The Bluespotted Ribbontail Ray Taeniura lymma is also known as the bluespotted ray, bluespotted fantail ray, bluespotted stingray and ribbontail stingray. They are common inhabitants of the reefs on the Tanzanian coast and their coloration makes them very easy to identify.
Rays are closely related to sharks and they have cartilaginous skeletons rather than bone and they have no swim bladder. From a distance they can be confused with the newly reclassified Indian Ocean Blue-Spotted Stingray ( ( Neotrygon indica sp. nov) which was previously known as Neotrygon Kuhlii. These have a sharp tail with black and white lines on it.
APPEARANCE
The Bluespotted Ribbontail Rays have a yellow green to yellow brown coloured body with a prominent set of eyes that protrude above the body. The body is covered in bright blue spots of varying sizes and each individual has its own pattern of spots. The eyes are a bright yellow colour and they have the ability to change the size of their pupils. The pectoral fins form the disc of the ray and towards the rear of the body below the disc are the smaller pelvic fins.
The tail extends back from the disc and has a prominent blue stripe down either side. Towards the end of the tail are two spikes with venom. These can be seen pictured in images below. Alongside the eyes are two spiracles which are used to take water in and to push it over the gills. The underside of the body where the mouth is situated is a light grey- brown colour. Bluespotted Ribbontail ray’s grow to 35 cm in width and up to 80 cm in length and weigh up to 5 kg.
IN THE WILD
Being nocturnal feeders, during the day Bluespotted Ribbontail Rays are usually seen hiding under the over hang of corals. In the shadows the blue spots give quite effective camouflage. They will occasionally be seen hidden in the sand but this is not comm0n. When they are hidden in the sand and a diver approaches too close they will often break cover and take off at a high speed. They tend to swim low over the bottom kicking up sand and change direction every few meters and swim a zig zag course. On night dives they are often encountered over sandy areas and will generally take off at a high speed. As they have no swim bladder it is quite easy for them to sink to the bottom and sit there.
HABITAT
The Bluespotted Ribbontail Ray is found across the near shores of the Indian ocean and in the west Pacific. They are found between depths of 2-30 meters. Every spring large numbers are seen off the north coast of South Africa.
DIET
The Bluespotted Ribbontail Ray are nocturnal feeders , feeding on molluscs, polychaete worms, shrimps, crabs, and small benthic fishes. They have highly developed electromagnetic sensors and lateral lines which allow them to detect their prey hidden in the sand. Once found they envelop the prey with their disc and use their powerful mouths to crush them. The specimen below was photographed at night swimming over a sandy bottom searching for prey. The mouth can be clearly seen.
REPRODUCTION
Bluespotted Ribbontail rays exhibit Ovoviviparity or aplacental viviparity. This means that although internal fertilization occurs, individuals develop sustained by yolk rather than a direct placental connection. Additional nutrition is obtained from uterine secretions known as histroph. When fully developed the females give birth to between four and seven young. The young are approximately 12-14 cm wide and are fully developed, Being small they are adept at hiding. A newly born juvenile approximately 14 cm wide is pictured below. These are seen on the Tanzanian coast in early spring.
SELF DEFENCE
Although the Bluespotted Ribbontail Rays are very placid and almost never attack divers they should not be underestimated. Their tail has either one or two spines on it which have venom in them. These can be seen pictured below. They can give an extremely painful sting and one should always stay clear of rays. The treatment for such a sting would be hot water as hot as one can take it in the affected area. Aside from the venom the spines are capable of giving a deep physical injury which can be life threatening. Some twenty years ago a visiting yachtsman in Kilwa, Tanzania attempted to rescue one of these rays from a fishing net and one of the spines pierced his femoral artery. He bled to death in minutes. Best to stay well clear of any ray as Steve Erwin also found out.
COMMERCIAL EXPLOITATION
The Bluespotted Ribbontail Ray are caught and eaten in Tanzania by subsistence fishermen. They are usually speared in the shallows.
AQUARIUMS
Juvenile Bluespotted Ribbontail Rays are kept by some enthusiasts but they seldom live very long. Some Public aquariums with large tanks have succeeded in breeding them.
BLUESPOTTED RIBBONTAIL RAY CLASSIFICATION
Kingdom:Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass:Elasmobranchii
Order: Myliobatiformes
Family: Dasyatidae
Genus: Taeniura
Species:T. lymma
LITERATURE CITED
- The Reef Guide fishes, corals, nudibranchs & other invertebrates: East and South Coasts of Southern Africa by Dennis King & Valda Fraser
- Van der Elst, R. (1993). A Guide to the Common Sea Fishes of Southern Africa (third ed.)