VSI IR-604 Pupae sex separator. A successful application of the sterile insect technique and other strategies designed to eliminate large populations of insects relies on the efficient releases of competitive, sterile males into the natural habitat of the target species. As released sterile females do not contribute to the sterility of population in situ, systems for the separation of male from female individuals are needed. This is especially key for vector-transmitting species like mosquitoes, in which only females bite and transmit diseases.
While several genetic and transgenic approaches have been developed that permit male-female separation for some species, separation based on sexual size dimorphism continue to be a useful technique in the laboratory and in small to medium mass rearing settings for elimination of females. In general, female mosquitoes of many species such as Aedes and Culex but also Anopheles quadrimaculatus and A. albimanus are larger than males in the pupae stage.
Application of the IR-604 device to separate other insect species and development stages (e.g. pupae, larvae) is feasible if the individuals can be i) in an aqueous solution, and ii) hold an explicit size-dimorphism. See below for more information on size dimorphisms in insects and potential rearing effects on its extend.
The size-based pupae sex separator system IR-604 is a versatile tool for entomologists working in mass rearing or research facilities. Our model is based on the classical larval-pupal separator (narrowing glass plates, Fay-Morlan glass plate separator) but with a more convenient and efficient entering and washing/collection mechanism and three levels of separation - allowing in particular the more accurate fractionation of populations holding some overlap between the sizes of sexes (e.g. small females and large males). See pdf document below for details/specifications of VSI IR-604 Pupae Sex Separator and a brief manual.
Size dimorphism in insect larvae and pupae refers to the presence of size differences between males and females of a species. In many insect species, such as A. aegypti (see example Image), females are larger than males, a phenomenon known as "sexual size dimorphism". Here are some key points about size dimorphism in insects:
It is important to note that rearing conditions can influence the extent of size dimorphism in insect pupae. Nutrition is one key factor that can influence size dimorphism in insects - rendering a standardized feeding process imperative. Inadequate nutrition can lead to smaller body size, different feed application per tray will likely lead increased size heterogeneity and thus complicate sorting. Other environmental factors that can influence size dimorphism in insect pupae include temperature, humidity and/or photoperiod. For example, low temperatures can slow insect development, while high temperatures can accelerate development. In addition, social factors such as crowding can also influence size dimorphism in insect pupae. Crowding can lead to increased competition for resources, resulting in smaller or more heterogenic body size.
In summary, rearing conditions, including diet, temperature, humidity, photoperiod and social factors, can all influence the extent of size dimorphism in insect pupae. To utilise size dimorphisms to separate insect larvae or pupae by a size separator as the IR-604 (or other methods, as exemplified below), it is thus key to use constant and optimized (nutrition, temperature etc) rearing conditions, e.g. in standardized tray and rack systems, leading to most homogeniously sized male and female larvae or pupae.
There are several methods that can be used to separate insect pupae by size. Here some of the more common methods are given:
Overall, the choice of method for sizing insect pupae depends on the insect species, in particular size range between large and small fractions, the resources and equipment available, and the amount of pupae to sort. The effectiveness and efficiency of each method should be evaluated and compared to determine the optimal approach for the specific application. Vienna Scientific is willing to contribute to the design of automated, effective sorting systems, please get in contact.