Common
Names: Vermiculate River Stingray, Otorongo Ray, Jaguar Ray, Estrella Ray,
Star Ray, Tigrinus Ray, Tigrillo Ray, Carpet Ray, Motelo Ray, and Tortoise Ray.
Latin Name:
Potamotrygon castexi
Family:
Potamotrygonidae
A note on the identification of South American Freshwater Stingrays.
Dorsum patterns and colors are extremely variable
among the freshwater rays of South America making positive identification using
pattern and coloration alone extremely difficult. Some morphologically different
species occasionally display an almost identical pattern and to make
identification even harder there can be a degree of hybridization among
sympatric species. Important characteristics to help the observer overcome these
problems include the lateral markings on the tail, the presence or lack of
raised denticles along the tail, the ratio of tail length to disc length, and
the size and position of the eyes (although this last characteristic changes
with age).
Identification:
Tail powerfully built and noticeably longer than the body. Upper surface of tail
either irregularly light spotted o a dark background or covered in dark lines on
a lighter background. The lower half of the tail appears striped or barred when
viewed laterally. The body disc has a fine light edge which is not always
noticeable.
In
the aquarium trade Vermiculate River Stingrays are broken down into at least 5
'variants' according to their patterning:
-
Otorongo Ray (Jaguar Ray): displays a dense covering of light spots sometimes
forming an almost solid mass towards the centre of the disc. The outermost spots
are more defined and more broadly spaced.
-
Tigrinus Ray (Tigrillo Ray): similar to above but the orange spots fuse to form
a lattice of interconnecting broken shapes. Lighter outer spots more defined and
separated.
-
Estrella Ray (Star Ray): less densely covered in spots resulting in a starry
appearance. Central spots sometimes form clusters.
-
Motelo Ray (Tortoise Ray): similar to Otorongo pattern but the densely covered
spots form distinct closely grouped clusters resulting in a honeycomb appearance
or the plates on a tortoises back (but more numerous).
-
Carpet Ray: completely covered in light broken circles (formed from spots) and
spots on a dark background.
Size: Maximum disc
width 60cm
Habitat:
River Basins in South America.
Abundance
and distribution: Upper Amazon River basin (Guaporé, Beni, Solimões
and Marañon rivers) and Paraná-Paraguay basin. Restricted to Argentina, Bolivia,
Brasil, Paraguay, and Peru.
Behavior:
Reproduction:
Matrotrophic viviparity.
Observations:
Similar
species: Potamotrygon reticulata has very similar patterns but can be
differentiated by the single horizontal line running laterally along the tail.
In the southern part of its range P.castexi hybridizes with P.falkneri.
Reaction
to divers: Unknown but some South
American freshwater rays are known to act
aggressively when threatened.
Diving
logistics: There are currently no organized opportunities to interact with
freshwater stingrays but aquarist collecting sites include Paraguay, Peru, and
Brazil.
Other
diving locations submitted by readers:
References
and further reading:
Aqualog Freshwater Rays. Richard Ross &
Frank Schafer
Sharks and Rays Elasmobranch guide to the
World. Ralf M. Hennemann IKAN
Fishbase.com
