Thin leaf lettuce coral (Agaricia tenuifolia)

Description

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Thin leaf lettuce coral fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Thin leaf lettuce coral description

A delicate coral with flat, thin, upright plates, the thin leaf lettuce coral (Agaricia tenuifolia) forms elongated colonies which are brown, greenish or rust coloured with pale margins and orange tentacles ^{(3) (4)}. On reefs exposed to particularly high energy waves, the thin leaf lettuce coral forms box-like networks that are resistant to wave destruction. In lagoon environments with little wave actions, this species forms delicate frameworks ⁽¹⁾. 

The colonies of the thin leaf lettuce coral are composed of numerous tiny, anemone-like animals called polyps. The polyps secrete a hard skeleton, and the skeleton of each individual polyp is known as a ‘corallite’ ⁽³⁾. The corallites of the thin leaf lettuce coral are arranged in rows separated by ridges. The coral skeleton forms the bulk of the colony, with the living polyp tissue comprising only a thin veneer. Over successive generations, the growth of the corallites contributes to the formation of a coral reef ⁽³⁾.

Thin leaf lettuce coral biology

The thin leaf lettuce coral receives the majority of its nutrition from symbiotic algae, known as zooxanthellae, which live within its tissues. The algae provide the coral with nutrients through photosynthesis, and in return receive a stable environment in which to live. A dependence on photosynthesis restricts corals such as the thin leaf lettuce coral to living in relatively shallow, clear, warm waters, but enables them to grow quickly and form large reef structures ⁽³⁾. The thin leaf lettuce coral also feeds actively on tiny zooplankton, which it catches using stinging cells on the tentacles of the polyps ⁽³⁾. 

The thin leaf lettuce coral is hermaphroditic, meaning that each polyp contains both male and female sex organs ⁽⁵⁾. This species releases eggs and sperm into the water for external fertilisation, and the resulting larvae drift in the water column before eventually settling onto the substrate and developing into polyps ^{(3) (6)}.

In addition to reproducing sexually, corals are able to reproduce asexually by budding, forming new polyps by the division of existing polyps ⁽³⁾.

Thin leaf lettuce coral range

The thin leaf lettuce coral occurs in the Caribbean Sea and the southern Gulf of Mexico. It is common and abundant in the southern and western Caribbean but is less common elsewhere ⁽¹⁾.

Thin leaf lettuce coral habitat

The thin leaf lettuce coral is found on shallow reefs, where it occurs in areas exposed to waves, between depths of 1 and 15 metres ⁽¹⁾.

Thin leaf lettuce coral status

The thin leaf lettuce coral is classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾ and listed on Appendix II of CITES ⁽²⁾.

Thin leaf lettuce coral threats

With an estimated 20 percent of the world’s coral reefs already destroyed, the thin leaf lettuce coral faces many of the threats that are affecting coral reefs globally ^{(7) (8)}. Worldwide, there is increasing pressure on coastal resources resulting from human population growth and development. There has been a significant increase in domestic and agricultural waste in the oceans, poor land-use practices that result in an increase in sediment running on to the reefs, and over-fishing, which can have knock-on effects on the reef ⁽⁷⁾. 

However, the major threat to corals is global climate change, with the expected rise in ocean temperatures increasing the risk of coral ‘bleaching’, in which the stressed coral expels its zooxanthellae, often resulting in the death of the coral ⁽⁸⁾. Climate change may also lead to more frequent, severe storms, which can damage reefs, and rising carbon dioxide levels may make the ocean increasingly acidic. Such stresses can also make corals more susceptible to disease, parasites and predators, such as the crown of thorns starfish (Acanthaster planci) ^{(7) (8) (9)}.

Thin leaf lettuce coral conservation

Parts of the range of the thin leaf lettuce coral fall within Marine Protected Areas ⁽¹⁾, although enforcement within these can often be poor ⁽⁹⁾. International trade in the thin leaf lettuce coral should be carefully regulated under its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) ⁽²⁾. 

Recommended conservation measures for the thin leaf lettuce coral include research into its populations, abundance, ecology and resilience to threats, as well as monitoring and regulation of its harvest for the aquarium trade ⁽¹⁾. It would also benefit from the expansion of Marine Protected Areas, together with further research into coral diseases, and efforts to combat climate change ^{(1) (7) (9)}.

Find out more

For further information on the conservation of coral reefs, see:

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

Authentication

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Glossary

Algae

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Asexual reproduction

Reproduction that does not involve the formation of sex cells (‘gametes’). In many species, asexual reproduction can occur by fission (or in plants ‘vegetative reproduction’); part of the organism breaks away and develops into a separate individual. Some animals, including vertebrates, can develop from unfertilised eggs; this process, known as parthenogenesis, gives rise to offspring that are genetically identical to the parent.

Colonies

A group of organisms living together. Individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or ‘individuals’), which are produced by budding and remain physiologically connected.

Fertilisation

The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.

Hermaphroditic

Possessing both male and female sex organs.

Larvae

Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Photosynthesis

Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.

Polyp

Typically sedentary soft-bodied component of cnidaria, a group of simple aquatic animals including the sea anemones, corals and jellyfish. A polyp comprises a trunk that is fixed at the base, and a mouth that is placed at the opposite end of the trunk and is surrounded by tentacles.

Symbiotic relationship

Relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).

Zooplankton

Tiny aquatic animals that drift with currents or swim weakly in water.

References

1. IUCN Red List (April, 2011)
   http://www.iucnredlist.org/
2. CITES (April, 2011)
   http://www.cites.org/
3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townville, Australia.
4. Coralpedia - Agaricia tenuifolia (April, 2011)
   http://coralpedia.bio.warwick.ac.uk/en/corals/agaricia_tenuifolia.html
5. Richmond, R.H. and Hunter, C.L. (1990) Reproduction and recruitment of corals: comparisons among the Caribbean, the Tropical Pacific, and the Red Sea. Marine Ecology Progress Series, 60: 185-203.
6. Veron, J.E.N. (1993) Corals of Australia and the Indo-Pacific. University of Hawaii Press, Honolulu, Hawaii.
7. Wilkinson, C. (2008) Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia. Available at:
   http://www.gcrmn.org/status2008.aspx
8. Carpenter, K.E. et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560-563.
9. Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka. Available at:
   http://data.iucn.org/dbtw-wpd/edocs/2008-012.pdf