RESUMO

Sponges have co-evolved for millions of years alongside several types of microorganisms, which aside from participating in the animal's diet, are mostly symbionts. Since most of the genetic repertoire in the holobiont genome is provided by microbes, it is expected that the host-associated microbiome will be at least partially heritable. Sponges can therefore acquire their symbionts in different ways. Both vertical transmission (VT) and horizontal transmission (HT) have different advantages and disadvantages in the life cycle of these invertebrates. However, a third mode of transmission, called leaky vertical transmission or mixed mode of transmission (MMT), which incorporates both VT and HT modes, has gained relevance and seems to be the most robust model. In that regard, the aim of this review is to present the evolving knowledge on these main modes of transmission of the sponge microbiome. Our conclusions lead us to suggest that MMT may be more common for all sponges, with its frequency varying across the transmission spectrum between species and the environment. This hybrid model supports the stable and specific transmission of these microbial partners and reinforces their assistance in the resilience of sponges over the years.

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Inland waters experience extreme environmental conditions determining the evolution of several adaptive strategies of the fauna to these variable conditions. Freshwater sponges produce resisting bodies called gemmules that contain totipotent cells and specialized spicules (gemmuloscleres). Completely formed gemmules exhibit low metabolic rates and may become dormant during periods of environmental stress. Until now, few species had their hatchability tested against different environmental conditions. The purpose of the present study was to test the capacity of hatching gemmules of two freshwater sponge species (Heteromeyenia cristalina Batista, Volkmer-Ribeiro & Melão, 2007 and Radiospongilla inesi Nicacio & Pinheiro, 2011) from inland waters from different localities. Five assays were tested (A): A1 (water of sponge collection site); A2 (Pirangi River water); A3 (Araraquara Pond water); A4 (mineral water) and A5 (A1 after drying gemmules). For each assay, three replicates with 30 gemmules were used. The gemmules were observed daily during 30 days. Data analysis was performed using ANOVA and a posteriori Tukey test. Results showed that gemmules from both species submitted to A3 have not hatched, probably due to its very high conductivity. There was a significant difference between assays (A1, A2 and A4) and between species (F2, 12 = 77.2; P 0.001). Comparison between A1 and A5 showed significant differences between both assays and species (F1, 8 = 27.5; P 0.001). Radiospongilla inesi presented high hatching rate at all assays, while H. cristalina had a high hatching rate only on A1 and A5. Results clearly show that each species has a different capacity of hatching.(AU)

Ambientes de águas continentais estão suscetíveis a condições ambientais extremas, determinantes à evolução de várias estratégias adaptativas para estas condições variáveis. As esponjas de águas continentais produzem corpos resistentes chamados gêmulas, que contêm células totipotentes e espículas especializadas (gemoscleras). As gêmulas completamente formadas exibem baixas taxas metabólicas e podem tornar-se dormentes tipicamente durante períodos de estresse ambiental. Até agora, poucas espécies tiveram sua capacidade de eclosão testada frente diferentes condições ambientais. O objetivo do presente estudo foi testar a capacidade de eclosão de gêmulas para duas espécies (Heteromeyenia cristalina Batista, Volkmer-Ribeiro & Melão, 2007 e Radiospongilla inesi Nicacio & Pinheiro, 2011) de esponjas de águas continentais em águas de diferentes localidades. Foram realizados cinco ensaios (A): A1 (água do local da coleta das esponjas); A2 (água do Rio Pirangi); A3 (água da Lagoa Araraquara); A4 (água mineral) e A5 (água do local da coleta das esponjas). Para cada ensaio, três réplicas com 30 gêmulas foram usadas. As gêmulas foram observadas diariamente durante 30 dias. A análise de dados foi conduzida usando ANOVA e o teste aposteriori Tukey. Os resultados mostraram que gêmulas de ambas espécies submetidas ao A3 não eclodiram, provavelmente devido à alta condutividade. Há diferenças entre os ensaios (A1, A2 e A4) e entre espécies (F2, 12 = 77.2; P 0.001). Ao comparar A1 e A5, houve diferenças significativas entre ambos os ensaios e espécies (F1, 8 = 27.5; P 0.001). Radiospongilla inesi apresentou alta taxa de eclosão em todos os ensaios enquanto que Heteromeyenia cristalina teve uma alta taxa de eclosão apenas no ensaio com água do seu ambiente natural. Os resultados mostram claramente que cada espécie tem diferente capacidade de eclosão.(AU)

