Walking with Gosse – almost...

My annual "Coming up for Air" trip to Torbay [1] was in September this year. Fortunately, the weather was good, so I walked along the coast to re-visit places that were so important to me when I was growing up. Returning home to land-locked Hertfordshire, I then read what Philip Henry Gosse wrote in Land and Sea [2] about the parts of the Torbay shore that I had strolled through, and this made me appreciate Gosse's wonderful enthusiasm even more than usual.

I began by walking along the beach at Paignton and followed the strand line, always an interesting place to a Natural Historian. Unfortunately, there was little to see on this occasion and it was quite different to the strand line after a storm, when masses of algae are washed up. Like Gosse, I had always enjoyed exploring this evidence of the marine world of the bay, particular treasures being blue-rayed limpets attached to straps of brown algae, now torn from their anchorage. Of all the organisms I saw, I don't know why these limpets so appealed to me, but they are certainly attractive to the human eye (see below). 

In Land and Sea, Gosse describes their appearance:

The shell is of unimpeachable symmetry, polish, and delicacy; it is of a translucent horn-colour, and its summit is marked with three fine lines of the most brilliantly-gemmeous azure.

Not all the creatures washed up are so obviously attractive and, even fifty years ago, there was also much evidence of human pollution, with tar balls and pieces of net being common. Flotsam and jetsam are a rich source of natural materials, like wood, to the avid beachcomber, but there is now much more plastic refuse on beaches, as we continue to regard the sea as a convenient dumping place. I am impressed that artists like Jo Sayer can turn these plastic objects into attractive works of art that tell stories about what we are doing to Nature [4].

After the sands, I walked over Roundham Head and then on to Goodrington Sands (the sequence is shown in order in the photographs below; a route that Gosse walked in the opposite direction [2]). There was no promenade at Goodrington in the mid-nineteenth century and, while I took the promenade walk and cliff path on this visit, as a boy I preferred to scramble over the rocks when the tide was low, just as Gosse would have done.

 Gosse has a vivid description of some fisherman he encountered on Goodrington Sands:

..away across the heavy sands, in which we sink at every step, away obliquely to the left, where another bold headland, Roundham Head, breaks the sweep of the bay, and for the present shuts out Torquay from our view.

There is our working ground, at the foot of those red cliffs. We diverge a little from a straight line, and approach the edge of the sands, in order to see what those two men are so busy about, as they trudge along the water-line with stooping backs and downward gaze. Oh! they are fishermen taking solens, or razor-fish, as they call them. Each carries a light, narrow, but deep spade in his hand, and, as he marks a little jet of clear water that spirts upward from a small hole in the sand, he rapidly thrusts in his instrument, and adroitly jerks out his prey.. .. The man scarcely deigns it a glance, thinks nought of its curious structure, cares only for the halfpence it will bring him in the fish-market, jerks it into his basket, and watches for the next jet of water with which the frightened and retiring mollusc shall betray its place of retreat.

Razor clams (see below) are still a prized delicacy and they are certainly very effective at burrowing. Being a Natural Historian, Gosse was fascinated by this, but, as he pointed out, the clams were merely a commodity to the fisherman.

It was not only the wonders of Natural History that inspired Gosse, but the knowledge that all he saw was evidence of God. To him [2]:

..the inimitable, unapproachable, incomprehensible impress of Deity is there. Augustine says, "The soul bending over the things Thou hast made, and passing on to Thee who hast made them, there finds its refreshment and true strength."

Thus would I desire to contemplate the works of God, as bringing to my sense ever-fresh proofs of His all-pervading care, of His wondrous skill and wisdom, of His glorious majesty and power. Above all, they are the productions of the august Word: it is not that they were made by One who is infinitely great, but far removed from me, so that I can only reverently admire Him at an immeasurable distance. No; they are productions of the mind and hand of the Word (John i 3)..

..Yet let me not be mistaken. The study of the creatures could never teach me this. Notwithstanding all that they eloquently declare of the eternal power and Godhead of the Creator, they are ominously mute when I ask them how He will deal with me, a sinner.

All this comes as no surprise to those that know Henry Gosse's work and life. However, my appreciation of him does not extend to the religious views that made him such a devout Creationist. I find it baffling, and it is one of the reasons why I have never read any of Gosse's books on religious themes (listed in [3]). I admire his work in Natural History and enjoy his company in my imagination during my nostalgic visits to Torbay, but why did he have such a need to proselytise? Was he trying to convince himself?

[1] http://www.rwotton.blogspot.com/2013/05/coming-up-for-air.html

[2] Philip Henry Gosse (1865) Land and Sea. London, James Nisbet & Co.

