401 research outputs found
Development of the larval parasitoid fly, Exorista larvarum (Diptera: Tachinidae) with emphasis in its movements and attachment strategy to the host tissue
No full textExorista larvarum (L.) is a polyphagous gregarious larval endoparasitoid of Lepidoptera. Female flies deposit macrotype eggs on the host surface. The newly-hatched larva penetrates the host integument, induces the formation of a primary integumental respiratory funnel and develops through three larval instars. Pupation generally occurs outside the host larval remains.
The morphology of larval E. larvarum was studied in its factitious host Galleria mellonella (L.) (Lepidoptera: Pyralidae). Last instar host larvae were exposed for parasitization to female flies and removed when the 3 - 5 eggs had been laid on their body. Parasitized larvae were dissected and fixed every day of the parasitoid development, which lasts 3 - 4 days from egg hatching to pupal stage at 26°C. Specimens were embedded in Histoplast II and sections 5 - 7 μm thick were stained with hematoxylin - eosin and Masson΄s trichrome stain. To obtain sections of better quality, the cryosection and rapid microscopic analysis were also used. Frozen sections were stained with azan or hematoxylin - eosin.
Here, we focus on the integument and related structures participating in the movements and attachment process of E. larvarum larva to the host tissue. The tachinid larva penetrates the host using the robust cephalopharyngeal skeleton that undergoes changes during larval development. Using mouthhooks, it feeds on host hemolymph and subsequently on fat body and other host tissues. During larval development the digestive tract gradually becomes more extensive and denotes a great increase in the third instar, which abandons the funnel and migrates in the host body cavity. The tracheal system with prominent respiratory plates is well developed in all larval instars. The larvae are equipped with a thick anal hook and numerous cuticular spines supporting the larva in their attachment to the respiratory funnel. The external morphology of E. larvarum larvae of all instars was studied by electron microscopy. The behaviour of E. larvarum larvae in the host tissues and the escape of the advanced-third instar larvae from the host carcass were documented in vivo using the light microscope
Penetration and encapsulation of the larval parasitoid, Exorista larvarum (Diptera: Tachinidae) in the factitious host Galleria mellonella (Lepidoptera: Pyralidae)
No full textThe tachinid fly, E. larvarum is a polyphagous larval endoparasitoid which deposit macrotype eggs on the host exoskeleton. The newly-hatched larvae burrow through the host integument, leaving a dark spot in the point of their penetration as a result of cuticle melanisation. The attachment of E. larvarum larvae to the host tissues and formation of the hemocyte capsule surrounding the tachinid larva were studied in the last larval instar of the wax moth, Galleria mellonella (L). Parasitization was carried out according to the standard laboratory procedure. The parasitized larvae were examined, dissected and fixed every day of the parasitoid development, which lasts 3 - 4 days from egg hatching to pupal stage at 26°C. Standard histological techniques were used. The material was embedded in Histoplast II and sections 5 - 7 μm thick were stained with hematoxylin - eosin and Masson΄s trichrome stain. As the parasitoid first and second instar larvae are more difficult to be sectioned, the cryosection and rapid microscopic analysis were used to obtain sections of better quality. Frozen sections were stained with azan or hematoxylin - eosin. Our histological examination showed that the endoparasitoid penetration induces the host cellular defence resulting into the formation of a hemocyte capsule consisting of a multi-cellular sheath. This enveloping capsule later undergoes melanisation, which is more evident towards the abdominal part of the parasitoid larval body. The tachinid larva uses this encapsulation response, as well as the integument reaction to wounding, to build the respiratory funnel. The encapsulated larva is attached to the respiratory funnel via an anal hook and cuticular spines and remains in contact with the outside air with its posterior spiracles until the third instar (when the funnel is abandoned). The respiratory funnel was also studied by scanning electron microscopy
De schoffel legde het af tegen de gifspuit die meer doodt dan we dachten
No full textOp woensdag 29 november aanstaande vindt op verzoek van D66, GroenLinks en CU in Den Haag een hoorzitting en rondetafelgesprek plaats over de teruglopende biodiversiteit en de oorzaken daarvan. In de aanloop naar het debat, publiceren professor Louise Vet en professor em. Joop van Lenteren op Foodlog een tekst in drie delen. Daarin schetsen ze hoe biodiversiteitsverlies heeft kunnen ontstaan. Vandaag het eerste deel, over de historie en huidige situatie: van geïntegreerde plaagbeheersing naar chemische bestrijding
In minder dan 20 jaar naar volledige ecologische gewasbescherming
No full textVandaag vindt op verzoek van D66, GroenLinks en CU in Den Haag een hoorzitting en rondetafelgesprek plaats over de teruglopende biodiversiteit en de oorzaken daarvan. In de aanloop naar het debat, publiceren professor Louise Vet en professor em. Joop van Lenteren op Foodlog een tekst in drie delen. Daarin schetsen ze hoe biodiversiteitsverlies heeft kunnen ontstaan. Vandaag het laatste deel, over maatregelen die het vervangen van chemische bestrijdingsmiddelen door alternatieven stimuleren
Geëcologiseerde samenleving versus arme mensen
No full textNiemand weet hoeveel milieubelasting de aarde precies kan hebben, maar een ecologische crisis van ongekende proporties ligt voortdurend op de loer, stellen Stijn van Gils en Louise Vet. Ze pleiten voor radicale veranderingen in de maatschappij. Zo’n ‘geëcologiseerde samenleving’ is volgens hen niet alleen goed voor de aarde, het geeft ook nieuw economisch perspectief. Ralf Bodelier vindt echter dat de ecologen Vet en Van Gils te weinig rekening houden met miljarden armen
Zoekgedrag bij sluipwespen. Deel 1. Olfactorische orientatie op microhabitat en gastheer
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