Assuntos

RESUMO

Inland waters experience extreme environmental conditions determining the evolution of several adaptive strategies of the fauna to these variable conditions. Freshwater sponges produce resisting bodies called gemmules that contain totipotent cells and specialized spicules (gemmuloscleres). Completely formed gemmules exhibit low metabolic rates and may become dormant during periods of environmental stress. Until now, few species had their hatchability tested against different environmental conditions. The purpose of the present study was to test the capacity of hatching gemmules of two freshwater sponge species (Heteromeyenia cristalina Batista, Volkmer-Ribeiro & Melão, 2007 and Radiospongilla inesi Nicacio & Pinheiro, 2011) from inland waters from different localities. Five assays were tested (A): A1 (water of sponge collection site); A2 (Pirangi River water); A3 (Araraquara Pond water); A4 (mineral water) and A5 (A1 after drying gemmules). For each assay, three replicates with 30 gemmules were used. The gemmules were observed daily during 30 days. Data analysis was performed using ANOVA and a posteriori Tukey test. Results showed that gemmules from both species submitted to A3 have not hatched, probably due to its very high conductivity. There was a significant difference between assays (A1, A2 and A4) and between species (F2, 12 = 77.2; P 0.001). Comparison between A1 and A5 showed significant differences between both assays and species (F1, 8 = 27.5; P 0.001). Radiospongilla inesi presented high hatching rate at all assays, while H. cristalina had a high hatching rate only on A1 and A5. Results clearly show that each species has a different capacity of hatching.

Ambientes de águas continentais estão suscetíveis a condições ambientais extremas, determinantes à evolução de várias estratégias adaptativas para estas condições variáveis. As esponjas de águas continentais produzem corpos resistentes chamados gêmulas, que contêm células totipotentes e espículas especializadas (gemoscleras). As gêmulas completamente formadas exibem baixas taxas metabólicas e podem tornar-se dormentes tipicamente durante períodos de estresse ambiental. Até agora, poucas espécies tiveram sua capacidade de eclosão testada frente diferentes condições ambientais. O objetivo do presente estudo foi testar a capacidade de eclosão de gêmulas para duas espécies (Heteromeyenia cristalina Batista, Volkmer-Ribeiro & Melão, 2007 e Radiospongilla inesi Nicacio & Pinheiro, 2011) de esponjas de águas continentais em águas de diferentes localidades. Foram realizados cinco ensaios (A): A1 (água do local da coleta das esponjas); A2 (água do Rio Pirangi); A3 (água da Lagoa Araraquara); A4 (água mineral) e A5 (água do local da coleta das esponjas). Para cada ensaio, três réplicas com 30 gêmulas foram usadas. As gêmulas foram observadas diariamente durante 30 dias. A análise de dados foi conduzida usando ANOVA e o teste aposteriori Tukey. Os resultados mostraram que gêmulas de ambas espécies submetidas ao A3 não eclodiram, provavelmente devido à alta condutividade. Há diferenças entre os ensaios (A1, A2 e A4) e entre espécies (F2, 12 = 77.2; P 0.001). Ao comparar A1 e A5, houve diferenças significativas entre ambos os ensaios e espécies (F1, 8 = 27.5; P 0.001). Radiospongilla inesi apresentou alta taxa de eclosão em todos os ensaios enquanto que Heteromeyenia cristalina teve uma alta taxa de eclosão apenas no ensaio com água do seu ambiente natural. Os resultados mostram claramente que cada espécie tem diferente capacidade de eclosão.

