Barnacles uncovered

On New Year’s day I was drawn to the sea for a walk to clear the toxins of the previous nights festivities. The long sandy beach at Slapton eventually made way for some rocks where we rested to enjoy a lunch of leftover Scotch eggs and shortbread. Whilst relaxing, my eyes became focussed on a more macro world of animals on the rocks as the tide went out.....

 

Acorn barnacles with limpets

....Most people have had the painful experience of barnacle encrusted rocks whilst rock pooling at the seaside. These creatures commonly coat rocks alongside other shelled animals, but are in fact very different in origin. Molluscs such as limpets and periwinkles are relatives of snails using a muscular foot to move and graze the rock surfaces whilst carrying their protective shells with them. The barnacles that hurt our feet are the static adult forms that await the tide to come in to feed, using feathery legs (cirri) that emerge when their opercular plates are opened, like a scene from Dr No. These cirri are thrown out and back like thin clawing hands, netting plankton and detritus. It is however the young barnacles that give themselves away as crustaceans, relatives of crabs, prawns and shrimps. The free-swimming larvae travel with other sea plankton, moulting several times before settling down to a ‘fixed’ life on a rock. They literally cement themselves down head first once they have selected a spot, ideally rough and shaded, orientating themselves across the current to maximise feeding (Yonge, 1976).

The commonest forms of barnacle on British shores are various types of acorn-barnacles. The species are distinguished by the number of shell plates (six in British spp as opposed to four with the Australian invader, Elminius), and the shape of the opercular openings which vary from oval to kite to diamond (Oakley, 2010). The image is probably of Chthamalus sp with kite shapes. One of the commonest British species is Semibalanus balanoides, which has a fascinating sex life - To overcome the reproductive challenge of separate sexes, each glued down and surrounded by armour plating, the male organ is gigantic (equivalent to 20 metres in human terms) – once the males have completed copulating with the females fertilizing up to 8000 eggs the mighty organ withers away and the males turn into females for next season (The Seashore, 2013).

Oakley, J. (2010) Seashore Safaris. Cardiff: Graffeg Books

The Seashore (2013) [online] www.theseashore.org.uk  [Accessed January 10^th 2013]

Yonge, C.M. (1976) The Sea Shore (The New Naturalist series). London: Collins

Stunning bird!

A few weeks ago I was with my wife in the Buckfast Abbey cafe after a long walk, enjoying an Earl Grey tea and admittedly a rather indulgent cake. The cafe has an external patio area with a glass screen to enable views of the grounds. We watched a pair of busy Pied Wagtails (Motacilla alba) that seemed to be enjoying chasing each other around the gardens below. Suddenly one of them hit the glass with quite a thud, rousing tea drinkers from their afternoon stupor.  The bird landed on a roof below and stood almost motionless, panting with its beak wide open. It stayed like this in apparent shock for over 10 minutes and remained that way as we left.

This type of occurrence is commoner than I realised. A US report claims that collisions with clear and reflective materials such as glass are the second highest man-made mortality factor for birds worldwide, only superseded by habitat destruction (Klem, 2008). This amounts to billions of deaths from head trauma; far higher than hunting, road kill, and domestic cats. There have been many prominent campaigns against hunting birds and more recently wind turbine objectors have frequently cited bird kill as an argument against their installation, and yet the far greater toll from glass gets conveniently ignored. The birds appear to treat these barriers as invisible. This type of death is no discriminator of an individual’s level of fitness, unlike more natural mortality factors. The RSPB recommends the use of silhouette images of birds of prey on windows to deter birds, particularly on large glass areas such as patio doors, or where birds might perceive a clear pathway through structures. Other solutions include netting or hanging objects in front of windows, placing feeders closer to windows to reduce the speed of impact, angling windows at 20-40 degrees also to reduce impact, and more novel use of one-way films that create patterns and shades rendering them relatively opaque (Klem, 2008).

Meanwhile at home I accidently discovered last year that my stuffed Barn Owl place on one of our deeply recessed window ledges appeared to be putting off birds coming anywhere near the back of our house – perhaps not a practical large scale solution!

