Stingray

The Basics

The stingray is a cartilaginous fish that can be found in temperate and tropical marine and freshwater habitats around the world. These fish belong to the order Myliobatiformes and are closely related to sharks. Instead of sharp teeth, like the sharks, some species have a barb at the end of their tail that can be used to pierce potential predators. These barbs are venomous.

Stingrays have a flattened body that has pectoral fins and a long tail. Its coloration usually reflects the shading on the ocean floor enabling it to camouflage itself and hide from predators such as sharks. Its eyes are situated on its dorsal (top) side, whereas the stingray’s mouth, gills, and nostrils are found on its underbelly. These cartilaginous fish use their pectoral fins for locomotion. Most stingrays swim by moving their body like a wave, while others flap their paired fins like wings. Their tail can be used to help maneuver them in the water.

Like the shark, stingrays have electrical sensors called ampullae of Lorenzini. These organs are found by the stingray’s mouth and sense the natural electrical charges that other animals emit. Many ray species also have jaw teeth which they use to crush mollusks such as mussels, clams, and oysters.

During reproduction, the males court the females by following them and biting at her pectoral disc. Stingrays reproduce sexually when the male puts one of his two claspers into her vent. Stingrays are ovoviviparous which means that they give birth to live young. The litters consist of five to 13 offspring. The embryos develop in the female’s womb without a placenta, Instead, the embryos have a yolk sac from which they absorb the nutrients that they need, and after this, the mother provides uterine milk. Once they are born, the young usually disassociate from the mother and swim away and require no maternal care. There are some exceptions to this, such as the giant freshwater stingray (Himantura chaophraya), where the mother looks after her young and they swim with her until they are roughly one-third of her size.

Stingrays are considered to be at risk and several species are listed as vulnerable and threatened by the IUCN. The main threats to stingrays are habitat loss, overfishing, and climate change. The main threat is overfishing as rays are not only harvested for their meat but also for their gill plates which are used in traditional Chinese medicine.

Stingray Families

1. Hexatrygondae (sixgill stingray) – the sixgill stingray is the only species in this family and like its names suggests it has six gills. Another distinguishing feature of this ray is its triangular-shaped snout and gill arches.
2. Plesiobatidae (deepwater stingray) – the deepwater stingray, also known as the giant stingaree, is the sole species found in this family. This stingray lives at depths of over 2,200 feet (670.5 meters)!
3. Urolophidae (stingarees) – these rays are relatively small and are found in warm, shallow waters that usually have sandy bottoms where they can bury themselves. There are two genera and approximately 35 species belonging to this family.
4. Urotrygonidae (round rays) – as the name suggests, the round rays have a round body with a slender tail and no dorsal fins. They are most commonly found in the warm waters of the Caribbean Sea and along the coastlines of North and South America.
5. Dasyatidae (whiptail stingrays) – whiptail stingrays get their name from their tail – it’s shaped like a whip and has a venomous barb on the end. Most whiptail species are found in marine environments, although some species are found in rivers such as the giant freshwater stingray of Southeast Asia.
6. Potamotrygonidae (river stingrays) – these freshwater stingrays are found in rivers in tropical and subtropical South America.
7. Gymnuridae (butterfly rays) – rays in this family have a flattened body and a shorter tail than other ray species and can grow quite large. Some butterfly ray species can reach up to 13 feet ( 4 meters) across!
8. Myliobatidae (eagle rays) – unlike other ray families, species belonging to the family Myliobatidae are found swimming in the pelagic zone of the open ocean and can often be observed jumping out of the water. Notable species include the common eagle, banded, mottled, and bat eagle rays.

Fun Facts about the Stingray!

Stingrays are a diverse group of fishes that can be found in a range of marine and freshwater habitats. Most commonly found in warmer waters, stingrays are cartilaginous fish that are closely related to sharks. Like sharks, they have been around for a really long time and they also lack a swimbladder. Stingrays also have several other biological adaptations that have helped them to persist for millions of years. Let’s take a closer look!

Venomous Barbs

While not all stingrays have barbs on their tail, a large proportion of them do and these barbs are venomous! The barb is fairly long and pointed and has several serrations that go in the opposite direction – making it look almost like a Christmas tree in shape. The barbs are used to deter potential predators.

The barb contains a venom gland that injects venom into the stingray’s victim. The venom is potent and contains neurotoxins, enzymes, and the neurotransmitter serotonin which slows blood circulation and restricts smooth muscle contraction preventing dilution of the venom.

Stingrays are usually gentle, docile animals that will not go out of their way to attack. However, they are the most common cause of fish-related injury in humans. People should be cautious when swimming in an area where stingrays are known to live. While a sting from a stingray is rarely fatal, it can be extremely painful. One way of avoiding this is to shuffle your feet in the sand when walking in shallow waters that are home to these rays. This will warn them that you are there and prevent you from stepping on them and being struck by their barb. If you do get stung then it’s best to treat the wound with hot water and see a doctor immediately.

Stingrays Were Alive During The Jurassic

Rays are thought to date back over 150 million years to the Jurassic Period, meaning that stingrays have outlived the dinosaurs! Luckily, their teeth and scales can fossilize which has allowed scientists to discover how long they have been around. It’s rare to find a complete skeleton however as their skeleton is constructed from cartilage which doesn’t fossilize. Stingray fossils are common, especially fossilized teeth, but only a few examples of complete stingray fossils exist.

Buoyancy

Unlike most fish, stingrays don’t have a swim bladder – an organ that makes fish buoyant – so when they aren’t swimming they start to sink. However, they use the flattened shape of their body and their pectoral fins to glide through the water. The shape of their body and the lack of a swimbladder help them to sink to the ocean floor and hide from predators in the sand. This helps the stingray to conserve energy.

Several other fish species also lack a swimbladder including the stingrays close relative, the shark!

Stingrays have Spiracles

Like all fish, stingrays breathe underwater but they don’t take water in through their mouths and pump it through their gills as fish do. Instead, stingrays have spiracles which are openings they use for gas exchange. These openings are located behind their eyes and the stingrays use these to take water in. The water can then be pumped through their gills which are located on their underside. The stingray’s mouth is then free to eat as it does not need to take in water. Also, this adaptation allows the stingray to breathe when it is buried in the sand.