Bird of Paradise

Alfred Russell Wallace writes (1869):

<One of my objects in coming to the Far East was accomplished. I had obtained a specimen of the King Bird of Paradise (Paradisea regia), which had been described by Linnaeus from skins preserved in a mutilated state by the natives. | knew how few Europeans had ever beheld the perfect little organism I now gazed upon. ...

Image courtesy https://birdoftheweek.home.blog
2022/03/25/bird-239-king-bird-of-paradise/

The remote island in which I found myself situated, in an almost unvisited sea, far from the tracks of merchant fleets and navies ; the wild, luxuriant tropical forest, which stretched far away on every side ; the rude, uncultured savages who gathered round me—all had their influence in determining the emotions with which I gazed upon this "thing of beauty.” I thought of the long ages of the past, during which the successive generations of this little creature had run their course—year by year being born, and living and dying amid these dark and gloomy woods, with no intelligent eye to gaze upon their loveliness; to all appearance such a wanton waste of beauty. Such ideas excite a feeling of melancholy. It seems sad that on the one hand such exquisite creatures should live out their lives and exhibit their charms only in these wild, inhospitable regions, doomed for ages yet to come to hopeless barbarism ; while on the other hand, should civilized man ever reach these distant lands, and bring moral, intellectual, and physical light into the recesses of these virgin forests, we may sure that he will so disturb the nicely-balanced relations of organic and inorganic nature as to cause the disappearance, and finally the extinction, of these very beings whose wonderful structure and beauty he alone is fitted to appreciate and enjoy.> 

* Alfred R. Wallace. 'The Malay Archipelago' (1869) chap.31.

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.

Shrews in my roof

18th August 2014

Today I took the opportunity to do some desk work out of doors, sitting on the terrace by the front door and proof-reading a book for a friend. Leaves were brushing the back of my neck from time to time as the wind stirred the vine there. It is a feature of the Bungalow garden: climbing up to the eaves and muffling the front of the house with a bright green jungle of stalks and questing tendrils.

The roof comes down to head height beside the front door. Twenty years ago we had a nest of hornets there. They were no bother - we saw them coming and going: they saw us doing the same; one of them was always on guard by the door to greet returning nest-mates and keep a weather eye open on the world; low-frequency murmurings heard at night, like Spitfires warming up on a distant aerodrome. I heard something different up there last week: a conversational twittering, scratchy and sporadic, like the sound of bats  - or pixies. I could not quite locate the source: was it coming from a chimney stack or a hole in the tiles? I had a vision of furry faces swivelling about in the semi-darkness of the roofspace, discussing something important.

My reading was disturbed by rustling among the leaf litter under the vine. Nothing to be seen. A few minutes later the rustling came from higher up among the thicket of leaves. A quick movement, and there - silhouetted by sunlight crossing a branch in the heart of the leafage - unmistakably a shrew, climbing about, hunting and exploring; perhaps nervously taking its first foray out of the nest, its nose twitching about in frenetic hyper-mobility. The identity of my nattering neighbours became clear.

The locals call a shrew a 'ranny'. I'd like to think that the Latin name for a Common Shrew, Sorex araneus, owed something to the East Anglian dialect, or some obscure Viking root of it revived by Linnaeus who named them. Its name has another dimension for me: odour. It reminds me of the word 'rancid', and shrews have a reputation for smelling bad.

Shrews in my roof.... The twittering is apparently a 'low amplitude, broadband, multi-harmonic and frequency modulated' sound used as a form of echolocation [1]. Coupled with a rosette of stiff but sensitive whiskers around their snout and a good sense of smell, that must be how they they find their way around in the roof. Their eyesight is said to be poor. Judging by size, I think mine are most likely to be the Common Shrew rather than the Pygmy Shrew.

I have always thought of shrews as being members of the Order Insectivora, along with hedgehogs. However recent genetic studies have shown they are part of an Order Soricomorpha (''shrew-forms') which they share with moles and a rare family from the West Indies called the solenodons. The latter are living fossils, with relatives dating back to Cretaceous times, over 65 million years ago, and teeth which can deliver a poisonous bite like a snake. Other shrews, including the Common Shrew, are said to have a poisonous bite, but this is due to a toxin present in the saliva [2, 3, 4]. 'It is a ravening beast, feigning itself gentle and tame, but being touched it biteth deep, and poysoneth deadly', says Topsell [5]. I have not yet tested the truth of this.

There is something primaeval about this animal. How old is the species Sorex araneus? Scientists have traced shrew origins back to the Heterosoricidae, a family living in North America in Middle Eocene times, about 45 million years ago; behind them must lie some ranny-like Cretaceous mammal, as yet unknown. Later, the Soricinae family evolved, to which my Sorex shrews belong, and the earliest fossils of the genus are found in Germany, in the Middle Miocene, c.11 million years ago [6]. The earliest likely British record for S.araneus is from Hoxne, Suffolk, dated 400,000 BP [7]. The site is no more than two miles away from my house as the crow flies, and only yesterday in geological time. The species itself is not quite as ancient as I had imagined.

