I have now been told that the ichneumonid that is ovipositing from under the leaf is one of the Ctenopelmatinae, possibly one of the Campodorus sp., which have been reared from Nematus sp. larvae.
The under-the-leaf oviposition technique is not in the literature, so this might be one of the first times it has been observed, and certainly the first time it has been recorded. One reasonable theory is that the larvae are very aggressive with their defence reflex (a sudden whipping of the rear of the body, pulling it up into the characteristic 'S' shape), so the Campodorus is actually protecting itself from the Nematus larva's protection reflex. This ties in nicely with the observation that the secondary parasite checks for the presence/absence of this response before it lays its own eggs from a straddle position. I suspect that the Campodorus egg subdues the Nematus larva to some extent (but why? Certainly, it differentiates an already parasitised larva from a clean one, thereby avoiding duplicate [and therefore wasteful] primary parasitisation, but it also makes it easier for the secondary parasite to detect the primary parasite and lay its own egg. A double-edged sword. )
Moving on to the Entoloma from Ards forest: it appears to be Entoloma serrulatum. These are the spores:
Magnification is 400x, the spores are mounted in water and the individual spores are around 10 microns long.
6 comments:
"I suspect that the Campodorus egg subdues the Nematus larva to some extent (but why?..."
um, by accident? That it just so happens that the egg or early-stage larva interferes with the sawfly's nervous system. And both parasite and hyperparasite have 'learnt' to interpret / use that behaviour. I suppose a number of complicated behavioural traits may originally have evolved in this way.
The more one learns about species inter-relationships in nature the more one marvels.
Nice shot of the spores by the way.
The whole concept of causing a circumstance which benefits a species that is your predator is counter-intuitive. However, if that circumstance so benefits your predator to an extent that it would wipe you out, then the predator would also perforce die out. So we are left with the conclusion that the paralysing effect of the primary parasite benefits the primary parasite more than it benefits the secondary parasite, however that benefit may manifest itself. Truly wonderful.
On reflection, I think I have the crux of the matter. We know that the secondary parasite lays more than one egg...I showed the sequence last year. Now...the primary parasite has a very large target to hit (the whole larva), so it will lay an egg in the host in a vast majority of attempts. The secondary parasite has to hit the egg of the primary parasite, which will be extremely difficult. So it lays a few in the hope that one will hit. Many attempts will fail. There we have it. The secondary parasite is less advantaged by the paralysis, so the whole sequence works.
QED.
Hmm - I wonder why the secondary parasite doesn't wait a bit till the primary one has hatched - a larva would be a hell of a lot easier to hit than an egg! Are you suggesting that all bar one of the eggs laid by the straddling ich fail to hatch, or at least fail to hatch so the grub can find the primary parasite and so dies? - under those circumstances surely it'd simply eat the sawfly larva wouldn't it?
>I wonder why the secondary parasite doesn't wait a bit till the primary one has hatched - a larva would be a hell of a lot easier to hit than an egg!
It might well do.
>Are you suggesting that all bar one of the eggs laid by the straddling ich fail to hatch, or at least fail to hatch so the grub can find the primary parasite and so dies?
Most certainly.
>under those circumstances surely it'd simply eat the sawfly larva wouldn't it?
I don't think so, otherwise it would just be a primary parasite. There is a lot of anti-rejection in this process, and I suspect that the host will reject the secondaty parasite quite effectively.
In terms of size, the primary parasite is slightly larger than the secondary parasite, so there wouldn't be enough food left for more than 1 anyway.
"There is a lot of anti-rejection in this process, and I suspect that the host will reject the secondary parasite quite effectively."
Ah, yes, I hadn't taken that into account - chemical presumably. Fascinating.
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