Spiny Lobster with black sac

I tried to get an answer to this on another board but none could help. I'm sure it's a simple answer but it's driving me crazy so please help if you can.

I shot this pic in the middle of the off season here so I am assuming this is some kind of reproduction action.

I would have got a better angle but she was in a small hole. Her legs were working the eggs frantically. Not sure what the legs were doing but moving. I'm guessing she was oxygenating them. Maybe she was laying them?

I'm including 2 pix. One showing the whole scene and a close-up of the mysterious black sac.

Sorry about the pic quality but it was the best I could get under the circumstances:

hmmm ... never seen such a thing before

it could a parasitic organism, at first glance it looks like the so-called "externa" (external sac) of a rhizocephalan cirripedian (highly modified parasitic barnacles) but what is the strange black mass inside ??? I am really puzzled, but will ask my colleagues

rhizocephalans have been reported in shrimps, hermits and crabs, and should occur in spiny lobsters

more later ...

Art

Thanks Art!

Glad to hear I'm not the only one puzzled. Looking forward to any more you come up with.

Hi again

it's probably not a parasite, a parasite would have yellowish or whitish eggs inside, not a black mass (unless it's something really bizarre)

one of my Australian colleagues replied to my message:

I think the black sac could be a necrotic 'tar spot' that has remained due

to ineffective removal during mating and fertilisation. We have photographs

of what sounds like a similar structure found on Panulirus cygnus. If you

send me a photograph I will compare it to ours and see if they are the same

lesion.

I sent him the photos for confirmation, and will keep you posted

cheers

Art

me again

here another hypothesis (from a colleague in UK) about the mysterious black sac:

I am a pathologist with an interest in crustaceans. If this is not a

parasite externa or another symbiont attached to the ventral abdomen, it

could be a growth of some type. Tumours are very rare in the crustaceans but

I would be keen to take a look. On the other hand, it could be a

Rhizocephalan externa that has somehow become necrotic and melanised via a

host response or other infection. Have you got the specimen fixed or is the

animal still alive?

I guess you haven't preserved the specimen ?

cheerio

Art :freak:

No, beside the fact that I quit killing these things years ago, it was peak NO lobster season and she was carrying eggs, They probably would have jailed me if I took her. :freak:

Thanks for the effort. I hope we learn more.

Hi

I got several other replies, one guy suggested (without having seen the photos) it could be a coccoon of a turbellarian worm or a leech, which is very unlikely

the consensus seems to be a "tar spot", especially since it's an ovigerous female

a tar spot is a necrotic spermatophoric sac; normally the spermatophore is removed by the female (I guess ?), but if something goes wrong, it remains attached, and the cells and sperm inside the sac perish and become melanized

cheers

Art

Thanks Art!

So let me see if my lay brain got it right. A male typically attches this sac of sperm on the female to fertilize the eggs but it is normally another color. If it doesn't get removed or something else goes wrong it dies and/or rots and turns black. That about it?

Well that's a lotmore than I knew before. I believe you have helped me. Mahalo for your time and effort.

Tuga

I got some more replies from my colleagues over the week-end

here are two:

1) Sorry for the delay in replying. I can't offer up much in the way of ID,

but I can tell you that it really does not look anything like a rhizo. In

fact, I have never seen a rhizo which hung so far away from the body

ventrally. They tend to place themselves in ways that minimize possible

detachment. Also, a black rhizo seems unlikely (they tend to be either tan

or very pale or a color that mimics the egg mass color of the host).

2) From the pictures it looks like the animal has some additional things hanging off the abdomen, possibly dead eggs or a necrotic exopod from a pleopod. My guess is that one of the pleopods has somehow been altered. I think Grant is on the right track. The dark mass of the spermatophore just doesn't look this way. Have you examined the animal and observed the other things hanging from the abdomen? You may be able to excise the object at the base and pickle it for histology. Since Panulirus are pretty good groomers, I'd be surprised if the item were a sponge or something attached to the host.

pleopods are abdominal swimming legs

the second is against the hypothesis of a tar spot

will see what the others say

cheers

Art

hi again

actually your photo created some confusion among my colleagues

here another "anti-tar spot hypothesis" reply:

I checked out those photos and I have never seen anything like that before!

It does not look like a usual tarspot (which is usually closely applied to

the sternum), but it could also be an old one that is necrotic and falling

off. Equally though it could be a necrotic rhizo. as suggested by others. It

is a tough call. If I was a betting man, I would put some money (just a

little) on the parasite hypothesis

ciao

Art

Well at least I feel better about not knowing what it was. I didn't mean to get the scientific community in an uproar though.

If I had known how unique it was, maybe I would have grabbed it. Who knows, I coulda had a black sac named after me.

This is fun...

Thanks Art

black sac .. hmmm .. not sure, but a snapping shrimp named after you - EASY !!!

are you in Hawaii ? I tried to get photos of some Hawaiian alpheids, without much success