Spiny Lobster with black sac
Posted 05 November 2003 - 11:43 AM
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:
Posted 06 November 2003 - 09:27 AM
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 ...
Posted 06 November 2003 - 01:26 PM
Glad to hear I'm not the only one puzzled. Looking forward to any more you come up with.
Posted 07 November 2003 - 09:02 AM
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
I sent him the photos for confirmation, and will keep you posted
Posted 07 November 2003 - 09:12 AM
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 ?
Posted 07 November 2003 - 01:54 PM
Thanks for the effort. I hope we learn more.
Posted 09 November 2003 - 02:20 PM
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
Posted 09 November 2003 - 04:38 PM
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.
Posted 10 November 2003 - 10:54 AM
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
Posted 10 November 2003 - 03:32 PM
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
Posted 10 November 2003 - 08:03 PM
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...
Posted 11 November 2003 - 01:45 PM
are you in Hawaii ? I tried to get photos of some Hawaiian alpheids, without much success