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Several groups of sponges are able to excavate galleries and tunnels in calcareous substrata such as limestone rock, shells, calcareous algae and coral skeletons. Within the genus Cliona, some species share the common traits of being brown to olive-green in color, and harboring photosynthetic, unicellular dinoflagellates (zooxanthellae). These Cliona spp. have been grouped as the Cliona viridis species complex. Several species of this complex completely encrust the excavated substratum with a thin veneer of tissue and, when colonizing dead exposed parts of live coral colonies, they are able to undermine or overgrow and thus kill live coral tissue as they advance predominantly laterally. In the course of our taxonomic and ecological studies of Caribbean brown to brown-black encrusting Cliona, we found an as yet undescribed species that stands out by having tylostyle megasclere spicules with narrow heads and lacking the usual microsclere spicule complement of spirasters. This species, named and described here Cliona acephala n. sp., has so far been found exclusively in the Santa Marta area, Caribbean coast of Colombia. Previous studies with ITS2 ribosomal DNA showed it to be genetically distinct from other Caribbean encrusting species belonging to the Cliona viridis species complex, vis. Cliona aprica, Cliona caribbaea, Cliona tenuis and Cliona varians, but making it genetically closer to Indo-Pacific Cliona orientalis. An intriguing possibility, to be addressed with further studies, is that C. acephala n. sp. may have been introduced to the Caribbean. However, until proved otherwise, we regard the material presently described as distinct.

The new discovery by Vicente et al. (2014) of specialized epizoic symbioses between sponges of the genera Plakortis and Xestospongia revealed the obligate interaction of two new Plakortis spp. associating with Xestospongia deweerdtae and a new Xestospongia sp. In this study we formally describe the two new Plakortis spp. as Plakortis deweerdtaephila sp. nov. (previously reported as Plakortis sp. 1), Plakortis symbiotica sp. nov. (previously reported as Plakortis sp. 2) and describe the new Xestospongia sp. epibiont as Haliclona ( Halichoclona ) plakophila sp. nov. Plakortis deweerdtaephila associates only with X. deweerdtae , and has very small to large straight diods (24.2–233.7 μm long) and triods (26.4–102.6 μm long) that form large ectosomal circular meshes (114–329 μm diameter). P. symbiotica associates with both X. deweerdtae and H. plakophila, has larger curved diods (71.9–141.8 μm long) and triods (20.4–70.6 μm long) that form smaller ectosomal circular meshes (43–121 μm diameter) than P. deweerdtaephila . Phylogenetic analysis of cox1 and cob gene fragments revealed a strongly supported clade that grouped both Plakortis spp. nov. distantly from any other known Plakortis spp. H. plakophila is described as a thin encrusting veneer of tissue with occasional papillae, so far only found associated with P. symbiotica in La Parguera, Puerto Rico. Phylogenetic analysis of 18S rRNA and cox1 gene fragments place it distantly from any known clade of Haplosclerida. We found a new associated morphotype of X. deweerdtae from Bocas del Toro Panama, which completely overgrew P. deweerdtaephila . In addition, free-living morphotypes from Panama produce larger S-shaped and round bracket shaped strongyles never before observed for this species, leading us to redescribe X. deweerdtae . All X. deweerdtae morphotypes shared >99% sequence homology of cox1 , 18S rRNA and 28S rRNA genes with the holotype of X. deweerdtae . This study highlights the highly variable morphological characters of X. deweerdtae influenced by lifestyle and environmental factors. This is also the first time that an obligate symbiosis with a heterospecific sponge is used as a key taxonomic character.

Although there is a long history of taxonomic investigation in Caribbean sponges, there are still many undescribed species. Furthermore, field observations and corroborating morphological analyses are revealing that what was believed to be single, somewhat variable species, may consist of two or more species, often easier to distinguish once well characterized. This is the case for Dragmacidon reticulatum (RidleyDendy, 1886) (Porifera, Demospongiae, Axinellida, Axinellidae), a rather well-known sponge, with an ample distribution and presence in rocky and reef environments of the tropical and subtropical Western Atlantic, with local records in the majority of the countries of the area, from Bermuda to Brazil. Field observations and a detailed review of material from different areas, including some type specimens, led us to the distinction of two different species in terms of external morphology, size of spicules, and skeletal architecture. The distinction was confirmed in the Bahamas and Santa Marta, Colombia, where the two species coexist. One of the species is Dragmacidon reticulatum sensu stricto, but for the other there is need to erect a new name, for which we propose Dragmacidon alvarezae n. sp. The purpose of the present work is to describe, illustrate and compare these two species.

