Introducing my 9 Coral Species!

For my experiment, I will be comparing the acclimation capacities between 9 coral reef species and here I will introduce each species and provide a couple of fun facts about them! 

These species were chosen because they are common reef building species and are found in abundance all over the Indo-Pacific region. They have a variety of morphologies, from branching to massive colonies, and have contrasting reproductive strategies. When we look at the phylogenetic tree of all hard corals, or scleractinians, these coral species are spread out among the tree. These factors will allow for better comparisons and are ultimately why I chose these species for my study. 

The first species I will be working on is Pocillopora damicornis or the Cauliflower Coral. This species is extremely common in the Pacific Ocean - ranging from Panama to Australia to the Philippines to Japan. This species is a branching coral and is considered to be a main reef building coral. It reproduces asexually by fragmentation and sexually by either type of sexual reproduction - broadcast spawning or brooding. 

 

A bit about coral sexual reproduction: 

There are two types of sexual reproduction in corals: broadcast spawning and brooding. 

Broadcast spawning is when a coral releases its eggs and sperm into the water column simultaneously. Once in the water column, sperm will fertilize the eggs. Once fertilized, the egg will develop into a swimming larvae which will eventually find suitable habitat. Upon settling on an appropriate reef substrate, the new coral recruit will grow (slowly) into an adult! 

While broadcast spawners have their eggs externally fertilized in the water column, brooders fertilize their eggs internally. Larvae develop within the coral and eventually are released from the coral to settle as recruits and grow into adults. 

In our facility at Oregon State University, we have P. damicornis species that are brooders and we have been successful in getting them to reproduce in our tanks. Below is a picture of a one-year old recruit - so tiny! 

 

The second species is Acropora hyacinthus or the Brush Coral. This species is another branching coral, and reproduces by broadcast spawning. This genus of coral (Acropora) is considered to be very susceptible to coral bleaching and disease and is often slow to recover. Two of its sister species found in the Caribbean, Acropora palmata and Acropora cervicornis, are critically endangered. A great deal of conservation and restoration organizations worldwide are growing and replanting these species onto degraded reefs in hopes of restoring their populations. Research like mine can help feed into these conservation efforts to help restore these species and ensure their future survival. 

 

Next up is Platygyra daedalea, a beautiful brain coral! This is a very common species found in the Indo-Pacific with populations seen in the Red Sea, Arabian Gulf, Indian Ocean, and Australia - to name a few. This coral typically has brown walls with green valleys (as seen below), but other species have blue or grey. This species forms massive boulder shaped colonies on the reef and its polyps are situated in the winding valleys. 

 

The fourth species is Acanthastrea echinata or the Starry Cup Coral. This species is widespread across the Indo-Pacific and is found in a variety of reef habitats - shallow, high light reefs as well as deep, low light reefs. It is considered to be very tolerant to a variety of threats, like coral bleaching and disease, but has not been extensively studied. They are voracious nocturnal predators and will use filaments to devour any organisms (including other corals!) within reach. We've accidentally put this species in close contact with the other 8 species and have come in the next day to find that species totally wiped out. Yikes! Additionally, this species is very popular in the coral trade and has been bred to showcase a variety of colors. 

 

The fifth species is Turbinaria reniformis or the Yellow Scroll Coral. This species' name is derived form the greek word turbinatus or cone-shaped because it usually grows in a conical or cup shape. This coral's polyps are only found on the upper side of the skeleton, as seen here. If we were to flip this coral over, you would find no polyps, only a smooth exterior. This species is gonochoristic, with colonies being either male or female. At the time of reproduction, they release either eggs or sperm into the water column. 

 

Next is Porites sp. I have included "sp." after the genus name because we aren't entirely sure what species it is and therefore will need to sequence it's DNA and examine its skeleton to elucidate which species it belongs to. Currently, I think it is Porites cylindrica, but we will soon find out! This genus of coral has been used to reconstruct past marine surface conditions. Using isotopes, scientists have measured the amount of oxygen within the coral's skeleton to determine the temperature as well as growth rates throughout various time periods. This branching species is found all throughout the Pacific Ocean and is a very important coral for a variety of reef fish.

 

Next up is Galaxea fascicularis or the Star Coral. This coral is one of my favorites, as it is just so unique and strikingly beautiful (even though all corals are beautiful in my opinion!)! This coral polyps are very distinct and it's polyps are typically open during the day and its tentacles are very obvious, as seen in the picture below. The tentacles typically have white tips and some tentacles are modified into "sweeper tentacles", which can extend up to 12 inches to defend itself from nearby organisms. This species of coral can reproduce asexually through budding as well as sexually through broadcast spawning. This coral even has beautiful fluorescence! 

 

Eighth is Favia sp. Here again, we're not entirely sure what species this is, but sequencing will provide more insights! As you can see in the image below, each polyp seems to have a combination of colors - super interesting! Different colonies exhibit different color combinations. Just like Platygyra daedalea, this species of coral forms massive, boulder shaped colonies on the reef. And just like the last species, this species has sweeper tentacles that can sting other species nearby. This coral is also rather tolerant to coral bleaching but is greatly affected by disease. 

 

And lastly, the ninth species I will be experimenting on is Hydonophora rigida or the Horn Coral - another one of my favorites! Personally, I think it looks like the tips of asparagus, haha! This coral fluoresces brilliantly and almost looks a bit furry when its tentacles are exposed. The polyp construction is rather interesting in this species as it forms mounds down the branches. This species is considered to be rather tolerant to coral bleaching. Just like the last two species, this coral is deadly when placed close to other organisms. 

 

Thanks for tuning in! To learn more about these species and other coral species from around the world, check out Corals of the World!