Dr KARL SHUKER

Zoologist, media consultant, and science writer, Dr Karl Shuker is also one of the best known cryptozoologists in the world. He is the author of such seminal works as Mystery Cats of the World (1989), The Lost Ark: New and Rediscovered Animals of the 20th Century (1993; greatly expanded in 2012 as The Encyclopaedia of New and Rediscovered Animals), Dragons: A Natural History (1995), In Search of Prehistoric Survivors (1995), The Unexplained (1996), From Flying Toads To Snakes With Wings (1997), Mysteries of Planet Earth (1999), The Hidden Powers of Animals (2001), The Beasts That Hide From Man (2003), Extraordinary Animals Revisited (2007), Dr Shuker's Casebook (2008), Karl Shuker's Alien Zoo: From the Pages of Fortean Times (2010), Cats of Magic, Mythology, and Mystery (2012), Mirabilis: A Carnival of Cryptozoology and Unnatural History (2013), Dragons in Zoology, Cryptozoology, and Culture (2013), The Menagerie of Marvels (2014), A Manifestation of Monsters (2015), Here's Nessie! (2016), and what is widely considered to be his cryptozoological magnum opus, Still In Search Of Prehistoric Survivors (2016) - plus, very excitingly, his four long-awaited, much-requested ShukerNature blog books (2019-2024).

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Showing posts with label Mysteries of Planet Earth. Show all posts
Showing posts with label Mysteries of Planet Earth. Show all posts

Friday, 7 August 2020

A TRIO OF MEDITERRANEAN MYSTERY SNAKES


A horned viper – the identity of Tunisia's tantalizing taguerga? (public domain)

Many mystery serpents have been reported from remote, little-explored, inaccessible and/or inhospitable regions of the world – but not all. Down through the ages, a number of mysterious, unidentified forms have also been documented from various countries and islands lying on either side of the Mediterranean Sea, including the following thought-provoking threesome.


THE COLOVIA – A MEDITERRANEAN MEGA-SNAKE?

In various of his writings, veteran cryptozoologist Dr Bernard Heuvelmans referred to the alleged presence in the Mediterranean provinces within France, Spain, northern Italy, and Greece of an unidentified snake claimed by observers to be 9-12 ft long (and occasionally ever longer).

Other mystery beast investigators have also reported this serpentine enigma, which is often said to be dark green in colour, and in Italy is referred to as the colovia. One such snake was actually responsible for a traffic accident when it unexpectedly crossed a busy road near Chinchilla de Monte Aragón, in Spain's Albicete Province, on 22 July 1969. Back in December 1933, a colovia was tracked down and killed in a marsh close to the Sicilian city of Syracuse, but its carcase was not preserved.

Eastern Montpellier snake (Barbod Safaei/released into the public domain)

If we assume that the colovia's dimensions may well have been somewhat exaggerated or over-estimated by eyewitnesses, a plausible identity for it is the Montpellier snake Malpolon monspessulanus. Named after a city in southern France, this mildly-venomous rear-fanged colubrid is common through much of the Mediterranean basin. It is quite variable in colour, from dark grey to olive green, and can grow up to 8.5 ft long, possibly longer in exceptional specimens. Its presence has not been confirmed in Sicily nor anywhere in mainland Greece (its eastern subspecies, M. m. insignitus, deemed a separate species by some workers, occurs on a number of Greek islands, as well as on Cyprus), but these areas are certainly compatible with its survival.

So perhaps reports from there of unidentified colovia-type mystery snakes indicate that the Montpellier snake's distribution range within Europe's Mediterranean lands is even greater than presently recognised.


THE VIRGIN MARY SNAKES OF CEPHALONIA

Cephalonia is the largest of western Greece's seven principal Ionian islands, lying in the Ionian Sea - which is in turn an elongated embayment of the Mediterranean Sea. Every year on 16 August – known here as the Feast of the Assumption of Our Lady (the Virgin Mary) – the small southeastern village of Markopoulo hosts a Marian celebration, but its most famous, and mystifying, attendants are not of the human variety. Virtually every year for more than two centuries, during the fortnight leading up to this festival considerable numbers of snakes mysteriously appear at the foot of the Old Bell Steeple by Markopoulo's Church of Our Lady, and just as mysteriously vanish again when the festival ends.

Their unusual behaviour has earned these serpents the local names of 'Virgin Mary snakes' and 'Our Lady's snakes'. This religious association is heightened by the small black cruciform mark that they allegedly bear on their heads and also at the forked tip of their tongues. They all appear to belong to the same single species, but which one this is does not seem to have been formally ascertained by herpetologists. However, they have attracted the attention and interest of several correspondents of mine, as first revealed in my book Mysteries of Planet Earth and now in greater detail here.

Four-striped snake (public domain)

According to one of them, Cephalonia chronicler Victor J. Kean, these snakes are non-venomous, are said to have "skin like silk", and are popularly believed by the villagers to possess thaumaturgic powers. One plausible candidate is the four-striped snake Elaphe quatuorlineata, a non-venomous constricting species of colubrid that occurs on Cephalonia, and whose head can bear a variety of dark markings, especially in its bolder-marked juvenile form. Moreover, herpetologist Dr Klaus-Dieter Schulz has pointed out that this species is known to be associated with Christian traditions elsewhere in southern Europe, including the annual snake procession at Cucullo, Italy, in honour of St Dominic.

