Help with woodlouse anatomy pls.

[Bruce Williams]

Took the following pic today. I didn't have to turn this character over, it just lay like that for about 5 minutes before turning over and making a bolt for cover. The insert pic is of the same woodlouse as he was makinging his getaway.

The first pic just shows the underside of the woodlouse and the second pic is the same but annotated (and with a question mark).

1. Does anyone know if this is a male or a female?

2. Does anyone have any idea what the (circled) finger-like protusions are between epimera (1 and 2), (2 and 3) and (3 and 4)?



Help appreciated as always.

Bruce

[Pudding4brains]

Hi Bruce,

Nice image, as always

Originally Posted by Bruce Williams

1. Does anyone know if this is a male or a female?

It's a female, you can tell by the length of the 1st & 2nd pleopods. They're somewhat covered by the legs in your image but the long points/extensions of a male would still show.

A male underside is here.
A pregnant female here

2. Does anyone have any idea what the (circled) finger-like protusions are between epimera (1 and 2), (2 and 3) and (3 and 4)?

I'm actually not sure I haven't done any dissecting and "detailed anatomy" yet and my images aren't usually good enough to show such details Just quickly checked with some 4-5 books and none list these I can only speculate they might have something to do with the pores these critters are supposed to have on the epimera (but I can never find on any images - too small).

If no one else here knows I'll check with some dutch expert later.
Cheers!
Arp

[Bruce Williams]

Thanks Arp, two very interesting and helpful photos. From now on I'm gonna be on the lookout for a pregnant female to photograph. At least there's no shortage of potential subjects eh?

Bruce

[Bruce Williams]

Arp - Came across these unusual pics of O. asellus and thought you might be interested in taking a look. Common woodlouse - Oniscus asellus: More Still Images - ARKive

Bruce

[Pudding4brains]

Hi Bruce,

Thanks for the link - they're certainly good pictures, but I don't quite see what's "unusual" - am I missing something?

Or it must be this: "It is ARKive's long-term aim to compile audio-visual records, where such media exists, for the 16,000-plus animals, plants and fungi currently threatened with extinction" - combined with the fact that they've only got images of A. vulgare, O. asellus and P. muscorum which are just about the commonest Woodlice around; hardly threatened with extinction those, or at least no more so than, say ... Homo sapiens ??

[Pudding4brains]

Hi again,

Originally Posted by Bruce Williams

From now on I'm gonna be on the lookout for a pregnant female to photograph.

Should be able to find plenty from late spring onward, but might even be able to find some now - I've just found a (very) pregnant Trichoniscus pusillus last week - expecting the little (minute! - see below) ones any day now

Before mom gets pregnant you should be able to find scenes like this:


I've also just uploaded a higher res version of a pregnant mom to WATW so you can somewhat recognize the little, already hatched mancas sitting in the brood-pouch :


Not sure if I'd already linked this one somewhere on WAB, but these would be the next stages:


Cheers!
Arp

P.S.: To give you an idea of the daunting task of photographing freshly born Trichoniscus:

The little 3,5mm red one is a "large" adult Trichoniscus (probably T.pusillus). The center one is a medium sized adult Oniscus asellus (about 13mm), top right is a juvenile (something like 4-6 months probably?). The white one on the bottom is an adult Haplophthalmus danicus - about the size of newly born Oniscus asellus. Now imagine the size of a newly born Trichoniscus

[Pudding4brains]

Okay, sorry CNR ... I know - it's way off-topic ... but there she is:

[Bruce Williams]

Thanks Arp, I took time to REALLY examine your pics and enjoyed every one. I must make more use of WATW,

...as to why I found the pics on my recent link interesting:

I had just read about the woodlouse's unusual two stage moult (I was researching a front-end exuvia pic of mine). Apparently they moult every couple of months - first the back half and then a couple of days later the front half.

The photo at bottom left (Common woodlouse moulting 1) shows a woodlouse just about to complete the moult of it's front-end and you can see a clear difference in colour between the 2 day old back-end and the emerging new front-end. I found this interesting. Ditto the last pic Common woodlouse moulting 2.

Here's my exuvia pic (I'm fairly sure it's from Porcellio scaber):


Bruce

[Pudding4brains]

Hi Buce,

Originally Posted by Bruce Williams

Here's my exuvia pic (I'm fairly sure it's from Porcellio scaber):

Yes, I'm pretty sure you're okay with P. scaber there

As for the images on ARKive:
This one is indeed just tossing off the front end, but with this one I'm not at all sure - that looks much more like one that still has it's loosly fitted front end "on" (about to shed it over the next days or so) and is happily munching away at the shedded skin of a colleague. You might imagine that the need to stock up on calcium while shedding to rebuild/harden the new shields and eating dead mates or shedded skins is an excellent source

I'll see if I have some pix of shedding woodlice that are up to WATW quality standards later.

[Bruce Williams]

Arp - Can see exactly what you're getting at with QUOTE: looks much more like one that still has it's loosely fitted front end "on" (about to shed it over the next days or so) and is happily munching away at the shedded skin of a colleague.

The dull, translucent(ish) look to the front end looks much more like it's just about to be shed rather than "brand new" exoskeleton. So in some ways even more interesting (to me) from an instructional point of view.

Thanks for confirmation on ID.

Bruce