Motoro Stingray: River Stingray from the Amazon

Published on July 3, 2019
Motoro Stingray: River Stingray from the Amazon

A motoro stingray is not a small ray like the hystrix ray, but the demand keeps rising because of its different body markings in each specimen, and the price is lower.

Fish keepers will always dream of including species of stingray in their aquariums, but the problem lies in the stingray’s size and the tank to house it in.

The aqua trade business claims that this is saleable of all the stingray species, but raising a freshwater stingray involves knowledge, experience, and a lot of maintenance costs.

It is not the fish for every household aquariums, so gather all crucial information and secure first the requirements before purchasing a motoro ray.

Scientific Classification

  • Scientific Name: Potamotrygon motoro
  • Kingdom: Animalia
  • Family: Potamotrygonidae
  • Phylum: Chordata
  • Genus: Potamotrygon
  • Class: Chondrichthyes
  • Subclass: Elasmobranchii
  • Order: Myliobatiformes
  • Species: P. motoro

Common names

Ocellated stingray, ocellate river stingray, spotted river ray, peacock-eye stingray, black river stingray, Royal Motoro stingray and a lot more.

Origin and Distribution

motoro stingray fish origin

We can find species of tropical stingray in Río de la Plata, Mearim, Orinoco and Amazon River Basins in the tropical countries of South America.

They thrive in enormous numbers because of the natural ecosystem, the rivers of Argentina, Peru, Colombia, and Brazil can provide.

To date, you can also find similar species in river systems in Australia, Southeast Asia, and Africa.

In Thailand and Cambodia, they caught a giant freshwater stingray, a reason to battle for the record-breaking catch.

There are various pet fish stores in North America that are offering species of motoro stingray that came from South America.

Some freshwater stingrays prowl in muddy areas and floods where currents drive them to wander. They can appear after a storm, and the coastal people can eat its meat that tastes close to crab.

Characteristics

A motoro stingray is the most popular and widespread species of stingray nowadays.

It is the first known freshwater stingray from the Potamotrygonidae Family.

Stingrays are relatives to sawfish, skates, guitarfish, and sharks because they lack the actual bones structure but cartilaginous skeletons.

This stingray species vary in body appearance, which includes different patterns, color variation, and a more pronounced spotting.

At present, you will see more body designs of a motoro ray in the trade market. Aquarists can now breed hybrid specimens locally. Exotic fish like this is a common sight in aquaria around the globe.

The body of a motoro ray is also wide and flat like all other ray species, but the measurement can reach 30 inches in diameter when grown. Its prominent base color is dark brown or grey. They appear attractive because of its many design patterns and diverse spot shapes because of hybrid reproduction.

If you are looking for the original ones that came from its natural habitat in the Amazon, you need a lot of skill to distinguish one from the other. Although there are few differences, an expert aquarist has keen eyes for this, so seek help.

What Makes Ocellate River Stingray Unique?

In 1678, Lorenzini discovered the ampullae of a stingray. This feature makes it easier for a Stingray to detect potential prey or a threat against predators.

Lorenzian ampullae is an unusual feature that receives electromagnetic impulses in the water. The motoro stingray and the rest of its relatives have this electrosensitivity that can also detect temperature gradients.

These jelly-like pores near the stingray’s mouth serve as an electroreceptor of electrical fields coming from aquatic animals.

Rays can breathe no matter how they bury themselves on the sea floor or in the substrate. The spiracles positioned on top of their heads just near their eyes is a feature for breathing underneath.

This unique feature pumps and kicks in water to its gill plates. Perhaps this feature pays off its unusual eye placement.

The Notorious Tail

As the name suggests, a ray can sting with its poisonous barb on its tail, which is almost flat in appearance and can measure 6 cm long. It releases toxic mucus all around the barb, possibly making a deadly attack when angered.

They used these scales present on the tails as a defense mechanism when harassed or attacked by predators or stepped on by humans.