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Sponges collected on the Guyana Shelf, predominantly in Suriname offshore waters, by Dutch HMS 'Snellius' O.C.P.S. 1966, HMS 'Luymes' O.C.P.S. II 1969, and HMS 'Luymes' Guyana Shelf 1970 expeditions are described in this study. Sponges were obtained by trawling, dredging or grabbing on sandy, muddy, shelly, and fossil reef bottoms at 88 stations between 19 and 681 m depth. A total of 351 samples were identified to species level, each consisting of one or more specimens of a given species from each individual station (together comprising 547 individuals and fragments). The collection yielded 119 species together belonging to all sponge classes, but in large majority are Demospongiae. All species are identified to species level, occasionally tentatively, and all are described and illustrated. A new subgenus is proposed, Tedania (Stylotedania) subgen. nov. and a previously synonymized genus, Tylosigma Topsent, 1894 is revived. Thirtysix species were found to be new to science, excluding the first Central West Atlantic record of the genus Halicnemia, not named at the species level because of lack of sufficient material. The new species erected are, in alphabetical order: Amphoriscus ancora sp. nov., Biemna rhabdotylostylota sp. nov., Callyspongia (Callyspongia) scutica sp. nov., Chelonaplysilla americana sp. nov., Cladocroce guyanensis sp. nov., Clathria (Axosuberites) riosae sp. nov., Clathria (Clathria) gomezae sp. nov., Clathria (Microciona) snelliusae sp. nov., Clathria (Thalysias) complanata sp. nov., Clathria (Thalysias) zeai sp. nov., Coelosphaera (Coelosphaera) lissodendoryxoides sp. nov., Craniella crustocorticata sp. nov., Diplastrella spirastrelloides sp. nov., Epipolasis tubulata sp. nov., Erylus rhabdocoronatus sp. nov., Erylus surinamensis sp. nov., Geodia pocillum sp. nov., Geodia sulcata sp. nov., Hemiasterella camelus sp. nov., Hymedesmia (Stylopus) alcoladoi sp. nov., Hymenancora cristoboi sp. nov., Penares sineastra sp. nov., Hymerhabdia kobluki sp. nov., Leucosolenia salpinx sp. nov., Petrosia (Strongylophora) devoogdae sp. nov., Placospongia ruetzleri sp. nov., Pyloderma tropicale sp. nov., Raspailia (Parasyringella) thamnopilosa sp. nov., Raspailia (Raspailia) johnhooperi sp. nov., Sphaerotylus bouryesnaultae sp. nov., Spirastrella erylicola sp. nov., Stelletta vervoorti sp. nov., Suberites crispolobatus sp. nov., Tedania (Stylotedania) folium subgen. nov. sp. nov., Timea tylasterina sp. nov., and Tylosigma ostreicola sp. nov. Two new combinations are proposed: Amphimedon nanaspiculata (Hartman, 1955) comb. nov. and Oceanapia ascidia (Schmidt, 1870) comb. nov. In addition, for two preoccupied combinations, new names, Coelosphaera (Coelosphaera) barbadensis nom. nov. and Hymedesmia (Hymedesmia) rowi nom. nov., are erected. The spatial distribution of the collected specimens over the Guyana Shelf was traced and the results were compared with existing information on bottom conditions. There was a convincing correlation between the location of fossil reefs and other hard substrates such as shell ridges with peaks in the occurrence of species diversity and specimen numbers. Stations made on sand and mud bottoms away from these zones of hard substrates were generally poor in species, but some were found to be rich in individuals of specialized soft bottom dwellers such as Tetilla pentatriaena, Tribrachium schmidtii, Fangophilina submersa, and Oceanapia species. The species composition of the Guyana Shelf was compared with that of neighbouring regions of the Caribbean and from North and East Brazil (Díaz in Miloslavich et al. 2010; Muricy et al. 2011). About 35% of the species encountered are widespread in the Central West Atlantic, occurring both to the north and to the south. Indications that the Guyana Shelf sponge fauna is clearly transitional are southernmost occurrences for Caribbean species (about 30%), and northernmost occurrences of Brazilian species (13%), with a high proportion (25%) of new species, which may be expected to have distributions extending to the Caribbean, to Brazil or both regions.

