Ferment

The garden is - as ever - a wealth of life: a ferment of greenery and flies, birds and song, sunlight patterns on leaves: myriad changes in which each moment is entirely and absolutely different from any other in the world's story. 

Here is my key point: the ceaseless difference at the core of existence: the ever-new.

Were there ever to be a recurrence it would surely signal the end of this world. 

There are repeat elements, for instance the nodding of a branch in the wind, the structure of the song-thrush's call, the form of a daisy flower. But this all happens within the frame of the phenomenal present, which is a process of ceaseless self-differentiation. Every instant is utterly new in detail, unrepeatable.

Clinging On

As the human world reels under the malign influence of Coronavirus, my thoughts turn to Cretaceous barnacles. 

This sudden interest in extinct cirripedia is prompted by a paper published a month ago by Professor Andy Gale: New thoracican cirripedes (Crustacea) from the Cretaceous of Europe and North Africa.[1] It announces the discovery of new extinct genera and species of barnacle. There are two sorts: the acorn/wart-type (sessile) barnacles familiar from rocky shores and the stalk-type (pedunculate) 'goose barnacles' sometimes found attached to drift wood. 

I have never really thought about these crustacea before. They are easily overlooked - that is until you gash your hands or feet on them at the seaside, or eat them in a Portuguese restaurant. What crystallises my interest in them now is that one of the Zeugmatolepadid family now bears my name: Subsecolepas holtwilsoni. It is a lepadid barnacle - one of the stalked type. My thanks go to Andy for the honour. I think its taxonomic status is:

Phylum - Arthropoda

Clade - Mandibulata

Clade - Pancrustacea

Subphylum - Crustacea

Class - Maxillopoda

Infraclass - Cirripedia

Superorder - Thoracica

Order - Pedunculata

Suborder - Scalpelliformes

Clade - Thoracicalcarea

Family - Zeugmatolepadidae

Subfamily - Martillepadinae

Genus - Subsecolepas

Species - holtwilsoni 

Andy Gale is one of a very small band of palaeontological researchers active in the field of fossil cirripedes. Their most illustrious forebear is Charles Darwin. Thomas Withers was active from 1910 to the 1960s, and catalogued the fossils specimens at the Natural History Museum, London. " There can be no doubt the Wither's 'Catalogues' are to fossil lepadomorph and verrucomorph barnacles what Darwin's 'Monographs' are to Recent barnacles."[2] Andy has been one of the most prolific cirripede researchers in recent decades, focusing on the Cretaceous Chalk and publishing many papers. He says that S.holtwilsoni is common in chalk of the Upper Campanian stage in the UK, and that 400 fossil specimens have been found at various old pits in the Norwich area. He named it after me for helping him dig in these pits and for having been involved in their conservation, including Keswick, Catton, Cringleford and Whitlingham.

Collecting samples at Keswick, 2015

I have not visited any chalk pits lately. Britain today is in emergency 'lock-down', and I feel sorry for city-dwellers cooped up in flats and terraced houses. At least I have an extensive wildlife garden to ramble in, and I also enjoy exploring the meaning of our geological heritage.

Crustaceans of the Campanian seas are a great imaginative diversion - a dépaysement, as the French say. Geology and palaeontology call us out of our own time and down into the profound depths of planetary and biological evolution. I try to imagine the lifeworld of the extinct species that now bears my name.  

Here are photos of the type specimens of S.holtwilsoni, variously sourced from chalk pits at Keswick and Cringleford, and all are now archived in the Natural History Museum. They show elements of the set of hard, calcareous plates which enclose the head of the barnacle. 

Type specimens of Subsecolepas holtwilsoni. Image courtesy Andy Gale [1]

Stalked barnacles from JG Wood: 'The Illustrated Natural History'; Routledge, London, 1863

Darwin's drawing of a Middle Jurassic stalked barnacle Pollicipes concinnus,
as found attached to the shell of an ammonite.[3]

Contemporary stalked barnacles attach themselves to floating objects, particularly driftwood, turtles and ships. According to Andy Gale, S.holtwilsoni and other Zeugmatolepadids probably had a similar lifestyle, attaching to the shells of free-swimming ammonites and seabed-dwelling inoceramid bivalves as well as floating wood.[1, p.245] There must have been a steady rain of their plates falling into the carbonate-rich mud of the sea floor, perhaps 100 to 500 metres down.[4] 

The Campanian stage spans from 83.6 to 72.2 million years ago.[5], and chalk of this age is well-represented in Norfolk and Suffolk. I have visited many quarries of this period in the Gipping valley and Norwich areas. At Keswick and Cringleford I helped clear the chalk exposures so that Andy Gale could record the geological succession and take samples. The samples are treated with glauber's salt and freezing in a repeat process until the miniscule fossil fragments - echinoid spines, bits of coral, fish scale, shell, etc - are freed from their chalky matrix and can be examined under a microscope.  