Rays shed its barb, and new ones will grow to replace them, six months at the most. Discarded spines fell on the bottom and are visible to the eyes.

There is no report that a stingray has been aggressive with its fish keeper. Even if you don't know how to be sociable with them, they can be friendly to humans.

What happened with Steve Irwin, “the crocodile hunter” of Australia, was an isolated case of fatal human encounters with a ray.

A river stingray won’t cause death, but when stung, will create a painful wound. Every fish enthusiast should know the proper handling of a stingray to maintain its peaceful behavior.

How it Behaves

Stingrays are peaceful and friendly when they sense no trouble, contrary to popular beliefs that stingrays will come at humans waving their stinger tails and attacking at once. They are interactive to humans, and we can even feed them by our hands.

It appears surprising for many people that there is what we call a river stingray or a tropical stingray. Yes! Rays inhabit freshwater, too. The motoro rays are the ones you can find in the river, sneaking along brackish waters of the tributaries and to the sea and ocean to join its relatives.

They stay on the seafloor for an extended period wherein they bury themselves in the sand, hiding or camouflaging. Humans can step on them and might result in the ray’s terrible revenge–the sting.

They make use of their big bulging eyes that are the only ones exposed when they bury their bodies in the sand. They have excellent eyesight and the distinct sense that they use for hunting prey, for smelling bits and pieces of food, and for defending themselves against aggression.

Like all other rays, the motoro stingray gives off a large amount of waste. In the wild, these wastes will flow with the rivers’ current. However, in captivity, effective filtration can maintain proper water parameters when keeping a ray.

The Best Diet for Motoro Stingray

In the wild, a river stingray will feed mostly on meat animals like crustaceans and invertebrates, shellfish and fish that are not half as big as their size. They are carnivores and voracious eaters that’s why their wastes come out in large quantities.

While in captivity, many hobbyists will allocate a large amount of money for its sustenance for food and nutrition. They can teach a motoro ray through the human hand feeding or a tweezer if you are not yet comfortable using bare hands.

When a stingray has just arrived at its new home, try to settle him by feeding live blackworms, earthworms, white fish, shrimps, tilapia, bloodworms and more of its kind. When the ray gets acclimated to its new environment, you can feed it with frozen meat, shrimp pellets, cichlids pellets, and tablet foods like granules and sinking pellets.

Housing and Water Parameters

Maintain pristine water by understanding its nitrogen cycle. Your motoro ray must conform to levels of nitrate, nitrite, and ammonia. Rays produce ammonia, the quantity of which depends on their size.

A functional chemical and biological filtration is a must for considerable tanks to maintain proper water conditions. A freshwater stingray does not need salty water unless required, like in diseases, stress, and a high level of nitrite to bolster its immune system. However, consider also the salt tolerance of other fish in your tank.

To keep the ideal water temperature, you may use a branded heater. You can also use a gravel cleaner to maintain a rich substrate. A water change of 25% to 50% weekly is ideal but treat the tap water first with a water conditioner before pouring it in.

Water Requirements

  • Temperature:  75° F to 82° F
  • pH level: 6.8 to 7.6
  • Alkalinity:  18 ppm to 70 ppm
  • Ammonia:  0
  • Nitrates: less than 10 ppm
  • Trace elements: preferably RO/DI trace elements restored

Housing Requirements

When housing a motoro stingray, remember the more significant the tank, the better. For long-term housing, a length of 72–84 inches with a depth of 24 - 36 inches is ideal for your new pet. Height does not matter, but if you can provide more the better.

For a juvenile stingray, you will need a 75-90 gallon tank. When it reaches adulthood, it will require a larger space, so a 180-gallon tank is an ideal size.

Instead of buying an aquarium now and then, you can expect the maximum size of a ray, around 30 inches across its body, and provide a suitable tank ahead.

Since stingrays have a habit of burying themselves in the sand, provide a soft and deep substrate for this exotic pet. Decorations and rockscape must be smooth with no sharp edges.

