Anatomy and development of thrips relative to Tospovirus acquisition
Moritz G
Martin-Luther-University Halle-Wittenberg, Developmental Biology, Domplatz 4, 06108 Halle, Germany.
Correspondence: gerald.moritz@zoologie.uni-halle.de
Tospoviruses are now recorded from more than 500 plant species in over 50 families. These viruses use only about 11 thrips vectors to move from one plant to another. The transmission of the virus by adult thrips is only successful if the first or early second larval stage acquires the virus during feeding on infected plant tissue. Wijkamp I et al. 1996 (Annals of Applied Biology 129: 303每313) determined a median acquisition access period (AAP50) and pointed out that transmission ability increases with the length of the AAP on virus-infected material given to thrips larvae of Frankliniella occidentalis. On the other hand Sakurai T et al. 2002 (In: Marullo R, Mound LA, editors. Thrips and Tospoviruses: Proceedings of the 7thInternational Symposium on Thysanoptera, 51每57. Canberra: Australian National Insect Collection) describe intraspecific variation in transmission of TSWV from several populations of western flower thrips in Japan and pointed out that males transmit TSWV with higher efficiencies than females. Developmental studies of ontogenetic stages of thrips including their inner morphology let these results appear in a completely new light (Moritz G et al. 2004. Virus Research 100: 143每149). The so called short germ band in thrips shows a top-down-segmentation with a successive segment specification ((Tautz D. 2004. Developmental Cell 7: 301每312)). Shortly after katatrepsis the lobed salivary gland material appears behind the brain. In the first larval stage, the small time frame for virus acquisition is determined when the epithel cells of the mid gut and the salivary gland cells come in tight contact because the brain is displaced out of the small larval head by large cibarial muscles. Variable acquisition rates are the result of movements of the brain and the growing mid gut in size and length. An effective virus transfer cell ensemble exists only for a few hours. The reposition of the brain and the formation of the oscillatory flight muscles end the possibility to acquire tospoviruses definitely
Thrips Identification: Classical, digital or molecular?
Moritz G1, Mound LA2, Kumm S1
1 Martin-Luther-University Halle-Wittenberg, Developmental Biology, Domplatz 4, 06108 Halle, Germany.
2 CSIRO Entomology, P.O. Box 1700, Canberra, ACT 2601, Australia
Correspondence: gerald.moritz@zoologie.uni-halle.de
Situation: In the last decades the importance of pest thrips has increased considerably worldwide. These species are usually highly adaptable, with a well developed resistance against certain insecticides and with a tendency to be vectors of fungi, bacteria and viruses. Some of them are invasive, and are notorious for causing extensive crop damage (Morse CG, Hoddle MS. 2007. Annual Review of Entomology 51: 67每89). Their identification is important to understand their biology and to empower integrated pest management strategies. However, it is questionable how effective current taxonomic methods and research are to adequately serve these problems and future scenarios. Classical Identification: The development of dichotomous keys is time consuming, expensive to print, of most use to professional taxonomists with good reference collections and libraries, and mostly focus on specific thrips taxa of local interest; their effective market niche is thus limited. In contrast, computing power is now inexpensive and available globally, and we should not ignore this availability (Cranston PS. 2005. Systematic Entomology 30: 1每3). One recent development that makes dichotomous keys more functional is the software Phoenix (For further information: http://www.lucidcentral.com) that involves scanning a printed key and then manipulating it electronically. Digital Identification: Several computerized identification and information systems, especially for pest thrips, are available (Moritz G et al. 2001. http://lucidcentral.com/keys/viewKeyDetails.aspx?id=218; 2004. http://lucidcentral.com/keys/viewKeyDetails.aspx?id=304. These systems provide fully illustrated and user-friendly means of recognising most of the thrips species that have been recorded as pests in various parts of the world, and moreover, the 2001 version provides information about all of the recognised families of these insects. These multivariate computer keys have important advantages and features and include a range of information on the host plants, distributions and body structure of these thrips. Furthermore, you can use expert routes combined with original computerized colour pictures, movie clips and the possibility to compare the identified species with other species of the key. Molecular Identification: The latest thrips key combines an illustrated visual key with molecular methods based on the ITS-RFLP technique and allows the identification of all ontogenetic stages including eggs. Limitations and problems occur only in species pairs of recent origin (Tautz D. 2003. Trends in Ecology and Evolution 18: 70每74), for example Frankliniella bispinosa and F. tritici.
