New species of cave dwelling reef coral discovered

New coral species Leptoseris troglodyte. Photo courtesy of Naturalis

October 2012. Its closest relatives are larger, have symbiotic algae in their soft tissue and need sunlight to grow. The new species has no such algae and its tissue is colourless. When other reef coral species lose their algae, they may die, a recurring disease known as coral bleaching.

Coral specialist Dr. Bert W. Hoeksema of Naturalis Biodiversity Centre in Leiden, (The Netherlands) recently published the description of a new coral species that lives on the ceilings of caves in Indo-Pacific coral reefs. It differs from its closest relatives by its small polyp size and by the absence of symbiotic algae, so-called zooxanthellae.

Symbiotic relationship
This discovery sheds new light on the relation of reef corals with symbiotic algae. The new species has adapted to a life without them. Consequently, it may not grow fast, which would be convenient because space is limited on cave ceilings.
Reef corals in shallow tropical seas normally need the symbiotic algae for their survival and growth. Without these algae, many coral reefs would not exist. During periods of elevated seawater temperature most reef corals lose their algae, which leads to a dramatic whitening of the reefs, a coral disease known as bleaching.

Most reef corals generally do not occur below 40m depth, a twilight zone where sunlight is not bright anymore, but some species of the genus Leptoseris are exceptional and can occur much deeper. At greater depths, seawater is generally colder and corals here may less susceptible to bleaching than those at shallower depths. Despite the lack of zooxanthellae and its small size, the skeleton structures of the new species indicate that it is closely related to these Leptoseris corals, although it has not been found deeper than 35 m so far.

The species is named Leptoseris troglodyta. The word troglodyta is derived from ancient Greek and means "one who dwells in holes", a cave dweller. Its distribution range overlaps with the Coral Triangle, an area that is famous for its high marine species richness. Marine zoologists of Naturalis visit this area frequently to explore its marine biodiversity.

The discovery was published in the open access journal ZooKeys.