When he paid a visit to Markopoulo on 16 August one year during the mid-1990s, Alistair Underwood from Preston, in Lancashire, England, observed the Virgin Mary snakes congregating outside the Church of Our Lady, where they were freely handled by the local villagers, who even draped them fearlessly around their necks. The villagers also allowed them to enter the church, and to make their way towards a large silver icon of the Virgin Mary. Some websites that I have seen in which this ceremony is described (e.g. here) claim that the species in question is the European cat snake Telescopus fallax. This is a colubrid that is indeed native to Cephalonia and several other Greek islands too. Moreover, it is actually venomous, but because it is rear-fanged its venom is rarely injected in defensive biting, so it is not deemed to be a threat to humans.

19th-Century engraving of a European cat snake (public domain)

According to Cephalonian researcher Spyros Tassis Bekatoros, the only years in which the Virgin Mary snakes have not made an appearance at Markopoulo's Marian festival are those spanning the German occupation of Cephalonia in World War II (during which period the occupying forces may have banned the Marian festival after learning about its ophidian participants), and the year 1953, when much of the island was devastated by an earthquake. This latter information may hold clues concerning the link between these snakes and the festival.

Although snakes are generally deaf to airborne vibrations (i.e. sounds), they respond very readily to groundborne ones. Consequently, Alistair Underwood suggested that the increased human activity and its associated groundborne vibrations during the Marian festival and its preceding preparations may explain the coincident appearance of the Virgin Mary snakes during those periods. If so, then the exceptional terrestrial reverberations that occurred during the 1953 earthquake would have greatly disturbed the snakes, disrupting their normal behaviour and obscuring the lesser vibrational stimuli emanating from human activity at the Marian festival that year.


THE HORNED TAGUERGA OF TUNISIA

In the first volume of his scholarly publication Exploration Scientifique de la Tunisie (1884), French archaeologist and diplomat Charles Tissot reported the alleged occurrence of a very sizeable Tunisian mystery snake known as the taguerga, which supposedly bears a pair of short but sharp horns on its head. Vehemently believed by the locals to be extremely venomous, this greatly-feared reptile is said to be as thick as a man's thigh, and to attain a total length of 7-12 ft. It reputedly frequents the mountains of southern Tunisia's Sahara region.

Horned viper (Patrick Jean, released into the public domain)

The locals consider taguergas to be specimens of the common horned viper Cerastes cerastes (a species that is indeed native to Tunisia) but which have attained an exceptionally venerable age and have continued growing throughout this abnormally-extended period of time, thus explaining their great size, as horned vipers do not normally exceed 3 ft long. Conversely, Dr Bernard Heuvelmans speculated that it may be a puff adder Bitis arietans, which sometimes bears horn-like scales upon its head. However, this species only rarely exceeds 5 ft long, and is not known to occur in Tunisia, although it is recorded from Morocco.



For an additional Mediterranean mystery snake, please click here to access my ShukerNature blog article investigating the possible taxonomic identity of St Paul's mystifying Maltese viper.

St Paul bitten by Malta's alleged viper, engraving by Hendrik Goltzius, c1580 (public domain)




Tuesday, 6 November 2018

BLACK-AND-WHITE ...AND WEIRD ALL OVER - SOLVING THE MYSTERY OF THE STRIPED MANTA RAYS


Magnificent painting portraying William Beebe's striped manta ray (© William M. Rebsamen)

In 1999, my book Mysteries of Planet Earth became the first cryptozoologically-oriented book to include a specific section on what must surely be one of the most strikingly beautiful mystery beasts ever reported, and its coverage was greatly enhanced by the inclusion of a spectacular full-colour painting of this animal - another first for it - prepared specially for my book by renowned cryptozoological artist William M. Rebsamen (and which also opens this present ShukerNature blog article). Neither of us realised at that time, however, that only a few years later I would actually witness just such an animal, and in a wholly unexpected manner. The following article – the most detailed that I have ever prepared on this particular subject and constituting a ShukerNature exclusive – contains not only all of the information that I included in my 1999 book but also various additional cases uncovered by me since then, including my own afore-mentioned observation. So where better to begin it than with that observation – and here it is.

On 20 July 2005, I was sitting in front of the television at home in the UK, flicking idly between channels, when I happened to click onto Channel 5, and within a few seconds beheld an extraordinary sight. The programme being screened was a documentary entitled 'Whale Shark: Journey of the Biggest Fish in the World'. However, the fish that I was staring at in amazement was anything but a whale shark. It was a giant manta ray Manta birostris - a huge, superficially nightmarish beast popularly dubbed a devil-fish (see also here) due to its mouth's pair of demonic, horn-resembling, laterally-sited cephalic fins, and its huge batwing-like pectoral fins, uniformly dark on top, white below...except that this particular manta's pectorals were most definitely not uniformly dark on top. Instead, they were dramatically adorned by a longitudinal series of white v-shaped chevrons, and also sported pure white wing tips. This spectacular vision soared gracefully through its underwater domain for a few moments before the camera moved on to other subaqueous delights, and it did not appear again.

