring the behavioral responses of Aedes aegypti, Aedes albopictus, and Anopheles sinensis larvae when exposed to the predator. The results show that Tx. splendens prefers to consume Ae. aegypti larvae. The larvae exhibited different behavioral responses when Tx. splendens was present which suggest vulnerability in the presence of predators. “Thrashing” and “browsing” activities were greater in Ae. aegypti larvae. Such active and risky movements could cause vulnerability for the Ae. aegypti larvae due to increasing of water disturbance. In contrast, Ae. albopictus and An. sinensis larvae exhibited passive, low-risk behaviors, spending most of the time on the “wall” position near the edges of the container. We postulated that Ae. aegypti has less ability to perceive cues from predation and could not successfully alter its behavior to reduce risk of predation risk compared with Ae. albopictus and An. sinensis. Our results suggest that Tx. splendens is a suitable biocontrol agent in controlling dengue hemorrhagic vector, Ae. aegypti.

Saprophytic and Potentially Pathogenic Fusarium Species from Peat Soil in Perak and Pahang

UNLABELLED We conducted several aviary experiments to investigate the influence of colours in quantity judgments of two species of birds; house crow (Corvus splendens) and common myna (Acridotheres tristis). Different quantity (in seven different food proportions) of mealworms were presented nonsequentially to all birds using artificially coloured red mealworms, for experiment 1, and using artificially coloured green mealworms, for experiment 2. Both red and green coloured mealworms have no significant effect on house crows quantity judgments (red: ANOVA F6,30 = 1.748, p = 0.144; and green: ANOVA F6,30= 1.085, p = 0.394). Common myna, however, showed a strong influence of red colour in their quantity judgment ( ANOVA F6,30 = 2.922, p = 0.023) as they succeeded in choosing the largest amount of food between two cups, but not when offered food using green coloured mealworms ( ANOVA F6,30 = 1.183, p = 0.342). In the next experiment, we hypothesised that both house crow and common myna will prefer red coloured food items over green coloured food items, when factors such as the amount of food is equal. We chose to test red and green colours because both colours play an important role in most avian food selections. Results showed that there were no significant differences in the selection of red or green coloured mealworms for both house crows ( ANOVA F6,30 = 2.310, p = 0.06) and common myna ( ANOVA F6,30 = 0.823, p = 0.561).

Cryptic coloration of Macaranga bancana seedlings: A unique strategy for a pioneer species.

ABSTRACT Macaranga bancana is considered as a successful pioneer plant species. Usually found in disturbed and open areas, most of the current research focused on its relations with ants. One of the unique feature of the plants is that the seedling leaves are red, resembling and almost matching the background. Using a portable spectrometer, we measured the color reflectance of M. bancana seedlings (less than 20 cm in height). We also measured the leaf litter reflectance, adult M. bancana leaves and also seedlings of several other species found in the vicinity of M. bancana seedlings. The reflectances of M. bancana seedlings are very similar to that of the leaf litter background. We suggest that this cryptic coloration is crucial during the early stages of the plant when it still cannot rely on the protection of ants.

Lethal and Sublethal Impacts of Predaceous Backswimmer Anisops wakefieldi (Hemiptera: Notonectidae) on the Life-History Traits of the New Zealand Mosquito Culex pervigilans (Diptera: Culicidae)

ABSTRACT The presence of predators can have dramatic consequences on prey communities, not only by the direct effects of consumption but also through sublethal effects. We investigated the survival rate and subsequent life history of the mosquito Culex pervigilans Bergroth under the influence of its major predator, the backswimmer Anisops wakefieldi White. We established a field experiment with various treatments: 1) control without predators, 2) free-roaming A. wakefieldi (with one, three, or nine A. wakefieldi per container), 3) caged A. wakefieldi (empty cage without predators, with one, three, or nine A. wakefieldi in each cage, and 4) A. wakefieldi cues (with cues concentrations of one, three, or nine A. wakefieldi). Cx. pervigilans eggs were then taken from these four experimental treatments and reared in two different laboratory conditions: 1) in clean water without any traces of predators, or 2) in water with the same treatments as in field. The survival rate of Cx. pervigilans was significantly reduced by the presence of predators or their cues. Even after a brief exposure to waters containing predators or residual cues, the subsequent progeny and the ontogeny of the remaining survivors were still affected. The percentage of eggs that hatched, and the resulting mosquito population, was influenced by the presence of predators or their cues. Our results suggest that sublethal effects may be carried by surviving individuals primarily through the effects of stress, perhaps by epigenetic mechanisms. We may expect to observe similar plasticity in species or populations with high temporal or spatial variability in predation.