Klem, D (2008) Avian mortality at windows: The second largest human source of bird mortality on Earth. Proceedings of the Fourth International Partners in Flight Conference: Tundra to Tropics. 244–251

Last summer rays

Back in early September I was in North-West Wales enjoying a late burst of summer warmth in the shadows of Snowdonia. Walking some of the lanes I was struck by the number of Goldenrod (Solidago virgaurea) plants and how unfamiliarly small some of them seemed. I have since learnt that this species is very variable and can appear in dwarf-like forms (Stace, 2010). More recently I came across the bright yellow burst of this late flowering plant nearer home on the side of a Devon stream (see image).

The genus name, Solidago is derived from the Latin meaning to ‘make whole’ and  Goldenrod has certainly a long history of traditional medicinal use, particularly as a diuretic and urological disease. Hawes (2010) suggests harvesting the whole flowering plant and dry for use with herbal infusions for urinary problems with regular doses helping to reduce the risk of kidney stones. Other suggested uses included a hot dose to treat runny nose symptoms of colds and a tincture for catarrh and hayfever. More contemporary studies by scientists have shown some anti-cancer potential of Goldenrod (Gross, et al., 2002). I do wonder at the contrast of traditional and modern medicine and how different health benefits have been discovered over the ages. How did people learn to test different plants for the varying ailments as they evolved in their communities? Was it simply trial and error or did they have better developed intuition that they learnt to trust.

In the meantime the Goldenrod plants are now slowly being absorbed back into the autumnal earth to hide their powerful secrets until next spring.

Gross,S.C., Goodarzi,G., Watabe,M. Bandyopadhyay,S., Pai,S.K. and Watabe, K. (2002)  Antineoplastic Activity of Solidago virgaurea on Prostatic Tumor Cells in an SCID Mouse Model. Nutrition and Cancer, 43(1): 76–81

Hawes, Z (2010) Wild Drugs – a forager’s guide to healing plants. London: Octopus Publishing Group Ltd.

Stace, C.A. (2010) New Flora of the British Isles (3^rd edition). Cambridge: Cambridge University Press.

Four and twenty blackberries

It is that time of the year that the hedgerows are bursting with the black-ripe fruits of Blackberry and elder, ink-blue sloes, bright red haws and browning hazelnuts. But not this year. The few blackberries I have seen are mean looking, grizzled and diminished. Flies hungrily surround the few succulent fruits. Hazelnuts that I scooped up in handfuls last year, cracked and roasted for my morning muesli with blackberries, are all but absent. A quick scan of the internet revealed that I am not alone in noticing the poor crop this year of blackberries. The Guardian (2012) reported on this a few days ago, “the cool, wet spring and summer has delayed the season for berries on bramble, blackthorn, elder and other bushes, and these are only beginning to ripen. They also seem to be smaller than usual.”   

So what is actually causing such low yields in much of Britain? Could it be that the prolonged poor weather reduced insect activity so much that many bramble flowers were simply not pollinated? I know anecdotally that local beekeepers in unprecedented action had to feed their bees this spring/summer on sugar solution, as they were starving from not being able to go out and forage. Combine this with a lack of warm temperatures to ripen the fruit, and it is hardly any wonder there is such a low yield.

What will the impact on wildlife that feast on this autumn harvest? Blackberries are a vital food supply for a wide range of mammals such as badgers, dormice, hedgehogs and foxes; birds like blackbirds, bullfinches, chaffinches, magpies and song thrushes; and insects including butterflies, wasps and moths (BBC, 2012). I will therefore be leaving what’s left of the sad blackberry crop to these creatures and adapt my muesli mix, making use of some garden autumn golden raspberries planted this year. Let’s hope our British wildlife can be equally adaptive.

BBC (2012) Blackberry crop threatened by record dry spring [Online]   http://www.bbc.co.uk/blogs/natureuk/2011/06/blackberry-crop-threatened-by.shtml [Accessed 26/09/12]

Guardian (2012) Plantwatch: This autumn likely to provide a brilliant display of colours [Online]  http://www.guardian.co.uk/science/2012/sep/21/plantwatch-autumn-leaf-colour?newsfeed=true [Accessed 26/09/12]  

The knock out nuptial gift

What a washout of a summer. As I sit typing this blog the rain is lashing against the skylight – again! It’s not just the volume of water that this summer has thrown at us that has turned the British summer into a damp squib, but the wind ripping through plant and canvas. We were seriously concerned about my brother camping a couple of weeks ago in nearby Brixham, wondering if their new tent would take the pounding. It’s easy for the human species to hide from the worst of the elements, but think of more delicate nature accustomed to light summer breezes and warm nectar. Honey bees have been so short of food that many beekeepers have had to take the unusual step of feeding them this summer with sugar solution. But what of other not so pampered invertebrates, such as butterflies and moths. No doubt we will feel the impact for years to come.

