Wednesday, 28 February 2018

The antics of sea monkeys

Human imagination is powerful and, as a result, we can readily be taken in by the power of advertising. One example of which I am especially fond is that of sea monkeys, sold through advertisements in children’s comics in the last century (see below), but still available today.

The excerpt from the advertisement shown above sums up the enjoyment that we are likely to have by watching the antics of sea monkeys and we hold the miracle of life, being able to create them by adding powder from a series of bags to an aquarium tank of water. The bags contain salts, nutrients, and the encysted eggs of brine shrimps (Artemia) that hatch to produce larvae in the saline water and these metamorphose into adults (see below) after a few days. The idea of branding the shrimps sea monkeys came from Harold von Braunhaut, a New York entrepreneur, and he encouraged us to imagine that the Artemia swimming around in tanks, some of which had lenses set into the plastic to allow a better view, had faces and were performing tricks.

I wonder how many of those who had sea monkeys (and we had some in our household when our children were young) overcame their disappointment that they were shrimps and not little monkeys, by considering the biology of these remarkable animals. The name brine shrimps gives away the habitats in which they are found – small freshwater pools with high levels of salinity, especially during drying events. Artemia can tolerate salinities from 25-250 g/L (sea water is usually 35 g/L) and they can do this because they have an impervious exoskeleton that prevents osmosis and thus water incursion at low salinities and dehydration at high salinities. That in itself is something that promotes wonder, as does their ability to reproduce parthenogenetically.

When their pools begin to dry, encysted eggs are produced and these withstand extremes of temperature, very low oxygen tension, and the presence of poisonous gases (although experiments conducted by NASA, and others, suggest they may be susceptible to the deleterious effects of cosmic rays [1,2]). They are effectively as dry as the dried pool in which they are found and are referred to as being is a state of cryptobiosis – meaning that all signs of life are hidden. They can remain in this state for years and that is why living Artemia soon appear in sea monkey tanks after we have added powder to the water. It also explains why they return after we add fresh water to a dried-out tank.

The encysted eggs of brine shrimps are not the only examples of cryptobiosis; many seeds and spores can also remain in long-term dormancy before returning to resume their “normal” life when conditions become suitable. More unusually, there are creatures that can become dried during other phases of their life cycle – tardigrades and nematode worms provide examples, as do the larvae of an African midge (Polypedilum vanderplanki) that become dried with the temporary rain pools in which they live. Animals that become cryptobiotic as larvae or adults replace water with organic compounds that maintain the integrity of tissues and, as with the production of encysted eggs by Artemia, the metabolic changes required for survival are triggered by changes in water quality that indicate that drying is about to occur.

If we are amazed by the antics of sea monkeys, how much more amazed are we that several different lineages of animals have evolved cryptobiosis and the ability to become dried? And independently, at that.

Friday, 9 February 2018

Sea Serpents

In his fascinating book [1] about the sea monsters that adorn various early maps, Chet Van Duzer writes:

I would suggest that sea monsters on maps have two main roles. First, they may serve as graphic records of literature about sea monsters, indications of possible dangers to sailors – and datapoints in the geography of the marvellous. Second, they may function as decorative elements which enliven the image of the world, suggesting in a general way that the sea can be dangerous, but more emphatically indicating and drawing attention to the vitality of the oceans and the variety of creatures in the world, and to the cartographers artistic talents.. ..During the Renaissance, sea monsters on maps reflect and express an increased general interest in wonders and marvels.. ..the more exotic the creature depicted, the better, and the study of both maps and images of exotic creatures was thought to sharpen the intellect and be educational. Maps decorated with sea monsters, by implication, would offer the viewer an even richer intellectual experience.

If that is the case, the map produced by Olaus Magnus (1490-1557), and shown below, must have been of great significance. Of the many sea monsters depicted, perhaps the most well-known is the sea serpent described by Olaus as follows [1]:

Those who do their work aboard ship off the shores of Norway, either in trading or fishing, give unanimous testimony to something utterly astounding: a serpent of gigantic bulk, at least two hundred feet long, and twenty feet thick, frequents the cliffs and hollows of the sea coast near Bergen. It leaves its caves in order to devour calves, sheep, and pigs, though only during the bright summer nights, or swims through the sea to batten on octopus, lobsters, and other crustaceans. It has hairs eighteen inches long hanging from its neck, sharp, black scales, and flaming red eyes. It assaults ships, rearing itself on high like a pillar, seizes men and devours them.

Such a creature (the red “snake” attacking a ship in the image below) would deter fisherman, and other sailors, from entering Scandinavian waters and, as Van Duzer points out, this may be one of the reasons for the location of sea serpents, and other monsters, on maps.

Sea serpent myths have a wide distribution and examples have been described by Aristotle, Pliny the Elder and many others [2]. Although there were sightings of serpents from Norwegian waters in the Nineteenth Century, the most well-known observation of one of the creatures was made by Captain Peter M’Quhæ of H.M.S.Daedalus off the south-west coast of Africa. As an Officer in the Royal Navy he was viewed as a reliable source and The Times of 9th October 1848 carried a report of M’Quhæ’s sighting. His letter to The Admiralty was quoted by Philip Henry Gosse in The Romance of Natural History [3] and it contains the following description of the creature: was discovered to be an enormous serpent, with head and shoulders kept about four feet constantly above the surface of the sea, and, as nearly as we could approximate by comparing it with the length of what our maintopsail-yard would shew in the water, there was at the very least sixty feet of the animal [at the surface of the water], no portion of which was, to our perception, used in propelling it through the water, either by vertical or horizontal undulation..

