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What do freshwater stingrays eat?

What do freshwater stingrays eat

What do freshwater stingrays eat?

So what exactly do what do freshwater stingrays eat? Making sure your fish have a healthy and varied food diet to eat can help make sure they will thrive and have a long life span.

Stingrays and Arowanas have a high metabolic rate.  So you will find that your stingrays in particular, are continuously on the lookout for food.

Many stingray enthusiasts use sinking pellet food for carnivorous fish with good results. We have tried and tested various diets over the years.  Our stingrays love a diet which includes mussels, baby squid, prawns and white bait.  We can’t help but give them what they want.

If you are pellet feeding your rays maybe try and supplement their diet with frozen fish too.  We think you rays will love you for it.

If you would like to find out more about frozen food for your stingrays we would be happy to share our experiences with you – just let us know.

 

 

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Freshwater stingray history

freshwater stingray history

Freshwater stingray history

All stingrays both fresh and saltwater belong to the class Chondrichthyes. This includes all 850 species of sharks, rays, skates and chimaeras. Based on fossil remains it is known that this class of fish have been around since the Palaeozoic period (250 million years ago approx.), however it is believed that the adaption of the flattered (ray like) body only occurred in the Jurassic period some 100 million years ago. Freshwater stingray history is certainly an interesting topic for the fish keeper of today.

The development of the body shape and the loss of a swim bladder enabled these early rays to hide and lay practically invisible to a predator and to its pray. Rays have developed powerful jaws designed for crushing shells and molluscs which is a primary food source for these animals. Fossil remains prove that little has changed in the anatomy of stingrays over the last 50 million years.

Class

Chondrichthyes (Cartilaginous Fish)

Subclass

Elasmobranchii (Sharks, rays and skates)

Order

Rajiformes (rays and skates)

Family

Dasyatidae (stingrays)

Family

Potamotrygonidae (river rays)

 

 

Freshwater stingray history – How did Stingrays adapt to Freshwater?

There are many theories on how the south american stingray adapted to freshwater to create a new family Potamotrygonidae (river rays).  A longstanding hypothesis suggests that before the Andes mountains were created about 80 million years ago, marine rays from the Pacific lived in and around the coastal areas near the Amazon and became tolerant to brackish water. Over time the Amazon reversed its flow as the Andes were formed.  The reversal of the river meant that stingrays became trapped in freshwater.

Another proposal put forwarded based upon DNA sequencing suggests that stingrays evolved far more recently. The theory suggests that marine rays from the Caribbean infiltrated into rivers draining into the Atlantic Ocean. If this theory is correct, then it suggests that the adaptation of the freshwater stingray could have been as recent as 20 million years ago.

It is not possible to know which theory of freshwater evolution is correct.  However it is extremely likely that the did develop from marine rays. Ray fossils prove that freshwater and marine rays have changed little in the last 50 million years.

Freshwater stingray history – The adaptation to freshwater

Sharks and rays are inherently marine animals simply based on their physiology. Seawater is usually saltier than the blood of most fishes, but instead of actively pumping ions and other solutes out of their bodies like marine bony fishes, elasmobranchs simply match their internal osmotic concentrations to that of their external environment. They do this by maintaining concentrations of organic solutes (namely urea and an enzyme called trimethylamine oxide or TMAO) within their bodies. Although urea is toxic to fish, the TMAO counteracts the protein-de-stabilizing effects of urea. Excess monovalent ions that they ingest, namely sodium and chloride, are eliminated from the body via specialized rectal glands.

Amazonrivermap
The Amazon River

Since Amazonian rays live in freshwater, they have exactly the opposite problem of their marine cousins: instead of losing water to their external environment, they have to worry about gaining it, since their internal osmotic concentrations are higher than that of the water in which they live. One result of this situation is that freshwater stingrays no longer have any need for rectal glands, and these structures are now vestigial (greatly reduced in size and no longer capable of secreting salt).

They have also lost the ability to retain urea, allowing them to sever their ties with the ocean and evolve into exclusively freshwater organisms.

Freshwater stingray history – Taxonomy

The family of Potamotrygonidae belonging to the genus Potamtrygon consist of about 20 species of rays. In 1986 Ricardo Rosa re-assessed the taxonomy of freshwater stingrays.  This can be tricky. Most rays are highly polymorphic. This means that variations is patterns, physical structure and tail length are highly common.

The word Morph describes different looking specimens in the same species. In only a few cases the ray has a constant shape and pattern. A good example of a non-polymorphic species is the Tiger Ray which has a consistent colour, pattern and shape between specimens. On the other hand a great example of a highly polymorphic species is the Motoro stingray. This ray has many pattern variants and shapes within its species.

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12 simple steps to get your new stingray into your aquarium

How to get your new stingray into your aquarium

How to get your new stingray into your aquarium

How to get your new stingray into your aquarium is a question we often get. We recommend following our 12 simple steps to introduce your new stingray into your aquarium.  This advice is offered with good intent and is based on a system that works for us with the hundreds of rays that we have introduced to our aquariums.

1.Your ray will typically be packed in a plastic bag inside a poly box. Once you receive your ray or arrive home don’t delay.

2.There are a few methods that people adopt but we will offer you advice on our preferred method which is to slowly empty the bag with the ray and its water into the poly box (make sure it’s clean).

3.Once the ray is safely in the poly box in its water that it has arrived in you can start a trickle of water into the box from your aquarium. A tip; use a 6mm airline tube and start a syphon. The water will very slowly start to fill up the box.

4.Using a 6mm airline tube the water will be slow enough that the ray should easily be able to become used to your tanks water parameters and conditions.

6mm tube

5.When the box becomes full, empty the water out of the box until a quarter empty and repeat process. As an approximate guideline you want to complete at least 2-3 complete fill and empties of the poly box over a 45 min to 1 hour period.

6.Watch your ray.  Its breathing should be relaxed and slow. If the ray is gasping continue to acclimatise and check your water parameters.

7.Now your ray is ready to enter into your tank.

8.If it is possible to scoop the ray up in a plastic container and lower it into the tank this is the least stressful way for the ray to enter your tank.

9.If this is not possible then using a net slowly allow it to swim into the net. If possible, try to have its head in the belly of the net and the tail out the end to help limit the chance of the barb becoming tangled.

10.Turn the light off and allow your ray to become accustomed to its new home.

11.Your ray will have been starved for its trip so it will be hungry. After about 30 mins try it with a small amount of food.

12.If your ray is entering a tank with other tank mates we advise that you keep a watch to ensure the ray is not being bullied or the other way round too.