[3] R. B. Freeman and Douglas Wertheimer (1980) Philip Henry Gosse: A Bibliography. Folkestone, Wm. Dawson & Sons.

[4] https://flotsamweaving.com/

An explanation for religious visions?

Hallucinations are characteristic of some forms of mental illness and can be frightening, causing distress to those who endure them. They can also occur after taking hallucinogenic drugs, with the possibility of both pleasant and unpleasant "trips".

Visions are part of the lore of religions like Judaism and Christianity. These visions may result from mental illness or from drug use, but they also occur when these conditions do not apply. There may be an expectancy of seeing an angel, or the Virgin Mary, and an excited mental state may be common in these cases, but no drugs are involved and nor is mental illness. What then is the basis of these visions?

Let's begin to answer that question by looking at two visions described in the Holy Bible:

Daniel's vision [1]

Having seen a number of animals (this must have been in a dream as he was lying face down?), Daniel then recounts:

 ..there stood before me as the appearance of a man.. ..he came near where I stood: and when he came, I was afraid, and fell upon my face.. ..as he was speaking with me, I was in a deep sleep on my face towards the ground: but he touched me, and set me upright

Cornelius' vision [2]

Cornelius was a devout Christian centurion who:

..saw in a vision evidently about the ninth hour of the day an angel of God coming in to him..

I assume that the ninth hour was in daylight and that his vision was not a dream, but we have no information on his state of wakefulness.

Both these visions, and those of others, could be explained by Charles Bonnet Syndrome. Charles Bonnet was born in Geneva in 1720 and qualified as a lawyer, although he probably never practised the law [3]. He was always fascinated by Natural History and wrote papers in the field of Entomology while still training to be a lawyer, later making many contributions to Botany when his eyesight began to fail during his twenties. Bonnet could then no longer work on small-scale observation and it was not only his sight that failed - he already had hearing loss from the age of seven [3]. As someone who suffered from sensory deprivation, he became interested in this subject and the way that it influenced the incidence of visions. He studied the phenomenon in his elderly grandfather and it is from these descriptions that he is best known in the medical world.

We can describe Charles Bonnet Syndrome (CBS) as [4]:

..the occurrence of recurrent or persistent complex visual hallucinations often of a pleasant nature, which may be considered pseudohallucinations, in individuals with preserved insight and intellectual function without altered consciousness, cognitive or psychiatric disturbances, sleep disorders, or focal neurological lesions and often associated with ophthalmic pathology. CBS occurs predominantly in elderly, visually impaired people.

Further in their review, Menon and colleagues [4] state:

The typical CBS hallucination has been variously described as a sudden sharply focussed, immobile image, most often the face or figure of a person, which occurs when the patient is alert, with eyes open and vanishes spontaneously after a period of seconds.

However, there are other causes than failing eyesight for the occurrence of hallucinations [4]:

Charles Bonnet-type hallucinations have also been documented in the absence of ocular or neurological disease, in type II diabetes mellitus with normal vision, in leprosy, in association with HIV infection.. ..and in the elderly, where they can occur in the absence of apparent cause.. ..it is interesting that fatigue and disturbances of vigilance have been implicated as relevant to the emergence of hallucinations, as they are more likely to occur during states of drowsiness.

Knowing this about the incidence of CBS, does it provide an explanation for the visions of Daniel and Cornelius described above? Could the phenomenon explain other visions that are so vivid to "observers" that do not have mental illness or use drugs? The visions are certainly real to those that have them and this is not surprising if they result from the neural pathways used to interpret visual images from the eyes via the optic nerves. It is rather like a mental short-cut that accesses the processing power of the brain, without the need for a direct stimulus.

[1] http://www.kingjamesbibleonline.org/ section of Daniel Chapter 8

[2] http://www.kingjamesbibleonline.org/ Acts Chapter 10 verse 3

[3] Thomas R. Hedges Jr. (2007) Charles Bonnet, his life, and his Syndrome. Survey of Ophthalmology 52: 111-114.

[4] G. Jayakrishna Menon, Imran Rahman, Sharmila J. Menon and Gordon N. Dutton (2003) Complex visual hallucinations in the visually impaired: the Charles Bonnet Syndrome. Survey of Ophthalmology 48: 58-72.

Bird of Paradise Flowers

The striking flower arrangement shown above is by Jane Hass and features two blooms of Strelitzia reginae, commonly known as the Bird of Paradise Plant, or the Crane Flower. These names were given to the plants because they reminded some observers of the two birds, but only an avid Creationist would believe in such mimicry, or that they were devised for our visual pleasure. S. reginae is native to South Africa, where it grows on river banks and in woodland clearings, and it was so attractive to collectors that seeds have been exported widely and the plant grows well in warm climates. It is the official flower of the City of Los Angeles [1].