Fossil residues from the Chalk (40x magnification)

  

The contrast between the physical reality of an old chalk pit, with its crumbly, scrub-infested chaos, and the clarified world of knowledge compiled by over 150 years of scientific research into the Chalk is remarkable. We now know much about the Earth's geography during the Campanian, for example that Europe was an archipelago of islands.[6] We know much about biodiversity and details of climate and chemistry.[7; 8]  

 

The world as it was in the late Cretaceous. Image courtesy Andy Gale [1]

All this is wonderful, radical stuff to explore during COVID-19 lock-down. Like astronomy, geology has the power to frame human life against an almost infinite scale of time and space. Like pedunculate cirripedes, we cling for a few seasons to our floating attachment points and then - like them - our debris will inevitably find its way to the metaphorical sea floor. Perhaps only our names, inscriptions and genetic coding will survive us, for a century or two at most. The history of taxonomic revision makes clear that not even species names backed up with diligent taxonomic description may be proof against time. 

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REFERENCES

[1] - Gale, A.S. New thoracican cirripedes (Crustacea) from the Cretaceous of Europe and North Africa. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 295 Heft 3 (2020), pp.243-282. [Link accessed May 2020]
[2] - Southward, AJ. Barnacle Biology. CRC Press, 1987; chapters 2.1 and 2.2.
[3] - Darwin, CR. A monograph on the fossil Lepadidæ, or pedunculated cirripedes of Great Britain. Palæontographical Society, London, 1851 Plate 3, Fig.1. Downloadable here. [Link accessed May 2020]
[4] - Rawson, PF. Cretaceous: Sea Levels peak as the North Atlantic Opens, in: Brenchley, PJ & Rawson, PF (eds). The Geology of England and Wales. The Geological Society, 2006; 2nd Edition. 
[5] - Lee, JR, et al (eds). British Regional Geology. East Anglia. British Geological Survey, Fifth Edition, 2015.
[6] - Csiki-Sava, Z et al. Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. Zookeys, no.469, January 2015, pp.1-161. [Link accessed May 2020]
[7] - Jarvis, I, et al. Late Cretaceous (Campanian) carbon isotope events, sea-level change and correlation of the Tethyan and Boreal realms. Palaeogeography, Palaeoclimatology, Palaeoecology, no.188, 2002, pp.215-248.
[8] - Skelton, PF et al (eds). The Cretaceous World. The Open University / Cambridge University Press, 2003.

THANKS TO

• Andy Gale, for naming the extinct beastie.
• Gilbert Addison, for suggesting the title of this article.

A Blackthorn Spring

Cold winds easterly have been blowing across East Anglia for the past week, though temperatures are set to rise this weekend.  Blackthorn blossoms are flourishing in this 'blackthorn spring': their froth of cold, white flowers starting out of the rattling, winter blackness of branch and twig.

Prunus spinosa, is respected by country dwellers for its fruit (sloe gin), its hard, durable wood and particularly for its long, piercing thorns like stiletti. They are able to pass straight through clothing, gloves and even boot soles and car tyres - things I know from experience.

I now have a terrible story to relate. It was told me by my friend C. and began about a month ago when her boyfriend D. was working in a Suffolk wood. Blackthorns make bristling thickets that require careful handling. Even though he was wearing goggles, a chance branch whipped his forehead and embedded a spine in his brow down to the bone. Naturally he pulled it out, but that evening redness and swelling set in, followed later by deep inflammation. Over the following days his condition worsened as his head swelled up and he became very unwell, with symptoms similar to sepsis (blood poisoning). Luckily neighbours noticed his silent home and telephoned C. She drove over immediately and what she found appalled her; a man in delirium, shivering with fever, with a necrotic lesion on his forehead. He was taken to hospital by ambulance and given intensive care. Over the next few days the hallucinations faded - at one time he said he thought his bed was surrounded by tall trees - and his temperature subsided. It was evident that he would need a skin graft to repair the damage, but this would have to be delayed because the hospital had started dealing with a flood of Coronavirus casualties. That is the situation now: D. is waiting and convalescing, wearing a head bandage and lucky to be alive.

What is it about blackthorn that makes it wound so grievously?

A look through my bookshelf did not turn up much useful information.

"A scratch from the thorns would cause blood poisoning. This was thought to be because Christ's crown of thorns was made from it".(1)

"Long associated with dark forces".(2) 

"Other tannin-rich barks were also used [for making inks] particularly those of blackthorn ...".(3)

A trawl through the WWW was more promising.

