Rays are undoubtedly one of the most interesting, extraordinary and strange creatures that live in the sea. A flying carpet, a stealth bomber, a giant bat . . . these are just some of the nicknames people use when they see them for the first time. Rays are flat fish that belong to the same family as sharks and have also evolved as sharks. Unlike other fish, sharks and rays have no bones and the skeleton is composed of cartilage, which is weaker than bone but has the advantage of flexibility and resistance against diseases.
Stingrays typically lead a social life, and they are to be found in all the oceans.
Most of the cartilaginous creatures have venomous spines at the base of their tail. These spikes are for protection only and can cause sharp pain to inexperienced predators. When it stings, the tip is broken and remains inside the body of the victim, and can cause a number of infections. Anyone who gets stung will suffer from acute pain and possibly from necrosis at the point of injury and in extreme cases, death. Their greatest enemies (except for humans) are their relatives, the sharks.
In addition, some of them have long tails that resemble a whip and these are equipped with formidable spikes, and some of them have short tails.
Rays can be seen in sandy areas, coral reefs and open water.
Of all the species that live in the sea, this is undoubtedly one of the most interesting species, including some of the most bizarre-looking creatures, which are for the most part shy, but some of them are also very sociable.
The species of rays can be divided into three different groups according to the regions in which they live, their body structure and their method of hunting:
Manta ray: spectacular and unique. They can be seen swimming in large schools of up to several dozen, in the southern part of the Red Sea. They live in open water, where they filter their food: plankton. The filtering action is performed by their network of gills; lobes that look like arms help by directing the water towards the mouth, and from there to the gills. These lobes are located at the front of the head and give them the appearance of a devil with horns. In the past the mantas had been attributed with qualities associated with bad luck and many sailors believed that bad luck would come to anyone harming them.
The plankton collection process looks like racing pilot demonstrating aerial performance. The manta identifies large concentrations of plankton called ‘plankton clouds’ and performs a lot of strange rotations within these clouds. The large body – over 6.5 meters, and enormous weight of up to 2 tons – is home for many creatures, including fish that accompany them everywhere.
Stingrays: the largest and most diverse group of rays. These fish are flat and round and have a long tail; their bodies are adapted to the areas that they inhabit – sandy beds. Thanks to their structure these camouflage artists manage to cause a swirl of water by flapping their “wings”, which lift sand onto their bodies so that only their eyes – which are set in the uppermost part of their head – protrude. Their food consists mainly of invertebrates living in those same sandy areas. Craters on the sea bed are often evidence of hunting areas. The mouth of the stingray is located on the lower side of the body, and its eyes are on the upper side, so actually a stingray cannot see its food, and it is only by using its sensors that a stingray can identify and catch its food from the sand. The tail is one of the identifying marks of the stingray – long and sometimes armed with sharp points along it, in addition to as many as 3 venomous spines at the base of the tail.
Some live in shallow water, for example the bluespotted ribbontail reef stingray, taeniura lymma, which lives mostly in shallow lagoons in the areas of the reef. While it searches for food it creates clouds of dust. It has sapphire-colored spots on its body, hence the name.
The marbled electric ray (torpedo sinuspersici) belongs to this group: it generates electricity using special organs in the pectoral fin. The electricity it produces helps it find and paralyze potential prey, which do not see the electric ray as it is usually completely covered with sand.
Spotted eaglerays – aetobatus narinari: excellent swimmers that live in the coral reef and on the rocky bottom. Their food consists of mollusks with they gather using a special tooth that is suitable for scratching the shellfish from its base, and by using strong teeth that are designed for cracking, which are located deep inside the mouth; these teeth provide them with the ability to crack the hard structure, remove the shells, and get a meal. They are up to 3 meters in size and the origin of their name is the way that they swim, which is reminiscent of a bat.
Some of the rays are particularly friendly: at Sting Ray City in the Bahamas, local stingrays have gotten used to coming to feeding grounds and tourists can hand feed them fish and invertebrates. Around the world there are several places where they can be hand fed. However, beware not to try and feed stingrays in the sea.
At the Underwater Observatory Park the stingray caregivers place the food into their mouths and take advantage of this opportunity for an up-close visual inspection of their body. In the shark pool one can see a spotted eagleray eating shellfish directly from the hands of the diver, and those with good hearing can actually hear the sound of the shell being cracked.
Nowadays, most of the danger to rays comes from humans – especially fisherman – and the destruction of habitats and hunting grounds.
Written by: Aviv Levi – The Scientific Director of the Underwater Observatory Park.