Monday, July 25, 2011

River monsters and a really old citation...

Airing on Animal planet is a show featuring Jeremy Wade called River Monsters. Jeremy Wade is an angler and biologist traveling all around the world fishing for what they call river monsters. A common denominator for these fish is that they are often large and look weird. Some of them are venomous and have caused rare deaths. Often the species he targets isn't very new to science and often common in the aquarium trade. However the show never seem to acknowledge the knowledge present on these species in the scientific literature or in the aquarium hobby. They present each species as if it was new and almost unknown, probably due to dramaturgic effects...

In the episode 'Silent Assassin' (S03E05) we follow Jeremy to the Parana river in Argentina where he follow up stories and victim accounts of stingray "attacks" in the river. According to the locals theres a mysterious stingray living in the river attacking and killing locals and their animals. Instead of doing research in the field of stingrays he sets out on a mission to catch this 'river monster'. Most of the people a bit interested in Elasmobranchs would be aware of the family of stingrays inhabiting the river systems of South America, Potamotrygonidae. However the episode overlook this fact and attribute the attacks to a mysterious ray. This mysterious ray however is a rather well known member of the Potamotrygon genus, actually one of the bigger species if not even the biggest. The species of freshwater stingray in this case is Potamotrygon brachyura. This species was described by Albert Günther (back then named Trygon brachyurus) in the article "A contribution to the knowledge of the fish fauna of the Rio de la Plata" in 1880 so it is not totally new to science. In the episode they wrongly assign this species into the family Dasyatidae and shows a picture of a general whiptail stingray which is the common name of the family. However the Potamotrygon genus is one of four genuses in the family Potamotrygonidae or river stingrays. They are thought this mistake not completely wrong due to the closest extant sea living relatives of river stingrays are thought to be stingrays of the genus Himantura in the Dasyatidae family. 

River stingrays are generally docile and generally only sting victims in self defense. Thats what their poisonous spine are for, self defense, and nothing else. So I think its a overstatement to talk about attacks when often the rays are being stepped on.

Albert C L G Günther (1880). A contribution to the knowledge of the fish fauna of the Rio de la Plata Annals and Magazine of Natural History, 6, 7-13

No comments:

Post a Comment