What we need to know


A zoanthid of the species Zoanthus sansibaricus.
Image: Gary Cranitch.

 

12 September  2010
 
 
"Zoanthid research is a poster child for the good and the bad points of coral reef science," says Associate Professor James Reimer of Japan's University of Ryukyus.
 
Professor Reimer is studying the colonial anemones known as zoanthids on the CReefs expedition to Lizard Island. Zoanthids are related to other anemones and to hard corals.
 
"Zoanthids are everywhere in oceans around the world, so there is a great opportunity to learn more about them – but they are not a well-studied group, and there are very few scientists working on them, so most biodiversity surveys just ignore them," he says.
 
"They produce chemicals, which may have commercial or medical applications, and they produce palytoxin, one of the most toxic substances known in nature," he says.
 
The palytoxin produced by zoanthids can be absorbed through intact skin, and even in small quantities, can be fatal to humans if it is ingested or enters the blood stream.
 
It has been reported, for example, that a home aquarist was poisoned when he accidentally brushed an open cut on his finger against a Parazoanthus species. He was lucky to recover: his zoanthid was found to contain more than two milligrams of palytoxin per gram, enough to kill 125 grown men.
 
Despite these unusual characteristics, as yet very little work has been done to investigate zoanthids.
 
"Essentially, the example of the zoanthids shows how little we know about coral reefs," he says.
 
According to Professor Reimer, zoanthids are common on coral reefs, but they are not as big as many corals – most zoanthids polyps are less than three centimetres across – and unlike hard corals, zoanthids don't form skeletons, so they don't leave any trace behind them when they die.
 
Professor Reimer suggests this makes zoanthids more cryptic than corals; that is, they are less obvious and a little harder to study.
 
Professor Reimer will compare the zoanthids he finds at Lizard Island with specimens found on other CReefs trips to Heron Island and Ningaloo Reef, and those found in Japan, Singapore, Madagascar, the Indian Ocean and elsewhere.
 
He will also compare recent information to those few studies that have been conducted in the past.
 
"I'm excited to join the CReefs expedition to Lizard Island. We can learn a lot from this project," he says.
 
"Through this research, we can start to get a better global picture. We can start to get an understanding about the common species, at least. Then groups that have previously not been well-studied, such as zoanthids, can be included in biodiversity surveys, and can be considered in planning for the management and conservation of marine areas," he says.