Trinidadian Luminous Lizard

No light-emitting lizard has ever been described. That's why the little-known story of Trinidad's bioluminescent lizard is remarkable. It began in March 1937, when hunter and zoologist Ivan T. Sanderson ventured to Mount Aripo in Trinidad. While fishing for crustaceans in the murky underground pools, he noticed a faint light in a crevice beneath a rock ledge. Suddenly, it went out, so Sanderson shone his flashlight and, to his surprise, saw a small lizard. When he tried to capture it, the creature didn't run away. It simply turned its head. Then, astonished, Sanderson saw the lizard's sides glow briefly "like ship's portholes." The phenomenon repeated itself several times. When Sanderson caught the reptile, he noticed the light was bright green, similar to the fluorescent hands of his watch.

Science had never seen a similar case. Sanderson, thrilled by the discovery, described it in his book Caribbean Treasure (1939). The captured male lizard was unremarkable except for its bioluminescence. It had a pointed snout, short limbs, a long tail, a dark brown body, and a salmon-colored belly, fading to yellow at the throat.

Its body was covered with large, rectangular scales. Its only distinguishing feature were circular eyes, or "portholes," on either side of its body—large, round, black spots extending from the nape of its neck to its groin. In the center of each was a white, bead-like spot, the source of a mysterious glow. After conducting preliminary tests, which involved alternating exposure to heat and cold, wet and dry air, gentle tickling, loud whistling, and exposure to bright light, Sanderson concluded that the glow appeared in response to sudden, disturbing stimuli (a loud whistle, a sudden puff of air, a flash of light), rather than being a permanent characteristic of the animal. He also noted that the glow was brightest when it appeared after a period of rest, especially after intense glowing.

The researcher brought the curious creature back to Europe, where zoologist H.W. Parker examined it and identified it as a familiar but extremely rare reptile called Proctoporus (Oreosaurus) shreyei . At the time, natural history collections held only one specimen: an adult female and a juvenile. However, for the first time, a male had been captured, and the species' bioluminescent properties were noted.

Sanderson also captured seven other specimens in Trinidad. Parker examined them and reported his findings in 1939 in the journal of the Linnaean Society of London. He concluded that the characteristic circular spots were a male characteristic, and that the skin within the white spot was twice as thin as the black border and translucent, devoid of any pigment. In other words, each such specimen was, almost literally, a circular window within a black frame.

However, the mechanism by which light is emitted from these peculiar "illuminators" has not been explained. Parker did not find any nerve endings or significant blood supply in these parts of the body. He therefore eliminated the possibility of a direct connection between bioluminescence and the nervous and circulatory systems. He also did not observe any glands or structures capable of reflecting light in these areas.

Regardless of their function, the "illuminators" were characterized by an extremely simple structure. Parker therefore proposed three possible explanations for the light emission. First, during the animal's life, the spots could have contained some substance that emitted light during disintegration (as in the case of various luminescent fish) or that glowed when exposed to light (like fluorescent paint). The third possibility is reflective tissue beneath the transparent spots. Parker rejected the fourth explanation, linking the light emission phenomenon to clusters of bioluminescent bacteria in the center of the black halo, because he did not detect their presence.

Parker's work was continued by other zoologists. They examined specimens of this and related lizards to see if they emitted light. However, they did not observe this phenomenon. When, in 1960, they presented negative results on P. achylens from Venezuela and the species Neusticurus ecpleopus ocellatus (characteristic "porthole"-shaped spots are present in both species), American biologists Dr. Williard Roth and Cari Gans challenged Sanderson's claim of bioluminescence in P. shrevei . However, Sanderson was a trained zoologist, and Parker's histological studies convinced him that the "portholes" were actually light organs. So who is right? If P. shrevei is the only lizard species capable of bioluminescence, comparative studies of related species are worthless.

But besides Sanderson, only one zoologist has studied bioluminescence in P. shrevei . Perhaps he failed to stimulate the animal with the appropriate stimuli to induce the glow?

Only further detailed research will ultimately solve this mystery. However, this is hampered by the rarity of P. shrevei. Furthermore, a colleague of American cryptozoologist Chad Arment, who searched for the luminescent lizard in Trinidad in late 1998, noted that sixty years after Sanderson's expedition, the area had undergone significant changes. Therefore, the location where Sanderson first found the specimen could not be located. This means that there may be no light at the end of the tunnel of research on the bioluminescent lizard from the exotic island