nightfly's picture

Prawn shed skin.

Observed: 26th August 2012 By: nightflynightfly’s reputation in Invertebratesnightfly’s reputation in Invertebratesnightfly’s reputation in Invertebratesnightfly’s reputation in Invertebratesnightfly’s reputation in Invertebrates
Prawn shed skin.
Prawn shed skin.
Prawn shed skin.
Prawn shed skin.
Description:
Identifications
Species interactions

No interactions present.

Comments

ChrisMcA's picture

two examples?

The 1st seemed a sure palaemon,but instead of claws seems to have a pair of cricket bats!. (couldnt match it in Collins).The 2nd looks a good deal like Euailus Gaimardii (Collins,to 10cm) ie a Humpback prawn (Hyppolytidae),& unlike most Humpbacks in Collins has a large rostrum.
Did you save them?

nightfly's picture

Sorry Chris I didnt keep this

Sorry Chris I didnt keep this thing.

Cathal.

nightfly's picture

Hi Chris,Its the same

Hi Chris,

Its the same object in both pics, it looks quite different in the 2nd pic as it collapsed a bit as I held it out of the water, hence the hunched appearance. It was so very fragile.

I noticed those paddle like structures, for a minute I thought it was the flattened head of a shrimp after all but I think they are just more conspicuous than usual as a result of this being a shed skin. They are kind of floating free here whereas they would be more tucked in and held tightly together on the live animal.

The pools this was found in are populated with a very common rockpool prawn, they were all over the place yesterday but this particular pool had a lot of shed skins in it. I didnt snap a prawn yesterday as I have done so so many times in the past but I might have an image of one to put in as a crop in one of the pics of other organisms I took yesterday......

Cathal.

nightfly's picture

Just had a look through

Just had a look through yesterdays pics, one prawn is there in the bucket but too out of focus to be worth posting. I will dig out another prawn pic from before and stick it up for you to have a look at. The same kind of rockpool prawn which I believe is the same species as the one above.

http://www.ispot.org.uk/node/290313

Cathal.

Nick Upton's picture

Exuvium

I think the "cricket bats" may be two sides of the thorax split apart and swung forward during the moult. Lobsters, shrimps and prawn thoraxes often split along the midline during the moult eg http://www.lobstermanspage.net/lobstrs/molt.html They look like Palaemon sp. to me, but species ID needs REALLY clear views of the rostrum to check the curve of it and how many/where the spines are. P. serratus is maybe the most likely, but can't be sure.

Nick Upton, naturalist and photographer.

nightfly's picture

Ive looked at some intact

Ive looked at some intact prawns since this post and the cricket bats arent in any way abnormal, they are there at the front of the head but its how they sit is the issue. In my pic above they are splayed out and they are being viewed from below whereas the rest of the skin is almost being looked at in profile. Wish I knew what they were called, possibly mandibles? Many prawns had moulted in that particular pool that day, just the ordinary rockpool prawn that I am familiar with with the fine reddish lines. They could well be P serratus but for all I know at this stage I am viewing several species and dont know it.

Cathal.

nightfly's picture

Pic of live Paelemon added

Pic of live Palaemon added with the paddle like structures indicated as they appear from above on the live animal. Hope this explains these structures which I dont know the correct name of.

Cathal.

ChrisMcA's picture

Apologies Cathal, I couldn't

Apologies Cathal, I couldn't credit the 2 photos being the same thing. But this is odd:obviously your 3rd shot shows these paddles (it's the 1 you posted before & I was going to ID it as P.elegans), as do several other Ispots. But my collins '96 guide doesn't show any such 'paddles' in any Palaemon. None of MarLIN's 6 P.serratus has them (well possibly 1); in P. elegans the 1st is without; 2nd has them it seems.None of Habitas's 3 palaemons (2 are P.elegans) has them,& there's a Dutch site diverosa.com (in google images, P.serratus) with 8 of P.e+P.s all without them. I tried prawn anatomy & 1 showed "Antennal scale" & googling that gave 2 images 1 very like.

nightfly's picture

Hi Chris,I think that flat

Hi Chris,
I think that flat structure is visible in all but 2 of Marlins images of P.serratus. I think its present in them all but in the 2 birds eye view shots the prawn is looking straight up at the camera and the structure isnt obvious as a result of the angle of view. Its a similar case with profile shots, the thinness of the structure is hard to see from the side.

Still havent a clue what its name is though?

Marlin describe the antenna as consisting of 2 parts in their page on P. serratus:

"Below the antennule is the antenna, which is divided into two parts; the short flat segment (scaphocerite) and the long whip-like flagellum."

I wondered if the short flat scaphocerite might be it but I'm not convinced that is refering to the thing we are talking about.

Cathal.

nightfly's picture

This is odd Chris, I must

This is odd Chris, I must look at some other images myself to see the with and without examples for comparison. Yeah the 2nd pic of the shed skin is a bit confusing, as I said that was how it ended up when I took it from the water-the intention was to try to capture the serrated spike and I didnt try too hard to make it sit right as it would have disintegrated very easily. I just posted 2 shots of the same thing, one as found and another out of the water. I wonder would the size/presence of the paddles be related to age, sex or season etc?

Cathal.

ChrisMcA's picture

You're right on the name

You're right on the name Cathal (& so was I with the synonym 'antennal scale') The 'paddles' are scaphocerites; see http://www.chucksaddiction.com/shrimpanatomy.html

nightfly's picture

Now we know what to call the

Now we know what to call the paddles Chris, cheers for that. Ispot continues to be a great source of learning.

Cathal.

dejayM's picture

Late

Better late than never (isn't it?).
Excellent post, lovely pics, nice comment trail.
Add the Tag ProjectM1 please (it's never too late!)
ð

nightfly's picture

Hi Derek and Chris,I see I

Hi Derek and Chris,

I see I have 2 agreements above from you both on this exoskeleton being P. serratus. Thank you.

I have still not got fully to grips with separating Palaemons. I think I need to invest a bit of time in them. At this point I am not fully confident I was right to bring this to species, are there not other Palaemon species which can have an upturned rostrum?

Sorry for the doubt but its all for accuracy and clarity in the long run, can you give me more confidence that this is identifiable as P. serratus from the images available?

Has either of you seen many prawns in rockpools that are Palaemons other than serratus? To date all the rockpool prawns I have looked at appear to be the one species and I think they are serratus, I can find no other one, so far!

Cheers,

Cathal.