Thinly encrusting sponges are diverse and ecologically important, but their taxonomy is challenging. In the Greater Caribbean, the recognition of species of Clathria (Thalysias), most of which are encrusting, is still problematic. Here we describe and clarify the taxonomy of eight species, three new to science, from material collected mostly in Colombia. These are C. (T.) virgultosa, C. (T.) curacaoensis, C. (T.) venosa, C. (T.) minuta, C. (T.) oxeota, C. (T.) sulfocleistochela n. sp., C. (T.) chelosigmoidea n. sp., and C. (T.) opalina n. sp. Underwater color photographs are provided, together with drawings of spicules and skeleton, and SEM images of spicules. Two other well-established Caribbean species of the subgenus, vis. C. (T.) isodictyoides and C. (T.) collosclera (both from Curaçao) were not found in the studied material. A key for their identification is provided. Three more records, C. (T.) fascicularis Topsent, 1889, C. (T.) procera (Ridley, 1884) and C. (T.) basiarenacea (Boury-Esnault, 1973) are outlined for further study.

The genus Agelas comprises a group of tropical and subtropical reef sponges that contains large, long-lived, often brightly colored and conspicuous species, distributed throughout the tropica l western Atlantic, temperate northern Atlantic (Mediterranean Sea), and western and central Indo-Pacific Realms. Among tropical sponge genera, Agelas is one with similar species richness in the Greater Caribbean in comparison to the Indo Pacific. The presence of verticillated acanthostyle spicules and a fibroreticulate skeleton of spongin fibres cored and/or echinated by spicules characterize this group. Taxonomic identification relies on a combination of characters, where external morphology and color play a key role, owing to the paucity of microscopical characters. Thus, there is still a great deal of taxonomic confusion, even for the more common species. We carried out a detailed revision of Agelas species throughout the Greater Caribbean area using classic taxonomic tools. Samples and observations covered Colombia, Belize, Jamaica, the Bahamas, Barbados, Curaçao and Venezuela, and included type material from major museum collections. According to our results, the genus Agelas in the Caribbean has at least thirteen valid species, viz. Agelas sceptrum (Lamarck, 1815); A. dispar DuchassaingMichelotti, 1864; A. dilatata DuchassaingMichelotti, 1864; A. clathrodes (Schmidt, 1870); A. cervicornis (Schmidt, 1870); A. conifera (Schmidt, 1870); A. schmidti Wilson, 1902; A. tubulata Lehnertvan Soest, 1996; A. wiedenmayeri Alcolado, 1984; A. citrina GoteraAlcolado, 1987; A. sventres Lehnertvan Soest, 1996; A. repens Lehnertvan Soest, 1998; and A. cerebrum Assmann et al., 2001. We found that variation of microscopic characteristics like skeleton arrangement, number of verticills and their spines, and spicule length and width, can be used as taxonomic tools, but only in a thorough comparison with other species in the same sub-regional context. Thus, a certain degree of familiarity with the genus' regional variation is often required. The richness and distribution of these species in the Caribbean area show north/south differences and other ecological patterns are evident.

Although there is a long history of taxonomic investigation in Caribbean sponges, there are still many undescribed species. Furthermore, field observations and corroborating morphological analyses are revealing that what was believed to be single, somewhat variable species, may consist of two or more species, often easier to distinguish once well characterized. This is the case for Dragmacidon reticulatum (Ridley & Dendy, 1886) (Porifera, Demospongiae, Axinellida, Axinellidae), a rather well-known sponge, with an ample distribution and presence in rocky and reef environments of the tropical and subtropical Western Atlantic, with local records in the majority of the countries of the area, from Bermuda to Brazil. Field observations and a detailed review of material from different areas, including some type specimens, led us to the distinction of two different species in terms of external morphology, size of spicules, and skeletal architecture. The distinction was confirmed in the Bahamas and Santa Marta, Colombia, where the two species coexist. One of the species is Dragmacidon reticulatum sensu stricto, but for the other there is need to erect a new name, for which we propose Dragmacidon alvarezae n. sp. The purpose of the present work is to describe, illustrate and compare these two species.