..The diameter of the serpent was about fifteen or sixteen inches behind the head, which was, without any doubt, that of a snake; and it was never, during the twenty minutes that it continued in sight of our glasses, once below the surface of the water; its colour a dark brown, with yellowish white about the throat. It had no fins, but something like the mane of a horse, or rather a bunch of sea-weed, washed about its back..

There are differences to the sea serpent described by Olaus Magnus but, as with all descriptions of these creatures, it is large and snake-like. Gosse, who was a literalist Christian and believer in Creation, had sufficient faith in M’Quhæ’s sighting to propose that the sea serpent was an enaliosaur; spending many pages of The Romance of Natural History sifting through the conclusions of others. 

What did M’Quhæ, and others aboard his ship, see? Given that humpback whales using bubble nets could be the origin of belief in the kraken [4], the answer may lie with the behaviours of contemporary marine animals, although there is no obvious explanation for the appearance of the sea serpent. There are many who still wish to believe in the survival of dinosaurs, and the well-established mythological importance of snakes and dragons with extraordinary powers certainly influences our imagination.

[1] Chet Van Duzer (2013) Sea Monsters on Medieval and Renaissance Maps. London, The British Library.

[2] Joseph Nigg (2013) Sea Monsters: The Lore and Legacy of Olaus Magnus’s Marine Map. Lewes, Ivy Press.

[3] Philip Henry Gosse (1860) The Romance of Natural History. London, J. Nisbet and Co.

The copy of Olaus Magnus's map used in the illustrations above come from Nigg's book (see reference [2]).

Friday, 2 February 2018

Charles Kingsley and Henry Gosse go dredging in Torbay

During the Nineteenth Century explosion of interest in the Natural History of shores, there was also much to discover about animal life in shallow coastal waters and this tempted naturalists like Edward Forbes to use dredges to bring animals to the surface, where they could be examined more closely.

In his biography of his father, Edmund Gosse describes a dredging trip that Philip Henry Gosse made with his good friend Charles Kingsley in Torbay. Although Kingsley is best known as the author of The Water Babies, Hereward the Wake and Westward Ho!, like many other Victorians he had a passion for Natural History and wrote Glaucus to summarise his knowledge and to inspire others [1]. The book contains many glowing references to Henry Gosse, and Kingsley was clearly a great admirer. This is what Edmund wrote [2]:

Charles Kingsley was several times our companion. The naturalists would hire a small trawler, and work up and down, generally in the southern part of the bay, just outside a line drawn north and south, between Hope’s Nose and Berry Head. I think that Kingsley was a good sailor; my father was a very indifferent one, and so was I; but when the trawl came up, and the multitudinous population of the bottom of the bay was tossed in confusion before our eyes, we forgot our qualms in our excitement. I still see the hawk’s eyes of Kingsley peering into the trawl on one side, my father’s wide face and long set mouth bent upon the other. I well recollect the occasion (my father’s diary gives me the date, August 11, 1858) when, in about 20 fathoms outside Berry Head, we hauled up the first specimen ever observed of that exquisite creature, the diadem anemone, Bunodes coronata; its orange-scarlet body clasping the whorls of a living Turritella shell, while it held in the air its purple parapet crowned with snow-white spiky tentacles.

Was this the specimen that Henry used in making the illustration for his important work Actinologia Britannica (shown below)? This is how Henry describes his discovery of these sea anemones (since re-named Hormathia coronata [3]) [4]:

This fine species first occurred to myself when dredging off Berry Head [seen in the far distance in the photograph below], in about 20 fathoms, in August 1858. Three or four specimens came up in about the same number of hauls. In every case the animal was adherent to the shell of the living Turritella terebra, a mollusk which is so abundant there that the dredge comes up half filled with it. The base of the Bunodes clasps the long turreted shell, nearly enveloping it when adult, only the apex and the mouth of the shell being exposed.

It is not unusual for sea anemones of some species to associate with the shells of living snails and the relationship appears to be mutualistic – the anemone being moved around and the mollusc gaining protection. No doubt, Charles and Henry were thrilled not only with the capture of Bunodes, but with the abundance of Turritella.

Perhaps you don’t have the same level of enthusiasm for sea anemones and snails, but can appreciate the enthusiasm of others at a time when there were many discoveries to be made? Although not a good sailor, Henry made trips by boat because he was very curious about all marine creatures not just those of the shore, which was his usual haunt and where he collected many specimens to be returned to his aquarium tanks in Sandhurst, his home in St Marychurch, Torquay. Edmund describes his appearance when out collecting [2] and I used this quote in an earlier blog post, in which I contrasted the decorum, and modesty of dress, required by women collectors [5]:

Even as a little child I was conscious that my father’s appearance on these excursions was eccentric. He had a penchant for an enormous felt hat, which had once been black, but was now grey and rusty with age and salt. For some reason or other, he seldom could be persuaded to wear clothes of such a light colour and material as other sportsmen affect. Black broadcloth, reduced to an extreme seediness, and cut in ancient forms, was the favourite attire for the shore, and after being soaked many times, and dried in the sun on his somewhat portly person, it grew to look as if it might have been bequeathed to him by some ancient missionary long marooned, with no other garments, upon a coral island. His ample boots, reaching to mid-thigh, completed his professional garb, and when he was seen, in full sunlight, skimming the rising tide upon the sands, he might have been easily mistaken for a superannuated working shrimper.

What a lovely description – and how nice to have it to complement the image of formal photographs (see below, for example). I can easily visualise Henry busying himself around the coast, completely absorbed in his work and caring little about appearances. Maybe that’s why he is a hero of mine, just as he was for Charles Kingsley?

[2] Edmund Gosse (1896) The Naturalist of the Sea-shore: The Life of Philip Henry Gosse. London, William Heinemann.

[4] Philip Henry Gosse (1860) Actinologia Britannica: A history of the British sea-anemones and madrepores. London, John Van Voorst.