The morphology and biology of the entomophilic Thripinema fuscum (Tylenchida: Allantonematidae), and the histopathological effects of parasitism on the host Frankliniella fusca (Thysanoptera: Thripidae)

Abstract

We used light and electron microscopy to detail the in vivo life cycle of the nematode Thripinema fuscum and to determine the effects of parasitism on tissues of the thrips host Frankliniella fusca. The parasitic T. fuscum female produced eggs within 4–5 days after ingress and the host haemocoele became packed with eggs and developing juvenile nematodes. Mature juveniles migrated to the hindgut and fully developed juveniles first emerged from the posterior end of the male or female F. fusca 9 days after parasitization. Parasitization induced a displacement of the host alimentary tract, an atrophy of the ovaries and fat body, and an alteration of energy and waste reserves in host tissues. Our observations reveal a specialized relationship showing that this parasite is well adapted to exploit the host digestive, reproductive and excretory systems.

Keywords:

• thrips
• parasitic nematode
• in vivo development
• host–parasite interactions
• histopathology

Acknowledgments

We thank Karen Kelley and Kimberly Kelley from the Electron Microscopy and Bioimaging Laboratory at the University of Florida; Verena Lietze, Senior Biological Scientist from the Entomology and Nematology Department at the University of Florida; and Neil Sanscrainte, Biological Science Laboratory Technician at the Mosquito and Fly Research Unit of USDA, ARS, for assistance with the scanning electron microscopy and micrographs. We thank Judy Gillmore, Senior Laboratory Technician at the University of Florida, for greenhouse space, and James Boyer, Coordinator of Research from the Plant Science Research & Education Unit, for aid in the collection of study organisms. Mrittunjai Srivastava, Senior Biological Scientist at the University of Florida assisted with the manuscript figures.