Large Jellyfish at Rhossili

 

Yesterday (27th July 2014) I walked along Rhossili beach from one end to the other and back again – a distance of about 10 kilometres. I followed the high tide strand line most of the way and saw 16 large Barrel Jellyfish, also known as Dustbin-lid and Root-mouthed Jellyfish (Rhizostoma octopus Linnaeus) – but there could have been more. They were various sizes and states of maturity. I put a seashell beside each one I photographed to give an idea of scale. They were different shades of pink and blue colour. Their condition varied, too. Some were freshly dead and well preserved but others had been split or torn, and some were beginning to decompose by “melting” into the sand. They were lying at different angles. Some were dome upwards and others were upside down. All are harmless – no danger from stings to holiday makers. They are a relatively common sight on beaches of the Gower Peninsula in South Wales. However, they have been appearing in very large numbers along the Coast of Devon and Cornwall this summer, which is an unusual occurrence, and there has been a lot of coverage of the phenomenon in the media. There are more posts about Barrel or Dustbin-lid Jellyfish elsewhere in Jessica’s Nature Blog from sightings in previous years on Gower.

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Lyme 8

 

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Lyme 7

 

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Seafood – Mosaic in an Underpass

Mosaic of old-fashioned fishmongers shop

This delightful mosaic of a seafood display in an old-fashioned fishmonger’s shop is one of many public art mosaics decorating pedestrian underpasses in Newport, South Wales.

Detail of crabs in a mosaic picture of a fishmonger shop

Detail of fish depicted in a mosaic

Close-up detail of lobsters in a mosaicCOPYRIGHT JESSICA WINDER 2014  All Rights Reserved

At Dogs Bay

Dogs Bay in Connemara has a wonderful white sandy beach composed of the tiny shells of microscopic one-celled creatures that live mostly on the mud of the ocean bed. These animals are called Foraminifera. When they die, millions upon millions of their calcium skeletons, bearing many chambers and holes, and not visible to the naked eye, wash ashore to form this unusual sand. This is such a rare occurrence that Dogs Bay beach is the only one composed of foraminifera in the northern hemisphere.

The bedrock of the land around this wonderful white sandy shore is made up of volcanic rocks including granite that has many different colour forms and patterns due to the different mineral crystals that it contains – if you get up really close to see it. The granite outcrops on the shores often have a rounded surface where ice sheets or glaciers passing over them have ground them smooth. The waterside rocks form attachments for a variety of seaweeds, along with many seashore creatures, particularly gastropod molluscs like periwinkles and limpets, whose brightly-coloured empty shells accumulate at the base of boulders low down in the intertidal zone.

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Moon Jellyfish Art

Swimming Moon Jellyfish

Slowly pulsating bells of Moon Jellyfish swimming near the surface of shallow water over seabeds of swaying seaweed.

Swimming Moon Jellyfish

Swimming Moon Jellyfish

Swimming Moon Jellyfish

Swimming Moon Jellyfish

These images were previously displayed on my other site Photographic Salmagundi; and on Jessica’s Nature Blog there is also a  short video of one of the slowly swimming Moon Jellyfish that were the subject of this artwork.

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Tube-worm Holes in Ringstead Chalk Boulders

Close-up of tube-worm holes in a chalk boulder

Pebbles and beach stones riddled with small holes are a common beachcomber’s find. These small burrows and borings in the stone are frequently made by marine worms. The worms themselves, and the mud and sand tubes in which they live within the burrows, are usually absent. However, on the water’s edge in many coastal locations, if you know where to look, it is possible to spot the burrows still occupied by the worms; this is usually in large and mainly immovable boulders, or in the bedrock of the beach platform, or the base of a cliff face. The worm itself is almost impossible to see because at low tide, when the rock is exposed to the air, it retreats into the tube and burrow. Though sometimes, apparently, its two palps or feelers can be seen protruding from the hole and waving around vigorously. I haven’t observed that myself so far.

Without microscopically examining the actual worms, it isn’t possible to say with a 100 per cent certainty what these worms are. Nevertheless, there are enough characters available to say that these are most likely to be marine polychaetes of the Spionidae, and probably one of the Polydora group, maybe Polydora ciliata (Johnston).

All the Polydora species make a U-shaped tube from small particles of mud, or whitish calcareous matter if they have been burrowing into calcareous algae, shell, or limey stone; all this is stuck together with secreted mucus. The tube is normally embedded in the burrow that it has excavated. There are two holes in the mud tube, one at the front and one at the back end – but they lie side by side because the tube and burrow are U-shaped. In the examples photographed here, many worm tubes are packed together, and there are instances where the chalk burrows have joined together and broadened out into deeper, less well-defined, depressions.

