Motoro Ray

Name: Motoro Ray
Scientific name: Potamotrygon motoro
Range: Amazon Basin
Habitat: freshwater rivers
Status: not considered an endangered species 
Diet in the wild: consists of crustaceans, mollusks, and small fish which swim near the bottom.
Diet in the zoo: earthworms
Location in the zoo:  James R. Record Aquarium

Physical description: 

  • max size: 45cm (18 inches) 
  • Body length up to 18 inches. 
  • Weight 8-10 lb. 
  • Color is golden with dark spots. 
  • Tail has a barb on the base. 
  • Ears are just behind the eyes. 
  • Background 

     The motoro is one of three main species of the Potamotrygonidae family. The three main genera of freshwater stingrays from South America are Potamotrygon, Plesiotrygon and Paratrygon.  The motoro ray is in the species Potamotrygon.  The origin of the Potamotrygon is that they are usually neotropical river stingrays that have adapted to freshwater by using a salt secreting rectal gland as well as a suppressed concentration of urea in body fluids. These stingrays are normally found at the bottom of rivers feeding on almost anything on the river bottom.  The typical diet in the wild is mainly  small fishes, insects and crustaceans.  They also posses a powerful sting that can cause severe pain that normally requires medical attention. The stingers are replaced up to three times a year.  The species are typically not very fast swimmers.  The technique used in order to capture prey is to trap the prey under its disc, then slowly adjusting its mouth to the trapped prey until they can swallow it.

    General information: 

    Stingrays are in general considered to be a group that is known for intelligence. Stingrays are agile and extremely graceful swimmers, but the majority of the time in a motoro's life is spent hiding by lying almost completely covered in sand on the river bottom waiting for prey to swim by. Since the motoro does not use speed to catch prey it must rely on  its coloration.  The motoro's color patterns  provides the ray with the adequate camouflage needed while waiting for its next meal to swim by. To this day it is largely considered a mystery on the migration patterns of the motoro

    Special anatomical adaptations:
    One key adaptation that the motoro ray possesses is that its gills are located on the top of the head. This adaptation allows the motoro to breathe comfortably while waiting under the sand for food.  Although the stingray does have a poisonous stinger the stingray is a very gentle and peaceful animal. The sting it delivers is a painful one, but the motoro is definitely not aggressive toward humans. The primary use of its stinger is in self-defense. More often then not the cause of a human to be stung by one of these gentle creatures is if they are stepped on.  One way to prevent this from happening is for people to shuffle their feet while traveling in areas of water that may be inhabited by rays.  There is no surprise that people step on these creatures because they do lie motionless buried in the sand, and they are very well camouflaged. When a motoro is stepped on it subconsiously elicits a reflex response that causes the ray to raise its tail and extend the stinger perpendicularly. People who are stung are usually stung in the calf area.


    Rays of the Fort Worth Zoo:

    It is sad for me to say that one of the Ft. Worth Zoo's motoros died early in November this year.  It became lodged between a tree and the wall of the tank.  Fortunately the other motoro is still very healthy.  The zoo is curently looking for a male that they can breed with the female that they currently have.

    Personal Observations: 

    The motoro at the zoo acts much like it would if it was in nature.  It sits on the bottom of the tank ignoring the other fish.

    Source Materials and Related Links:

    List of Zoo Home Pages.
    Ray's Freshwater Sting Rays:
    Bud's Freshwater Sting Rays:
    Le fish Corner:
    Thanks to Bud and Le Fish Corner for the use of the pictures

    Page author: Ian Kirkpatrick 

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