Identification of an aquaculture poriferan "Pest with Potential" and its phylogenetic implications.

Correct identification and classification of sponges is challenging due to ambiguous or misleading morphological features. A particular case is a blue keratose sponge occasionally referred to as the "Blue Photo Sponge" among aquarists, which appears frequently (and in several cases unintended) in private aquaria. This spicule-less species, occasionally specified as Bergquist, Cambie & Kernan 1990, not only displays a high phenotypic plasticity in growth form and colour, it also proliferates in aquacultures under standard conditions unlike most other sponges. Therefore, this species is regarded as a pest for most aquarists. In turn, the ease of cultivation and propagation in aquacultures qualifies this species as a model organism for a wide array of scientific applications. For these purposes, correct identification and classification are indispensable. We reconstructed ribosomal gene trees and determined this species as (De Laubenfels, 1954) (Phyllospongiinae), distant to , and corroborated by skeletal features. Additionally, the resulting phylogeny corroborated major shortcomings of the current Phyllospongiinae classification-its consequences are discussed.