|Shapiro ilan, David|
Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/18/2000
Publication Date: 7/1/2000
Citation: Shapiro Ilan, D.I., Lewis, E.E., Paramasivam, S., Mccoy, C.W. 2000. Nitrogen partitioning in Heterorhabditis bacteriophora-infected hosts and the effects of nitrogen on attraction/repulsion. Journal of Invertebrate Pathology. v.76. p.43-48. Interpretive Summary: Entomopathogenic nematodes are tiny round worms that kill many important insect pests, but do not harm humans, other animals, or the environment. It is important to understand factors that affect the behavior of these nematodes so that we can apply them more effectively. In this study we studied the release of nitrogen from insects that were infected with entomopathogenic nematodes. We found that small amounts of nitrogen, released from the infected insect early after infection, attract other nematodes, whereas greater amounts of nitrogen (released later in infection) repel other nematodes. Therefore, manipulating the nitrogen in soil where nematodes are applied may increase or decrease the ability to kill pests.
Technical Abstract: Entomopathogenic nematode behavior is affected by the condition of their infected hosts. We hypothesized that nitrogen compounds released from infected hosts may be one factor affecting entomopathogenic nematode host finding and infection behaviors. Our objectives were to investigate the partitioning of nitrogen in Galleria mellonella (L.) infected by Heterorhabditis bacteriophora Poinar, and to determine attraction and repulsion of H. bacteriophora to various quantities of nitrogen. Volatile (ammonia), organic, and inorganic nitrogen forms were monitored during the course of infection. Approximately 0.052 mg of nitrogen were released from a single infected host as volatile ammonia. Most of the ammonia release was detected within the first 3 d post-inoculation. Organic nitrogen increased during the course of infection whereas inorganic nitrogen decreased. The net nitrogen change in the infected host consisted of a loss of approximately 47 mg, most of which was lost within the first week of infection. Accelerated loss of nitrogen early in the infection process was likely correlated with activity and growth of bacterial symbionts. Increased organic nitrogen was likely associated with nematode reproduction within the host. Attraction or repulsion of H. bacteriophora to nitrogen (ammonium hydroxide) was measured on agar quadrant plates. Nematodes were attracted to 16 and 160 ug of nitrogen and repelled by concentrations of 1600 and 8,000 ug. Our data indicate that nitrogen released from H. bacteriophora infected hosts attracts nematodes at lower levels (early in the infection) and repels them at higher concentrations (later in the infection process).