Common Eagle Ray [Myliobatis aquila]

Eagle rays (the Myliobatidae family of fish) are a family of mostly large rays living in the open ocean rather than at the bottom of the sea. Eagle rays feed on snails, mussels and crustaceans, crushing their shells with their extremely hard teeth. They are excellent swimmers and are able to jump several metres above the surface.

The taxonomy of this group is uncertain; it is placed either in the order Myliobatiformes or Rajiformes. There are eight genera belonging to the eagle rays: Myliobatis (common eagle rays), Rhinoptera (cownose rays), Pteromylaeus (bull rays), Aetobatus (bonnet rays), Aetomylaeus (smooth tail eagle rays), Californica (bat rays), Mobula (devil rays), and Manta (manta rays). (In some taxonomies the devil rays and manta rays are placed their own family, Mobulidae.) [text source:Wikipedia]

Picture: Towers, Egypt by Sami Salmenkivi


Manta ray [Manta birostris]

x Manta

The Manta ray, Manta birostris, is the largest of the rays, with the largest known specimen having been about 7.6 m (about 25 ft) across, with a weight of about 2,300 kg (about 5,000 lb). It ranges throughout all tropical waters of the world, typically around coral reefs. Mantas have been given a variety of common names, including Atlantic manta, Pacific manta, devilfish, and just manta. Some people just call all members of the family stingrays, though stingrays comprise a separate family of rays (Dasyatidae).

Mantas are most commonly black dorsally and white ventrally, but some are blue on their backs. A manta’s eyes are located at the base of the cephalic lobes on each side of the head, and unlike other rays the mouth is found at the anterior edge of its head. To respire, like other rays, the manta has five pairs of gills on the underside. To swim better through the ocean, they have a diamond shaped body plan, using their pectoral fins as graceful “wings”. Distinctive “horns” (from which the common name Devil ray stems) are on either side of its broad head. These unique structures are actually derived from the pectoral fins. During embryonic development, part of the pectoral fin breaks away and moves forward, surrounding the mouth. This gives the manta ray the distinction of being the only jawed vertebrate to have novel limbs (the so-called six-footed tortoise, Manouria emys, does not actually have six legs–only enlarged tuberculate scales on their thighs that look superficially like an extra pair of hind limbs). These flexible horns are used to direct plankton, small fish and water into the manta’s very broad and wide mouth. The manta can curl them to reduce drag while swimming.

Taxonomically, the situation of the mantas is still under investigation. Three species have been identified: Manta birostris, Manta ehrenbergii, and Manta raya, but they are quite similar, and the latter two may just be isolated populations. The genus Manta is sometimes placed in its own family, Mobulidae, but this article follows FishBase taxonomy, and places it in the family Myliobatidae, along with eagle rays and their relatives. Mantas are filter feeders: they feed on plankton, fish larvae and the like, passively filtered from the water passing through their gills as they swim. The small prey organisms are caught on flat horizontal plates of russet-coloured spongy tissue, that span the spaces between the manta’s gill bars.

Mantas are extremely curious around humans, and are fond of swimming with scuba divers. Although they may approach humans, if touched, their mucus membrane is removed, causing lesions and infections on their skin. They will often surface to investigate boats (without engines running). They have the largest brain-to-body ratio of the sharks and rays. Mantas are known to breach the water into the air.

Picture: Komodo, Indonesia by Sami Salmenkivi

Bluespotted Stingray [Dasyatis kuhlii]

(Red Sea)


Bluespotted stingray, (Dasyatis kuhlii) also known as Kuhl’s Stingray is a stingray. It is light green with blue spots. Their disk width hovers around 67 cm.

Dasyatidae is a family of rays, cartilaginous marine fishes, related to skates and sharks. Most dasyatids are relatively widespread and unlikely to be threatened, there are several species where the conservation status is more problematic, leading to them being listed as vulnerable or endangered by IUCN.

Dasyatids are propelled by motion of their large pectoral fins (commonly mistaken as “wings”). Their stinger is a razor-sharp, barbed, or serrated cartilaginous spine which grows from the ray’s whip-like tail (like a fingernail), and can grow as long as 37 cm (about 14.6 inches). On the underside of the spine are two grooves containing venom-secreting glandular tissue. The venom contains the enzymes 5-nucleotidase and phosphodiesterase which breakdown and kill cells; and the neurotransmitter serotonin which provokes smooth-muscle contractions. This gives them their common name of stingrays (a compound of “sting” and “ray”), but the name can also be used to refer to any poisonous ray. Divers often refer to them as “Sea Devils”. (source: wikipedia)

Picture 1: Red Sea, Egypt, picture 2: Zanzibar, Tanzania by Sami Salmenkivi