Limpets on rusty iron

I like the appearance of rust and I’m always looking out for interesting colours, patterns, and textures in oxidising iron. A good place to look is the metalwork on seaside groynes and piers which are invariably corroded by seawater. I find it amazing that small seaside creatures like limpets settle in these seemingly inhospitable locations where they eek out a living by grazing the microscopic algae that coat the surfaces. In their turn, as the limpets cling on to these man-made objects, the shells become stained by the orange of the rust and the green of the algae so that they blend into the overall constantly evolving design.

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Baby barnacles on Rhossili rocks

It’s not just the birds, bees, and educated fleas that do it, the barnacles do it too ….. breed in springtime, that is! The results were there for everyone to see, with millions of miniscule baby barnacles smothering the rocks at Rhossili in Gower in early April.

Each newly settled barnacle measured just a millimetre or so. [It was at the limit of the camera's capability to focus - so apologies if the images are not as sharp as they could be]. The baby barnacles develop from free-swimming cyprid larvae that are only 500 – 800  µ m long. The cypris is the final stage in the larval development of the acorn barnacle – following six consecutive stages as a nauplius larva.

The cypris looks a bit like a tiny clam or an ostracod with two large shells or valves hinged on the dorsal surface and open on the ventral one. Six pairs of fringed appendages used in swimming hang down from between the valves. The cypris has sense organs to detect suitable surfaces on which to settle. It also has small antennules at the head end which it uses to crawl over the chosen substrate before performing a head-stand and cementing itself into position on its back. Newly settled barnacles are referred to as spat.

The shell of the settled acorn (or sessile) barnacle has six over-lapping calcareous side panels making an approximately cone-shaped wall. The animal lives within this ‘box’. Four more hinged plates create a lid to the box that can be opened and closed. Once the new adult-like shell form is developed, the fringed swimming appendages or natatory cirri of the larva can then be protruded through the hinged lid plates to seive food particles from seawater.

[You can see more detail in the photographs if you click on the images once, or twice. If you look carefully, you should be able to recognise a few cyprid larvae with their smooth, glossy translucent shells, in the process of settling amongst the recently metamorphosed miniature adult forms].

The young barnacles settled on every patch of smooth, bare rock where it was available at the base of Rhossili cliff – but also on top of other living adult barnacles, on the old white calcareous bases left by detatched large Perforatus perforatus barnacles, on limpets, and on mussels.  Only the dog whelks with their variously coloured shells seemed mostly free from spat fall as they feasted on the mussels and barnacles.

 

Revision of a post previously published 18 May 2010

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Seven small rockpools at Winspit

 

Small rock pools are scattered across the rock ledge at Winspit. Some are shallow and others are deep. Some are on the general surface and others are embedded in rock clefts. Most are rounded in outline but a few are differently shaped.  Some of the pools shown here seem almost like the shape of an eye or a mouth.

The colours and patterns made by the various seashore creatures and seaweeds found in and around the rockpools make attractive natural arrangements and designs. The pools and their inhabitants are very decorative features on the seashore even if you do not know what everything is called. 

These are really remarkable rockpools and unlike any that I have seen before. The general surface of the rock in this location is covered with an almost continuous coating of encrusting calcareous algae. This is Lithamnion, usually pink or purplish, but in many areas here it is bleached-out and white. Patches of smooth black encrusting lichen, and microscopic green algae, are interspersed with the Lithamnion to form an irregular  background patchwork of colour.

The purple-tipped, grey-green tentacles of Snakelocks Anemones clustered en masse in some pools. Tufts of filamentous red seaweeds were dotted all over the place and seemed to have a penchant for settling like plumed feathers on the conical shells of living limpets. The arcticulated, calcareous, pink and white branches of Coral Weed created tufts in pools and extensive carpets on the flat rock surfaces.

Yellow Rough Periwinkles grazed the red seaweeds. The unusual green Velvet Horn seaweed was growing in some pools. A few pools had nothing but pebbles swirling round and around at the bottom – preventing any organisms from settling. The red Beadlet Anemones were such a dark colour they looked almost black. Altogether this small area of shoreline with its numerous rockpools is a most unusual-looking place.

Another set of odd-shaped rockpools is described in Cart tracks and square rockpools at Winspit ………and for more details about the weeds and invertebrate seashore creatures mentioned above, you can use the SEARCH BOX on the top right-hand side of the blog’s home page, or the INDEX OF CATEGORIES, to locateother postings on the subjects.

 

 

 

 

 

Revision of a post first published 8 December 2009

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Tiny Tidepool 1

Tiny Tidepool 1

►

 

This short video clip shows two small limpets (Patella sp.), with shells colourfully adorned by a coating of microscopic green algae, and patches of pale purple encrusting calcareous seaweed (Lithamnion sp.). The underwater pair are jostling against each other in a tiny tidepool at Fall Bay, Gower, UK.