There have been a few decent interludes and I have tried to get to the coast for the occasional walk. The resilience of nature to grab these weather opportunities is somewhat reassuring. One species that has particularly drawn my attention are Six-spot Burnet moths (Zygaena filipendulae), whizzing from one purple flowered Knapweed to another. These day flying moths make the most of heat and sunshine. My friend Mary from Nottinghamshire spent years protecting and observing a ‘colony’ of Burnet moths living precariously on a busy verge, noting the emergence of the black & red adults on hot days. The caterpillars are equally colourful, yellow with broken black lines running the length of their body. However they are adept at protecting themselves by turning themselves into living cyanide pills for any unwary predators. Many plants produce cyanogenic glucosides to deter grazing animals, but these caterpillars are able to biosynthesise these chemicals for their own defense (Zagrobelny, et al., 2008). Perhaps more fascinating, when adults mate the males transfer a ‘nuptial gift’ of cyanogenic glucosides to virgin females, which it is suggested by researchers is then used for her own defence or to protect her eggs (Zagrobelny, et al., 2008) – indeed further experiments indicated that females can detect how much the males possess and reject those with low concentrations.

I just hope that these stunning moths are as adept at coping with the vagaries of the increasingly volatile British summers as they are at developing chemical weapons.

Zagrobelny, M., Bak, S., Møller, B.L (2008) Cyanogenesis in plants and arthropods. Phytochemistry, 69:457–1468

The pharmaceutical poppy

There was no mistaking the identity of the Yellow Horned-poppy (Glaucium flavum)  scattered liberally along the shingle of nearby Slapton beach last week. The large yellow flowers are dwarfed by the extravagant sickle-shaped, horn-like seed pods that grow up to a foot long.

This predominantly coastal plant has been adopted for centuries as a traditional medicine, including use by the Vikings of Norway and Denmark (Psychoactive Herbs, 2012).  Over more recent decades, scientists have developed techniques to extract alkaloids from this plant, the main representative being glaucine (named after the plant). This has led to pharmaceutical use in drugs as a cough suppressant, anti-inflammatory and analgesic. There has also been a degree of recreational use due to its opiate like effect (Psychoactive Herbs, 2012).  A more innocent application is as a fuel for lighting by using oil from the seeds (PFAF, 2012). A recent development is the use of glaucine based creams as a cosmetic treatment for cellulite. The glaucine appears to impact fat cells by causing them to release fat as well as inhibiting new fat cells in favour of collagen-producing cells, resulting in “fat being replaced by firmness” (Lipotherapeia, 2012).

So as the Vikings landed on British beaches did they seek out the Yellow Horned-poppy to; stop coughs, get pain relief, have some fun or simply to firm up their buttocks?
 

Lipotherapeia (2012) Is glaucine, an extract of the common yellow poppy, the ideal anti-cellulite cream ingredient? [Online]  http://www.lipotherapeia.com/cellulite-questions-answers/is-glaucine-an-extract-of-the-common-yellow-poppy-the-ideal.html [Accessed 13/07/12]

Psychoactive Herbs (2012) Yellow Horned Poppy Extract, Glaucium flavum. [Online]  http://psychoactiveherbs.com/catalog/index.php?cPath=170_193 [Accessed 13/07/12]

Plants for a Future (PFAF) (2012) Glaucium flavum – Crantz. [Online]   http://www.pfaf.org/user/plant.aspx?LatinName=Glaucium+flavum [Accessed 13/07/12]

The pretty hungry caterpillar

We have been watching a group of very colourful caterpillars in the garden over the last few days. Many of you will recognise these caterpillars from the image, but perhaps have wondered what species it is and whether the adult is equally visually stunning. A strong clue to the caterpillars identity is its favourite food plant, Mullein, and hence its name the Mullein Moth (Shargacucullia verbasci). Our particular caterpillars featured are feeding on Great Mullein (Verbascum Thapsus) with its distinctive velvety elephant ear-like leaves - or what’s left of them. This moth will also feed on other Verbascum species, but also Figwort (which I have more frequently observed) and Buddleia.

