On balance

Few beings are more bizarre when you come to them for the first time than the Crown of Thorns Starfish (COTS). What could be stranger than an animal with multi-axis symmetry that digests living 'rock' (coral) by extruding its stomach? [1]

Monster Mash

Their role in a so-called 'balance of nature' ['dynamic system'?] has been debated (see, for example What is natural? by Jan Sapp). A recently published paper by Hugh Sweatman suggests that a 'healthy' coral reef, with plenty of small inverbrates to eat the juvenile starfish, copes better with COTS (press report). Good news, perhaps, until something bigger comes along.

Note

1. There's a useful Q&A on COTS by Peter Moran of AIMS