ORIGINAL PAPER Gal Haspel Æ Eran Gefen Æ Amos Ar J. Gustavo Glusman Æ Frederic Libersat Parasitoid wasp affects metabolism of cockroach host to favor food preservation for its offspring Received: 22 October 2004 / Revised: 16 February 2005 / Accepted: 17 February 2005 / Published online: 29 April 2005 Ó Springer-Verlag 2005 Abstract Unlike predators, which immediately consume their prey, parasitoid wasps incapacitate their prey to provide a food supply for their offspring. We have examined the effects of the venom of the parasitoid wasp Ampulex compressa on the metabolism of its cockroach prey. This wasp stings into the brain of the cockroach causing hypokinesia. We first established that larval development, from egg laying to pupation, lasts about 8 days. During this period, the metabolism of the stung cockroach slows down, as measured by a decrease in oxygen consumption. Similar decreases in oxygen con- sumption occurred after pharmacologically induced paralysis or after removing descending input from the head ganglia by severing the neck connectives. However, neither of these two groups of cockroaches survived more than six days, while 90% of stung cockroaches survived at least this long. In addition, cockroaches with severed neck connectives lost significantly more body mass, mainly due to dehydration. Hence, the sting of A. compressa not only renders the cockroach prey helplessly submissive, but also changes its metabolism to sustain more nutrients for the developing larva. This metabolic manipulation is subtler than the complete removal of descending input from the head ganglia, since it leaves some physiological processes, such as water retention, intact. Keywords Ampulex compressa Æ Periplaneta americana Æ Oxygen consumption Æ Parasitoid Æ Venom Abbreviations SEG: Subesophageal ganglion Æ TTX: Tetrodotoxin Introduction Most predators kill their prey and consume them immediately, and most venomous predators are no exception to this rule. In contrast, parasitic animals do not necessarily kill their host/prey. They often alter the behavior of their hosts in many ways, including photo- taxis, locomotion, behavioral fevers, foraging behavior, reproduction and a variety of social interactions, to name a few (see Moore 2002, for review). Although the alteration of host behavior by parasites is a widespread phenomenon, underlying mechanisms are only begin- ning to be deciphered (Moore 2002; Beckage 2002). The most fascinating examples of behavioral manipulation are seen in arthropods parasitized by various species of parasitoid wasps. For instance, the aculeate wasp Ampulex compressa (Sphecidae) uses an unusual strategy to incapacitate its prey, the cockroach Periplaneta americana, which serves as a food supply for its larvae (Williams 1942). Unlike most other venomous hunters, the wasp stings and injects its venom directly into spe- cific head and thoracic ganglia of its prey (Haspel et al. 2003). This venom injection induces a transient paralysis of the front legs (Haspel and Libersat 2003) followed by grooming behavior and then by a long-term hypokinesia of its cockroach prey (Weisel-Eichler et al. 1999; Weisel- Eichler and Libersat 2002; Libersat 2003). In this state, the cockroach remains alive but immobile and unre- sponsive, and serves to nourish the wasp larva (Williams 1942). The long lasting lethargic state occurs when the venom is injected into the head but not when it is in- jected only into the thorax (Piek et al. 1989; Fouad et al. 1994). Under laboratory conditions, and if not parasit- G. Haspel Æ J. G. Glusman Æ F. Libersat (&) Department of Life Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva, 84105, Israel E-mail: libersat@bgu.ac.il Tel.: +972-8-6472112 Fax: +972-8-6461870 E. Gefen Æ A. Ar Department of Zoology, Tel-Aviv University, Tel Aviv, Israel Present address: G. Haspel Department of Pathology, Harvard Medical School, Boston, MA, USA J Comp Physiol A (2005) 191: 529–534 DOI 10.1007/s00359-005-0620-1