Biology:Orbicella
| Orbicella | |
|---|---|
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| Orbicella faveolata | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hexacorallia |
| Order: | Scleractinia |
| Family: | Merulinidae |
| Genus: | Orbicella Dana, 1846 [1] |
| Species | |
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See text
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Orbicella is a genus of stony corals in the Merulinidae family. The Orbicella species complex comprises three sister species, namely Orbicella faveolata, Orbicella annularis and Orbicella franksi, all of which are shallow-water, zooxanthellate species and are native to the tropical western Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico.
These corals are ubiquitous and major reef-builders in the Caribbean. Their similar colony morphologies misled scientists to historically lump them into a single species, Montastraea annularis, which included three morphotypes “bumpy”, “columnar” and “massive”. These growth forms were believed to arise as a response to abiotic factors (e.g., depth, light availability). This taxonomic classification was challenged by further ecological, reproductive, genetic, and morphologic evidence, which led to the re-description of three separate species, Montastraea faveolata (massive), M. annularis (columnar) and M. franksi (bumpy).[2][3][4]
A taxonomic revision published in 2012 established that the “Montastraea annularis species complex” formed a separate clade now in the genus Orbicella with three species names (O. faveolata, O. annularis, O. franksi).[5] O. annularis and O. faveolata are commonly called the boulder star coral [6] and the mountainous star coral,[7] respectively.
Characteristics
The colonies of these corals are massive and form dome-shaped mounds, with uneven surfaces and bulging projections. The corallites are small and closely packed. These corals are mostly some shade of light brown but sometimes have green oral discs.[8]
Skeleton properties
Orbicella skeleton is made from CaCO3 in the crystal form of aragonite. The growth rate has been correlated with depth.[9] In addition, the skeleton also contains brucite [Mg(OH)2] in the interseptal spaces (microbialites). These brucite particles encrusts microbes growing inside the coral skeleton.[10]
Speciation and reproductive barriers
Speciation is the gradual process by which species originate. Speciation can be studied from many perspectives, but regardless of the point of view it often requires reproductive isolation between species. In the case of the Orbicella, these species are broadcast spawner corals and release gametes annually in the same evening into the water column. The night of spawning is normally in August and September, the warmest months of the year, and five to eight nights after the full moon. Some authors argue these species, specifically O. annularis and O. faveolata, spawn simultaneously,[11] but most reports support that the Orbicella species are temporally isolated by a few hours.[12][13] It is thought that the specific timing of these spawning events is dictated by light availability and perceived sunset/moonrise times. Sperm and eggs are released packed in small bundles that break open when they reach the water surface due to the surface tension. Timing is important to improve the chances of gametes finding each other in the water column. Hybridization studies reported some success in crossing O. annularis and O. franksi. Yet crosses with O. faveolata are consistently unsuccessful. However, these crosses were done in laboratory conditions that are not natural (covering O. annularis in advance to trick it into spawning earlier) so these crosses are unlikely to occur in nature. Furthermore, in nature gametes get diluted and age quickly.[12] Hence, Orbicella species are reproductively isolated by at least these two ways, allowing for species distinction and evolution.
Species
The following species are currently recognized by the World Register of Marine Species :[1]
- Orbicella annularis (Ellis & Solander, 1786)
- Orbicella faveolata (Ellis & Solander, 1786)
- Orbicella franksi (Gregory, 1895)
References
- ↑ 1.0 1.1 Hoeksema, Bert (2015). "Orbicella Dana, 1846". WoRMS. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=758259.
- ↑ Weil, Ernesto; Knowlton, Nancy (1994). "A Multi-Character Analysis of the Caribbean Coral Montastraea annularis (Ellis and Solander, 1786) and its Two Sibling Species, M. faveolata (Ellis and Solander, 1786) and M. franksi (Gregory, 1895)". Bulletin of Marine Science 55 (1): 151–175. http://www.ingentaconnect.com/content/umrsmas/bullmar/1994/00000055/00000001/art00008.
- ↑ Knowlton, Nancy; Weil, Ernesto; Weigt, Lee A.; Guzmán, Héctor M. (1992-01-17). "Sibling Species in Montastraea annularis, Coral Bleaching, and the Coral Climate Record" (in en). Science 255 (5042): 330–333. doi:10.1126/science.255.5042.330. PMID 17779583. Bibcode: 1992Sci...255..330K.
- ↑ Knowlton, Nancy (1993-01-01). "Sibling Species in the Sea". Annual Review of Ecology and Systematics 24 (1): 189–216. doi:10.1146/annurev.es.24.110193.001201.
- ↑ Budd, Ann F.; Fukami, Hironobu; Smith, Nathan D.; Knowlton, Nancy (2012-11-01). "Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia)" (in en). Zoological Journal of the Linnean Society 166 (3): 465–529. doi:10.1111/j.1096-3642.2012.00855.x.
- ↑ "WoRMS - World Register of Marine Species - Orbicella annularis (Ellis & Solander, 1786)". http://www.marinespecies.org/aphia.php?p=taxdetails&id=758260.
- ↑ "WoRMS - World Register of Marine Species - Orbicella faveolata (Ellis & Solander, 1786)". http://www.marinespecies.org/aphia.php?p=taxdetails&id=758261.
- ↑ "Montastraea faveolata (Ellis 1786)". CoralPedia. University of Warwick. http://coralpedia.bio.warwick.ac.uk/en/corals/montastraea_faveolata.
- ↑ Dustan, P. (1975-11-01). "Growth and form in the reef-building coral Montastrea annularis" (in en). Marine Biology 33 (2): 101–107. doi:10.1007/BF00390714. Bibcode: 1975MarBi..33..101D.
- ↑ Nothdurft, Luke D.; Webb, Gregory E.; Buster, Noreen A.; Holmes, Charles W.; Sorauf, James E.; Kloprogge, J.T. (2005). "Brucite microbialites in living coral skeletons: Indicators of extreme microenvironments in shallow-marine settings". Geology 33 (3): 169. doi:10.1130/g20932.1. Bibcode: 2005Geo....33..169N.
- ↑ Sánchez, Juan; Alvarado, Elvira M; Gil, Maria; Charry, Henry; Arenas, Olga; Chasqui, Luis H; García, Rocio (1999). "Synchronous mass spawning of Montastraea annularis (Ellis & Solander) and Montastraea faveolata (Ellis & Solander) (Faviidae: Scleractinia) at Rosario Islands, Caribbean coast of Colombia". Bulletin of Marine Science 65 (3): 873–879. https://www.ingentaconnect.com/content/umrsmas/bullmar/1999/00000065/00000003/art00026.
- ↑ 12.0 12.1 Levitan, Don R.; Fukami, Hironobu; Jara, Javier; Kline, David; McGovern, Tamara M.; McGhee, Katie E.; Swanson, Cheryl A.; Knowlton, Nancy (2004-02-01). "Mechanisms of Reproductive Isolation Among Sympatric Broadcast-Spawning Corals of the Montastraea annularis Species Complex" (in en). Evolution 58 (2): 308–323. doi:10.1111/j.0014-3820.2004.tb01647.x. PMID 15068348.
- ↑ Levitan, Don R.; Fogarty, Nicole D.; Jara, Javier; Lotterhos, Katie E.; Knowlton, Nancy (2011-05-01). "Genetic, Spatial, and Temporal Components of Precise Spawning Synchrony in Reef Building Corals of the Montastraea annularis Species Complex" (in en). Evolution 65 (5): 1254–1270. doi:10.1111/j.1558-5646.2011.01235.x. PMID 21521188.
Wikidata ☰ Q18748030 entry
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