The caterpillars seem unconcerned with their high visibility ‘jackets’, almost advertising their bright yellow and black markings – this is presumably to warn any predators not to eat them because they taste bad. This stunning colouration is in stark contrast to the adult moth form which at rest appears to mimic a dead plant stalk.

Many gardeners are all too acutely aware of how prone their Verbascums are to attack by the caterpillar of the Mullein Moth, which can consume much of a plant's entire foliage in a day. I counted only about three caterpillars on our Great Mullein and today we are left with little more than a stump. However this is where their colouration works against them as they are easy pickings for green-fingered predators!

A Lizard's tale

A few weeks ago I was lucky enough to spot a Grass snake (Natrix natrix) crossing our local country lane. I managed to grab it momentarily to get a good look before releasing it into the hedge. Then last week during the warmer weather I spotted another much smaller snake-like animal, a Slow worm (Anguis fragilis)- the Anguis is taken from the Latin, 'slim' and 'snake'. However, as many of you will know it is not a snake, but a legless lizard, being distinguishable by its closable eyelids which is why it is also called the Blind-worm – snakes do not have any eyelids.

This particular specimen was behaving rather too true to its name, being rather sluggish and easy to catch. I was concerned about its safety as we have a high cat population locally, one of its not uncommon garden predators. Like other lizards the Slow worm does have a curious defence, the ability to lose its tail to escape predation using a mechanism known as ‘caudal autotomy’. By detaching a section of its body that then independently writhes vigorously it distracts its predator whilst it makes its more genteel escape. Perhaps it is this tail breaking trick that provides the ‘fragilis’ part of its Latin name. I have witnessed this phenomena and it is quite a sudden and amazing sight, with the tail demanding attention. Theseverance of its tail is a reflex achieved using a fracture plane (‘line of weakness’) in the caudal vertebrae. However it can only do this once and the new tail grows back significantly shorter than the original (Fuke, 2011), and can take several years (Bryant & Bellairs (1967). Despite the immediate advantage of surviving an attack, the tail loss has potential significant costs such as reduced locomotion and it has been shown to have a negative impact on reproductive success (Maginnis, 2006).

This all leaves me pondering the question, how does an individual Slow worm that can live 20 years plus determine the significance of every one of the many threats it will experience and decide on each occasion whether to play its one 'joker’.

Bryant, S.V. and Bellairs. A. (1967) Tail regeneration in the lizards Anguis fragilis and Lacerta dugesii. Journal of the Linnean Society of London, Zoology, 46(310): 297-305

Fuke, C. (2011) A study of a translocated population of Anguis Fragilis in Cornwall, UK. The Plymouth Student Scientist,4(2):181-221

Maginnis, T.L (2006) The costs of autotomy and regeneration in animals: a review and framework for future research. Behavioral Ecology, 17(5): 857-872.

Classy jumper

The recent improvement in the weather has triggered a burst of insect life as they respond to the early summer heat. This has shifted the hazards as I run the local lanes, from leaping giant puddles to avoiding swallowing the local insect fauna. Whilst on a slower ecological circuit, I was drawn to the numbers of flies, beetles and bees feasting on the abundant Alexanders flowers and other plants. It was however a red and black ladybird-coloured insect that particularly caught my eye, poised on a nettle. I took a couple of images before my macro lens became too intimate with the beast and in a flash it was gone. Back at home I was quickly able to identify it as one of our most visual frog hopper species, the Red-and-black Froghopper (Cercopis vulnerata). These bugs are also known as ‘spittle bugs’ and cuckoo-spit insects’, due to their nymphal stage habit of living in a protective mass of froth or spittle (Chinery, 1977).

