Stingray

Stingrays are a diverse group of cartilaginous fish belonging to the suborder Myliobatoidei. This means their skeletons are made of flexible cartilage rather than hard bone.

Today, scientists recognize about 220 known species organized into 29 different genera. These animals are vital components of marine and freshwater ecosystems. They are found in many environments across the globe. Some live in warm, coastal tropical waters. Others inhabit the dark, deep ocean. A few specialized species even live in freshwater rivers.

Stingrays have a highly specialized anatomy that helps them survive in varied habitats. Their mouths are located on the ventral side, which is the underside of their bodies. They possess hyostylic jaw suspension, a mechanism where the mandibular arch is held by the hyomandibula. This allows the upper jaw to be highly mobile and protrude outward. Their teeth are actually modified placoid scales. These teeth are regularly shed and replaced throughout the animal's life. Most species have large, flat teeth designed to crush hard-shelled prey.

Breathing is a complex process for these fish because they use two different methods. Most of the time, they take water in through their mouths. The water then passes through the gills for gas exchange. However, many stingrays are demersal, meaning they live near the bottom. They often bury themselves in the sand to hide from predators or wait for prey. When their mouths are covered by sediment, they use spiracles. Spiracles are small openings located just behind the eyes. These allow the ray to draw clean water directly into the gills.

To find food, stingrays rely on more than just sight. Because their eyes are on top and their mouths are on the bottom, they cannot see prey once it is captured. They use smell and specialized organs called ampullae of Lorenzini. These are electroreceptors that sense the natural electrical charges of other animals.

Some rays use a strategy called "tenting" to hunt. They press their pectoral fins against the sea floor and lift their heads. This creates a suction force that pulls prey underneath their bodies. Large pelagic rays, like the manta, use ram feeding to catch plankton. They swim through patches of plankton to consume vast quantities of food.

Stingrays move through the water using their paired pectoral fins. This is different from sharks, which rely mostly on a single caudal fin. There are two main types of pectoral fin locomotion. Undulatory locomotion involves shorter, thicker fins for slow movement on the bottom. Oscillatory locomotion uses long, thin fins for faster speeds in open water.

This movement allows them to adapt to either benthic or pelagic lifestyles.

The history of stingrays spans millions of years of evolution. They diverged from their closest relatives, the panrays, during the Late Jurassic period. They continued to diversify throughout the Cretaceous period.

Fossil evidence, such as teeth, has been found in sedimentary deposits worldwide. The oldest known taxon is "Dasyatis" speetonensis from the Hauterivian of England. Some fossils, like the extinct Cyclobatis, show how different species evolved similar body plans. Other fossils, such as the Lessiniabatis from Italy, show unusual features like very short tails.

Reproduction in stingrays involves complex biological and social behaviors. Many species are ovoviviparous, meaning they give birth to live young in litters. These litters typically range from five to thirteen offspring. In some species, the mother provides uterine "milk" after the embryo's yolk sac is depleted.

Mating can involve long periods of social interaction and aggression. In the Atlantic stingray, males may mate for seven months. This long period is linked to increased levels of androgen hormones. Scientists believe these hormones drive the aggressive behaviors seen during courtship. Unfortunately, many species are now threatened or vulnerable to extinction. This is often caused by unregulated fishing practices worldwide. As of 2013, the IUCN has listed 45 species as vulnerable or endangered.