The method by which the worms create the burrows is thought to be an almost incidental process. The worms initially settle and manufacture their mud tubes in the shelter of slight cracks and crevices in rock or shell surfaces, or between sessile barnacles, or amongst soft algae in rock depressions, and other such places on the seashore where it always remains damp at low tide. The metabolism of the living worm leads to the production of slightly acidic waste. Over time, the seepage of these waste products gradually eats into and dissolves the rock or shell on which the worm tube lies, enabling the worm to retreat further and further into the safety of the substrate. The burrow formed like this reflects the shape of the U-shaped mud tube.

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A Masked Crab at Studland

A Masked Crab waiting for the tide to come in

I saw a little Masked Crab (Corystes cassivelaunus Pennant) on Knoll Beach at Studland the other day. It was an unusual sighting for that location. The crab was alive – but lucky to be so. It had buried itself in the wet sand to survive the rigours of exposure at low tide. There are not many other places for an animal to hide on this part of the beach.

The small crab, only a couple of inches long, would probably have stayed out of view until the tide came in again – except that this was the afternoon that several schools decided that it was just the right moment for the students to run on the beach while the sun was shining. The youngsters pounded their way along the shore and one of them stepped on the very spot where the crab was sheltering. Being disturbed by this close encounter, it surfaced, all covered in wet sand, as I walked past it and eastwards in the direction of Shell Bay.

I was surprised to see this same little seashore creature again as I made my way back along the water’s edge going westwards. I know it was the same crab because it was almost the only live thing I found, and certainly the most interesting. It was one of those days when there was not much at all newly washed ashore: a few fresh clumps of spindly red seaweed, some brown Sea Oak and strands of kelp, a few pieces of translucent green Sea Lettuce, and some clusters of Slipper Limpets. Lots of empty bivalve shells.

On this second meeting with the Masked Crab, the creature was more active and had got rid of the sand which had been covering it before. It was waiting for the waves. I have seen this activity previously in Masked Crabs on Rhossili Beach on the Gower Peninsula. The animal sits facing the sea, using its legs to brace itself against the oncoming water. Its two fringed antennae can be joined together to form a single tube and this was projecting forwards and upwards – looking very much like an angler holding a fishing rod. It was fascinating to watch the way to crab parted and then joined the antennae, moving them side to side as if using them to gauge the speed and timing of the next wave. The antennae form a breathing tube when the crab is buried.

I took a few photographs of the Masked Crab and some short video clips which you can see below. I hope that you will appreciate that it was a bit difficult to film the crab in action because of its small size and the necessity for recording it in such a low position – plus the imminent drenching of both the crab, the camera, and the photographer.

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Goose Barnacles at Ringstead Bay

I always like to find Goose Barnacles (Lepas anatifera) on flotsam at the beach. These strange creatures live attached to items that free-float around the oceans of the world; and we only see them when they wash ashore, as they did yesterday at Ringstead Bay in Dorset, England. Thousands of these strange marine creatures were clustered onto a tree trunk and its branches that lay freshly beached on the shingle. All the pebbles here seem to have returned now – it was only a week or so ago that they had all more or less disappeared following stormy weather.

Click here for more information about Stranded Goose Barnacles and Goose Barnacles on Rhossili Beach in Jessica’s Nature Blog.

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Handbook of the Marine Fauna of North-West Europe

Aside

This is an invaluable book that I regularly use.

 

The Handbook of the Marine Fauna of North-West Europe does what it says on the cover, and the Amazon reviews reflect its usefulness:

When Peter Hayward and John S. Ryland first published Marine Fauna of the British Isles and North-West Europe, it became an instant classic in the marine reference literature. Now with Handbook of the Marine Fauna of North-West Europe, the same editors offer a concise, practical guide to over 1,500 species from the major marine phyla-from sponges to fish-in a format that is ideal for field use. With its simple dichotomous keys, individual descriptions, profusion of illustrations, and extensive reference section, the book allows for rapid and easy identification of all but the rarest marine animals found on the sea shores and shallow sublittoral zones of the region. Students, researchers, and amateurs interested in zoology, marine biology, and ecology will all want to own a copy of this unique field guide.

“The essential guide for any aspiring marine biologist”, 16 Dec 2011
By Magnus Johnson (UK):

This is a core text that we use at the Centre for Environmental and Marine Sciences for our undergraduate courses in Marine Biology and Ecology. It is “the book” to use as a starting point and it is generally enough until you get to postgraduate level or need to specialise in a particular group of animals (it doesn’t cover algae obviously). For each group there is an introductory section that gives you a guided tour of body parts. This is usually followed by a key to families which is generally easy to follow once you have the taxa specific nomenclature in your head. Handy references to diagrams direct you examples of each family. Once you have identified your specimen down to family there is a key to species. For most taxa each species has a succinct description with details of their distribution and colouration that allows you to confirm your identification.