Each flower consists of bright orange sepals and darker petals and these emerge from a spathe (the pointy section that looks like the beak of the bird in our imagination). At the base of the petals is a nectary containing sugars that change in their composition over time [2], although we do not know the reason for this.

Nectar is produced by almost all flowering plants and provides an attractant for animals that use it as an energy source and then collect pollen that is transferred to another plant to ensure fertilisation. Most commonly, the pollinators are insects and the plant loses sugars (produced abundantly during photosynthesis), and some of the pollen (many bees collect this, for example), but the mutualism between the plant and the pollinating insects is clearly of benefit to both and is a very successful strategy. Insects are not the only pollinators, however, and S. reginae is fertilised by birds, with its pollen formed into threads and aggregates [3] to enhance attachment and transmission. The most common pollinator is the Cape Weaver (Ploceus capensis – see below), that feeds on the pollen aggregates as well as the nectar and transfers pollen on its feet while visiting another flower [4,5], with the rigid spathe providing an ideal initial landing place. 

Visits by weaver birds have described by Hoffman et al. [6]:

Landing of the bird on the blue sheath-forming petals exposes the hidden pollen to the feet of the bird, while the bird probes the corolla tube with its beak and extends its tongue to reach the nectar.. .. Once landed and feeding, these birds have been observed to seldom move their feet, thus keeping self-pollination low.. .. As a consequence, the best place for the bird to feed is also the best position for pollination.

Sunbirds (Cinnyris spp.) also visit S. reginae plants, but it is likely that they play little part in pollination and they are regarded as "nectar thieves" [5]. As Coombs and Peter note [7]:

The nectary of S. reginae is covered by the convoluted bases of the two fused petals forming a barrier to the opening of the corolla tube.. ..The behaviour of sunbirds indicates that they are nectar thieves and can manipulate the nectar barrier with their beaks to gain access to the nectar without causing obvious damage to the flowers of S. reginae.

Pollination in S. reginae is thus an example of the evolution of a strategy that depends on mutualism, with other species taking advantage of the "gifts" provided by the plant. 

So what happens when seeds are taken to other countries? An abundance of imported seeds ensures that plants can be grown without the need for fertilisation, but we now know that S. reginae is pollinated by indigenous birds. The common yellowthroat of southern North America (Geothlypis trichas – see below), a type of warbler, feeds on nectar and, just as with the weaver birds in Africa, picks up pollen on its feet. As Hoffman et al. point out [6] it is unlikely that "adaptive floral changes have started the association" in the very short time during which S. reginae have been grown in the USA, but the behaviour of the warblers allowed them to discover the nectaries and release pollen on to their feet and thus ensure fertilisation. All this mimicking an association that evolved over very long time periods in South Africa where the plant is endemic.

It is interesting to speculate on how yellowthroats developed this behaviour. The bright sepals of S. reginae may be an attractant to many animals, including the insects and other invertebrates on which the warbler feeds. Could it be that the habit of feeding on nectar, and picking up pollen on the feet, happened through successive visits of some birds to feed on insects; a behaviour that became established in populations as a result of learning from other individuals? Whatever its origins, it is another example of the wonder of evolution and of Natural History.

 

[1] http://www.dailynews.com/lifestyle/20140320/get-to-know-the-official-flower-and-tree-of-los-angeles

[2] Eva C. Kronestedt-Robards, Maria Greger and Anthony W. Robards (1989) The nectar of the Strelitzia reginae flower. Physiologia Plantarum 77: 341-346.

[3] ] Eva Kronestedt-Robards (1996) Formation of the pollen-aggregating threads in Strelitzia reginae. Annals of Botany 77: 243-250.

[4] Adrian J. F. K. Craig (2014) Nectar feeding by weavers (Ploceidae) and their role as pollinators. Ostrich 84: 25-30.

[5] G. Coombs, S. Mitchell and C. Peter (2007) Pollen as a reward for birds. The unique case of weaver bird pollination in Strelitzia reginae. South African Journal of Botany 73: 283.

[6] F. Hoffmann, F. Daniel, A. Fortier and S.-S. Hoffmann-Tsay (2011) Efficient pollination of Strelitzia reginae outside of South Africa. South African Journal of Botany 77: 503-505

[7] G. Coombs and C. I. Peter (2009) Do floral traits of Strelitzia reginae limit nectar theft by sunbirds? South African Journal of Botany 75: 751-756

Crocosmia, invasion, diabetes and obesity

The rich flora of southern Africa has provided us with many garden plants, including members of the iris family that naturalise readily [1]. Among the most popular of these plants is montbretia, or coppertips (Crocosmia x crocosmiiflora – a cross of C. aurea and C. pottsii [2]), the result of horticultural inter-breeding and now popular world-wide for its attractive foliage and, especially, its orange-red flowers.

