Natural Selection and Evolution of Blue-Spotted Ribbontail Stingrays
It is said that stingrays and rays of all kind have evolved from sharks. Animal Planet explains it as, “[a] ray is basically a fattened out shark with a long tail.” You can see the similarities between the two, such as gills, crushing plates in the jaw, and a cartilage skeleton. If you flatten out a shark, get rid of the dorsal fin, widen the pectoral fins, and change the caudal fin to a tail, you have ray. You can see how they evolved from the pictures below, from left to right.
It is said that stingrays and rays of all kind have evolved from sharks. Animal Planet explains it as, “[a] ray is basically a fattened out shark with a long tail.” You can see the similarities between the two, such as gills, crushing plates in the jaw, and a cartilage skeleton. If you flatten out a shark, get rid of the dorsal fin, widen the pectoral fins, and change the caudal fin to a tail, you have ray. You can see how they evolved from the pictures below, from left to right.
Adaptations:
*Placement of Eyes - Strategically placed eyes help to see predators when they are buried and hiding in the sand, which is also another behavioural adaptation to be discussed. The environmental factor that could have caused this is an ice age, where the ray’s prey all died out so they had to hide in sand to escape its predators. It learned to bury itself in sand, but to see out of the sand, it would need eyes on top of its head to know when to skedaddle. Because of this, rays with eyes closer to the top of its head would be naturally selected and this would cause directional selection. (You can see this in the graph below.)
*Placement of Eyes - Strategically placed eyes help to see predators when they are buried and hiding in the sand, which is also another behavioural adaptation to be discussed. The environmental factor that could have caused this is an ice age, where the ray’s prey all died out so they had to hide in sand to escape its predators. It learned to bury itself in sand, but to see out of the sand, it would need eyes on top of its head to know when to skedaddle. Because of this, rays with eyes closer to the top of its head would be naturally selected and this would cause directional selection. (You can see this in the graph below.)
*Burying and hiding itself in sand - Because of food shortages and predators still thriving, the stingray had to learn how to survive. They started burying themselves in sand to escape their predators and avoid being eaten. Due to this adaptation, you can now see more stingrays with eyes on top of their head, as referred to above.
*Tail – Stingrays evolved from sharks and over time the shark’s dorsal fin developed into the whip-like tail we see on stingrays today. The tail is useful because it aids in helping the stingray bury itself in sand to hide from predators. Also, the tails may have up to five spines at the base of the tail which contain toxins and is why they are referred to as venomous. (Fun fact: If a stingray uses one of its spines to defend itself, it will break off but a new one will start growing back immediately.) Climate change could have led to change in predators, which is why they needed new ways to hide and defend themselves. Also, the tail might not have been enough to protect itself, so venomous spines were developed too.
*Smell and Electroreceptor – Since stingrays are mostly active during the night, they can’t rely on their eyesight for hunting prey. It is said that the stingray always had a sense of smell, but it has strengthened over time. “Electroreception is the biological ability to receive electrical impulses.” It detects its surroundings and environments and works like a compass; some even say the rays can sense the earth’s magnetic fields. The change to mostly sandy environments and smaller prey could have led to this adaptation. Also, its eyesight and position of its eyes on top of its head could’ve had something to do with it too. You can see the evolution of Electroreception over time in the picture below. Sharks and rays are highlighted.
*Smell and Electroreceptor – Since stingrays are mostly active during the night, they can’t rely on their eyesight for hunting prey. It is said that the stingray always had a sense of smell, but it has strengthened over time. “Electroreception is the biological ability to receive electrical impulses.” It detects its surroundings and environments and works like a compass; some even say the rays can sense the earth’s magnetic fields. The change to mostly sandy environments and smaller prey could have led to this adaptation. Also, its eyesight and position of its eyes on top of its head could’ve had something to do with it too. You can see the evolution of Electroreception over time in the picture below. Sharks and rays are highlighted.
Summary 1:
In the above diagram (EVOLUTIONARY TREE TIMELINE), you can see where the stingrays evolved from sharks. Batoidea, the last seen branch in this diagram, includes rays, skates, and sawfish. They evolved about 145 million years ago, during the Cretaceous period and their population really started growing during the Cenozoic era, about 65 million years ago.
Summary 2:
During the Cretaceous era, there is a relatively warm climate which created shallow inland areas, to where the stingrays most likely evolved. This led to new habitats with new smaller, prey, resulting in the evolution of filter-feeding sharks and rays. Four key adaptations separated them from earlier species. They were: size, a very large or nearly terminal mouth, reduced dentition, and elaboration of gill tissues.
Summary 3:
The Giant Freshwater Stingray is a species that is at risk of going extinct as of right now. This is because of its habitat as well as its body size. It can grow to be over 6 feet across and weigh over 1200 pounds. It also has a gray body color, which doesn't ward off predators. Its body size makes it easy to accidentally catch by fishermen and its color doesn't ward off predators. These adaptations make it vulnerable. You can see a picture of below.
In the above diagram (EVOLUTIONARY TREE TIMELINE), you can see where the stingrays evolved from sharks. Batoidea, the last seen branch in this diagram, includes rays, skates, and sawfish. They evolved about 145 million years ago, during the Cretaceous period and their population really started growing during the Cenozoic era, about 65 million years ago.
Summary 2:
During the Cretaceous era, there is a relatively warm climate which created shallow inland areas, to where the stingrays most likely evolved. This led to new habitats with new smaller, prey, resulting in the evolution of filter-feeding sharks and rays. Four key adaptations separated them from earlier species. They were: size, a very large or nearly terminal mouth, reduced dentition, and elaboration of gill tissues.
Summary 3:
The Giant Freshwater Stingray is a species that is at risk of going extinct as of right now. This is because of its habitat as well as its body size. It can grow to be over 6 feet across and weigh over 1200 pounds. It also has a gray body color, which doesn't ward off predators. Its body size makes it easy to accidentally catch by fishermen and its color doesn't ward off predators. These adaptations make it vulnerable. You can see a picture of below.
Summary 4:
Unlike the Giant Freshwater Stingray, the Blue-Spotted Ribbontail Ray, pictured above, is small in size and has adapted coloration to ward off its predators. Its small size makes it easy to hide in caves or even under sand, so predators have a harder time finding it. Also, the small size makes it easier to maneuver out of fishing nets and it can dart quickly to avoid them. The coloration wards off predators because they don’t want to be stung. Its signature blue spots serve as a warning to other species.
Unlike the Giant Freshwater Stingray, the Blue-Spotted Ribbontail Ray, pictured above, is small in size and has adapted coloration to ward off its predators. Its small size makes it easy to hide in caves or even under sand, so predators have a harder time finding it. Also, the small size makes it easier to maneuver out of fishing nets and it can dart quickly to avoid them. The coloration wards off predators because they don’t want to be stung. Its signature blue spots serve as a warning to other species.