Tag Archives: seashells

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.

 

A Shell Collecting Bonanza on Looe Beach

After a week of ear-numbing northerlies, the low January sunshine is at last winning through. Junior sets to work with his bucket and spade, attempting to create a sand fort that can be seen from space while I take a stroll at the water’s edge.

Looe Beach - a herring gull is also checking out the pile of shells at the water's edge
Looe Beach – a herring gull is also checking out the pile of shells at the water’s edge

The stretch of sand that forms Looe beach is ideal for summer holidaymakers to lounge on, but generally offers little to the rockpooler, unlike the surrounding shores. Today is different; probably due to a combination of large tides and strong winds from an unusual direction.

Glistening mounds of shells are heaped the length of the shore, and are being nudged onwards by the incoming tide. They crack under my feet despite my efforts not to trample them. 

Shells on Looe beach
Shells on Looe beach

It’s not unusual to see the odd limpet or a few mussel shells here – the harbour is carpeted with them – but this haul of shells is not just large, it’s more diverse than usual. There’s such a kaleidoscope of blues, whites, oranges and pinks that I have to get in close to focus on individual shells. Continue reading A Shell Collecting Bonanza on Looe Beach

Colourful and Endearing – Video: Meet the Flat Periwinkle

If you’ve ever collected shells on the shore, you’ve probably homed in on the bright yellow, orange, white and even chequerboard colours of the flat periwinkle. Their shells look like a miniature version of the garden snail, but smaller, tougher and much, much brighter.

Flat periwinkle in a Cornish rock pool
A flat periwinkle on the mid-shore seaweed

This time of year, when the seas are rough and the lower shore is hard to reach, I love to search among the seaweeds of the mid and upper shore. The flat periwinkles’ vivid colours shine out like jewels among the tangle of brown seaweeds.

On a damp day at my local beach, it doesn’t take me long to find dozens of them. They’re in no danger of drying out today so they’re busy grazing, tentacles waving from side to side, black eyes on the lookout for crabs and other predators.

An orange-banded flat periwinkle on the move - showing its eye and tentacles.
An orange-banded flat periwinkle on the move – showing its eye and tentacles.

Close-up they’re endearing little things, a herd of gentle grazers feeling their way through the swathes of seaweed. In this video you can see how they search out food with their tentacles. Watch them reaching out their proboscis mouth, pink radula pulsing as they rasp away at the seaweed.

In a patch of seaweed around five metres square, I find a huge variety of colours. These variations probably offer some protection from predators, as does the covering of microalgae on many flat periwinkles, which gives them a green colour.

Some flat periwinkles are white or cream coloured
Some flat periwinkles are white or cream coloured

Whatever the reasons for their varied colours, they make the flat periwinkle one of the most striking shells on the shore. (Note: If you collect shells, please always remember to check they’re empty before you take them home.)

Some flat periwinkles are black or brown. The variety probably provides protection from predators.
Some flat periwinkles are black or brown. The variety probably provides protection from predators.

It’s so easy to get close to these animals and watch them in action. Look out for them next time you’re at the beach.

 About flat periwinkles…

There are two species of flat periwinkle, Littorina obtusata and Littorina mariae. In theory L. mariae has a flatter profile and is the smaller of the two with a thicker shell, but on the shore they vary and mix so it is hard to distinguish between the two species.

Generally, you find Littorina obtusata on the mid-upper shore, especially on egg wrack and Littorina mariae on the lower shore, especially on serrated wrack. The main difference is that L. obtusata tucks into the seaweeds it lives on, whereas L. mariae likes to graze on organisms that live on the its preferred seaweeds. Each one prefers to live on the seaweeds mainly found on its own zone of the shore.

The animals in these pictures are almost certainly Littorina obtusata given their location and diet. However, as far as I know the only way to be certain is to examine the animal’s penis – not something I intend to do. The Field Studies Council have a great paper on the habits and identification of the two flat periwinkle species (including penis shapes) here: http://fsj.field-studies-council.org/media/342551/vol7.3_202.pdf. Take a look if you’d like to know more.

A tiny yellow flat periwinkle grazing among the Cornish rock pools.
A tiny yellow flat periwinkle grazing among the Cornish rock pools.