Thine State of Submission

By Talbrett Caramillo
 

Figure 1 Adult female Doryctobracon areolatus (Spepligeti), a parasitoid wasp of Anastrepha spp. Photograph by Charles Stuhl, USDA-ARS-CMAVE Gainesville, Florida.

Imagine that you are an insect currently in the larval stage of your development, living freely on the forest canopy, awaiting the next phase of your lifecycle which would be to cocoon yourself and metamorphize into that next stage where you might sprout wings and take to the skies. Suddenly, you are confronted by an enigmatic figure possessing a neurotoxin capable of rendering you a zombie, harboring dark complex eyes that peer deep into your soul with sinister goals in mind: to find that suitable host species, paralyze them, and lay the progeny within that target host so that the future of that species may continue their way of life. Such organisms exist in this world we inhabit, they are known as the parasitoid wasps.

Background 
  In the world of parasites, there are many forms of organisms that are specifically adapted to their hosts. Such parasitic specifications are none more impressive than that of the world of wasps belonging to the order Hymenoptera, and their parasitoid lifestyle, and are often referred to as ecological specialists. Though some may recognize this order as being a primarily eusocial, most wasp species are known to be solitary creatures. One good quality of wasps is that they do not target people specifically, but if you happen to find yourself falling into their target host species range you might want to tread lightly. Wasps have a specific species that they must target, and some have even evolved neurotoxins in order to “zombify” their hosts. They don’t lay their eggs in external environment locations, but instead they lay their eggs within their targeted hosts that have been immobilized by the highly specialized venom as previously mentioned. Finally, wasp’s contribution to insect diversity is none more appreciated than by the ever so important field of agriculture. These wasps target pest species that would otherwise decimate valuable crops, costing farmers millions of annual revenues. Though farmers consider insecticides for pest control, I would argue that methods of utilizing natural pest control such as the wasps, as an adequate replacement for insecticides. Pest control is reasoning enough helping highlight these specialized organisms and continue to live their unique example of parasitism.

Diversity of Wasps  
The vast diversity of wasps is apparent in their different body sizes, but also their target host species. Some species are so small they would not be readily noticed without an untrained eye, while others can be about as big as one’s thumb. One such example of target host diversity, is that some wasps will target caterpillars, spiders and roaches just to name a couple of examples. Most wasps are very much small individuals, such as Chalcid wasps and contains over 20,000 different species of wasps. One can also imagine that different species of wasps will also have different techniques in which they subdue their hosts. The wasp’s size is one of their most distinct features, in that they are usually much smaller in comparison to their target host species. Being smaller, means they must have adaptations that make them much quicker than the host, and most can strike in their targets in an instance.

 
Host Manipulation
The search for suitable hosts is a highly specialized process but finding that unfortunate victim is merely the beginning of this mind-altering experience. In one of the most well studied examples, the Jewel Wasp targets cockroaches and controls the unlucky individual into following it into a burrow of its choosing. This host manipulation mechanism is made possible through their venom which is comprised of a variety of neurotoxins that target a certain region of the roaches’ Central Nervous System (CNS). Much of these mechanisms are present in other species of wasps and their preferred target host species. In the case of the Jewel Wasp, once it finds a target roach, it then attacks and uses a system of chemical cues within the roach’ CNS to correctly distribute the venom, making the roach manageable.  

Benefits of Parasitoid wasps 
Much of the benefits associated with the parasitoid wasps can be found in their ability to control pest species, that may otherwise become overpopulated and decimate the agricultural markets. Some might even go as far as to use wasps as bio-controls of these pest species, but there could be problems associated with the introduction of a species to a new ecological system. Though they are efficient controllers of pests, the wasps are highly susceptible to pesticides that might be ever present in most agricultural operations. In closing, parasitoid wasps are a unique example to the world of parasites. Their lifestyle seems taken straight out of a horror movie, and their unfortunate hosts that exhibit the zombie state. Thought they are fun to learn about and study, you do not want to find yourself as the target host species of these efficient killers.

References

E. Zchori-Fein et al. “A newly discovered bacterium associated with parthenogenesis and a change in host selection behavior in parasitoid wasps.” Proceedings of the National Academy of Sciences Oct 2001, 98 (22) 12555-12560; DOI: 10.1073/pnas.221467498

Gal, Ram et al. “Sensory Arsenal on the Stinger of the Parasitoid Jewel Wasp and Its Possible Role in Identifying Cockroach Brains.” PLoS ONE 9.2 (2014): n. pag. Web.

Zhu, Feng et al. “Symbiotic Polydnavirus and Venom Reveal Parasitoid to Its Hyperparasitoids.” Proceedings of the National Academy of Sciences 115.20 (2018): 5205–5210. Web. 9 Mar. 2020.

  https://projects.ncsu.edu/cals/course/ent425/library/compendium/hymenoptera.html