Development, individual larva

The larval development of the same insect was followed recently also by means of Calvet microcalorimeters [104], Individual larvae could be monitored continuously over 40 days in their metabolic behaviour. Figure 14 shows the strong increase in heat production rate up to the larval stage L7, the subsequent drop to the extremely low level of pupal metabolism and the intensive fluctuations in heat dissipation because of locomotor activities. Moreover, moulting phases were indicated by a drastic decrease of heat production down to 7 to 20 % of the preceding value followed by a rapid increase to the next maximum. These results should be compared with the very early investigations of Taylor and Crescitelli [92] on the same organism (section 5.2.). 

The basis of the difference in these sensitivities is not known but, in principle, it can be assumed that the temperature cue is, in some way, sensed by larvae and this is transduced through a molecular pathway or cascade. The consequence of this process is different (quantitative, qualitative or both) gene expression and this is the basis of the switch between the heterogonic and homogonic routes of development. For individual worms, this process is a binary choice. However, this process applied at a population level will result in a change in the proportion of worms that develop by each route. 

Embryo/larval viability (see Note 10) and development can be evaluated under a microscope at various timepoints during the incubation period. This ability to do sequential assessments of the same individual embryo/larva is one of the greatest advantages of this model over mammalian systems. 

Unlike most of their close relatives, barnacles are hermaphrodites, but individuals usually cross-fertilize. One barnacle can transfer sperm to its neighbor by way of a long, extensible tube. Fertilized eggs develop into zygotes that later form swimming larvae. Eventually, the larvae settle on a substrate, exude a brown glue that anchors them in place, and metamorphose into the adult form. 

The potential for using endocrine imbalance as a means of insect pest control was suggested by Williams (9,10) He proposed that exposing immature insects to juvenile hormone (JH) at the time of metamorphosis, when JH is normally absent, would cause abnormal development and individuals incapable of survival. Since insect metamorphosis is unique, JH disruption would affect only insects. This would result in an environmentally safe approach to insect control as compared to current chemical pesticides which are less insect specific and more biocidal. The JH approach to pest insect control is most effective when adults are the destructive stage, and commercial preparations of JH mimics are available for use in the control of adult flies, mosquitoes, and fleas and, recently, for cockroach reproduction. However, many pest insects are destructive as larvae. 

An automated NIRS system capable of scanning individual grains containing late-instar larvae of S. oryzae, R. dominica, or S. cerealella at the rate of 15 kernels/min has been developed in the United Kingdom (Chambers et al., 1998). The system was effective and could detect the infestation irrespective of the type/class of wheat, its protein content (range 11.32 16.2%) and moisture content (range 10.0 13.2%). The minimum detectable size of the insects by NIRS varied between species. As identified by x-ray analysis, the NIRS system has been shown to detect R. dominica as small as 1.1 mm2 with 95% level confidence, whereas for S. oryzae it was 2.0 mm2, and for S. cerealella 2.7 mm2. For a particular insect species, the accuracy of detection increases as insect development proceeds. Accordingly, in S. oryzae the accuracy of detection of first instar larvae was 10%, second instar larvae 24%, third instar larvae 82%, fourth instar larvae 95%, and the accuracy was 100% for pupae and adults. 

Johnson et al. (1973) first proposed the feasibility of application of an immunoassay method for the detection of insect pest contamination in food commodities. In their studies, crude extracts of individual insects such as D. melanogaster (eggs and adults), Plodia interpunctella (larvae), T. confusum (larvae), Ephestia elutella (larvae), S. oryzae (adults), and S. granarius (adults) served as antigens for the development of appropriate antibodies in rabbits. Subsequently, immunochemical tests comprising immunodiffusion and passive hemagglutination were conducted with insect extract samples to detect the pest. 

A reduction of the vector population through elimination of larval breeding sites and use of larvicides may be one of keys for the prevention of dengue fever and West Nile fever outbreaks. An increase in the number of WNV-infected patients on the west coast of the USA caused the first domestically imported case in Japan in 2005. Establishment of national countermeasures, such as strengthening of quarantine organizations and vector surveillance around the international air and seaports, is needed in the absence of an effective vaccine. Extensive source-reduction countermeasures of mosquito larvae by local government and individuals must be developed at a community level. 

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