Not having tuned in to this programme from the beginning, I had no idea where the striped manta had been filmed, but the very next section of the documentary stated that the whale shark star of the show had now reached the Mozambique Channel, apparently having travelled there from the Seychelles region of the Indian Ocean. So this may have been where the manta footage had been shot.

A typical, non-striped specimen of the giant manta ray, as depicted in an 18th/19th-Century illustration from Iconographia Zoologica (public domain)

What made this serendipitous sighting so notable was that for a great many years (right up to the time when I viewed the above-cited TV programme, in fact), mainstream zoology had tended not to recognise the existence of mantas other than the mundanely standard dark-dorsal, pale-ventral version. Yet there on screen was positive proof that at least one manta of a decidedly more flamboyant variety was indeed real. Nor was it unique. Several other specimens have been documented down through the decades, exhibiting a range of patterns, and spied in many different oceanic localities.

The earliest one that I have on record, and which remains the most famous (it was the subject of William Rebsamen's magnificent painting), was witnessed on 27 April 1923 by American naturalist William Beebe and several others while aboard his expedition vessel Noma, as it approached Tower Island in the Pacific Ocean's Galapagos archipelago. The manta ray briefly struck the side of the vessel and then sped swiftly away along the surface, providing its observers with an excellent view. According to Beebe, who later sketched it:

From tip to tip of wings it was at least ten feet, of somewhat the usual manta or devil-fish shape, except that the wings were not noticeably concave behind, and the lateral angles were not acute. The cephalic horn-like structures were conspicuous and more straight than incurved. In general the back was dark brown, faintly mottled, while the most conspicuous character was a pair of broad, pure white bands extending halfway down the back from each side of the head. The wing tips also shaded abruptly into pure white.

Documenting this dorsally-bicoloured manta in his book Galapagos: World's End (1924), Beebe considered that it may represent an unknown species.

Beebe's sketch of the striped manta ray observed by him off the Galapagos archipelago's Tower Island in 1923 (public domain)

In Vol. 12 of the now-defunct International Society of Cryptozoology's scientific journal Cryptozoology (covering the period 1993-1996), German researcher Gunter G. Sehm's paper on striped manta rays surveyed some other specimens. In 1924, fr example, a small manta was harpooned off the shore reef at Kiribati's Fanning Island (renamed Tabuaeran). Its dorsal surface was blue-black but also bore two large ash-coloured v-shaped chevrons that spanned the entire dorsum from left pectoral edge to right. In 1934 this specimen was deemed a new species and dubbed Manta fowleri, but its separate taxonomic status is no longer recognised.

In 1975, British Museum ichthyologist Alwyne Wheeler's book Fishes of the World contained a colour photograph of a manta ray that appeared to have some white striping on its right shoulder, although few details can be discerned because the picture had been taken side-on. A year later, a book by Pierre Fourmanoir and Pierre Laboute detailing the fishes native to the waters around New Caledonia and the New Hebrides included a colour photo of a manta ornately adorned with dorsal white banding and cephalic fins. In his paper, Sehm also included three hitherto-unpublished stills from a 30-second footage of film showing a manta with a pair of striking, laterally-sited, v-shaped dorsal markings, filmed off the coast of Mexico's Baja California by Sigurd Tesche, which had been broadcast by German TV on 28 December 1989 within a programme entitled 'Sharks: Hunters of the Seas'.

Correspondent Alan Pringle contacted me shortly after watching, on 7 November 1999, a BBC1 television programme 'Holiday Guide to Australia', to inform me that it had contained a snippet of film depicting a manta with two converging longitudinal dorsal white bands, filmed from above by a helicopter, as it swam above a reef in Australia's Great Barrier Reef.

A striped giant manta ray at Hin Daeng, Thailand, on 30 November 2005 (© Jon Hanson/Wikipedia – CC BY-SA 2.0 licence)

I learnt from fellow crypto-enthusiast Matt Bille that on 19 September 2003, yet another striped manta made an unexpected television appearance, this time in the American reality game show 'Survivor', when a manta ray sporting a very prominent pair of white shoulder markings, resembling filled-in triangles along the body, cruised fleetingly just under the clear waters off Panama's Pacific coast.

Not long after my own television sighting in July 2005, I was informed of two separate webpages each containing a colour photograph of a striped manta. One of these, which still appears here, shows a manta with symmetrical lateral chevrons resembling those of the Baja California individual, but it also has white rings around its cephalic fins, a pale patch at the dorsal tip of its left pectoral fin (its right cannot be seen dorsally), and what looks like a white dorsal tail surface. More photos of it have since appeared on Wikipedia and elsewhere online, confirming that it does have a white patch at the dorsal tip of its right pectoral fin too. It was photographed at Hin Daeng, off Thailand.