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A series of recent expeditions in fjords and canals of Southern Chilean Patagonia allowed the re-collection of Halisarca magellanica Topsent, 1901 and the discovery of a new species, Halisarca desqueyrouxae sp. nov. The material studied was collected at depths ranging from 3 to 30 m at latitudes comprised between 42° and 49°S. Both species share the same habitat and show a morphological plasticity, but differ in their colour. Halisarca magellanica is bright pink to whitish with three morphs whereas H. desqueyrouxae sp. nov. is light brown to beige with two morphs. An extensive investigation in TEM and SEM reveals several differences among cell types with inclusions between both species. Three distinct spherulous cells occur. Type 1 is shared by both species, Type 2 is occasional in H. magellanica but absent from H. desqueyrouxae sp. nov. Type 3 is rare in H. magellanica and occurs abundantly in half of the specimens of H. desqueyrouxae sp. nov. Granular cells are shared by both species but do not occur in all specimens. Microgranular cells are characteristic of H. magellanica. Both species also clearly differ by their endobiotic bacteria. Phylogenetic analysis of cox1 sequences places H. magellanica as a sister group to all other previously published Halisarca species sequences (9.1-9.7% difference) except H. harmelini, while H. desqueyrouxae sp. nov. is placed as a sister group to H. dujardini (2.3% difference).

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Alveospongia sinuosclera gen. nov. sp. nov. is described from shallow-waters off Canavieiras (Bahia, Brazil). The species bears an unusual morphology, combining saccular or alveolar, evenly perforated habit, and sinuous spiny microrhabdose microscleres. This sponge is tentatively classified within the Heteroxyidae Dendy (1905), on the basis of its confused choanosomal architecture of styles, and possession of spiny microrhabdose microscleres. Assays to generate DNA sequences from this material were unsuccessful. We emended the diagnosis of the family to include species bearing saccular/alveolar shape, microrhabdose acanthomicrostrongyles and styles/strongyles with modifications at the ends. The proposed new genus is compared to the remaining heteroxyid genera, as well as Crella (Crellidae), Batzella (Chondropsidae), Goreauiella (Astroscleridae) and Sceptrintus (Podospongiidae). A revised key for identification of Heteroxyidae genera is provided.

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Our ongoing studies of the Chilean sponge fauna revealed four new species of Lissodendoryx (Ectyodoryx) that are described here, including three from the fjord's region (< 30 m depth, L.(E.) ballena sp. nov., L. (E.) corrugata sp. nov.,      L. (E.) coloanensis sp. nov.), and one from the deep waters off Diego Ramírez Archipelago (ca. 2000 m, L. (E.) diegoramirezensis sp. nov.). In addition, the type of L. (E.) anacantha was revised and found to bear much larger acanthostyles than originally reported. Our results revealed skeletal architectures quite distinct from that reported from the type species of L. (Ectyodoryx), and not predicted in the current diagnosis of Lissodendoryx, requiring an amended diagnosis. Ectosomal megascleres also set the majority of the new species apart from the type species of L. (Ectyodoryx), which does not have terminally microspined (sub)tylotes. This character is widespread in Lissodendoryx and might be pointing to phylogenetic affinities across the current subgeneric arrangement. Further morphologic characters and alternative phylogenetic scenarios are discussed, including hymedesmiid and myxillid affinities of the species described here.