If you look closely, you can see short fine translucent tentacles which are the pallial gills protruding from the body all around the margin of the shells. These gills on the mantle skirt are usually hidden from view when limpets cling to exposed rocks at low tide. The manoeuvering of the limpets may be a preparatory behaviour for mating. Patella limpets have separate sexes but all hatch out as males and later may develop into female individuals. This is known as protandric hemaphroditism. Click here for more information about common limpets on the Marine Life Information Network. 

The Carboniferous Limestone rock outcrops on the beach have been eroded by the sea and weathered into thousands of scooped-out hollows that retain sea-water when the tide goes out. These pools are home to many seashore creatures and seaweeds. Most are entirely lined, as in this example, with a coating are the lilac/purple/grey Lithamnion calcareous seaweed. Small niches are occupied by other miniscule limpets, an edible blue-shelled common mussel (Mytilus edulis Linnaeus), and a dark red beadlet anemone -Actinia equina (Linnaeus). A single minute navy-blue arthropod Anurida maritima (Guerin) from the Neanuridae Family scuttles across the water on the surface film. 

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Rock pools on the Causeway

With the tide out, the extensive wave-cut platform that links the Rhossili headland to Worms Head is covered with rock pools full of seashore life – for some of which it is a permanent habitat, and for the remainder, a transient stranding.

In the bright sunlight of an early summer morning, a multi-coloured vista stretches far before the eye. The still water of the tide pools reflects the almost cloudless pale blue sky and contrasts with the rough grey rocks with their occasional patches of orange and pink. The seaweeds, like the purple coral weed and olive green kelps and fucoids, cover the low tide exposed surfaces and underwater, too. Limpets and winkles graze the algae-coated stone, joined in their shallow submarine world by shrimps, crabs, and fishes. The whole horizon a patchwork of biodiversity and colour.

The digital transformation of these photographs seeks to encapsulate the sense of space, brightness, colour, and wonder that I felt at the time.

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Seashore life on the rocks – Part 1

These photographs were all taken at low tide on the Carboniferous limestone rocks at Worms Head Causeway, Rhossili Bay, on the Gower Peninsula. A multitude of marine invertebrates can be found attached to the dry exposed rocks and in also underwater in the tide pools.

What I find particularly appealing is the way the many different natural colours and patterns of the rocks provide such an attractive background – almost as if the stage has been set for the pictures. The cracks and crevices that make up the varying surface textures of the rocks provide niches for colonisation by acorn barnacles and mussels – and are also modified by some creatures, like the limpets that slowly dissolve shallow circular craters during their lifetime of attachement.

 

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Barnacles on rusty iron

Barnacles (and a few limpets) growing on the multi-coloured and highly textured surface of rusty ironwork on a British seaside pier. I like the wide range of rust colours from dark blue to light orange and how they are distributed over the surface in a random way resembling a piece of bright abtract art; and the way that the acorn barnacles have become stained and incorporated into the natural design.

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“Velvet Horn” seaweed on Jurassic Coast

 

There are two types of Velvet Horn seaweed in Britain and one of them is now considered rare. I suspect that the specimens in the photographs are the less common of the two species, Codium tomentosum Stackhouse, but I can’t be sure without a microscopic examination – and I hesitated to pick a sample when there were only a few specimens.*

The quality of the pictures is not crystal clear but I risked life and limb to get the pictures of these relatively small algae growing low on the shore, in and around deep, circular rock pools. I only spotted the rather strange looking weed just as the location was being engulfed by the incoming tide – so the water was frequently in motion, the finer sediments suspended, and small bubbles were trapped everywhere. I got bruised knees and arms, as well as soaking wet trousers, as I tried to manoeuvre into suitable positions to take the shots.

* N.B. Since I first wrote this post, I have been back to the site and obtained a small piece of the seaweed. I have now examined it microscopically and can confirm that the specimen from which I took the sample is not C. tomentosum (the rare species) but C. fragile. In technical terms, the filament-bearing utricles  are mucronate (with a small sharp point at the end) and not rounded. I found many more Velvet Horns exhibiting a range of variation on my second visit and I cannot rule out that the rarer species may have been present as well but not sampled.

 

The dark green branched fronds seemed at first to glow in the seawater. On a second glance, the seaweed seemed to have been dipped in a gelatinous substance so that the light shone through the translucent outer layer, giving rise to the glowing halo effect. It was not until I enlarged the photographic image that I could see that the entire seaweed was actually covered in microscopically fine hairs radiating out at right angles to the axis of the stems or fronds. 

 

The generic Latin name Codium is derived from the Greek word kodion which means ‘the skin of an animal’ – on account of this seaweed’s hairy covering; and the common name of Velvet Horn refers to the similarity in shape and apparent texture to a deer’s antlers when first grown and covered in velvet-like skin.

The thallus or body of the Velvet Horn is between 22 – 37 cm long when growing in pools, dark green, spongy and simply (dichotomously) branched. There is no mid-rib and in cross-section it is cylindrical with slight flattening where the branches form (the axils). Inside, the ‘stems’ are made up from vertically entwined filaments that give rise to horizontal branchlets that form a continuous layer over the whole seaweed; the fine hairs grow on this layer. 

