A Very Green and Pleasant Walk

Last Saturday the Winterborne Walkers took to the hills.  Helen and Derek led us across soft green Dorset uplands flanking the valley in which the hamlet of Plush nestles.  Setting out from the Brace of Pheasants pub, our circular route  began with a climb up to a wheat field, through which a straight path led to the summit of Plush Hill.  We turned northeast to walk along the ridge of Cross Dykes on Higher Hill.  These were easy to pick out in the landscape later on, viewed from Ball Hill.  We descended via Sheeplands Copse to cross the road and ascend to Ball Hill.  Our way followed the Wessex Ridgeway, over the open high ground of Watcombe Hill until we started our descent, to the east of West Hill and returning to Plush.  We repaired to The Poachers Inn at Piddletrenthide for lunch.

At every point on our route we had spectacular views.  North we looked across Blackmore Vale, to unidentifed high points on the horizon.  Looking south we could pick out Hardy’s Monument.  Closer to the ground, we enjoyed a flock of Common Spotted Orchids on banks flanking the track through Sheeplands Copse.  We were lucky with the weather which was fair, with just the smallest of sprinkles at midday.  On Sunday it rained all day, the first, much needed downpour after a protracted period of dry weather.

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A Flotilla of Snails adrift on Rafts of Air

Many marine invertebrates spend their larval life either floating or swimming in the water column before settling on the bottom to assume their adult form and habit.  They may spend only a few hours, or may drift with the currents for several weeks or months and in the process achieve wide dispersal.

Despite the fact that the water column offers a such a large volume of living space, few molluscs have succeeded in adapting to a permanently pelagic existence but one such genus is Janthina, the Violet Sea Snails. They are known to exist in swarms covering as much as 200 nautical miles.  They live out their lives suspended upside down at the surface of the ocean.

To achieve flotation each snail constructs an individual raft of bubbles, and it is dependent on its raft for survival.  The snails cannot swim, and bubbles have a habit of popping, so each snail must continuously replenish its life support system.  Only the foot of the snail is involved in that process.

The sole of the foot is extended upwards to break the surface of the water and the sides of the foot fold over the depressed central area to encase a bubble of air.  Special glands on the foot coat the entrapped air with mucus, the encased air bubble then being pulled below the surface of the water and cemented to the existing raft with hardening mucus.  The entire sequence has been timed and occurs in ten seconds.  It may be repeated six to ten times in successions before a pause.

The raft, or float, of Janthina is firm, elastic and dry to the touch.  It varies from colourless to pink or violet in colour, which may be a result of age of the float.  Janthina produces eggs which hatch into young veliger larvae which swim freely in the water column.  Eventually they produce a long mucous string with a ball of air bubbles at the end.  This early buoyancy device brings the young snails to the surface where they can begin to construct the adult raft.

The colouration of these sea snails is a fascinating adaptation to life at the surface of the ocean.  What better coloured shell could an ocean-going snail possess than the violet blue shades common to all species of Janthina?  In matching the surrounding, mainly tropical, waters this is effective in concealing pelagic animals from visual predators. There are no known predators of Janthina but some fish and birds may eat them.

The potential camouflage achieved by the violet blue colour of the shell is enhanced by countershading.  Those regions of the shell directed downwards in the water are paler than areas of the shell visible at the surface.  This extra protective device means that potential predators approaching from below may have difficulty in distinguishing pale mauve shells against the light background of the sky, whereas predatory birds would find it less easy to spot Janthina from above because the dark violet colour blends into the dark background of the sea.

Because of their distinctive colour, unique in the realm of marine shells, it is worth keeping an eye out for a flash of violet blue when beachcombing, or walking the shores of the south and west coasts of the British Isles, particularly after intervals of stormy weather.

Janthina Ahoy

It’s been rather windy of late.  I don’t have the detailed information but I’m willing to bet that the western seaboard of the British Isles has been subjected to persistent, prevailing southwesterlies.  One of my friends in conchology, David Fenwick, has been in touch with news of some of the pelagic animals which find their way onto the strandlines of our beaches from time to time.

Pelagic animals are those that live out their lives at the upper levels of the water column in oceanic waters.  Often they float passively, driven by currents and climatic conditions.  It needs a sustained interval of more or less unidirectional windy weather to wash these animals ashore.

