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This chapter reviews the major known monospecific and multispecific sponge aggregations in the world's oceans. They are shown to occur from the intertidal to abyssal depths, in tropical, temperate, and high latitudes and sometimes to create

Geodia species north of 60°N in the Atlantic appeared in the literature for the first time when Bowerbank described Geodia barretti and G. macandrewii in 1858 from western Norway. Since then, a number of species have been based on material from various parts of the region: G. simplex, Isops phlegraei, I. pallida, I. sphaeroides, Synops pyriformis, G. parva, G. normani, G. atlantica, Sidonops mesotriaena (now called G. hentscheli), and G. simplicissima. In addition to these 12 nominal species, four species described from elsewhere are claimed to have been identified in material from the northeast Atlantic, namely G. nodastrella and G. cydonium (and its synonyms Cydonium muelleri and Geodia gigas). In this paper, we revise the boreo‐arctic Geodia species using morphological, molecular, and biogeographical data. We notably compare northwest and northeast Atlantic specimens. Biological data (reproduction, biochemistry, microbiology, epibionts) for each species are also reviewed. Our results show that there are six valid species of boreo‐arctic Atlantic Geodia while other names are synonyms or mis‐identifications. Geodia barretti, G. atlantica, G. macandrewii, and G. hentscheli are well established and widely distributed. The same goes for Geodia phlegraei, but this species shows a striking geographical and bathymetric variation, which led us to recognize two species, G. phlegraei and G. parva (here resurrected). Some Geodia are arctic species (G. hentscheli, G. parva), while others are typically boreal (G. atlantica, G. barretti, G. phlegraei, G. macandrewii). No morphological differences were found between specimens from the northeast and northwest Atlantic, except for G. parva. The Folmer cytochrome oxidase subunit I (COI) fragment is unique for every species and invariable over their whole distribution range, except for G. barretti which had two haplotypes. 18S is unique for four species but cannot discriminate G. phlegraei and G. parva. Two keys to the boreo‐arctic Geodia are included, one based on external morphology, the other based on spicule morphology. © 2013 The Linnean Society of London

Cárdenas, P., Rapp, H. T., Schander, C. & Tendal, O. S. (2009). Molecular taxonomy and phylogeny of the Geodiidae (Porifera, Demospongiae, Astrophorida) – combining phylogenetic and Linnaean classification.—Zoologica Scripta, 39, 89–106. According to the fossil records, the Geodiidae represents one of the oldest families of demosponges (Phylum Porifera). There are approximately 220 described extant species, geographically and bathymetrically widely distributed around the world. Species of this family all share a two‐layered cortex with ball‐shaped spicules called ‘sterrasters’ in the endocortex. However, molecular studies have questioned the monophyly of the group. Moreover, the evolutionary history and the intrafamily relationships of the Geodiidae are not fully resolved. Using a partial sequence of the cytochrome c oxidase subunit 1 (COI) gene and a partial sequence of the 28S rDNA gene (D1–D2 domains), we present the first molecular phylogeny focusing on this group. The congruent results from the two gene fragments suggest that (i) the Geodiidae is monophyletic, (ii) the Erylinae/Geodinae subdivision sensuSollas, 1888 is valid and that (iii) Isops and Sidonops are junior synonyms of Geodia. The synonymization of Isops and Sidonops implies that the oscule/pore morphology as a diagnostic character should be abandoned. Geodia hentscheli nom. nov. has been given for Geodia mesotriaena (Hentschel, 1929). This study served as the basis for a revised phylogenetic classification of the Geodiidae. Well‐supported clades led to the establishment of clade names following the PhyloCode. The Geodinae clade is strongly supported and notably composed of Depressiogeodia, Cydonium and Geodia. A morphological synapomorphy of Geodinae is the presence of euasters in the ectocortex. The Erylinae (Erylus, Penares, Caminus and Pachymatisma) form a strongly supported monophyletic group with three morphological synapomorphies: (i) loss of anatriaenes and protriaenes, (ii) microrhabds (or spherules) in the ectocortex and (iii) short‐shafted triaenes. The Erylus monophyly is ambiguous. Erylus species are distributed in three well‐supported clades. Finally, spicule homology in the cortex of the Geodiidae is discussed.

This chapter reviews the major known monospecific and multispecific sponge aggregations in the world's oceans. They are shown to occur from the intertidal to abyssal depths, in tropical, temperate, and high latitudes and sometimes to create