The bottom part of your tank is their usual territory, so make it spacious for them to swim, move, and bury themselves. Stingrays are not territorial creatures, so there is no worry for your other bottom dweller fish.

Moderate lighting is perfect for your motoro ray since they are bottom dwellers and can adapt to dim light to dark light at the river bottom. Apply a cycle of low-intensity lighting of 12 hours per day or 12 hours per night.

Before buying a ray, make sure that the edges of its disc have no “death curl,” meaning not curled upward. Reject the ones with injuries and see if they will respond to feeding.

Never purchase a just-arrived fish. Allow a week of a quarantine period if the ray can adapt to its new environment.

Likewise, in your home, do not mix it at once with your existing fish because a stingray needs some time to settle in.

The Best Tankmates

The best tank mates for a motoro stingray are none other than its kind. Rays are sociable with its cousins and can even swim in a school.

However, Severums, Arowana, Geophagus, Bichirs, and Silver Dollars can make a good friend with a freshwater ray.

exotic arowana breed

Make sure that the fish you will join with your stingray is big. Small fish are a temptation to eat. Choose peaceful tank mates who won’t nip fins and those that won’t steal food from others.

Avoid including Sucketmouths Catfish and Plecostomus, as they suck the rays' soft body, leading to injury.

Think of the space you have when you are housing a motoro ray with several other fish.

Remember to consider the rockscape, decorations, and aquatic herbs present in the aquarium.

A planted aquarium is fascinating to the sight, but make sure they blend well with all other biotas in the tank, the ray.

Breeding: Level Difficult

Breeding rays is delicate because it takes time, effort, and dedication. You will also need extra tanks for the offsprings.

The motoro ray has the most diverse body patterns of all the species of stingrays. You can imagine the offsprings of two hybrid specimens.

Since female rays are more massive because they have two uteruses, males are smaller. The female can have pups from two male rays at once.

When it’s breeding time, a male stingray will rely on its ampullae de Lorenzini to detect electrical signals for potential copulation from the female rays.

Male stingrays have pelvic fins known as “claspers,” which they used to inseminate the female rays. The male will follow her as a way of courting and will bite the female’s pectoral disc. Using one of his two claspers, he inseminates the female valve; thus, the reproduction begins.

In this period, her behavior transitions to care for its offsprings.  Her womb can sustain the embryos even without a placenta, but a yolk sac that absorbs all the nutrients she eats. Soon, the yolk sac will deplete, and the uterine milk replaces it.

A female ray is ovoviviparous. She can produce 5-13 live litters of pups. In two years, she can also store some sperm. Only when she thinks it’s suitable that she gives birth to a few litters.

Female Stingrays have a maternal instinct. They can protect their pups for three years until they mature and can go on their own. They will make sure that their offspring can now hide and bury their bodies in the sand with only the eyes exposed.

When the youngs camouflage and dwell most of the time at the river bottom, the mother river stingray can leave them for life.

It's Not Over Yet...

In some countries, a law prohibits the sale of stingrays, especially the rare ones like the Eclipse and Black Diamond Rays.

The South American government and environmentalists restrict the exportation of any species of freshwater stingray from the Amazon.

In some aspects, humans endanger the lifespan of rays, others are nearing extinction, and some become the exotic food on the table.

Because of this, the price of rays in the fish trade market rise, making it more difficult to purchase these exotic creatures.

Perhaps what you see in the fish trade market now are products of local hybrid breeding. The original ones are rare nowadays.

Only those who can afford and have a vast space for a massive tank at home can own the much sought-after freshwater stingray species.

For those seeking the original from the Amazon River, chances are slim. And if ever, the price will cost you an arm and a leg.

Aquarists can breed species of motoro stingray now to almost perfection. Their body patterns emerge in variation, and you will find only a slight difference with a river ray that came from South America.

Perhaps the local reproduction of stingrays these days is the answer to the rarity of the motoro ray species.

Featured image by By © Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons), CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=168357

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