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Guancha tetela was originally described as a species having a peduncle and a skeleton exclusively composed of sagittal triactines. Therefore, according to the most recent phylogeny of Clathrinida, it should be placed in the genus Clathrina. This species was collected on the Northeastern Brazilian coast in 1968 and it was not collected again until 2011 in Curaçao. In this study, we reanalyzed the type material and the new specimens from Curaçao under a morphological-molecular approach. Morphological analysis revealed the presence of tetractines in the skeleton of all the studied specimens, including a slide of the holotype. In the molecular phylogeny G. tetela grouped with genera containing tetractines, but as an independent new lineage, different from all the other genera of Clathrinida. Based on these results, we propose the erection of a new genus, Nicola gen. nov., to include species whose body is composed of tubes without anastomosis nor branches but that run in parallel and coalesce at the apical and basal regions. Moreover, the skeleton is exclusively composed of sagittal triactines and tetractines.

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The genus Neopetrosia was characterized by has fine brushes of oxeas issued from subectosomal tracts and compact choanosomal network. We report and describe here specimens collected in the coast of Brazil: Neopetrosia sulcata sp. nov. and Neopetrosia proxima. The first was previously recorded from Brazil as Neopetrosia proxima, but it was found that these specimens corresponded to a new species. Thus, we provide here the characterization of N. proxima from Brazilian coast. A taxonomic study of Brazilian samples is given, including description, illustrations and geographic distribution, combined with the comparison of the new species with all other descriptions of Neopetrosia from Atlantic.

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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.

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Disturbance releases space and allows the growth of opportunistic species, excluded by the old stands, with a potential to alter community dynamics. In coral reefs, abundances of fast-growing, and disturbance-tolerant sponges are expected to increase and dominate as space becomes available following acute coral mortality events. Yet, an increase in abundance of these opportunistic species has been reported in only a few studies, suggesting certain mechanisms may be acting to regulate sponge populations. To gain insights into mechanisms of population control, we simulated the dynamics of the common reef-excavating sponge Cliona tenuis in the Caribbean using an individual-based model. An orthogonal hypothesis testing approach was used, where four candidate mechanisms-algal competition, stock-recruitment limitation, whole and partial mortality-were incorporated sequentially into the model and the results were tested against independent field observations taken over a decade in Belize, Central America. We found that releasing space after coral mortality can promote C. tenuis outbreaks, but such outbreaks can be curtailed by macroalgal competition. The asymmetrical competitive superiority of macroalgae, given by their capacity to pre-empt space and outcompete with the sponge in a size-dependant fashion, supports their capacity to steal the opportunity from other opportunists. While multiple system stages can be expected in coral reefs following intense perturbation macroalgae may prevent the growth of other space-occupiers, such as bioeroding sponges, under low grazing pressure.

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Adverse natural conditions will, generally, induce gemmulation in freshwater sponges. Because of this environmental dependence, gemmoscleres are given exceptional value in taxonomic, ecological and paleoenvironmental studies. Other spicules categories such as microscleres and beta megascleres have received little attention with regard to their occurrence and function during the sponge biological cycle. Metania spinata, a South American species common to bog waters in the Cerrado biome, produces alpha and beta megascleres, microscleres and gemmoscleres. To detect the environmental factors triggering the production of all these kinds of spicules, the species annual seasonal cycle was studied. Artificial substrates were devised, supplied with gemmules and placed in Lagoa Verde pond which contained a natural population of M. spinata. Field monitoring was conducted for eight months in order to observe the growth of sponges and spicules formation. Samples of water were taken monthly for physical and chemical parameters determination. The appearance of the alpha megascleres was sequentially followed by that of microscleres, gemmoscleres and beta megascleres. The first ones built the new sponge skeleton, the last three were involved in keeping inner moisture in the sponge body or its gemmules. The water level, temperature and the silicon (Si) concentration in the pond were the most important factors related to this sequential production of spicules, confirming environmental reconstructions based on the presence or absence of alpha megascleres and gemmoscleres in past sediments.

