We discuss the implications of these findings to better interpret the phylogeography of barrel sponge taxa in the Indo-Pacific.

We compare our results with those from the studies on the congeneric barrel sponges Xestospongia muta from the Caribbean, and Xestospongia bergquistia from the Indo-Pacific, and observe a high degree of overlapping haplotypes between the three barrel sponge species, likely indicating the presence of ancestral polymorphisms.

We investigate over 200 barrel sponge samples from Indonesia, and neighbouring as well as more distant localities (Saudi Arabia, Tanzania, Thailand, Taiwan, Java, Sulawesi and the Great Barrier Reef, Australia) using the mitochondrial cytochrome oxidase subunit 1. However, the genetic variation of this iconic sponge in the region remains unknown.

Small gobies and invertebrates may inhabit the interior, as well. Reef debris often collects in the bottom of large sponges. It inhabits coral reef faces and drop-offs at depth of 50 to 130 feet (15 - 40 m), making it rather abundant in the Cayman Islands. The role of the so-called ‘giant barrel sponge’ for the reef ecosystem has been studied repeatedly, as have its various bioactive compounds. The giant barrel sponge is common throughout the Caribbean. Xestospongia testudinaria is one of the sponge species that dominates coral reef sponge communities in this region. In this area of ‘peak’ biodiversity, the origins of this high species diversity have often been debated. The Indonesian archipelago is a ‘hotspot’ for invertebrate biodiversity (‘Coral Triangle’).

Does the giant barrel sponge move