History: Potamotrygon

[Miles]

(No Sticky - Please)

I am creating this thread as a reference point and collective resource of the taxonomic history of the Genus Potamotrygon.

If anyone has interesting information or can provide links to websites that provide information on the History of how the genus 'Poatmotrygon' came to this day, please add..

I am finding that alot of the mis-identification and confusion with the species is largely due in part to incomplete work done by the research done in South America in the 1800s, early 1900s.. Many identifications are based off pencil drawings, or hand-written notes taken in the field.. With freshwater rays being so polymorphic, the basis for identification is very inconsistent.

If we, as a community, can gather an extensive amount of information and resources related to how each species was defined in the past.. perhaps it will open up the door in the future for a proper reclassification of the entire genus.. or just a better understanding and clarification.

MFK - If you hadn't noticed, this sub-forum is one of the leading discussion areas in the world for FW Stingrays.. We should be honored to have the likes of Frank, Andreas, Mark, Mike, David, etc frequent this forum.. If we can continue to discuss thoroughly this type of information, perhaps we can acquire scientists working in the field to join the discussion, who will be able to take further steps towards a resolve.

 

[Miles]

Schomburk 1860 - The Fishes of Guiana

Genus: Trygon

We have now examined all the drawings belonging to one great natural division of fishes, those with osseous skeletons; in the fresh waters of any country the catilginous species are of rare occurrence, their large size and predaceous habits requiring for them a wider range; several species of small rays, however, are found at a considerable distance inland in several of the Guiana rivers; three, those of which we possess drawing, approach nearest to the genus Trygon, while a fourth we can reconcile with no characteristics to which we have access; and it is possible that these entirely fresh-water skates may be found to vary considerably in their structure and economy. Of the first, our author thus writes:

"We are informed by Linnaeus that the Raya, or Rays, are exclusively inhabitants of the seas. I think a species has since been described by D'orbigny as inhabiting fresh-water rivers; Guiana, however, possesses several species, which consequently will prove new to Ichthyology. Their form is not different from those of the salt-water rays, and they are generaly armed with spines; some with the back more or less spiny; tuberculous, or smooth. The spine or prickle, in the freshwater Trygon is an equally dangerous weapon as that of its congeners which inhabit the sea, and wounds inflicted with it cause frequently severe inflammation. As they are generally frequent such places of the river where the bottom is sandy, and in which they bury themselves, in order the easier to entrap their prey, the Indians use the greatest precaution when they are obliged to draw their canoes over such shallow places. I have known several instances where, nevertheless, wounds have been inflicted, and a swelling of the part, and in some instances feverish symptons have been the consequence. The indians use sometimes the leaves of the aromatic guava, which grows so abundantly among the rocks in the rivers of the interior, and after having pounded them, they are put on the wound, but I do not think with much effect, at least in those cases where I saw it applied; laudanum in the first instance, and afterwards warm poultices of cassada-bread to subdue the inflammation, appeared to me the most effective remedy. The pain which the wound causes to the individual appears to be excruciating; no wonder, there, that the Indian is likewise under the idea that the spine which inflicts the wound is poisonous. The spine being serrated on each side with barbs and hooks, recurved towards the base, it may be expected that the wound becomes dangerous frmo its jagged nature, while the extraction must cause additional laceration. Dr. Hancock has known the part to mortality and to slough off, and then the healing process went on favourably. I have no doubt that much depends on the state and health of the individual who is wounded, and the cases which I have witnessed fortunetely came to those extremes.

"The spines are sometimes doble, and I have seen an instance whee there were three. One is generally larger than the other; no doubt a provision of Nature, that in case one was to break off, the animal may not be entirely deprived of its weapon of defence. Those barbs are decidous, and their size depends much on that of the individual. The Indians of the interior use the spines to arm their arrows with; but among many hundreds of which I have seen, none reached the length of three inches.