Montbretia has two methods of reproduction: fertilisation of the flowers by insects (and, in some closely-related Crocosmia plants, by wind or humming birds) to produce seeds; and vegetative reproduction, where each plant produces stolons, or runners, that form new plants when roots and leaves grow from nodes.

Flowering occurs over a period of days, with the first flowers at the base of the spike and then sequentially towards the tip, the production of seeds following the same sequence. This habit ensures that some flowers are likely to be fertilised during optimal conditions for pollination, and the seeds, similarly, are produced over time to ensure that dispersal is optimal. This flowering habit is a feature of many plants, but it is important to recognise that it evolved to the advantage of the plant a very long time before humans appeared. It was not designed by, and for, gardeners.

Vegetative growth by stolons ensures local colonisation and many gardeners like to divide dense clumps, as they tend to choke off other plants (a measure of the success of the strategy). Each individual montbretia grows from a corm and this develops after the successful germination of seeds and the growth of the first colonising plant. It is likely that the casual disposal of corms, rather than the spread of seeds, allowed montbretia (coppertips) to be such a successful coloniser of natural habitats, frequently forming large and vivid clumps on embankments and in coastal regions [2]. When established, its growth habit ensures its spread and it may now be regarded by some as a "wild flower".

 

Each corm is a store of starch grains produced synthetically after photosynthesis and this store allows the growth of leaves and stems at the beginning of the growing season. It is also used in shorter time scales to allow the efficient metabolism of the plant. Starch grains that are stored by plants for months often have their surface eroded [3], resulting from the action of naturally-occurring enzymes involved in releasing easily-metabolised sugars from the more complex starch. Among these is α–amylase and this enzyme is disabled in montbretia corms by the presence of a compound called montbretin. This ensures that starch grains are retained in good condition during resting phases, montbretin being of less significance when starch is being metabolised.

The presence of montbretin, the metabolism of the plant, the succession of flowers and seeds, and the vegetative spread by stolons, are all extraordinary adaptations that make montbretia such a successful plant and an effective invader. In addition, montbretia has recently received attention in the world human health, something which always results in wide publicity. It has been discovered that montbretin not only serves to protect starch grains from the action of α–amylase in Crocosmia corms, but may also inhibit the action of these enzymes in humans, something that offers the possibility of new drug treatments against diabetes [4]:

Type 2 diabetes mellitus is a condition that affects well over 320 million people worldwide and is closely associated with obesity. Among the oral antidiabetic drugs used for its treatment are the α-glucosidase inhibitors, which prevent hyperglycosemia by slowing digestion of starch and malto-oligosaccharides in the gut. Partial hydrolysis of starch is accomplished by salivary α-amylase, with principal cleavage provided by human pancreatic α-amylase (HPA) within the gut, generating linear and branched malto-oligosaccharides. These in turn are broken down to glucose by α-glucosidases that are anchored in the epithelium of the small intestine..

..Selective inhibition targeted at only HPA, the enzyme at the top of the starch digestion pyramid, could be used to quantitatively modulate blood glucose levels by restricting or even shutting down starch degradation, thereby minimizing the specificity problems that arise with currently available α-glucosidase inhibitors.

This is written in the technical language of a scientific paper, but Williams, Zhang et al. [4] then describe the selective nature of montbretin A (MbA) and its possible value in medicine:

Because MbA is such a potent inhibitor and is easily isolated from the corms of a readily grown plant (Crocosmia sp.), it has potential as a new agent for controlling blood glucose levels in diabetics and obese patients. 

So, the mechanism that evolved in Crocosmia to conserve starch grains is one in which the pharmaceutical industry is likely to show a great deal of interest, given the numbers of diabetics and the "epidemic" of obesity in many countries. This medical application could lead more people to think about the evolution of Crocosmia and its Natural History, helping us to move away from our dominant anthropocentric view and towards a sense of wonder in the capabilities of all living organisms. 

Well, it should do.

[1] Mark Van Kleunen, Steven D. Johnson and Markus Fischer (2007) Predicting naturalization of southern African Iridaceae in other regions. Journal of Applied Ecology 44: 594-603.

[2] http://www.nonnativespecies.org/factsheet/factsheet.cfm?speciesid=1040

[3] A. T Modi and R. Mare (2016) Alpha amylase activity and sprouting during short term storage of taro corms. Journal of Agricultural Science and Technology 18: 1053-1063.

[4] Leslie K. Williams, Xiaohua Zhang + 11 authors (2015) The amylase inhibitor montbretin A reveals a new glycosidase inhibition motif. Nature Chemical Biology: published online 27th July 2015 DOI 10.1038/NCHEMBIO.1865.