Portable test kit quickly detects coral-eating starfish on reefs
As if they don't already face enough challenges from bleaching, many of the world's coral reefs are currently being eaten by the crown-of-thorns starfish. A simple new portable test kit, however, could detect their presence sooner than ever before.
Aquatic organisms continuously shed their DNA into the water, as they slough off old biological tissue, excrete waste, and perform other bodily functions. That waterborne genetic material is known as environmental DNA – or eDNA – and it can be detected in water samples, even in very low concentrations.
As a result, by identifying the telltale eDNA signatures found in such samples, scientists can tell which organisms are present in a given area. In recent years, the process has been used to track fish migrations, warn of nearby great white sharks, and even search for the Loch Ness Monster.
Now, led by biochemist Jason Doyle, scientists at the Australian Institute of Marine Science have developed a field-deployable kit for detecting eDNA from the crown-of-thorns starfish in seawater samples. It incorporates the inexpensive Lateral Flow Assay technology currently utilized in home pregnancy tests, featuring a dipstick on which a stripe will appear if the targeted DNA is present.
The kit is very sensitive, responding to amounts of eDNA material as small as 0.1 picograms (a picogram is one one-trillionth of a gram). This means it can detect infestations while the starfish are still very young, small, and hidden by the coral – a point at which they likely wouldn't be noticed by divers who were visually inspecting a reef.
That said, Doyle doesn't see the kit as a replacement for divers. Instead, he believes it could be used to flag certain areas of a reef, where divers could then concentrate on searching out and removing the starfish before they cause much damage.
A paper on the research was recently published in the journal Environmental DNA.
And this isn't the first time we've heard about eDNA analysis being used to aid in coral reef conservation. Last year, scientists from the University of Hawaii at Manoa described a method of monitoring the abundance and variety of corals on a reef, by testing the water for their DNA.