【明報專訊】With their large pectoral fins (胸鰭) flapping like wings, manta rays are graceful swimmers inhabiting mainly in tropical and subtropical waters of the Indian and Pacific oceans.

Fins longer than a car

Rays are fish, and are closely related to sharks. Different from bony fish (硬骨魚) that we normally see in the market, rays and sharks are cartilaginous fish (軟骨魚) which means their skeletons are made of cartilage (軟骨). Rays are characterised by their flat bodies, enlarged pectoral fins that are joined to the head, and gill slits (鰓裂) on their underside. The pectoral fins of manta rays can be as wide as 5.5 metres, which is even longer than a private car.

Giant but gentle

Despite their magnificent size, manta rays are filter feeders (濾食者). They have teeth that are useless for feeding. Instead, when feeding, they swim through water with their mouth wide open. They unfurl their cephalic lobes (頭部肉瓣) to guide plankton (浮游生物) into their mouth and the food is filtered through the rakers in the gills.

Helpful little friends

Apart from their own companions, manta rays are often seen with another fish, called remoras (?魚). Remoras attach themselves to the ray's body and help clean the small pieces of food falling from the ray's month. Manta rays sometimes visit "cleaning stations" in coral reefs as well, where other small fish remove organisms or parasites from manta rays' skin.

Secrets in the body colour

Manta rays have countershading colouration, which means they are dark on the upper side and light on the underside. This gives them camouflage protection— if looked from above, the dark colour of their back blends in with the dark depths of the ocean; if looked from below, the white belly "disappears" in the sunshine.

Turn appreciation to protection

Attracted by the manta ray's size, appearance and the congregating feeding behaviour, divers are willing to travel far for a chance to have close encounters with these majestic creatures. This has contributed to the development of ecotourism in areas such as Hawaii, East Africa, and Indonesia.

Although loved by tourists, manta rays are threatened by overfishing, whether targeted or incidental. Currently, manta rays are listed as "Vulnerable" in the International Union for Conservation of Nature Red List of Threatened Species.

To support and conserve this majestic creature, you can help by not consuming medicines made from manta rays. Besides, your support for sustainable seafood is another way to contribute to a healthy ocean!

Text & photos: Ocean Park Hong Kong

■Glossary

unfurl (v)展開

filter (v) 過濾

congregate (v) 聚集

incidental (adj) 偶然的

[Smarties' Power English 第216期]