Host choice in braconid wasp Dinocampus coccinellae: laboratory experiments to identify relevant factors

Bc. Nikola Gramanová

Master's thesis

Abstract:

The first part of this thesis involves a literature review focused on the relationship between parasitoids and their hosts, including the way of life of parasitoids, parasitoid-host coevolution, their possible adaptation over time,and a description of the biology of Dinocampus coccinellae and Harmonia axyridis. The focus of the investigation was to determine the parasitoid's potential preference for specific host species, including their ability to select a more suitable host based on factors such as age, size, or gender, in order to optimize parasitization success. The thesis also includes two laboratory experiments on the success of parasitization of the ladybird H. axyridis by the parasitoid wasp D. coccinellae and host preferences of the parasitoid wasp. In the first experiment, we tested whether the ladybird age, body size, or the presence of the Hesperomyces virescens in H. axyridis influenced parasitiod preference and the parasitisation success of D. coccinellae. On the first day after hatching, the adult wasp was subsequently placed in four arenas (Petri dishes), spending ten minutes in each. Each arena contained one pair of ladybirds of the same sex(small x large, infected x uninfected, young x old individual). The findings revealed that parasitoid wasps did not display any discernible preference for larger body size, younger age, or uninfected hosts (i.e., hosts without Hesperomyces virescens). Host selection was ‘random’ in this case. In the second experiment the 20-second videos before the parasitoid attack were investigated if the Dinocampus wasp preferred more active (moving) H. axyridis individuals over less active ones. On the first day after hatching, the wasp was placed in a Petri dish where one of the combinations of ladybird pairs (F x F, M x M) was prepared. Each of the combinations of ladybird pairs (F x F, M x M) was observed for ten minutes by the parasitoid, and the entire process was recorded on camera for later analysis of movement. It was demonstrated that the wasp attacked moving ladybirds with higher probability than less active ones. At the same time, the behavior of the ladybird 3 seconds before the attack was observed. It was found that the highest number of attacks occurred on ladybirds that were moving quickly or at least slowly just before the attack.

Keywords

behavior, body size, Dinocampus coccinellae, host choice, movement activity, parasitoid, Harmonia axyridis

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 19. 4. 2023

Obhajoba závěrečné práce

• Obhajoba proběhla 16. 5. 2023
• Vedúci: doc. Ing. Michal Knapp, Ph.D.
• Oponent: Oldřich Nedvěd, externi

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Master programme:
Nature Conservation