Infected Slugs: Case #1

This is the first case I encountered and it affected me deeply. However, I did learn some valuable information to assist me in spotting future cases. For instance, one sign of infection is excessive mucus production. Slugs tend to secrete abnormal amounts of mucus only if they're agitated or disturbed, which suggests that the parasite does cause a degree of suffering, or at least triggers this secretion. The other obvious sign is a growth on the slug's body, which can take various forms, I'm assuming depending on the stage of parasitic development. It is usually a yellowish color. My hypothesis is that the parasites enter the slug by some route (perhaps the pneumostome) and lay their eggs inside its body. Then the egg mass grows and grows under the skin till it bursts or at least breaks through the skin, and then once they hatch the larvae either consume the slug or seek a new host. Unfortunately I have little evidence to corroborate this hypothesis. I've considered capturing an infected slug to observe the parasitic development, but I still can't quite get my emotions in line with my scientific curiosity. Another interesting note is the fact that another slug may come along and eat part of the infected one, even before it's dead. Apparently a slug can tell if one of its fellows is sickly or dead. Whether the parasites then take the consuming slug as a new host, I can't say, but I wouldn't rule that out.

So, as regards Case #1, I noticed this particular slug (Lehmannia valentiana) crawling up the side of the back porch, leaving an unusually thick slime trail, with some sunflower shells stuck to its body. A round growth was bulging from its right side, its cephalic tentacles were darkened and retracted, and it stopped going any further. It then rested there, peeling away somewhat from the wood, until another slug, who had consumed some of the slime trail, investigated and began to eat it, though it hadn't yet died.

Removing the sunflower shells, I uncovered a second, smaller growth on the left side. But you can see how lumpy the slug's body has become, indicating either organ displacement or further growths inside.

The slug is beginning to peel back from the wood. Presumably due to the adhesiveness of the mucus, the slug did not fall but hung there for a long time. 

Imagine being eaten alive--ugh!

And the slug can't express itself, can't defend itself against what is happening...so painful to watch.

The infected slug was hanging by its tail...

The infected slug has slid down further...

And the healthy slug begins to eat the sick one again.

I can't tell if those are protruding organs or simply the parasitic growth. At any rate the "bubble" has burst.

When I returned the next day, I found a rather desiccated, partially consumed body still clinging to the wood. What the parasites did or where they went, I don't know. 

I believe that small hole used to be the slug's pneumostome.

I still have no definitive evidence that parasites were the cause of the bulge in the first place. Perhaps some other illness...bacteria, maybe? So far I haven't seen a slug with a growth identical to this one, which resembles skin stretched to its limit, then bursting to expose organs. Am I observing two different maladies, or different versions of one?