The other page (no longer directly online at http://www.accessnoaa.noaa.gov/images/monitor1.jpg but still accessible here - thanks to the Wayback Machine Internet Archive) – in a website run by America's National Oceanic and Atmospheric Administration (NOAA) - showed an ornately-marked specimen with very extensive white wing tips linked posteriorly by a pair of white converging arcs, as well as white cephalic fins. No details of where this photo was taken were given.

The striped manta ray photograph formerly directly visible online in America's NOAA site (© NOAA – reproduced here on a strictly non-commercial Fair Use basis for educational and review purposes only)

In short, a diverse spectrum of striped mantas is on record, with no two alike, but collectively confirming that dorsally bicoloured individuals do indeed exist. So how can they be explained? Interestingly, some of them, notably Beebe's specimen, the Fanning Island manta, and the Baja California example, have conspicuously shorter-than-typical tails, and also the shape of their pectorals do not exhibit such marked convexity of the front edge and concavity of the trailing edge as those of 'normal' mantas do, leading Sehm to consider the possibility that these represent a separate taxonomic form. Equally, however, sometimes genes linked to colour or body pattern also influence the size or shape of an individual (pleiotropic genes), so there is no guarantee that these morphological differences have independent significance.

Moreover, it is known that attacks by other fishes can leave white marks on the dark dorsal surface of a manta. In fact, its dark pigment can even be removed merely by rubbing the surface, creating pale patches. And the elasmodiver website's manta page states that the wing tips often fade to white. Worth noting, incidentally, is that back in the early 2000s this latter site was one of the very few mainstream sources that openly acknowledged the existence of striped mantas, stating at that time: "Dorsum black or dark often with symmetrical white patches forming a chevron across the shoulders".

Intriguingly, Sehm attempted to explain away the white wing tips of Beebe's specimen as an illusion, claiming that what Beebe and his colleagues saw was the white undersurface of the wing tips upraised, fooling the observers into thinking that the dorsal wing tips were white. However, I do not believe this interpretation - the NOAA website's manta unequivocally possesses white dorsal wing tips, as did the specimen that I watched in the whale shark film. Instead, judging from the elasmodiver website's comments, it may be that white-tipped mantas are aged specimens. However, so precise is the symmetry of the white markings on all specimens of striped manta, whether they be wing tip markings, shoulder markings, or chevrons, that this seems unlikely - as do, for the same reason, explanations invoking injury or rubbing as the source of such markings.

A striped manta ray at Hin Muang, Thailand on 30 November 2005 (© Jon Hanson/Wikipedia – CC BY-SA 2.0 licence)

In 2005, within a Fortean Times article of mine devoted to these mystery mantas, I expressed the view is that a mutant gene allele was most probably responsible, engendering on rare occasions these stunning and sometimes quite elaborate patterns in mantas - analogous, perhaps, to black-and-white specimens of blackbirds, black bears, crows, and other normally monochromatic species, and creating an additional vision of wonder and mystery amid the breathtaking splendour present beneath the surface of our planet's mighty seas.

Sure enough, thanks to observations and photographs taken of many additional specimens since then, the existence of striped manta specimens is nowadays not only universally accepted among ichthyologists but also, far from constituting a separate species, is deemed to be nothing more than an expression of individual non-taxonomic variation within the long-recognised giant manta species Manta birostris.

Unrelated to such considerations but still worth noting, however, is that in 2009, a second, somewhat smaller, and non-migratory manta ray species, the reef manta M. alfredi, was officially distinguished, named, and formally described – see my Encyclopaedia of New and Rediscovered Animals, 2012, for more details.

A reef manta ray at Manta Alley, near Komodo, Indonesia, in September 2010 (© Alexander Vasenin/Wikipedia – CC BY-SA 3.0 licence)

But this is not all. In autumn 2014, a mainstream ichthyological discovery was made public via a scientific paper that revealed an exceedingly significant but hitherto entirely unsuspected aspect concerning the true nature of striped mantas. Ironically, however, this crucial find has attracted relatively little attention, especially in cryptozoological circles. Indeed, as far as I am aware, the following documentation of it by me is the first time that this remarkable discovery has ever been referred to in such a capacity, even though it holds the key to these distinctive fishes' very existence.

Published by the Biological Journal of the Linnean Society on 1 September 2014, the paper in question (click here to read it in its entirety) was authored by Csilla Ari, from the University of South Florida's Hyperbaric Biomedical Research Laboratory, and revealed for the very first time that giant manta rays possess the ability to change colour and pattern at will. Ari's study showed that a manta's typical (or, as termed in the study, its baseline) colouration state (i.e. its dark dorsal surface) can change rapidly at feeding times, or if it encounters another manta ray in close proximity to itself, or during intense social interaction between itself and another manta ray. And the precise nature of this colour change is a very noticeable increase in the brightness of hitherto pale, inconspicuous shoulder and pectoral wing tip markings.

In other words, when faced with any of the situations listed above, a typical dorsally-dark manta can transform directly into a striped manta!

