Chinese lettuce coral  (Mycedium elephantotus)

Mycedium elephantotus is classified as Least Concern (LC) on the IUCN Red List (1), and listed on Appendix II of CITES (3).

Growing vertically in fragile, fan-like plates (2) (4) (5), colonies of Mycedium elephantotus generally form tiers or whorl-like structures, although there is considerable variation in the shape and size of colonies at different depths (2). Mycedium elephantotus corallites (the hard calcareous skeletons secreted by the individual polyps) are rounded, raised above the colony surface and have a distinctly ‘nose-shaped’ appearance (4) (5). Adjacent corallites form ‘terraces’ around the colony, while those positioned one above the other often fuse along the corallite wall, forming crests and grooves which run vertically on the colony surface (2). Colonies of Mycedium elephantotus are usually brown, grey, green, white or pink in colour, with green, white or red oral discs (the soft tissue that surrounds the mouth of the anemone-like polyps) (4).

Mycedium elephantotus is found on reefs in the Red Sea, the Gulf of Aden, the Indian Ocean, around South-east Asia, Japan and the South China Sea, off the coast of Australia and in the west and central Pacific Ocean (1) (6).

Mycedium elephantotus is found in most reef environments and is particularly common on slopes and overhangs. It typically occurs between depths of 3 and 60 metres, although it is most abundant at around 15 to 20 metres (1) (2). 

The polyps in colonies of Mycedium elephantotus do not have tentacles, instead obtaining food by rapidly engulfing organic matter in a layer of mucus which coats the surface of the colony. The food particles remain tangled in the ‘mucus net’, and are moved passively to the mouths of the polyps using a combination of gravity and water movement. When the net touches the oral discs the mouth becomes exposed, allowing ingestion of the food/mucus package (2). 

Like other reef-building corals, Mycedium elephantotus has many microscopic, photosynthetic algae, called zooxanthellae, living within the polyp tissues. The coral and the algae have a mutually beneficial relationship; the coral provides protection for the algae, which in return provide energy and nutrients for the coral through photosynthesis. Both Mycedium elephantotus and its zooxanthellae are very sensitive to changes in water temperature and acidity, and any increase in the water temperature greater than one or two degrees above the normal average can stress the coral and cause ‘bleaching’, a phenomenon in which the coral expels it zooxanthellae and turns white (4) (7). 

Mycedium elephantotus has a clear annual reproductive cycle, although timing of the peak spawning period differs according to the location within the Indo-Pacific. This coral is a hermaphrodite, meaning that both male and female organs are present on the same individual (6).

Mycedium elephantotus is heavily targeted in some areas for the aquarium trade, while other local threats include invasive species, pollution, human development, tourism and recreation. In general, the major threat to all corals is global climate change, in particular increasing temperatures and ocean acidification, which lead to coral bleaching and increased susceptibility to disease (1).

Mycedium elephantotus is listed on Appendix II of the Convention of International Trade in Endangered Species (CITES), meaning that all trade in the species should be carefully monitored, and it is also known from several Marine Protected Areas.

Research on the population, ecology and habitat status of Mycedium elephantotus is urgently required, as well as further work to determine the resilience of this species to major threats. New protected areas should be identified and established, taking into account the need to provide additional protection to prevent the overexploitation of Mycedium elephantotus for the aquarium trade, while placing more emphasis on research into coral disease, pathogen and parasite management (1).

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

For further information on the conservation of coral reefs see:

• Reef Check:
  http://www.reefcheck.org
• The Coral Reef Alliance:
  http://www.coralreefalliance.org