I nowhere observed these rays in such abundance as in the river Tacutu, when that river was, in April 1839, on its lowest level. As they afford tolerably good eating, we took some pains to secure them. The Indian is always armed with a sharp pointed pole, which he thrusts before him when he is wading through shallow water which he thinks frequented by the sting-ray. The yellow colour of that fish, so much like the sand in which it buries itself, makes it the more dangerous; and as it strikes with the swiftness of an arrow, the wound itself would be frequently the first token of the approaching danger. The pole, there, serves as protection to dislodge the ray, which darts swiftly forward when it finds that the enemy is superior in strength. The Indian rushes after it, and is generally skilled enough to pierce and transfix the ray with the pointed pole. His first operation, if he has been successful, is to cut off the tail with its dangerous weapon, which he cuts afterwards out, and preseves it carefully for arrow-points.

"I have frequently observed that the rays, no doubt in consequence of the anguish when secured and transfixed by the poles, brought forth young ones. The embryos are, no doubt, as this is the case with Squali, developed in the ova-ducts or in the uterus. The spawn is otherwise wrapped in a strong flat shell of horny substance.

"Shagreen is prepared from several species of rays in Europe; whether the rays of Guiana would ever become of economical use in that regard is much to be questinoed, although they are to be found in such numbers; nor will they prove of much interest to the gourmand; but I and my companions have fared on a worse dish than stewed or boiled sting-ray during peregrinations; we have despired it when it constitued part of our entertainment in the wilds of Guiana."

 

[Miles]

Many-Spined Trygon

"This fish is from two to three inches in thickness, whereas some of the others do not measure more than one and a quarter. The eyes are prominent; breathing holes, five on eachs ide of the mouth; nostrils double, near the mouth; mouth semilunar; teeth, a file-like process. They feed on animal food, perhaps sometimes on vegetable, as their means of securing the former do not seem adapted for procuring a plentiful supply."

The letter-press to the to the Ichthyological plates of D'Orbigny has not yet appeared, so that we are ignorant of his observations regarding the fish, to which we have temporarily referred Mr. Schomburgk's drawing.

 

[Miles]

Ocellated Trygon

All the information that we have regarding this beautiful Trygon is, that it has "a series of rough flat teeth, in each jaw, like a file," and that it was taken in the Rio Branco in April. The general colour of the drawing is a yellow-umber brown, margined round the disc with pale scienna-red, the whole covered with yellowish white spots surrounded with a dark margin, large in the centre of the body, and gradually decreasing in size outwards, where they also become more numerous; a single row of weak spines runs along the upper ridge of the tail, which is also armed about its middle with one large serrated spine. In the drawing the length of the tail about equals that of the body from its insertino to the snout.

 

[Miles]

Spine-Tailed Elipesurus

"This ray was found in the Rio Branco at Fort San Joaqium, and here it is called Naree-naree; It was eighteen inches long, but very thin, and was without the horny spine which is generally found on this genus; a number of spiny excrescences cover the tail, which is much shorter than usual; it is of an ochreous color; the eyes are prominent, and nostrils very large; like others of the species, they dig holes in the sand, in which they lie flat, and there await their prey. They are used for food, but are not preferred to the others, and in the dry season, when other fish are plentiful, they are seldom killed. They are about eighteen inches by fourteen and a half or fifteen, in diameter."

The form is altogethor remarkable in the short or deficient tail, an organ among the rays which is generally in one way or other marked by considerable developments. These seem to be here confised to the strong spiny excrescences which cover its base, and are the only organs of defence with which the animal is furnished. The form of the body is more oval than those we have been examining; the color is uniformly of a bright ochreous yellow, covered with a series of dark reticulated markings.

 

[Miles]

-No information-

I could not find a few pages of Schomburgk's info.. Hopefully someone can elaborate.

 

[LiuHsi]

good stuff miles.

 

[StingrayFanatic]

Good Info. Why not sticky?

 

[Miles]

Good Info. Why not sticky?

People tend to skip over stickies and not notice when they get bumped.. Plus, this type of stuff might be boring to others.. kind of like that silly Paleo thread in the Photo Lounge..

 

[Nic]

good info miles...