A striped manta ray encountered at South Point, Pulau Sipadan, off the Malaysian state of Sabah on Borneo, in February 2010 (© Bernard Dupont/Wikipedia – CC BY-SA 2.0 licence)

Here is the principal Results paragraph excerpted from Ari's paper, detailing this extraordinary manta metamorphosis with reference to various 'before' and 'after' photographs of the mantas (these photos can be viewed directly if the paper is accessed using the above link):

Captive manta rays were observed to undergo rapid changes (within a few minutes) in their body coloration. Specifically, white markings appeared and changed intensity on certain body regions (Fig. 1, 2, 3, 4; the two most representative specimens from each species are shown). The intensity of the white markings would increase rapidly to the ‘intense coloration state’ (Fig. 1D, E, F, G, H, 2D, E, F) more times during the day within a few minutes, and then return to the normal ‘baseline coloration state’. Changes in coloration were observed to occur in temporal proximity to a variety of situations, including at feeding times (Fig. 1H), whenever a new manta ray was introduced to the tank, and during intense social interaction between the two manta rays (Fig. 1G). Feeding occurred twice a day and the rapid coloration changes started shortly (5–10 min) before each feeding on both specimens. The ‘intense coloration state’ was most intense during feeding and slowly returned to the ‘baseline coloration state’ over a period of 20–30 min after the end of the feedings. In addition, rapid coloration changes were observed in association with intense social interaction; for example, when Manta 2 was introduced into the tank or when mantas were chasing each other rapidly and closely, which appeared to comprise courtship behaviour.

In short, the striped manta state was not even a permanent one. Consequently, it would appear that in most if not all cases, such mantas that have been reported and photographed in the past were nothing more than normal mantas exhibiting the temporary pattern and colour transformation ability that had been discovered for their species by Ari. (Incidentally, Ari also revealed that reef mantas possess this same ability.)

The mystery of the striped mantas is a mystery no longer. True, there may be occasional specimens that do exhibit such markings on a permanent basis as an expression of individual non-taxonomic variation, but in most cases such markings would seem to be merely a temporary feature, induced on a non-permanent basis by various fluctuating external stimuli.

Finally: even though we now know the secret of the striped mantas, it is still thrilling when one of these spectacular creatures turns up unexpectedly – and that is precisely what happened to me a second time just last night. I had been watching the 2016 Disney cartoon film Moana, whose storyline was inspired by traditional Polynesian mythology and featured the famous demi-god Maui, when suddenly, in a split-second segment right at the end of the film, an animated striped manta sporting a vivid pair of white shoulder bars and pectoral wing tips soared majestically through the water just beneath the surface. A fitting finale, assuredly, for a movie of magic and mythology to feature a maritime denizen so long associated with mystery and mystification.

My very own striped manta ray – a model of one that I purchased at London Zoo in September 2014 (© Dr Karl Shuker/London Zoo)




Saturday, 3 June 2017

THE LIGHTBULB LIZARD OF BENJAMIN SHREVE - ILLUMINATING A HERPETOLOGICAL CONTROVERSY FROM TRINIDAD


Artistic representation of the Trinidad luminous lizard's possible appearance when glowing, as based upon Ivan T. Sanderson's claim (© Philippa Foster)

Among the fishes and several different taxonomic groups of invertebrate (including comb jellies, cnidarians, molluscs, insects, centipedes, millipedes, crustaceans, and annelid worms) are many bioluminescent species. That is, living creatures which actively carry out chemical processes to produce and emit light.

Officially, however, there are no bioluminescent species among the terrestrial vertebrates - but claims have been made that there may in fact be a notable exception of the reptilian kind.

I first learnt about, and then duly investigated, this fascinating yet surprisingly little-known case back in the mid-1990s, and here is what I uncovered at that time, followed by the extraordinary revelations that have occurred since then – yielding in this present ShukerNature blog article of mine the most comprehensive account ever published online.

A selection of fully-confirmed bioluminescent creatures depicted in a vintage illustration from 1890 (public domain)

In March 1937, during an animal collecting trip to the West Indies, American zoologist and cryptozoologist Ivan T. Sanderson visited Mount Aripo (aka El Cerro del Aripo), at 3,084 ft high the loftiest peak in Trinidad and part of this island's Northern Range. He had been capturing some freshwater crabs in a series of dark subterranean pools there when he suddenly spied a faint light in a crevice beneath a ledge. The light promptly went out, but Sanderson was curious to discover its source, so he flashed his torch into the crevice - and was most surprised to find a small lizard.

Attempting to coax it into his net, Sanderson gently tickled the lizard, but instead of running out it turned its head away - and as it did so, Sanderson was very startled to see both of its flanks momentarily lighting up "...like the portholes on a ship". When he finally succeeded in capturing it, this remarkable reptile lit up again, glowing brightly in his hand with a pale greenish hue that Sanderson subsequently likened to the glow produced by the hands and figures of a luminous watch.

As zoologists were previously unaware of any bioluminescent lizards, Sanderson was very thrilled by his discovery, which he documented in his book Caribbean Treasure (1939). Ironically, however, apart from its unique glowing ability the lizard, which was a male, seemed relatively nondescript in general appearance - with a long tail but short legs, a sharply-pointed muzzle, dark brown upperparts, and rosy salmon-pink underparts (turning yellow under its head) surfaced with large rectangular scales of plate-like form.

