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“A barrel of sponges: a Xestospongia testudinaria species complex in the Verde Island Passage, Philippines”
The giant barrel sponge Xestospongia testudinaria is a dominant member of the coral reef community in the Verde Island Passage (VIP) in the Philippines. However, little is known about its morphology and gene flow. Barrel sponge morphotypes, osculum diameter, body circumference, body length, spicule length, and spicule width were all recorded, analyzed and combined with mitochondrial COI gene results to establish a possible pattern useful to understand or refute the morphological concept of barrel sponge classification. ABGD analysis revealed four haplotypes for the VIP. Spicule variation showed no significant differences and no correlation among sites and haplotypes. On the other hand, colony dimensions showed no significant difference and no correlation among sites and haplotypes. Colony form showed significant variation within and among sites and significant differences linked with haplotypes. My research findings agree with global studies on barrel sponges, showing the vast majority of Xestospongia (including X. muta from the Caribbean) are of the same haplotype. The lack of variation between the common haplotype of X. testudinaria and X. muta suggests that X muta from the Caribbean is the same species as X testudinaria. Interestingly, the Coral Triangle region of the Indo-Pacific showed greater variation in haplotypes, especially within Indonesia and the Philippines than between these areas of the Coral Triangle and the rest of the world.