Abstract
Species of the genus Placospongia are common within the tropical Indo-West Pacific, demonstrating a wide variety of colors and either branching or encrusting growth forms. A revision of Indo-West Pacific Placospongia was undertaken based on a redescription of the holotypes of species of Placospongia from the Indian Ocean and Western Pacific and an examination of an additional 103 specimens of Placospongia ssp. collected from Indonesia (including Vosmaer and Vernhout 1902 material), Seychelles, India, Singapore and Micronesia. One mitochondrial (COI) and one nuclear (ITS) marker were subsequently used to differentiate species. All Placospongia species are characterized by selenasters and tylostyles in two size classes. The combination of microsclere diversity and morphology as well as megasclere size were shown to be informative morphometric characters, supported by molecular evidence. Live coloration and growth form is shown to be unreliable for diagnoses. The study of holotypes found that Placospongia mixta is a valid species and that two genus transfers are necessary: Geodinella anthosigma is a Placospongia and Placospongia labyrinthica is a Geodia. A new species is also described from an anchialine pool in Indonesia, Placospongia santodomingoae sp. n.; bringing the total fauna of Placospongia species in the Indo-West Pacific to five: Placospongia anthosigma, Placospongia carinata, Placospongia mixta, Placospongia melobesioides, and Placospongia santodomingoae sp. n. An identification key is given. Two additional species, possibly morphologically cryptic, have been identified by molecular markers.
Highlights
Species of the genus Placospongia in the tropical Indo-West Pacific occur in a wide variety of habitats such as marine lakes, coral reefs and mangroves
Vosmaer and Vernhout (1902) based their conclusions on a review of 26 specimens collected during the Siboga expedition to Indonesia, and this collection is presently housed at the Naturalis Biodiversity Center (Leiden, The Netherlands)
In the Indo-West Pacific at least five species of the genus Placospongia can be identified based on spicule morphology: P. anthosigma, P. carinata, P. mixta, P. melobesioides, and P. santodomingoae sp. n
Summary
Species of the genus Placospongia in the tropical Indo-West Pacific occur in a wide variety of habitats such as marine lakes, coral reefs and mangroves. According to the World Porifera Database (van Soest et al 2011) Geodinella anthosigma Tanita and Hoshino 1989 (type locality Sagami Bay, Japan) should be transferred to the genus Placospongia, and P. labyrinthica should be transferred to the genus Geodia. These suggested genus transfers have, not yet been published in the peer-reviewed literature. The authors did not investigate the spicule morphology of the specimens in their study, it is unclear which species name can be assigned to the different clades
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