Monday, 16 June 2014

Mermen and mermaids

Creatures with a human torso and a fish tail have appeared in the folklore and mythology of many cultures. 1 We know them as mermen and mermaids and examples became a popular feature of travelling shows and museums, Henry Gosse describing his great disappointment, as a boy, to discover the advertised mermaid was “a shrivelled and blackened little thing which might have been moulded in mud for aught I could see”. 1 It must have looked a little like the specimen shown below.

Frank Buckland, like Gosse an eminent writer and lecturer on Natural History, describes the body of merman he saw exhibited in London: 2

In the back parlour of the White Hart, Vine-court, Spitalfields, high and dry upon a deal board, lay this wonderful object - hideous enough to excite the wonder of the credulous, and curious enough to afford a treat to the naturalist. Such a thing as a merman or mermaid of course never really existed; I was therefore most anxious to examine its composition, which, by the kindness of the landlady (a remarkably civil woman), who removed the glass that covered her treasure, I was enabled to do. The creature (a gentleman, not a lady specimen of the tribe) was from three to four feet long. The upper part of its body was composed of the head, arms and trunk of a monkey, and the lower part of a fish, which appeared to me to be a common hake; and the head was really a wonderful composition: the parchment-like hideous ears stood well forward, the skin of the nose when soft had been moulded into a decided specimen of “the snub,” the forehead was wrinkled into a frown, and the mouth “grinned a ghastly grin;” the curled lips partly concealed a row of teeth, which in the upper jaw were of conical form and sharp-pointed, taken probably from the head of a hake, whose body formed the lower part of our specimen. the lower jaw contained these fish’s teeth, but conspicuously in front was inserted a human incisor or front tooth, and a vacant cavity showed that there once had been a pair of them. These were probably placed there to show the “real human nature” of the monster. The head had once been covered with hair; but visitors, anxious to obtain a lock of a merman’s hair, had so plucked his unfortunate wig that only a few scattered hairs remained: the relic-seekers are now, therefore, ignorantly treasuring in their cabinets [of curiosities] hairs from the pate of an old red monkey.

Buckland also examined a mermaid, about “half the size of her partner”. It, too, was formed from a monkey and a fish, but this time with glass doll’s eyes rather than the leather ones of the merman, that had pupils marked in black ink.

The popularity of such exhibits waned in the mid-Nineteenth Century and Buckland comments “The good folks of England are getting every year more and more educated, and mermaids do not take so well now as formerly..”. 2 The legendary P. T. Barnum advertised the mermaid in his museum with a highly imaginative painting to attract in customers. Of course, he knew the exhibit was not a mermaid and “Mr Barnum confessed that he did not pursue his studies in Natural History too far, or he might learn too much.” 2 Barnum justified the confidence trick by making no extra charge and there were many other things for visitors to see. He was a showman after all.

Any Natural Historian would see immediately that these exhibited mermen and mermaids were manufactured, yet reports of these creatures in their natural environment have been made by generations of sailors. These may have been sightings of sea mammals, especially manatees (left, below) and dugongs (right, below). One can only conclude that they were distant sightings to merit the belief that they were mermen or mermaids, or perhaps the sailors had been too long at sea and their imaginations had become overdeveloped?

Although no-one can believe in their existence in the real world, mermaids have had a lasting appeal in fiction, film and other media. After all, they come from another world and thus fit into the niche also occupied by angels, fairies and dragons. The best known story is The Little Mermaid by H C Andersen 3 and this formed the basis for the Disney film of the same name. Andersen describes how mermaids lived at the bottom of the ocean and had a class system, with at least one Royal Family that had six Princesses:

The whole day long they used to play in the palace, down in the great halls where live flowers grew on the walls. Whenever the high amber windows were thrown open the fish would swim in, just as swallows dart into our rooms when we open the windows. But these fish, now, would swim right up to the little princesses to eat out of their hands and let themselves be petted.. .. Each little princess had her own small garden plot, where she could dig and plant whatever she liked..

The story continues by describing how the princesses were allowed to swim to the surface of the ocean for the first time on their fifteenth birthday, reporting back on what each had seen. The youngest princess heard all the amazing descriptions, but had to wait and wait for her turn. When the day came and she arrived at the surface, she saw a handsome prince and rescued him from drowning after he became unconscious. The mermaid princess wanted to marry the prince, not only for love, but also to acquire immortality of the soul, as this was a feature of humans that mermaids lacked, but which could be acquired through marriage. The transformation from fish tail into “props” (legs) required a special potion prepared by an underwater witch - who improbably boiled the ingredients in “a caldron over the flames”. 3 The famous statue of the Little Mermaid in Copenhagen celebrates the transition to props from the fish tail and that explains why it appears like a nude of the period, with the outline of the tail barely visible. In the Disney film, which uses only superficial features of the complex story told by Andersen, the youngest princess appears as a mermaid Barbie Doll, with what appears to be a pull-on lower fish section and discretion maintained by having a bikini top.