Ivan T. Sanderson's book Caribbean Treasure (© Viking Press, reproduced here on a strictly non-commercial Fair Use basis only)

Its only distinctive features were its body's lateral eyespots or 'portholes', constituting a series of large circular black blots running from the neck to the groin on both flanks, because each of these blots contained a vivid white bead-like spot. And it was these spots that were the source of the lizard's apparent luminescence, as determined by Sanderson during some basic experiments:

We made it [the lizard] hot and cold, and moist and dry alternately; we blew a loud whistle in its ear, we tickled it, and we subjected it to flashes of bright light...This creature seemed to produce its light in response to sudden emotional disturbance, rather than through actual physical reactions...The loud whistle, sudden winds, and flashes of light greatly agitated our lizard, causing it to switch on its 'portholes'. We noticed that this light was much brighter the first time it was switched on after the animal had been quiescent for a period, and more especially after it had previously been subjected to intense illumination.

Eventually, Sanderson shipped off his amazing little lizard to the British Museum (Natural History) in London, where it was studied in detail by fellow zoologist H.W. Parker. It was found to belong to a species already known to science (indeed, Parker himself had formally named and described it in 1935), but only just. An exceedingly rare member of the tejid (aka tegu) family Teiidae, and normally measuring 11-15 cm long, it was called Proctoporus (=Oreosaurus) shrevei (in honour of the very gifted American amateur herpetologist Benjamin Shreve), and had hitherto been represented in scientific collections only by a single preserved juvenile and one preserved adult female. Sanderson's specimen was therefore the first male of this species to have been brought to scientific attention, and until now no-one had suspected that it may be bioluminescent when alive.

Proctoporus shrevei (copyright holder presently unknown to me despite my having made considerable efforts to discover this; reproduced here on a strictly non-commercial Fair Use basis only)

During his visit to Trinidad, Sanderson collected seven more individuals of this species, and as preserved specimens these too were examined by Parker. In a paper published by the zoological journal of London's Linnaean Society in 1939, Parker revealed that it was sexually dimorphic, with only the males sporting the distinctive 'porthole' markings (a further reason why no bioluminescence had been reported from the specimens procured prior to Sanderson's), and that in every porthole the epidermis of the white bead at the centre was less than half the thickness of the epidermis of the black ring surrounding it. In addition, the white bead's epidermis was transparent, lacking any form of pigment. In other words, each porthole literally constituted a black-edged circular window.

How the portholes functioned, however, remained a mystery, because Parker found no associated nerve endings or an increased blood supply, thereby eliminating any likelihood that they were directly connected with the sensory or circulatory systems. Nor did he find any ducts connecting them with the exterior, or any complex lenses or reflecting structures.

Whatever they were, therefore, these portholes were clearly very simple in structure, and Parker offered three possible explanations for their luminosity. In life, the portholes may contain some substance that either glows when it breaks down (the principle of bioluminescence in various fishes), or glows when exposed to light (as with the paint used in luminous watches). The third option is that the transparent central beads of the portholes are underlain with reflective tissue. (A fourth possibility, that the portholes contain glowing bacteria which create their luminosity, can be rejected, because Parker did not report the presence of any bacteria within them.)

Ivan T. Sanderson as a young man (copyright owner presently unknown to me despite considerable searches made; reproduced here on a strictly non-commercial Fair Use basis only)

Inevitably, the prospect of a luminous lizard duly attracted attention from several other zoologists, who studied specimens of P. shrevei and various related tejids to find out whether any of them really did glow - but none of them did! And so in 1960, reporting at some length in the journal Breviora their own negative findings with P. achlyens from Venezuela and Neusticurus [now Potamites] ecpleopus ocellatus from Peru (both of which possess porthole markings resembling those of P. shrevei), American biologists Drs Willard Roth and Carl Gans rejected Sanderson's claims regarding P. shrevei's bioluminescence.

Yet Sanderson was an extremely experienced field zoologist, and Parker's histological studies convinced him that the portholes were genuine luminous organs. So who was correct? If P. shrevei were the only bioluminescent species, this would of course render worthless any comparative studies with related species. Moreover, at the time of my own initial examination of this case, only one zoologist other than Sanderson had actually investigated luminosity with living P. shrevei specimens, and he may simply not have stimulated them sufficiently for them to light up. (I subsequently found out that this latter zoologist was Prof. Julian S. Kenny – see later.)

My above account presents the situation concerning Trinidad's intriguing 'glowing lizard' that I had uncovered during my mid-1990s investigations. Since then, however, much additional information has come to light (pun intended!), and, as I discovered after unearthing it, this extra data includes some very significant new insights into P. shrevei and its alleged bioluminescent capabilities.

