''Pavona cactus'', the cactus coral, potato chip coral or leaf coral, is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
colonial
Colonial or The Colonial may refer to:
* Colonial, of, relating to, or characteristic of a colony or colony (biology)
Architecture
* American colonial architecture
* French Colonial
* Spanish Colonial architecture
Automobiles
* Colonial (1920 au ...
stony coral
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a ...
in the
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Agariciidae
The Agariciidae are a family of reef-building stony corals. This family includes cactus corals, plate corals, and lettuce corals. Members of the family include symbiotic algae called zooxanthellae in their tissues which help provide their energ ...
. This coral is found in shallow waters on reefs and in lagoons in tropical parts of the
Indo-Pacific
The Indo-Pacific is a vast biogeographic region of Earth.
In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
region.
Description
Colonies of this species have vertical, irregular, two-sided fronds about tall and not more than thick. The
corallite
A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...
s housing the
polyps are very shallow and form widely separated rows parallel to the margins of the fronds. The bases of these fronds may be dead while the upper parts are still alive supported by the skeletal tissue below. The fronds may be clustered together in a supercolony formed from one or more individual colonies and extending for several metres (yards) across the
seabed
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...
.
[ This is a ]zooxanthellate
Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''Sy ...
species of coral, with symbiotic
Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
microscopic algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
living in its tissues. It is an olive green or a brownish colour.[
]
Distribution
''Pavona cactus'' is found in the tropical Indo-Pacific, its range extending from the Red Sea
The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...
and East African coast to Japan, Tahiti and Australia.[ at depths down to .]
Biology
The polyps of ''Pavona cactus'' extend their tentacle
In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...
s at night to catch plankton
Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...
. They also benefit and obtain nourishment from the intracellular zooxathellae. These use energy from the sun to turn simple substances into complex carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
s and the coral makes use of the surplus nutrients. The algae benefit from being in a protected, well-lit environment well clear of the seabed and by receiving nitrogenous waste from the coral.planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...
larva that settles on the seabed when it has completed its development. Here it undergoes metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...
to become a coral polyp which buds repeatedly to start a new colony.[ Another method by which colonies may increase in number is by fragmentation. If a bit of coral that has broken off a parent colony becomes wedged in a suitable position, it can continue to grow and reproduce by budding to form a new colony.][
]
Status
Although this coral is common and has a wide range, the International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
lists this species in its Red List of Threatened Species
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biologi ...
as being " Vulnerable".[ Under adverse conditions, such as a rise in sea temperature, this coral may expel its zooxanthellae and become bleached. It is then much more susceptible to disease. Coral reefs in general are under threat from a decline in the quality of the habitat through mechanical damage, pollution, sedimentation, ]ocean acidification
Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
and global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
and ''Pavona cactus'' faces another threat in that it is collected for the aquarium trade.
References
{{Taxonbar, from=Q3949854
Agariciidae
Animals described in 1775
Coral reefs