Strange to tell, shrews are one of the most studied animals on the planet. S.araneus is one of the few species whose genome has been completely mapped, and as a result we are able to carry out detailed studies of its subspecies and their distribution in time and space. Some surprising results have emerged. 30 years ago we thought it was just one species, but it now turns out to be five cryptic species, each with distinctive genetic signatures which directly contradict their apparent similarities in size, skeleton and bodily appearance [8]. Externally the look the same, but internally S.araneus is 'characterised by spectacular chromosomal variation' [8], and shows 'one of the most spectacular chromosomal evolutions ever recorded in mammals' [10]; it has evolved an extraordinary wealth of chromosomal races (karyotypes).

Since 1987 S.araneus has been the subject of a specialist research group called the International Sorex Araneus Cytogenetics Committee. Through the work of Jeremy Searle and others, it has been possible to divide the British population into six racial types and plot their geographies; from this we can work out the story of how the Common Shrew recolonised Britain after the last Ice Age, having spent it sheltering in a refugium area on the Continent, most likely in central Europe [8]. Some of the genetic diversity within the species seems to have adaptive value, as slightly different karyotypes are found in different habitats, for example shrews in bogs are different from those in dry grasslands [11]. Apparently shrews are a rapidly evolving species, and this helps adapt them to changing ecological niches and ultimately leads to the evolution of subspecies and - on a much longer time scale - species. I have no idea which race my shrews belong to, but quite possibly they are of the Oxford race discovered by Searle which is typical of Eastern England [12]. It now seems likely the fossil S.araneus from Hoxne is one of the cryptic subspecies. David Polly's research holds out the hope that we may eventually be able to tell them apart by the details of their molar teeth [8]. There is a lot more to shrews than meets the eye.

Tonight I saw one climb straight up a brick wall and disappear under the eaves. They are evidently bold and enterprising animals. They are also fevered and vulnerable beings, who live with death as a constant companion. Shrews have an incredibly fast metabolism, and when frightened their heart rate can shoot up to over 1200 beats per minute [13]; their digestion lives on a two-hour turnaround, so if they go without food for more than a few hours they will starve and quickly die [14]. I imagine they suffer greatly, passing their short and passionate lives in a ferment of hunger and competition for food and living space. I have often heard them shrieking at each other, hidden deep in the undergrowth of some grassy forest - 'a rapid succession of shrill cries, which pierce the ears like needles of sound'  [15]. Gladiatorial screams of defiance, triumph and submission! If I wanted to tame one I would have to bring it offerings of woodlice, beetles and spiders, and promise to keep it in solitude. 'They love the rotten flesh of ravens', says Topsell, but I think I'd have to draw the line there.

From Topsell, 1658.

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References

1 - http://en.wikipedia.org/wiki/Soricidae#Echolocation.
2 - Buczacki, S. 2002: Fauna Britannica; Hamlyn.
3 - Poisonous Shrews, at: Shrew Culture, Myths, Stories and Poisonous Facts; The Shrew (ist's) Site aka 'The Shrew Shrine' - online at: http://members.vienna.at/shrew/cult-poison.html [accessed Aug 2014].
4 - The poison is a paralysing organic peptide called Soricidin - see Wikipedia https://en.wikipedia.org/wiki/Soricidin  [accessed Aug 2014].
5 - Topsell, E. 1658: History of Four-footed Beasts and Serpents; London; p.406. Online at: https://archive.org/details/historyoffourfoo00tops [accessed Sept 2014]. 
6 - Rzebik-Kowalska, B. 1998. Fossil history of shrews in Europe. In: J. Wojcik, J. & Wolsan, M. (eds.): Evolution of shrews; Mammal Research Institute, Polish Academy of Sciences, Białowieza, Poland. 
7 - Schreve, D.C. 2000: The Vertebrate Assemblage from Hoxne, Suffolk. In: Lewis, S.G. et al (eds) 2000: The Quaternary of Norfolk and Suffolk Field Guide; Quaternary Research Association.
8 - Polly, D.P. 2003 - Paleophylogeography of Sorex araneus (Insectivora, Soricidae): molar shape as a morphological marker for fossil shrews; Mammalia 68.2.
9 - Borodin, P.M. et al 2008: Recombination Map of the Common Shrew, Sorex araneus (Eulipotyphla, Mammalia); Genetics 178.2 - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2248351/ [accessed August 2014]
10 -Taberlet, P. et al 1994: Chromosomal versus mitochondrial DNA evolution: tracking the evolutionary history of the southwestern European populations of the Sorex araneus group (Mammalia, Insectivora); Evolution, 48.3
11 - Wojcik, J.M. 1991: Chromosomal polymorphism in the common shrew Sorex araneus and its adaptive significance; Mémoires de la Société Vaudoise des Sciences Naturelles, no.19.
12 - Searle, J.B. & Wilkinson, P.J. 1987: Karyotypic variation in the common shrew (Sorex araneus) in Britain – a 'Celtic Fringe'; Heredity, no.59.
13 - Crowcroft, P. 1963: Shrews; Animals of Britain Series  no.17, Sunday Times Publications, London.
14 - Churchfield, S. 1988: Shrews of the British Isles; Shire Natural History, Princes Risborough.
15 - Wood, J.G. 1865: The Illustrated Natural History. Mammalia; George Routledge & Sons, London; p.434.
16 - Topsell, E. 1607: The History of Four-footed Beasts.