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Coral Polyp

Page history last edited by Matt Zeitouni 10 years, 10 months ago

CORAL POLYP

Page written by: Matthew Zeitouni

Description:

Coral are marine invertebrates, typically only a few millimeters in diameter and a few centimeters in length which live together to form impressive, dense colonies of individual “Polyps”. When coral polyps attach themselves onto rocks on the sea floor, they can divide or bud into thousands of clones which over a very long course of time (over thousands of years) can become what we call a coral reef. Coral reefs (such as the Great Barrier Reef) are sometimes deemed as the most diverse marine ecosystems, which possibly one quarter of all marine species depend on, despite the fact they cover less than two percent of the ocean floor. They are often referred to as the rainforests of the sea. There are many types of corals, but the principal types are Stony Coral, and Soft Coral, which can then be either Deep-sea corals or Shallow water coral.

Habitat:

Coral polyps are found living in dense colonies in many ranges of the world’s tropical oceans. They are located particularly close to the surface so the sun’s rays will strike algae that are found in their tissue, which they need to live (see symbiosis with algae below). Coral polyps also have venomous tentacles they stretch out to catch plankton and even some small fish, making Coral polyps carnivorous. They prefer living in temperatures of around 22-29°C which is rather warm. But coral polyps don’t just live up near the surface of the oceans, they are also found up to 6000 meters deep in dark, cold (-1^oC) waters; these exclusive corals are named Deep See Corals and they are just as common as shallow water corals. Deep-sea corals do not have the same algae in their tissue as shallow water corals but they grow much slower. Both deep and shallow ocean corals grow into reefs by attaching themselves to a rock on the ocean floor and then dividing or reproducing, when this is done though all the corals become connected to each other and act as a single organism.

Predator Adaptations:

Each coral polyp is carnivorous; they feed feed on a variety of small organisms, from microscopic plankton to even small fish. But being stuck to rocks on the ocean floor they cannot go out and hunt their prey; it must come to them. To attract their food they stick out their stringy long tentacles, which have stinging cells, named nematocysts that are all placed along the coral polyp’s mouth and take in any prey that swims too close. Coral polyps wait for their prey primarily at night all together. Coral Polyps rely mostly on microscopic Plankton for food, the most common plankton they consume is Zooplankton.

Prey Adaptation:

Coral polyps unfortunately face many predators, such as Parrotfishes, Butterflyfishes, and Seastars. And as mentioned in their predator adaptations, they cannot move and have no very efficient form of running away from enemies. But coral polyps have a trick or two for hiding from enemies. One trick the polyps use is to make a limestone cup which they can hide in during the day, then come out of at night to hunt. Another tactic they also use for hunting, are the stinging cells on the tentacles surrounding their mouths which extend out, and with literally thousands of individual polyps each doing this; it protects the whole coral reef very effectively.

Symbiotic interactions:

Coral polyps have close symbiotic interactions with the sea creatures in their environment. Nearly one quarter of all marine species depend on them for food to survive and shelter to live in as well as protect them, like the Porcupinefish and the Angelfish.

A more specific example of these symbiotic interactions is the symbiosis between Coral Polyp and Algae. Algae not only gives coral polyps their beautiful, vibrant colours but the algae have a strong, mutual symbiosis with nearly all types of Coral Polyps (as much as %30 of a coral polyp’s tissue may be plant material). First of all, Coral Polyps get most of their energy from the byproducts of the Algae’s photosynthesis (as well as from eating other small marine creatures; see predator adaptations). And with that the coral polyp gives the Algae some energy from its food, a safe shelter and the algae consume some of the coral polyp’s carbon dioxide. Coral polyps need these algae or they may lose vital nutrients they require to live, when this happens to a coral reef it called coral bleaching. Almost all deep-sea and shallow water corals require algae (deep-sea corals require algae less) and depending on what kind of coral polyp they are they may need different algae.

Species comparison:

A familiar species and close relative to these fascinating Coral Polyps is the Sea anemone which look very much like larger scale individual polyps. These creatures share some similarities as well as some differences in their habitats, predator adaptation, and prey adaptations. For convenience I have taken these three element's of an organisms niche and put them in venne diagrams below. There are a several differences and similarities to list but I will list the elements that are written on the page available here about the Sea anemone. Also below you may see a close up picture and an anatomy drawing of each organism.