Red Line Lizard Tetra Iguanodectes sp in the Wild

The legend says there is a half human creature which appears to people in the middle of nowhere, deep in the middle of the Venezuelan Amazonas jungle. Locals call it “The Primitive Man” and say that it is a bit smaller than a human, hairy and extremely aggressive. Outrunning it in the bush is impossible. His feet face backwards or to put it in another way, his heels face forwards, which give him a great running advantage. As I listen attentively I imagine it as a smaller version or a malnourished Sasquatch or Bigfoot. The passion and belief that I see in the faces of the people that tell me the horror stories makes me wonder if it really exists. I love to hear the Amazon tales and stories. They are filled with abundant wildlife, plants, rivers and fear of loneliness and the unknown.

So, here I am, alone, sitting next to a fantastic stream in the middle of nowhere, deep in the middle of the Venezuelan Amazonas impenetrable jungle. The greenness of everything around is so soothing and refreshing to my eyes. The jungle noises are faint but present at all times. The crystal clear water river in front of me trickles a gentile melody and ever-changing glittering stars dance to its beat over the gentle ripples on the surface of the water. I am placing my camera and other gear into the underwater cases when all of a sudden I hear the tall grass next to me shake. I get goose bumps from my head to my toes. I turn my head slowly and see a huge Golden Tegu lizard, Tupinambis teguixin, making its way towards the stream. Even though my mind tries very hard to convince myself “The Primitive Man” does not exist, I was really expecting it to come out of the bush and attack, bite, or probably beat me with a stick! I finish arranging my gear, take off my clothes and put on my dry suit. A few feet away the Golden Tegu is staring at me. I stare back at him and tell him, “Bet you have never seen a person with a wetsuit before, right?” I gently make my way into terra incognita or to be more precise, “aqua incognita.” The 25 °C water feels cold and as I sink below into the underwater world, I see fish fleeing frightfully from me, to them I am “The Primitive Man.”

The water current makes a pleasant whispering sound as it passes by my ears, this place is magical. Large amounts of aquatic plants line the banks of the river. The plants sway and wave in one direction as the water current moves them. They seem like they are dancing to me. I realize that I have been staring at them too long and try to break the trance. It is for sure one of the most enchanting movements on earth. The contrasts between dark and light, colors and movement bewitch me. Then, out of the dark come a school of fish. These are no ordinary fish. They are an undescribed species of tetra. A beautiful one, theIguanodectes sp, Red Line Lizard Tetra.

The Iguanodectes genus etymology “translates to” Iguana biter making reference to their very peculiar teeth which resemble the teeth of the Iguana iguana, reptile. The species in the genus are distributed in the Amazon, Tocantins and Orinoco River basins and coastal drainages near the mouth of the Amazon River. Up to now there are eight species in the genus and two to be described including this one which is hopefully going to be described soon by Dr. Cristiano Moreira from the Universidade Federal de São Paulo.

The Red Line Lizard Tetras are fascinating, medium sized pelagic fish that grow up to 9cm long. They are slow moving and seem to swim against the current in slow motion. Their slender bodies seem to wiggle as they swim against the water current. Their body movement remind me of the way a Green Iguana swings its body from side to side as it crawls up a tree. If you are very patient and take your time to approach them slowly, they will let you get quite close to them. These fish have been exported and sometimes sold in the hobby as Iguanodectes geisleri but they are definitely not I. geisleri because they have more than 25 anal fin rays. They also differ from Iguanodectes adujai by having a body height which is five times the standard longitude.

Red Line Lizard Tetras have a pink to red colored lateral stripe starting at the end of the operculum, thinning and ending below the adipose fin. They also have two red spots in the caudal peduncle over a large black spot both of which extend half way into the caudal fin. Their pectoral, dorsal, pelvic, anal and caudal have a strong yellow color that fades out towards the ends of the fins. Their body colors seems to vary or change a lot, from a light beige to a bright green. The color change seems too strong to be caused by the reflection of the colors from its surrounding habitat. Probably the color difference are due to gender, mood, how the light hits them, or probably just varies from specimen to specimen. The red spots on its caudal peduncle sometimes makes it resemble a traffic light. The red line they have right above their mouth makes them look as if it had red lipstick. Now this is what I call a cool aquarium fish.

It is possible to divide a stream into many different habitats; these habitats differ mainly in current speed,  substrate, depth, and plant growth or accumulation of driftwood, just to name a few. These smaller habitats, sections or systems are inhabited by permanent or transitory tenants. Red Line Lizard Tetras “hang around” three types of sections of the stream, all of them less than a meter deep. Their favorite section of the stream is the heavily planted river banks. These are less than 40cm deep with lots of aquatic plants and a medium fast current. They specifically like to swim in narrow corridors between the aquatic plants. I let go of a leaf underwater and it took the leaf around 5 or 6 seconds to travel 1 meter downstream. So, in the square meter in front of me where the Red Line Lizard Tetras were swimming they received an average water change of 72L per second. This is where their body color seemed the greenest.

The second preferred habitat are the river depositional zones. These lentic habitats have a very slow water current. It is one of those spots in the river where all the dead stuff winds up rotting. The aquascape is a monochrome of ocher tones. Dead leaves, fallen branches and all the silt deposit here. It all resembles a phantasmagoric, surrealist Salvador Dali painting. Probably this is a place where they take a break from the strong water current. It definitely was not a transitional zone, because they stayed there for long periods of time. In this spot their green body color was not so strong but still striking. With their green body, red stripes and yellow tones they resemble live moving ornaments between dead Christmas trees.

The third habitat in my opinion is one of the dullest sections in the river. This is the streams narrow deep straightaway or runs. The fast oxygenated water current seem to attract all the fast swimming tetras in the river. Everything here is a monochrome beige color but is a tetra paradise. The thin fallen tree branches vibrate as fast water pass by them. Here the Red Line Lizard Tetras are always hiding behind these branches which seem to shelter them and give them a break from the strong direct current. For some reason, here they seemed to lose most of their green coloration and turned almost beige. It seemed to me that I was looking at a different species but all the traits were the same except the lack of green coloration.

The Red Line Lizard Tetras are as peaceful as a fish gets and opposed to many other tetras of the same size it seems not to swim around too much and do not like open waters. It spends its day behind branches or behind aquatic plants where it seeks shelter from the direct water current. They feed on the organic material that is dragged by the water current and happens to come their way. I have also seen them picking on the periphyton and algae stuck or growing off the natural decor including aquatic plants leafs and fallen branches. They are one of those tetras that do not swim around much, they actually keep the same location for a long period of time in the river, just fighting the current without going anywhere. A good example would be a fly in a glass window, they have the effort but go nowhere. Once in a while they spot a succulent piece of algae growing on a rotting fallen tree branch, they take a bite and go back to the exact position they had when they started. So you can say they also resemble an Iguana because they feed on the green that grows on tree branches.

Many of the Red Line Lizard Tetras have marks on their bodies like they had been victims from a predator attack. They have what seem remnants of a war wound inflicted by a fish that swallowed all the tail and up to the middle of its body where it left a pressure scar. If the markings are really war wounds I wonder how or why they all managed to escape their aggressors. The markings seem to have been made by a non-piercing fish such as a Peacock bass because a fish like a piranha would just have chopped them in half. Making a highly crazy and science fiction inspired hypothesis, it seemed like they had the ability to expel a secretion from their cloaca that would make the predators release them.