Saturday, 31 October 2009

Climbing up the walls

Recent rain seems to have driven most of the invertebrates under cover. During the hot weather, the moths, crickets and beetles were so thick on the windows that I thought I was going to have to get one of those magnetic aquarium glass cleaners so I could clear a little space to see through. But showers over the past few days have been heavy enough to send the insects into hiding, while still being too light to bring out the really fascinating invertebrates.

But I can wait.

There are some interesting animals around now. This opilionid (harvestman) was resting on the wall in the shade of the patio. I've seen a few since I've been here, but this was the first one at close to eye height.



The abdomen was covered in a cluster of mites (the red blobs). A couple of mites were also attached to the legs.




Mites are common ectoparasites (external parasites) on arachnids and insects. They also occur on millipedes — you can often see them scurrying along a millipede's sides — and some land snails and slugs. The mites living on terrestrial molluscs are the most intriguing. Of course.The best known belong to the genus Riccardoella. These mites occur in Australia, but only on introduced snails and slugs. They don't appear to have made the leap scuttle across to our native species, although R. limacum is known to occur on the New Zealand slug Athoracophorus bitentaculatus, a relative of the Australian red-triangle slug (Triboniophorus graeffei). If any of you in RT slug land want to take a close look at these marvellous molluscs to see whether they're carrying mites, I'd be interested in hearing your reports. Riccardoella is particularly fond on popping in and out of the pneumostome — the breathing pore — which is at the apex of the triangle, on the right. That's where you're most likely to spot them.

Oh, this started with an opilionid, didn't it? For the record, the harvestman's body was about 4mm long. The leg lengths were 1st 30mm; 2nd 55mm; 3rd 30mm; 4th 40mm. An ID would be welcome.

10 comments:

Dave Coulter said...

Nice shot....by the way this NaNoWriMo looks pretty cool!

Anonymous said...

Opilionids just hanging around one by one, on the walls! Luxury.
Out on the patio we sit,
And the humidity we breathe...

Who's a q'lander now then? ;-)
Gangajang say this is Australia, but us SW WAliens know better :-)

A welcome return post, teacher.
However our dry season is upon us and although we can do plenty ticks on lizards and snakes, slug mite observations from here will have to wait until next year now.

d

Snail said...

Dave, NaNoWriMo is pretty good fun. If nothing else, it gets you writing!

D, it's lovely up here right now. Raining but still quite cool, so the humidity isn't unbearable ... yet. Watch out for those snail mites when it rains again --- they're mesmerising!

AYDIN ÖRSTAN said...

The mites are surprisingly large relative to the harvestman's body. About 1/8 maybe. Imagine having to walk around while carrying a bunch of red ectoparasites that big relative to your body.

Christopher Taylor said...

It's a minor male of Neopantopsalis, probably cf. quasimodo (though I can't tell for sure from the photo).

Anonymous said...

Christopher Taylor said...
and you'd better believe it ;-)
Hot off the press and
from the horse's mouth

d

Anonymous said...

AYDIN ÖRSTAN said...Imagine having to walk around while carrying a bunch of red ectoparasites that big relative to your body

... as the woman who gestated her and my twins complained for the first six months of those screaming red endoparasites' transformation into ectoparasites. ;-)

d

Snail said...

Aydin, we breed 'em tough here! I think that mite load is testament to the strength of chitin.

Christopher, thanks for the ID. As wonderful as they are, opilionids are a complete mystery to me. I will keep my eyes open for more.

And, d, thanks for tracking down Christopher's paper!

Kathie Hodge said...

That is a cool and delightfully freaky photo. And, whoa! I had no idea snails had mite "fleas." That is also very cool, though I'm sorry for the snails. I wonder how snails escape their mites? Why aren't they always infested?

Snail said...

I'm not sure whether the mites do lasting damage to the snails, although they are known to feed on snail haemolymph (blood). I'm not sure how a snail first becomes infected --- whether the mites hang around the eggs, waiting for them to hatch, or the snail gets it from a close encounter with another snail.