Mutant cushion star with seven arms

Fifteen Minute Rockpool Challenge (and some mutants)

I’m not sure who cancelled spring, but I’m not impressed. Yet again, the spring tides are accompanied by ear-numbing winds and a flurry of snow. Just the thought of plunging my hands into the pools makes my fingers ache, and yet, like the fool I am, I wade into the pools to see what’s there.

Due to my reluctance to leave my warm house, it’s half-past low tide by the time I hit the beach. The easterly winds are dashing the waves against the rocks and the gully I’d hoped to explore is well and truly submerged. All that’s left is an average-looking pool.

My average-looking pool for the 15 minute challenge
My average-looking pool for the 15 minute challenge

I’m tempted to give up and go home, but I’m always telling people that there’s something in every pool. That you just need to go slowly and look closely. I set myself a 15 minute challenge to find as many species as I can.

One of my first discoveries is this wonderful mutant cushion star. According to the books, these have five arms. Clearly this one hasn’t read the books. At some point it has lost one or more of its arms and in an incredible feat of regeneration it has sprouted an excess of new ones.

A Cushion star trying to pass as a seven-arm starfish.
A Cushion star trying to pass as a Seven-arm starfish.

In fact, this cushion star has put so much energy into sprouting arms that it now has a total of seven arms. I do sometimes see another species, the Seven-armed starfish, but they are bright orange and have longer arms so I’m not fooled. It’s a nice try though.

There are lots of molluscs including several colourful painted topshells.

Painted topshell
Painted topshell

Nearby, a colony of dog whelks huddles in a crack in the rock, around their yellow egg capsules.

A colony of dog whelks with their yellow egg capsules
A colony of dog whelks with their yellow egg capsules

It’s hard to see through the wind-rippled water into the tangled seaweed below, but this Calvadosia campanulata stalked jellyfish catches my eye. Its bright-white stinging cells stand out among the pink and red seaweed fronds.

Calvadosia cruxmelitensis stalked jellyfish
Calvadosia cruxmelitensis stalked jellyfish

There are several more stalked jellies, including this Haliclystus octoradiatus. This species has a blob between each pair of arms, which acts as a sucker (‘primary tentacle’)  allowing the jelly to flip upside down and cartwheel along the seaweed. This one seems to have two suckers between some of its arms. It also has an extra arm (nine arms instead of 8).

I start to wonder if this pool is going to be full of mutants with extra arms and tentacles.

Another mutant - a nine-armed Haliclystus octoradiatus stalked jellyfish with some extra primary tentacles.
Another mutant – a nine-armed Haliclystus octoradiatus stalked jellyfish with some extra primary tentacles.

The waves are breaking over the rocks and splashing over my back and the water level is rising precariously close to the top of my wellies. I take a few more quick photos of some wriggling worms, strawberry anemones and a banded chink shell just a few millimetres long.

Banded chink shell
Banded chink shell (Lacuna vincta)

As I leave the pool, I find a Saddle oyster shell. These small oysters attach to the underside of rocks and have round hole in the upper valve.

Inside of a saddle oyster shell showing its incredible mother-of-pearl colours
Inside of a saddle oyster shell showing its incredible mother-of-pearl colours

It may be a grey day, but the inside of the shell is coated in the most brilliant mother-of-pearl, shining with every colour of the rainbow. I’ll take it as a sign that spring’s on its way.

 

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