One’s rational side finds all this a bit much, but the mermaids and mermen in museums, side shows and literature are very obviously fantasy creatures and we can all enjoy that. In a wider context, there must be other imaginary things that we take to be real, but it is not always easy to see that this is so. Hopefully, Natural Historians are better able to differentiate the two, just as Barnum intimated.

1 Philip Henry Gosse (1861) The Romance of Natural History, Second Series. London, James Nisbet and Co..
2 Francis T Buckland (1860) Curiosities of Natural History Second Series. New York, Rudd & Carlton.
3 Hans Christian Andersen (1837) Eventyr, fortalte for BΓΈrn.

Wednesday, 4 June 2014

Why Drosophila is so interesting

We had to choose four topics to study in the final year of my Zoology degree. I took classes in Entomology, Crop Protection, Limnology and Genetics and the first three represented my main interests at the time. Genetics was added because I thought it would be useful to know something of this developing branch of Biology. It was 1967, and a current student of Genetics would barely recognise the subject matter of our course. There was little on genomes and nothing on the techniques that are now commonplace in Molecular Genetics. Our practical classes involved, among other things, making crosses between fruit flies (Drosophila melanogaster) and then counting each of the resulting categories of eye colour etc. in the following week. Although this was fun, I found myself being as intrigued by the larvae and pupae that were in the growth medium as I was in the adult flies.

Fruit flies emerge from a puparium (see below), the hardened skin of the last larval stage, in which pupation and metamorphosis occur. This re-organisation always amazes me, in the way it allows such different life styles for the flying adult and the crawling larva. Indeed, the evolution of a pupal stage allowed for the selection of these quite different body types and the use of the last larval skin shows economy of materials, as no other outer covering is required. Interestingly, the puparium splits at the same place in all individuals to allow the adult fly to escape and that adds to my sense of amazement. 

Fruit fly larvae are maggots (in colloquial language), and are remarkably similar in form to those of other, related, flies. We are all familiar with the maggots produced by house flies and blow flies and some will have come across the larvae of flesh flies (see below). Maggots crawl using muscle contractions along the body, aided by raised ridges that run transversely, and the contractions allow them to burrow through substrata. They are aided in their burrowing by being “pointed”, as this allows pressure to be exerted at the forward end of the animal, and they feed as they go, loosening the material in front. The larval head is much reduced and maggots tear at fruit or flesh using two mouth hooks that are extended and contracted, rasping away at whatever medium they are moving through. Food is broken up into a semi-liquid form that can be easily ingested, with saliva helping in this process.

Although those enjoying coarse fishing have a fondness for maggots as bait, most people (even Creationists!) find them unpleasant. This aversion stems both from their movement and the locations favoured by egg-laying adults - we have all encountered blow fly maggots in our dustbins or seen them moving over the rotting flesh of dead animals. The latter are of value to Forensic Entomologists, who can provide accurate estimates of the time of death by looking at the age of maggots, and the succession of various species, but, even these larvae are not looked upon with much pleasure. However, they are excellent examples of a highly successful natural design and their resistant cuticle makes them difficult to kill, as anyone pouring pest-control chemicals on to a domestic infestation will agree. Perhaps more people will appreciate maggots when they realise just how effective they are in wound cleaning? All the life stages are excellent examples of the wondrous powers of evolution in the selection of genetic mutations.

That brings us back to Genetics and the use of Drosophila in research. The fruit fly has become a very popular “model organism” and it has been used to investigate many facets of gene expression, one of the most recent being in the genetics of intelligence. 1 Modern Biology is characterised by a deterministic approach based on knowing the genome of a small number of organisms, and trying to find out which gene, or combinations of genes, control which processes. Underlying this is the idea that humans share genes with other organisms so that we can gain insights into the working of humans as a result. Many Biologists have become so obsessed with the anthropocentric approach that they ignore the Natural History of organisms and that is a pity. We know that Drosophila larvae and pupae are fascinating in their design and evolution, but who would have thought that there are Drosophila larvae living as predators on other invertebrates in African streams? 2 One presumes that the ancient ancestors of these flies were living in fruit that fell into water and the resistant cuticle of the larvae, their rasping mouth hooks, and their crawling and burrowing ability were excellent pre-adaptations for becoming an aquatic predator. Now that’s really interesting, isn’t it?

2 L.Tsacas and R.H.L.Disney (1974) Two new African species of Drosophila (Diptera, Drosophilidae) whose larvae feed on Simulium larvae (Dipt., Simuliidae). Tropenmedizin und Parasitologie 25: 360-377.