Thinly encrusting sponges are diverse and ecologically important, but their taxonomy is challenging. In the Greater Caribbean, the recognition of species of Clathria (Thalysias), most of which are encrusting, is still problematic. Here we describe and clarify the taxonomy of eight species, three new to science, from material collected mostly in Colombia. These are C. (T.) virgultosa, C. (T.) curacaoensis, C. (T.) venosa, C. (T.) minuta, C. (T.) oxeota, C. (T.) sulfocleistochela n. sp., C. (T.) chelosigmoidea n. sp., and C. (T.) opalina n. sp. Underwater color photographs are provided, together with drawings of spicules and skeleton, and SEM images of spicules. Two other well-established Caribbean species of the subgenus, vis. C. (T.) isodictyoides and C. (T.) collosclera (both from Curacao) were not found in the studied material. A key for their identification is provided. Three more records, C. (T.) fascicularis Topsent, 1889, C. (T.) procera (Ridley, 1884) and C. (T.) basiarenacea (Boury-Esnault, 1973) are outlined for further study.

The genus Agelas comprises a group of tropical and subtropical reef sponges that contains large, long-lived, often brightly colored and conspicuous species, distributed throughout the tropica l western Atlantic, temperate northern At lantic (Mediterranean Sea), and western and central Indo-Pacific Realms. Among tropical sponge genera, Agelas is one with similar species richness in the Greater Caribbean in comparison to the Indo Pacific. The presence of verticillated acanthostyle spicules and a fibroreticulate skeleton of spongin fibres cored and/or echinated by spicules characterize this group. Taxonomic identification relies on a combination of characters, where external morphology and color play a key role, owing to the paucity of microscopical characters. Thus, there is still a great deal of taxonomic confusion, even for the more common species. We carried out a detailed revision of Agelas species throughout the Greater Caribbean area using classic taxonomic tools. Samples a nd observations covered Colombia, Belize, Jamaica, the Ba hamas, Barbados, Curacao and Venezuela, and included type material from major museum collections. According to our results, the genus Agelas in the Caribbean has at least thirteen valid species, viz. Agelas sceptrum (Lamarck, 1815); A. dispar Duchassaing & Michelotti, 1864; A. dilatata Duchassaing & Michelotti, 1864; A. clathrodes (Schmidt, 1870); A. cervicornis (Schmidt, 1870); A. conifera (Schmidt, 1870); A. schmidti Wilson, 1902; A. tubulata Lehnert & van Soest, 1996; A . wiedenmayeri Alcolado, 1984; A. citrina Gotera & Alcolado, 1987; A. sventres Lehnert & van Soest, 1996; A. repens Lehnert & van Soest, 1998; and A. cerebrum Assmann et al ., 2001. We found that variation of microscopic characteristics like skeleton arrangement, number of verticills and their spines, and spicule length and width, can be used as taxonomic tools, but only in a thorough comparison with other species in the same sub-regional context. Thus, a certain degree of familiarity with the genus’ regional variation is often required. The richness and distribution of these species in the Caribbean area show north/south differences and other ecological patterns are evident.

Direct field observations often reveal distinct morphotypes within sponge species that had been described on the basis of preserved material from different locations. The genus Axinyssa von Lendefeld, 1897 was revised for the Caribbean by Diaz et al . (1993), defining a single species, Axinyssa ambrosia (de Laubenfels, 1936), with several junior synonyms, some of which varied in the predominant spicule complement. At Santa Marta, Colombia, we found two morphotypes of Axinyssa living sympatrically, with consistent differences in morphology and spiculation. Revision of types and part of Diaz et al . (1993) material confirmed these differences, leading to the distinction of two species whose valid names are Axinyssa ambrosia and Axinyssa yumae (Pulitzer-Finali, 1986). The purpose of this note is to redescribe these two species.