"On Tuesday evening I was scratched on the hand by a blackthorn, not deeply, but enough to draw blood. Fortunately, I know about blackthorn poisoning: it can be very unpleasant. A piece of blackthorn burying itself under the skin might cause severe infection, blood poisoning, swelling and pain. If left too long before treatment, amputation might be the result. Blackthorns are covered in unpleasant bacteria. If you have a piece buried in your flesh, the best course of action is to get yourself off to the hospital if you have a rapidly escalating and unpleasant reaction; don’t leave it until the area around the wound turns black. My light scratch was reacting badly to the blackthorn toxins within 5 minutes. I sprayed the area liberally with surgical spirits on my return home, which quickly reduced the angry redness and swelling. I woke in night with the swelling raging ... ".(4) 

A comment was appended to this blog post: "Our friend has just died from black thorn poisoning. Thought it was flu …".(5)

"Years ago I ignored a blackthorn wound. Within a week I had a red line running from the inside of my wrist to my elbow warning of the onset of sepsis".(6) 

"Blackthorn injury can give rise to a wide variety of manifestations ranging from mechanical dermatitis, cellulitis, abscess, foreign body granuloma, peritendinitis, tendinitis, pericapsulitis, synovitis to acute septic arthritis. Human synovial tissue is very prone to react to organic substances like blackthorns. Removal of the blackthorn fragments causes prompt resolution of the inflammation".(7)

It is clear that blackthorn wounds can be dangerous, particularly if remnants of thorn are left in the wound. I think D.'s injury was down to more than just a bad-luck thorn-prick.

"Why do [blackthorns] cause so much trouble? Clinical research undertaken at Oakham suggests that the painful tissue reaction to blackthorn injury is not caused by infection. In fact, contrary to popular belief among the equine veterinary community, the joint is sterile after a thorn penetration. The substances that make blackthorns black are alkaloids, and this thorn contains more alkaloids than other plants. Our research indicates it is this that causes the severe tissue reactions".(8)

The website 'Botanical Online' in its 'Blackthorn Toxicity' page states that the toxic principles of blackthorn are: prussic acid (seeds, bark, leaves); hydrogen cyanide (seeds); tannins. Anecdotal evidence from online discussion forums suggests that the blackthorn is particularly poisonous during the growing season.

So, I suggest that what makes a blackthorn wound so grievous is that the bark and thorns at this time of the year are exuding small quantities of plant toxins known as cyanogenic glycosides, notably hydrocyanic acid (HCN, aka prussic acid), "one of the most toxic of all plant compounds. ... The occurrence of cyanogenic glycosides is widespread. Amygdalin and prunasin are very common among plants of the Rosaceae, particularly the Prunus genus".(9) Oakham Veterinary Hospital is probably wrong about alkaloid poisoning: the blackness is caused by tannins, and the toxicity is caused by HCN. The presence of other pathogens such as bacteria from bird muck may play a secondary role, although I imagine most humans and other animals have a measure of immunity against them.

HCN has been tested as a chemical weapon to be absorbed through the skin. According to a Wikipedia, a concentration of 2000 ppm will kill a human in about one minute. "The toxicity is caused by the cyanide ion, which halts cellular respiration by acting as a non-competitive inhibitor for an enzyme in mitochondria called cytochrome c oxidase".  Basically, it kills cells. No wonder D. suffered toxic shock and now has a necrotic lesion on his head.

According to the University of Maryland, "All 400-plus Prunus species are toxic to livestock. ... The most commonly recognized species are the stone fruits: cherries, peaches, plums, almonds, apricots, and nectarines. All parts of the plant are toxic except the mature fruits. ... Hydrogen cyanide acts as a poison by preventing red blood cells from releasing oxygen".(10)

I think I now understand how D. came to be so badly affected by a single puncture wound. Fragments of thorn are likely to have released HCN which led to localised cell death, followed by toxic shock from sepsis and a dermal necrosis. His immune system struggled to cope with the chemical arsenal of Prunus spinosa, and also probably the effects of some bacteria and algal detritus.

I think it would be worth somebody researching more about HCN in blackthorn For instance, I'd like to know whether it is the live or dead thorns that do the most damage. The results would be worth publicising for farmers, gardeners and any other outdoors people likely to encounter this baleful, though attractive and interesting, bush. 

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SOURCES

(1) - R. Vickery (ed.). 'Unlucky Plants - a folklore survey'. Folklore Society, 1985.
(2) - Tess Darwin. 'The Scots Herbal'. Mercat Press, 1996.
(3)  - Richard Mabey. 'Plants with a Purpose'. Collins, 1977.
(4)  - Michael Griffiths. 'Blackthorn Poisoning. A warning'. The Wilden Marsh Blog, 3-12-2015.
(5) - Ibid, comment from 'Debra', April 17, 2018.
(6) - John Shelley. 'Nature. A Thorny Issue'. The Mayo News, 1 April, 2014.
(7) - H Sharma & AD Meredith: 'Blackthorn injury: a report of three interesting cases'. Emergency Medical Journal, vol.21, no.3, April 2004.
(8) - Oakham Veterinary Hospital, online: 'Blackthorn injury in hunters / sport horses'.
(9) - Andrew Pengelly. 'The Constituents of Medicinal Plants'. Allen & Unwin, 2009; pp.44-45.
(10) - Sara BhaduriHauck. 'Toxic Plant Profile: Prunus Species'. University of Maryland Extension, 3-8-2015.

All online sources accessed April 2020.

Text and pictures © TD Holt-Wilson, April 4th 2020.