When it comes to jumping stakes, few would bet against the flea when taking account of relative body weight. It turns out that froghoppers, such as C. vulnerata, produce a substantially better jumping performance. Starting with my puddle leaping efforts with a take-off force of about 2-3 times my body weight, the flea manages about 135 times, and froghoppers more than 400 times (Burrows, 2006). This is a very useful if you want to avoid predation or being eaten by a grazing cow. Researchers have shown that the key to this jumping performance is a spring-loading mechanism called the ‘pleural arch’, which the insect compresses like an archer’s bow in readiness for leaping to safety (Patek, et al., 2011). It is even cleverer than this when you consider the materials used to form the pleural arch; a sophisticated combination of chitinous material to store energy and ‘resilin’ to provide flexibility and shape restoration, has drawn comparisons with high performance composite bows (Patek, et al., 2011).

Such innovative mechanisms adopted by insects has inspired engineers and biologists to consider applications for human inspired devices. If we get another wet spell as bad as this April, I would be interested in a ‘human friendly pleural arch’ device to better avoid the puddles.

Burrows, M. (2006) Jumping performance of froghopper insects. Journal of Experimental Biology, 209: 4607-4621.

Chinery, M (1977) A Field Guide to the Insects of Britain and Northern Europe. London: Collins.

Patek, S.N., Dudek, D.M. and Rosario, M.V. (2011) From bouncy legs to poisoned arrows: elastic movements in invertebrates. Journal of Experimental Biology, 214:1973-1980.

Limestone lovers

Berry Head in South Devon is quickly becoming one of my favourite haunts with its rich botanical landscape and marine wildlife. Last September I blogged about one of its specialities, the White Rock-rose (Helianthemum apenninum), a nationally rare species (see http://nicksnaturenotes.blogspot.co.uk/2011/09/last-white-rock-rose.html). The unusual mix of physical geography and chemistry provided by the Devonian limestone sea cliffs of Berry Head provide conditions for the White Rock-rose shared only by a handful of other sites in the South West. I was visiting it again this weekend with friends and showed off the White Rock-rose amongst other more common plants. Towards the end of the afternoon we wandered up to the remains of the fort in search of summer migrant birds amongst the scrub. Resting my arms on the battlements and enjoying a Whitethroat and possibility of Cirl Buntings, I became curious about a stunted-looking plant which I had almost leant on. Closer inspection revealed what looked like a bonsai version of an umbellifer, a dwarf parsley or carrot plant. My companion with much pleasure eventually identified it as Honewort (Trinia glauca), which is indeed a member of the carrot family and another local limestone specialist. Apparently, in turf closely grazed by rabbits, plants of Honewort grow to no more than a few centimetres tall (BRC, 2012), as was the case with many of the Berry Head plants that we observed.

When I got home I looked at the distribution map on the National Biodiversity Network's Gateway (see http://data.nbn.org.uk/gridMap/gridMap.jsp?allDs=1&srchSpKey=NBNSYS0000003662) and fascinatingly it is found in almost the same isolated areas as the White Rock-rose. These rare fragmented habitats of dry limestone, with short-grazed south facing aspects have created almost identical conditions for such specialists to cling on to their slopes. However their hold is truly precarious, the species being listed as ‘Near Threatened’ (BRC, 2012). The challenge for the Honewort is made more challenging as it is dioecious (having separate male & female plants, requiring cross-pollination) and has poor seed dispersal, most likely reliant on ants (Carvalheiro, et al., 2008).

These two limestone loving species are literally hanging on in Britain, exposed to human disturbance.  This makes it all the more important to value these wonderful wildlife hotspots and for me to take more care where I lean my tired ‘binocular-ed’ arms.

BRC (2012) Online Atlas of the British and Irish flora [online] http://www.brc.ac.uk/plantatlas/index.php?q=plant/trinia-glauca [Accessed 7/5/12]

Carvalheiro, L.G., Barbosa, E.R.M. and Memmott, J.(2008) Pollinator networks, alien species and the conservation of rare plants: Trinia glauca as a case study. Journal of Applied Ecology, 45: 1419–1427

National Biodiversity Network's Gateway  (NBN) (2012) Grid map of records on the Gateway for Honewort (Trinia glauca) [online] http://www.brc.ac.uk/plantatlas/index.php?q=plant/trinia-glauca [Accessed 7/5/12]