News Paper
News Paper
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Shore Crab 'mugged'
by passing blennys
THREE blennys were responsible for 'mugging'
a Shore Crab and robbing it of its' earnings.

FIGHTING broke out, which continued for several minutes as the crab tried in vein to protect the hours of hard work it had invested in opening a mussel shell.

Before the Blennys were on the scene, the Shore Crab had spent two hours continuous labour, using its claws to scissor and pry the mussel open and had succeeded to where it could just reach inside the shell and grab the meat to begin claiming its reward.

It was however at this point, a passing Blenny became aware there maybe an opportunity of getting a convenient meal for itself and so 'set about' the crab to try its luck.

Although its efforts were unsuccessful alone, when other Blennys arrived, their combined efforts had effect:

In energy terms, the Blennys all profited by robbing the food. The crab lost a sizable amount of its payback, considering

the measure of energy it had spent on getting at the food in the first place and the mussel....
Well the mussel was the energy source itself in this case and so just lost.

If the Blennys hadn't turned up, perhaps the headline could have been:
"mussel mugged by passing Shore Crab".
But so it goes on, everyday, the basic struggle to survive and remain living each day.

'Safe Cracking' accomplished by breaking
the hinges.
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THE Shore Crab breaks through the protective shell of the mussel to get to the meat inside by attacking and breaking the hinge.

One end of the mussels' bivalve shell is hinged,

allowing the other end to open in order to filter feed and close in order to protect itself from unfavourable external conditions and also preditors.
The crabs claws are not powerful enough to crack the actual shell, so the time consuming work of 'scissoring' and prying at the hinge until it breaks, allows the crab to then reach in and grab the meat to eat. The crab in the picture took two hours to complete the break.
This two hour work is an investment of energy that must be regained in nutritional values, or else the crab will not grow properly and reproduce.

OK.. reproduction

Well OK it's..
...Longitudinal Fission!

The Snakelock Anemone (Anemonia viridis) has a method of reproducing itself, by tearing itself into two, a process known as Longitudinal Fission.

The case observed here occured in a small classroom aquarium and took twelve hours to complete.

The anemone was first noticed just to be acting in a perculiar manner from its usual static nature.  The body was becoming more stretched on the rock it was settled on and the tenticles moved in frenzied activity, followed by periods of apparent rest (much work may have been going on, on a cellular level).

A video camera was set up to record 'something' unusual, but it was not known what, or how long it would take.  After three hours, another video tape was sent for. Nothing had happened, besides the movement explained earlier. After 6 hours, another tape was sent for and phone calls made to friends to explain why we were 'missing' from usual life. The anemone was clearly stretching itself out on the rock now and it was clear something was going on, so the film kept rolling while supplies of coffee and bics were being shipped in.

Nine hours, more coffee, bics, phonecalls home and patience were administered as and when needed.  The anemone had let go of one side where it had stretched and 'pinged' itself over the edge of the rock... time to move the camera.
Once it got itself back on the side of the rock, noticeable transformations could be seen. The body was torn vertically up the column base and the anemone kept repeating a movement of relax and heave as it stretched and pulled itself in opposite directions.

The animation clip shown is of the final hour, where separation into two indivual animals finally occured.

fascinating... but who is the oldest? Does it mean they can't die of old age, if they did, then all would die at around same time no matter how many times they successfully divided.

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Crawled out the sea
to live on land
Common Blenny (Lipophrys pholis)
Choosing to be out of water

OFTEN said when talking about wildlife of long ago... "the xyz left the oceans to live on land", but there must have been a period during that time that the wildlife needed in order to adapt to the changes.

So are we in one of those periods here today, regarding the Common Blennys' habit of sometimes remaining on the tidal shore, in air, when the tide receeds?

Perhaps it is just a survival method. .....Safer out the water than to have to swim down at

the low tide waters, with the deeper residents?
Answers by email, if you have a thought or indeed a definitive answer.