In the photograph below, you can see a small specimen of green Velvet Horn attached to the rock on the right side of a deep, almost circular rock pool within a water-filled gully. Almost the entire rock surface is covered with white, bleached, calcarous encrusting algae. The red fuzzy blobs against this pale background are large limpets covered in fine red seaweeds. The long, thin, grey threads around the edge of the pool are the tentacles of many Snakelocks Anemones. 

 

Revision of a post first published 19 September 2009

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Limpets

This is some basic information about LIMPETS  - one of the most common types of British marine molluscs and a frequent find on most rocky shores. 

Seashore creatures: Molluscs: Gastropods: Limpets

Limpets Patella spp.

1. The cone shaped shells of limpets are familiar to most people.
2. Although there is no coiled shell these molluscs are related to the Gastropods like winkles and whelks but are a more primitive form.
3. The word Gastropod literally means stomach-foot – because these animals move around more or less on their belly.
4. They eat by scraping the algal film (slime) from rock surfaces and they also munch directly on macro-algae (large seaweeds).
5. In the mouth is a tongue-like, rasp-like, structure called a radula covered in rows of teeth with which it scrapes and files away at its food.
6. We are accustomed to seeing limpets at low tide, stuck on rocks, and sedentary.
7. However, when the tide is in and they are covered with water, they move around to feed – but they always return to the same place on the rock from which they started out.
8. Over the years, the limpet shell wears away an impression in the rock at its home base – partly through mechanical abrasion of the shell against the rock and partly through the effects of chemicals in the waste products.
9. You can see some of these circular depressions, representing the places once occupied by living limpets, in the photograph below.
10. Where the limpet has roamed around feeding, you can often find the marks left in the algal film by the repetitious scraping, first to the right and then to the left. You can see some of these curious zig-zag markings in the post Patterns made by grazing limpets.

For MORE INFORMATION about the common species of limpet you can look at the Marine Life Information Network site run by the Marine Biological Association of the United Kingdom.

Click on:  Patella vulgata and Patella depressa.

BOOK REFERENCES to limpets include: 

1. Barrett, J. and Yonge C. M. (1958 but reprinted many times) Collins Pocket Guide to the Seashore, Collins, ISBN 0 0 219321 3, page 130.
2. Gibson, C. (2008) Pocket Nature Seashore, Dorling Kindersley, ISBN 978 1 4053 2862 3, page 120.
3. Graham, A. (1971) British Prosobranch and Other Operculate Gastropod Molluscs, Keys and notes for the identification of the species, Synopses of the British Fauna No. 2, The Linnaean Society of London, Academic Press, ISBN 0-12-294850-5, page 40.
4. Hayward, P. J.  and Ryland J. S. (1995) Handbook of the Marine Fauna of North-West Europe, , Oxford University Press, ISBN 0 19 854055 8 (Pbk), page 502.
5. Hayward, P., Nelson-Smith, A. and Shields, C. (1996) Sea shore of Britain and Europe, Collins Pocket Guide, , ISBN 0 00 21995, page 180.  

[This is a revision of a post first published 12 February 2009].

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Limpets at Kimmeridge Bay

 

I just love limpets. The ones immediately above and below are just empty shells on the strandline. But living limpets are such hardy seashore creatures, quietly grazing and munching away at the algae and effectively keeping the populations of seaweed under control. You hardly ever see them moving but you can often see where they’ve been. They have a home territory to which they belong and, if they survive long enough, they leave a circular impression in the rock. They also leave trails in the surface algal film where they have been roaming and scraping with their rough tongues.

 

I would like to tell you with authority the names of the different species that illustrate this post. But I can only say with certainty that they are all Patella species and judging by the height of the shell and the position of the apex of the cone, there is probably more than one sort. The trouble is that limpet shells are so very variable; and I do not like to knock them off the rocks to see their hidden fleshy parts.

The three most commonly occurring species are the Common Limpet (Patella vulgata Linnaeus), the China Limpet (Patella ulyssiponensis Gmelin that used to be called P. aspera Roding), and the Black Footed Limpet (Patella depressa Pennant).

So, shown below is a selection of  pictures of limpets at Kimmeridge Bay.

 

This one was big and shows unusually noticeable growth stages as well as having patches of  the blue-green coppery colour I often remark on.

 

This one seems all alone in its spendid orange-stained setting.

And this cluster in a crevice of the rock pavement look as if they have been daubed with paint – which they might have been if they were part of an experiment. Perhaps someone knows.

Although I have never seen limpets budge from their home base, a video clip has been put on You Tube (by someone whose nom de plume is BoringPiddock) showing speeded-up footage of Kimmeridge limpets wandering around at night - six hours compressed into just 5 seconds -essential viewing! 

For more information about Kimmeridge Bay see the Purbeck Marine Wildlife Reserve Web Site.

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