Recruitment to the reef

 

column spacer Recruitment to the reef
 
 

Asexual reproduction

 
Asexual reproduction in corals/zoanthids is considered in this section. Click on an icon to learn about asexual reproduction in other reef organisms. hot buttons for asexal reproduction section of BCCR website hot-button icon for linking to the topic of asexual reproduction in seaweeds in BCCR website hot-button icon for linking to the topic of asexual reproduction in sponges in BCCR website hot-button icon for linking to the topic of asexual reproduction in gorgonians in BCCR website hot-button icon for linking to the topic of asexual reproduction in corals/zoanthids in BCCR website hot-button icon for linking to the topic of asexual reproduction in seastars in BCCR website hot-button icon for linking to the topic of asexual reproduction in tunicates in BCCR website
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of elkhorn coral taken from a video

"Sometimes, especially after storms, there will be broken bits of elkhorn coral lying around at the base of the colony...not on this one...but, when it happens, some of the bits may survive to produce new colonies." - Cayman Brac 2001

NOTE Acropora palmata

 
 

Asexual reproduction: corals

  photo collage of budding corals
Growth of corals is by asexual budding. Thus, each polyp divides into 2, and each of these into 2, and so on. The pattern is visible in the accompanying photograph of the flower coral Eusmilia.
 
 

photograph of photograph of finger corals regeneratingFragmentation of many species of corals through impact with floating objects, fish strikes, and careless boating and SCUBA activities may lead to new individuals if the broken bits attach and regrow. Compare normal and regenerative growth of finger corals in the accompanying photographs.

 

Normal growth of finger coral
Porites porites
(although not a
particularly healthy colony) 0.25X

 

Regenerative growth of numerous
broken bits of Porites porites 0.15X

 

photograph showing new finger coral Porites furcata growing on top of consolidated coral rubbleA researcher in San Blas Islands, Panama finds that coral rubble, such as that produced by fragmentation of finger corals Porites furcata, may be consolidated and stabilised by sponges, and then cemented together by carbonate-secreting organisms such as coralline algae and bryozoans. These processes provide a stable substratum for recruitment of new finger corals and other coral species. Experiments show that these processes of consolidation may be completed within 10mo. Wulff 1984 Coral Reefs 3: 157.

NOTE taxonomists are uncertain whether there are 3 species of Porites (porites, furcata, and divaricata) or just 3 different growth patterns (differentiated by degree of branching). For simplicity, in BCCR we will refer to them all as P. porites

 

Close examination of this photograph reveals new growth
of Porites porites on top of older finger-coral debris.
Note that some of the dead stuff is overgrown with red
filamentous algae and some with red coralline algae 0.75X

 

 


In the 1960s a researcher at Discovery Bay Marine Laboratory in Jamaica imported a few specimens of mushroom coral Fungia scutaria from Eilat, Israel for experimental studies. This was fine, except that instead of holding them in secure containment tanks in the laboratory he used the shallow forereef area of Discovery Bay itself to “house” them. A decade after his 1970 death a dozen or so individuals were gathered and disposed of, then forgotten, only to reappear in collections made from shallow waters of the Bay in 2003. Quite apart from the obvious question “what was he photograph of mushroom coral Fungia scutaria from Discovery Bay, Jamaicathinking?”, the discovery is remarkable in that, as reported by the current researchers, the specimens lived through 2 major hurricanes, a general collapse of corals followed by massive algal overgrowths in the Bay, and were overlooked for decades by many hundreds of students and researchers using the Bay for study. The interest of F. scutaria in this section of BCCR is in its propensity for asexual budding (see photograph). Bush et al. 2004 Coral Reefs 23: 234; photograph courtesy the authors.

NOTE the researcher in question, Dr. Thomas Goreau, is an iconic figure in coral-reef biology generally, and in Jamaica specifically. He founded the Discovery Bay Marine Laboratory, pioneered the use of SCUBA as a research tool, promoted the science of coral-reef biology throughout the world, and published many fine papers on coral biology in Caribbean and other world reefs

Non-indigenous mushroom coral Fungia scutaria from Discovery Bay,
Jamaica with asexual bud. The bud at this early stage is capable
of feeding and will fall off on its own when it gets too large

 
  drawing showing dispersal of fragments of staghorn coral by waves and currentsStaghorn coral Acropora cervicornis can reproduce by fragmentation, which involves self-weakening of the skeleton and subsequent breakage through waves, currents, and other physical stresses. If large enough to survive, the bits may disperse up to 50m within the reef-crest habitat. Bothwell 1981 Proc 4th Int Coral Reef Symp 2: 137.
 

photograph of elkhorn coralOwing to its bulkiness, elkhorn coral does not fragment or disperse as readily as the related lighter-mass staghorn coral, but it can happen during storms or other severe disturbance.

 

 

 

 

 

Elkhorn coral Acropora palmata
showing a broken end 0.25X

  photo collage showing breakage to elkhorn coralsExperimental fragmentation of elkhorn and staghorn coras Acropora spp. in Curacao to mimic storm and anchor damage results in some fusion of conspecific bits and cementation of the bits to the sea bottom within 3-4wk. Bak & Criens 1981 Proc 4th Int Coral Reef Sympos 2: 221.
  Features important for survival of pieces of elkhorn coral during their transport about the reef include size, presence of a mucous coating, edibility to predators, polyp size, and age.
 
 

Asexual fragmentation and regrowth in corals such as elkhorn corals seems like a good recruitment strategy. Along with the benefits, however, are several costs. Try to separate the "PROs" from the "CONs" in the following list, then CLICK HERE to see the correct listings. Note that not all features are mutually exclusive. Ideas from Bak & Criens 1981 Proc 4th Int Coral Reef Symp 2: 221.

Local amplification of well-adapted genotypes.
Don't need a sexual partner.
Increased propagation.
Unable to adapt to changing environment.
Increased abundance.
Quick to reach adult size.
Large size to start favours survival.
Quick start gives competitive advantage.
Negative growth of parent colony.
Increased disease susceptibility.
Loss of tissue.
Wider colonisation.
Limited genetic dispersal.
Decreased sexual reproduction.

image for "pro" features of asexual reproduction image for "con" features of asexual reproduction
 
 

Asexual reproduction: zoanthids

  photo collage of Caribbean zoanthids
Zoanthids are common and colorful cnidarians around coral reefs. Like corals, they are mostly colonial, and the polyps in a colony are interconnected. Growth of zoanthids is by asexual budding.
 
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