dejayM's picture

Painted top shell

Observed: 25th April 2013 By: dejayM
Biological Recording In ScotlandHighland Biological Recording GroupOrkney Biodiversity Records Centre
dejayM’s reputation in InvertebratesdejayM’s reputation in InvertebratesdejayM’s reputation in InvertebratesdejayM’s reputation in Invertebrates
on the baech
Stressmark
on the table
size
inside
P1030136
Description:

Conical and bright in the wet pebbles.
Interesting that they all seem to have stress marks.
................
Later addition of close-up. Whilst this LOOKS like an old healed fracture, every shell I posses has similar blemishes; see the diagonal one in Picture two.

Identifications
Species interactions

No interactions present.

Comments

gramandy's picture

an indicator...

...species for climate change.

markwilson's picture

topshells

Are they stress marks are are they seasonal?

dejayM's picture

disruptions..

Well Mark, I used the word Stress because they look like disruptions in the case. It may be that they are old and healed fractures.
This shows none
http://www.bioimages.org.uk/html/p7/p73287.php
This one shows a lot
http://www.flickr.com/photos/jen-the-wren/2547960786/
I have linked the above from the web.
But if you look at my North Sea ones, you will see disruptions in the obvious pattern.
Derek

markwilson's picture

topshells

Thanks

I think Monodonta shows an annual pattern so I was wondering if this was the same

Mark

dejayM's picture

cousin..

I wonder if you mean Monodonta lineata...
http://www.inaturalist.org/taxa/210222-Monodonta-lineata
the first time I have encountered iNaturalist - a kind of cousin!
Can YOU give me a link or an example the annual pattern on Monodonta?
Anyway, you may well be right but I am still thinking this is shell-stress and would like to know more.
I will put up another picture illustrating the disruption.
Thanks for your interest Mark.
Derek

gramandy's picture

what about....

...trawler/fishing damage?

dejayM's picture

fishing...

....yes Graham, it we accept they are fractures.
I think only scallop fishing might do this but it's worth remembering that they probably only feed in rocky areas -
"It is found on seaweed covered rocky shores, from extreme low water to a depth of 300 m.
It is frequently found under overhangs on the lower shore."
http://www.marlin.ac.uk/lzspeciesreview.php?speciesid=2849
Thanks
Derek

ChrisMcA's picture

They do look like fractures;

They do look like fractures; could it be bird attack or storm? Yours are only on 1 coil but http://www.ispot.org.uk/node/276704 shows damage across more than 1 coil.

nightfly's picture

Common Periwinkle often show

Common Periwinkle often show the same kind of damage/abnormality. I dont know what causes it.

Cathal.

dejayM's picture

stress marks

Yes Cathal. Look at my 'Greys' here too
http://www.ispot.org.uk/node/324592.
It would be quite an interesting study because my recent Painteds and those Greys came from the North Sea - quite damaged. Here in Scapa Flow, most shells seem near perfect.
Derek

bobthebirder's picture

fractures

For my final year degree project at Bangor I studied how shore crabs feed on dogwhelks. They get into the smaller shells by inserting one jaw of their strongest pincer as far as possible into the opening and breaking the entire shell in half by applying enormous pressure. If only larger shells were available they would break pieces away from the opening bit by bit, giving up if they did not get any food after a few tries. These topshells could show the results of failed attacks by shore crabs, followed by a period of regrowth.

Bob Ford

dejayM's picture

crabstresses

Yes Bob, rather rudely I had not acknowledged your suggestion before, sorry. It is very plausable but I am going to get more pictures this year. Thanks.
dj

JoC's picture

crab predation

I have only just noticed this from Bob and it seems a very plausible suggestion. I'll agree with it! Jo

Jo