Divergence in host utilisation by two spider ectoparasitoids within the genus Eriostethus (Ichneumonidae, Pimplinae)

What's gotten into you?: a review of recent research on parasitoid manipulation of host behavior

Some parasitoids modify the behavior of their hosts, benefiting themselves at the host's expense. This phenomenon is called 'manipulation', and current research on parasitoid manipulation of host behavior tends to fall into one of three categories. First, the frequency of manipulation and the magnitude of its benefits to the parasitoid remains unclear. Basic documentation of manipulations is thus a major research focus, with especially valuable recent data coming from spiders manipulated by Polysphincta wasps. Second, for a handful of systems, we now have sufficient phylogenetic and behavioral data to begin asking questions about how manipulation evolved. Finally, the field continues to probe the mechanisms through which parasitoids manipulate host behavior, and now examines the role of parasitoid symbionts in this interaction.

How the activity of natural enemies changes the structure and metabolism of the nutritive tissue in galls? Evidence from the Palaeomystella oligophaga (Lepidoptera) -Macairea radula (Metastomataceae) system

Insect-induced galls usually develop nutritional cells, which they induce and consume directly, and any metabolic modification of those cells may reflect changes of the insect's own metabolism. The system Palaeomystella oligophaga (Lepidoptera)-Macairea radula (Melastomataceae) presents a series of natural enemies, including parasitoids and cecidophages that can function as a natural experiment, respectively removing the specific galling feeding stimulus and providing a nonspecific one. Considering that the process of induction and maintenance of gall tissues strictly depends on the constant specific stimulus of galling, question I:What kind of metabolic changes these different groups of natural enemies can promote in chemical and structural composition of these galls? II: How the specialized tissues are metabolically dependent on the constant specific stimulus of galling in latter stages of gall development? Galls without natural enemies, with parasitoids or cecidophages in larvae or pupae stages were analyzed through histochemistry and cytological profiles and all compared to galls in natural senescence state. The analysis revealed the accumulation of proteins and lipids in typical nutritive tissue and starch in the storage tissue, as well a high integrity of cellular organelles and membrane systems on galls with gallings in the larval stage. Both parasitoids and cecidophages stop galling feeding activities, which resulted in the paralysis of the stimulus that maintain the metabolism of gall tissues, leading to generalized collapse. We demonstrate that the development and metabolic maintenance of a typical nutritive tissue in these galls are completely dependent on constant larval stimulus.

The changing use of the ovipositor in host shifts by ichneumonid ectoparasitoids of spiders (Hymenoptera, Ichneumonidae, Pimplinae)

Accurate egg placement into or onto a living host is an essential ability for many parasitoids, and changes in associated phenotypes, such as ovipositor morphology and behaviour, correlate with significant host shifts. Here, we report that in the ichneumonid group of koinobiont spider-ectoparasitoids (“polysphinctines”), several putatively ancestral taxa (clade I here), parasitic on ground-dwelling RTA-spiders (a group characterised by retrolateral tibial apophysis on male palpal tibiae), lay their eggs in a specific way. They tightly bend their metasoma above the spider’s cephalothorax, touching the carapace with the dorsal side of the ovipositor apically (“dorsal-press”). The egg slips out from the middle part of the ventral side of the ovipositor and moves towards its apex with the parted lower valves acting as rails. Deposition occurs as the parasitoid draws the ovipositor backwards from under the egg. Oviposition upon the tough carapace of the cephalothorax, presumably less palatable than the abdomen, is conserved in these taxa, and presumed adaptive through avoiding physical damage to the developing parasitoid. This specific way of oviposition is reversed in the putatively derived clade of polysphinctines (clade II here) parasitic on Araneoidea spiders with aerial webs, which is already known. They bend their metasoma along the spider’s abdomen, grasping the abdomen with their fore/mid legs, pressing the ventral tip of the metasoma and the lower valves of the ovipositor against the abdomen (“ventral-press”). The egg is expelled through an expansion of the lower valves, which is developed only in this clade and evident in most species, onto the softer and presumably more nutritious abdomen.