David sent me news of a beaching of Velella velellaVelella is a genus of free-floating Hydrozoans that live on the surface of the open ocean, worldwide, and is commonly known by the names by-the-wind sailor, purple sail, little sail, or simply Velella. These little organisms, relatives of the more familiar jellyfish, are the food of Violet Sea Snails,  Janthina janthina.   The snails also feed on other oceanic drift animals such as the Portuguese Man o’ War and rely on passive encounters with their prey.

David found two Violet Sea Snails this week on the beach at Sennen Cove in Cornwall.  They were still alive with their bubble rafts intact.  There were also thousands of Velella.  On taking the snails home and putting them in his tank, with some of their prey, they started to feed.

David sent me wonderful photos of the snails, which he generously allows me to reproduce hereIn one you can just see the ringed skeletal structure of the Vellella as the snail feeds on it.  Asked to confirm the snails’ identity, I was able to tell him these are the most common and the largest of the 4 species of Janthina.

David is a regular low-tider with an eye for noteworthy and unusual occurrences of the flora and fauna of the seashore and subtidal and he contributes information to the Marine Census of the Conchological Society.  He illustrates many of his finds on his website Aphotomarine.     Take a look at his other Janthina pictures. 

Next time I will tell you why the snails float upside down, and how they build their rafts.  I will also tell you about the Buoy Barnacle which David also found at Sennen.

Sanctuary in the Garden

With much of the house in a state where walls have been stripped back to their bare stones, it is fortunate that there will be plenty to keep us occupied in the garden.  After the initial euphoria of discovering that the orchid plants are in bloom, we realise that there is much to be done to bring the garden back to a state of cared-ness.

When I post a picture of a denuded salon sejour on Facebook, Maddy comments that it is no wonder we are spending so much time in the garden.  Over the succeeding week the garden becomes our source of fresh air and exercise, our recreation, and briefly on the penultimate day of our stay, a place to relax in the hammock with my current read.  Nick manages two fishing trips and brings home the fishy ‘bacon’.  Apart from our daily bread, fresh produce and eggs from a neighbour, we eat our way into our own stores.

We do spend Saturday evening with our neighbours.  I need the afternoon in the kitchen to cook up two curries and dall; this meal being laced with naan, poppadums, pickles and chutneys to provide an Indian supper which we then carry over the road and eat chez Poulet.

On the day before we leave it is a public holiday for the Feast of the Ascension.  We celebrate this with Francois and Anne when they BBQ for visiting family.  Fourteen of us sit out in perfect breezy, sunny conditions overlooking their beautiful garden and enjoy a feast of our own.

Anne and I have been swapping plants during our short stay at the house and when we leave for the ferry on Friday morning our car is loaded with pots containing plants destined for both my and Maddy’s gardens in Dorset.  This is the last consignment of plants which have been waiting in the wings, to cross the Channel.   Henceforth the pot management regime in France should be less onerous.  Sorting out the gravel garden at The Old Workshop is another project…..

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A Bee in my Bonnet about Wild Orchids

I’m buzzing because when we arrived in France after, for me at least, a lengthy interval away, I went straight outside to look at the leaf rosettes we had marked with wooden pegs in March.  Behold, Bee orchids.

It’s gratifying on a number of fronts; foremost I have been proved right, as has Dot, against the cautions preached by seasoned botanists.  Admittedly I thought the species we were looking at was the Green-winged orchid, on the basis of distributional information for northern France, and the preference this species has for damper habitat than bee orchids, for which I felt the waterlogging our lawn experiences in autumn and winter would be unfavourable.

So we have a minor nature reserve to manage and my first task is to cut away the grass around the orchids to help us mow the rest of the lawn.  This took all afternoon, after which more stakes had to be cut to mark out plants not previously identified.  In all we have 75 bee orchids, and as Nick reminded me, we would have had more than double that if he had not uprooted them with other ‘weeds’ during one of his lawn management sessions.

Not all the plants are sturdy and when we arrive many are still in bud.  There is blackening to some of the basal leaves which may either result from the extremely dry spring we have experienced, or possibly some late frost damage.

As the week progresses some of the orchids start to fail, they may not have liked to be exposed by my grass-cutting exercise.  Next year if the leaf rosettes appear I will try and group the plants, but not too closely, and keep areas unmown.

For the moment I just enjoying picking my way round the garden and relishing my ‘ownership’, as I go about the general clearance tasks we want to achieve before we leave for Dorset in a couple of days……

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