I know that parasitic wasp larvae can live for a long time inside their live host (eg. caterpillar), but I always thought that they kill the host when they eventually get out of it. But I've seen a film, where it's shown that not only can a caterpillar survive the emergence of a wasp larva, but also the parasites infect the host with some kind of virus that changes the behaviour of the caterpillar to protect the wasp’s pupa. Is it possible and common among parasitic wasps? What species of wasps and viruses cause such effect?
The species of wasp in the video you link to is Cotesia glomerata. Furthermore, there is at least one other species, Glyptapanteles, which parasitizes other caterpillar species in the same way and induces the same behaviour in its host.
I'm not sure which virus it is.
Is it possible? Of course, you have an example! Though, there is a small caveat. Some of the offspring sacrifice themselves to induce the behavioral change after the rest of the brood has emerged.
Is it common among parasitic wasps? No. While injecting offspring into host species is a common theme for parasitic wasps, and while there are a handful which somehow induce behavioral changes in the host animals - continuing the manipulation after leaving the host animal is extremely rare among parasites in general.
Another example is the wasp species Dinocampus coccinellae, which lays its eggs inside certain species of ladybug/ladybird - most notably the "twelve-spotted lady beetle" (Coleomegilla maculata). It also infects the "seven spot" ladybird.
(I'll stick with "ladybird" instead of "ladybug" for the remainder of this post.)
This is actually very similar to the Glyptapanteles example in the most-upvoted answer so far. (Though I would like to point out that OP's video in fact does not in fact show Glyptapanteles, but the extremely similar Cotesia glomerata.) In this case, though, only one egg is laid inside the host, and the wasp larva is nothing like as small relative to its host as the Cotesia and Glyptapanteles larvae were.
The wasp larva, after emerging from its ladybird host, spins a cocoon underneath the ladybird, between its legs, and pupates. Unlike Cotesia, this wasp larva needs to use its own silk and spin its own cocoon. The hard-shelled ladybird is trapped on top of the wasp pupa, rather like an armoured shelter. While mostly immobile, if potential predators/hyperparasites come close, the ladybird will thrash out at them with its limbs. I'm not sure if this is to attack them directly, or to deter them from coming close, or both.
Since no other larvae are left behind in the host, Dinocampus coccinellae must be using some other means to influence its behaviour after emergence. A virus, the "D. coccinellae paralysis virus", is injected by the adult wasp at the time the egg is oviposited. As well as suppressing the ladybird's immune system, it infects the ladybird's brain and may explain one or both of:
- The ladybird's general immobility after the larva emerges
- The ladybird's thrashing out at potential predators that may attack the larva.
The virus replicates rapidly but for unknown reasons doesn't spread to the beetle's brain until just before the larva emerges from her belly. At first the virus seems to build up harmlessly in brain cells, but as soon as the larva breaks out, these cells burst open, unleashing destruction all around them.
The researchers suggest that the beetle's own immune system may be responsible for this damage. They discovered that crucial immune genes are suppressed while the larva lives within the ladybug, but then reactivate after the larva emerges. The researchers speculate that the beetle's revived immune system discovers and attacks DCPV-infected cells. The self-inflicted brain damage could temporarily paralyze the beetle just when the newly vulnerable wasp larva needs protection.
DcPV is stored in the oviduct of parasitoid females, replicates in parasitoid larvae and is transmitted to the host during larval development.
If I understand correctly, this virus is not one of the so-called "polydnaviruses" injected by other species of parasitic wasp.
For some reason, the wasp prefers to parasitize female ladybird hosts, although I think it will still use male hosts in a minority of cases.
- Dheilly Nolwenn M. et al. (2015). Who is the puppet master? Replication of a parasitic wasp-associated virus correlates with host behaviour manipulation. Proc. R. Soc. B vol 282 issue 1803: http://doi.org/10.1098/rspb.2014.2773
- Maure F et al. (2011). The cost of a bodyguard. Biology Letters volume 7 issue 6: http://doi.org/10.1098/rsbl.2011.0415
- Davis D.S., Stewart S.L., Manica A. and Majerus M.E.N. (2006). Adaptive preferential selection of female coccinellid hosts by the parasitoid wasp Dinocampus coccinellae (Hymenoptera: Braconidae). Eur. J. Entomol., 103(1), 41-45. doi: 10.14411/eje.2006.006.
In the study by Whitfield 1990 (1) I found the information that the parasitic wasp from family Ichneumonidae have interesting symbiotic viruses called polydnaviruses. This virus stay as provirus in the wasps genome and is transmitted vertically between subsequent generations of parasitoid. It does not harm the wasp and it is transmitted to the wasps hosts (usually caterpillar). The virus does not replicate in the caterpillar, but alter it's physiology: supress immune response and metamorphosis and increases the amount of nutrients in caterpillars hemolymph.
Still, I have not found any references about this kind of virus altering the behaviour of the caterpillar after the emergence of wasps larvae.