Map of Trinidad, highlighting its Northern Range, where Mt Aripo is (public domain)

First of all, it is nowadays deemed not to be a true tejid, so it is housed within a separate taxonomic family, Gymnophthalmidae, which contains many species. These are sometimes referred to as microtejids, because they are smaller than true tejids. Also, they tend to be quite skink-like in appearance, with certain species possessing reduced limbs.

I was pleased to learn that following further field studies, P. shrevei is no longer considered to be as rare as previously claimed. Indeed, the IUCN officially categorises it as being of Least Concern, and the IUCN Red List website states: "...although the distribution [of this species] is limited (with an extent of occurrence of 210 km2), the population trend appears to be stable, there are no current threats, and it occurs in at least two protected areas".

In addition, the IUCN assigns this species to the genus Riama, although quite a few other authoritative sources checked by me retain it within Proctoporus (so I shall do the same here for text consistency purposes), and refers to it via a very memorable common name that ties in with its supposed abilities – Shreve's lightbulb lizard. But is this name warranted?

Mark O'Shea lecturing at West Midlands Safari Park, England (© Ghaly-Wikipedia – CC BY-SA 3.0 licence)

During my original investigations of Shreve's lightbulb lizard in the mid-1990s, I communicated with the West Midlands Safari Park's internationally-renowned herpetological expert Mark O'Shea, famed not only for his numerous scholarly publications but also for his fascinating TV show O'Shea's Big Adventure in which he travelled the world seeking rare or unusual reptiles and amphibians. Mark was very interested in this mystifying lizard species, and I was delighted when he subsequently visited Trinidad to look for it. His search featured in 'Exotic Island', the tenth episode of his show's first series, screened in 1999.

After arriving in Trinidad, Mark and his camera crew teamed up with Caesar, a local guide, and with Dr Victor Quesnel (named as Quinnel in some reports), a retired Trinidad-based economic botanist who was also a very knowledgeable all-round naturalist (he died in 2014). But before they set off on their arduous trek in the hope of emulating Sanderson's original success in encountering this island's luminous enigma in 1937, they were able to chat with Javrien Capriata (aka Capriata Dickson), who had been Sanderson's guide back then, and was now over 80 years old (Sanderson himself had died in 1973). Happily, Mark's search proved successful too, as the team found two specimens, a male and a female. (Moreover, during a much later expedition in 2008, Dr Quesnel actually rediscovered the specific cave where Sanderson had captured his lizard in 1937 but which had not been found since then; it is now known as Sanderson's Cave.)

These two lizards were duly videoed in a dark room by Mark's cameraman while they were being illuminated artificially and for a time after the artificial illumination had been turned off. The video was then viewed closely to see whether there were any signs of luminescence from them. Not surprisingly, the female lizard did not glow, as it lacked the all-important porthole markings. Conversely, the male did indeed appear to glow for a short time after the illumination had been turned off. Unfortunately, however, it was not possible to determine whether this constituted bona fide glowing from the lizard, or whether it was merely a trick of the light caused by filming and the camera adjusting to the darkness after the illumination had been extinguished.

Ivan T. Sanderson in later years (© Dr Bernard Heuvelmans)

During the first half of the year 2000, I exchanged a series of letters with herpetological specialist Hans E.A. Boos from Port of Spain, Trinidad's capital, who is extremely knowledgeable concerning the reptilian fauna of this island. Needless to say, therefore, one of the subjects that we discussed was P. shrevei and its alleged bioluminescence. Hans was very sceptical about this, and even more so concerning the reliability of Sanderson's eyewitness testimony (it has to be said here that Sanderson was well known for exaggerating claims at times, although this behaviour may have been caused by a brain tumour that developed over time and apparently contributed to his relatively early death, aged just 62).

In one of his letters to me, dated 22 January 2000, Hans revealed that he had kept specimens of this lizard species in captivity for a considerable time but had never seen them light up. He also noted that both Dr Quesnel and Trinidad-based zoologist/newspaper columnist Prof. Julian S. Kenny had attempted to repeat the conditions reported by Sanderson but again had failed to achieve any success in stimulating the lizards to illuminate. In a subsequent letter, dated 14 April 2000, Hans mentioned to me that during the previous evening he'd had dinner with Dr Quesnel and had discussed fully with him the subject of P. shrevei. Quesnel had announced that he planned to try to collect a couple more specimens and this time arrange for high-quality histological sections to be prepared, with the tissues of the portholes properly fixed, in the hope of deducing something new regarding their supposed luminosity.

On 3 October 2004, the Trinidad Express newspaper published a short article written by Prof. Kenny that expanded upon Hans's comment concerning his investigations of Shreve's perplexing little lightbulb lizard. After referring to Sanderson's capture and claims regarding this species, Kenny revealed that American zoologist Prof. E. Newton Harvey (died 1959), a leading authority on bioluminescence, had once asked him to conduct an experiment to confirm his belief that Sanderson's claims were unfounded. The Harvey/Kenny experiment involved injecting some living specimens of P. shrevei with 1:10000, and 1:1000 doses of adrenalin. This treatment had already been shown to trigger light production in bioluminescent fishes, but it did not induce any reaction in the lizards.

Prof. E. Newton Harvey (public domain)

Also in 2004, what is acknowledged to be the defining scientific paper dealing with this contentious species' reputed glowing behaviour was published in the Caribbean Journal of Science. One of its three authors was Dr Quesnel, who revealed that, in fulfilment of his hopes expressed to Hans Boos in 2000, he had indeed succeeded in conducting further field investigations of P. shrevei, in May 2001 and again in May 2002.

Two male specimens were captured in rock crevices near to a cave entrance at the summit of Mount Aripo – i.e. the same general locality as Sanderson's own discovery. After examining them in the field, Quesnel took them to a field station for further investigation, where they were studied under light and dark conditions at different times of the day. Yet no observations, either in the field or at the field station, revealed any light emission from the portholes. The same was true with a third specimen that had been captured and studied previously by Quesnel. Clearly, therefore, they did not appear capable of bona fide bioluminescence, i.e. the active generation of light by living organisms via chemical means.

But what about the prospect that the portholes were highly reflective, or perhaps even phosphorescent? (That is, reflecting incident invisible light as visible light but over a longer time period than in fluorescence and without heat.)

Vintage illustration from 1904 depicting a further selection of known bioluminescent creatures (public domain)

To test this possibility, Quesnel directed high-intensity light from a xenon lamp at the lizards from varying angles. No light was emitted by the lizards, thereby demonstrating that they were not phosphorescent. However, light was readily reflected by their porthole (ocellar) scales. As Quesnel et al. explained in their paper:

...if P. shrevei is observed along the same plane from which light is directed, the normally obvious white ocelli cannot be seen against the reflection from all other scales. But, when viewed from an angle oblique to the light source, the ocelli appear brighter, while surrounding scales show no reflection. By varying the angle of reflected light, an illusion is created that the ocellar scales are intermittently emitting light, thus providing an explanation of Sanderson's original account of the lizard "switch[ing] on its portholes." The illusion produced by the reflective scales also explains recent accounts, as well as Sanderson's description of the white ocelli "remain[ing] plainly discernable in a darkened box when the rest of the animal was invisible." The ocellar scales reflect and intensify ambient light while the darker ground coloration renders the rest of the lizard invisible in a dimly lit environment.

It was also noted that the illusory effect of the reflective porthole scales was enhanced by a varying in intensity of the black pigment surrounding these scales, and that this varying of the black pigment's intensity appeared in turn to be dependent upon the lizards' stress levels - because it became darker when the lizards were first handled, but faded somewhat after several minutes. The black pigment surrounding the porthole scales heightened their reflective effect, making them look a brighter white:

When viewed immediately after handling the lizards, the ocelli appear to pulse or fluctuate in brightness as the surrounding pigment changes intensity. After a quiescent period, the ocelli are still reflective but do not appear as bright as when the surrounding skin pigmentation is darker. Again, this could explain Sanderson's description that light from the lizard "was much brighter the first time it was switched on after the animal had been quiescent for a period of time," and "after one brilliant display... it refused to shine with full brightness." The darker dermal pigmentation, presumably associated with higher stress levels during handling, heightens the reflective appearance of the white ocellar scales. Decreased pigmentation during inactive periods gives the illusion that the lizard is not producing light at full intensity.

In short, these studies appear to have comprehensively refuted Sanderson's claims that Shreve's lightbulb lizard is bioluminescent. Instead:

...the lizard's unique scales act like small parabolic mirrors, reflecting light at oblique angles. The intensity of this reflectivity is, in turn, influenced by the intensity of surrounding dermal pigmentation and by the angle at which a lizard is oriented relative to a light source. Thus, ocellar reflection produces an illusion that light is emitted by P. shrevei at varying intensities, a phenomenon which obviously has confused a number of persons.

Partial view of the Northern Range, Trinidad, whose Mount Aripo is home to Shreve's still-mystifying microtejid (image cropped) (© Sanjiva Persad/Wikipedia – CC BY 2.0 licence)

Even so, one major light-related mystery concerning Shreve's very surprising microtejid still remains unsolved. Namely, why has so remarkable a morphological feature as this lizard's parabolic mirror scales evolved in the first place, and why only in male specimens?

These are questions that the study of Quesnel and his co-workers did not seek to answer, although, as they did point out, P. shrevei is a reclusive nocturnal species that inhabits dark localities and whose behaviour in the wild is unknown – all of which make any attempt at speculation fraught with difficulty. Nevertheless, it occurs to me that in view of their sex-specific and also age-specific occurrence, perhaps these scales' light-reflecting abilities function as a means of visual communication by which adult males attract adult females for mating purposes. An alternative option is that this light-reflection ability is used as a defence mechanism, to startle or ward off potential predators, but if this were true, why do only males possess the necessary scales?

Clearly it is high time that some comprehensive field studies were conducted in relation to this small yet very thought-provoking lizard, neglected by science for far too long, in the hope of finally shedding some much-needed light (in every sense!) upon the currently cryptic purpose(s) of its unique parabolic portholes.


The present ShukerNature blog article is a greatly expanded and fully-updated version of a short account that appears in my book Mysteries of Planet Earth (1999).