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The genus Jaspis comprises 32 valid species, six of which were previously recorded from the Atlantic Ocean. Two species have already been recorded from the Brazilian coast: J. johnstonii and J. salvadori (Rio Grande do Sul and Espírito Santo States respectively). Their respective type specimens, deposited at Muséum National d'Historie Naturelle, Paris (Jaspis salvadori, holotype) and at Universalmuseum Joanneum, Zoology Center of Natural History, Austria (Jaspis johnstonii, syntype) were reexamined, but due to differences in spicule composition these records are considered to be invalid. The present paper describes five new species of Jaspis collected on the Brazilian coast (Jaspis atolensis sp. nov., J. iacuitaster sp. nov., J. corticomicroxea sp. nov., J. variaster sp. nov. and J. gigoxea sp. nov.) bringing the total number of species worldwide to 36, all of which were compared in tabular format. The type species, Jaspis johnstonii, was also redescribed.

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Comprising 56 species, Timea Gray, 1867 belongs to the monotypic family Timeidae Gray, 1867, with both family and genus characterized by the presence of (sub)tylostyles as megascleres, and euasters as microscleres. Two new species are described from the coast of Rio de Janeiro state, Timea berlincki sp. nov. and Timea clandestina sp. nov., the first of which also from São Paulo state (southeastern Brazil). Both are compared to other species based on their morphological and skeletal characters. Records of all species of the genus worldwide are tabulated and discussed, and an identification key for Tropical western Atlantic species of Timea is offered.

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A new species of freshwater sponge, Heteromeyenia barlettai sp. nov., is proposed here based on specimens discovered in a private aquarium in São Paulo, Brazil, and most likely inadvertently collected from the Paraná Basin. The present study also presents a redescription of H. insignis on the basis of the specimen reported upon by Volkmer (1963), collected from the Atlântico Sul Hydrographic Basin. Spicule measurements (n=30) were made for comparison with other Heteromeyenia species. This is the first time that H. insignis has its complete set of spicules studied under SEM. After comparison with the redescription of the type of H. baileyi, we also find characteristics that justify the maintenance of H. insignis as a valid species. A key to species of Heteromeyenia is provided.

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Three species of Desmacella Schmidt, 1870 are described from the Brazilian coast: Desmacella microsigmata sp. nov., Desmacella tylovariabilis sp. nov. and Desmacella annexa Schmidt, 1870. The new species were compared with Desmacella species from the Atlantic Ocean, which differ by the size of their spicules and by the presence of microspined sigmas. Desmacella annexa was found to have microspined toxiform microxeas and sigmas. Desmacella now contains 31 species distributed worldwide.

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A thin fiber-less sponge from Caribbean reefs (Bocas del Toro, Panama) with close genetic affinities (based on 18S and 28S nuclear ribosomal RNA gene sequences) to large fan-shaped fiber-bearing sponges (Ianthella and Anomoianthella) from the Indo-Pacific Ocean is here presented. We describe its overall external morphology, histological features, and ultrastructure. Its genetic distance from the only previously known fiber-less verongid genus, Hexadella, prompted the need to erect a new genus to classify this species. This novel species constitutes the first record for a member of the family Ianthellidae in the Caribbean. The characterization of the family Ianthellidae (sensu Cook and Bergquist, 2000) is here modified by: i) highlighting the cavernous nature of the choanosome, with many lacunae and channels reported for all genera included in the family; ii) extending the family distribution to the Caribbean; and iii) adding a fourth genus to the group of verongids with eurypylous chambers. The possession of a cellularized cortex (10-300 µm in thickness) is here proposed as a potential synapomorphic character of the Ianthella-Anomoianthella-Vansoestia clade. The main issues regarding the suprageneric classification of verongids are discussed.

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Over the past decade, development along the northern coast of Jamaica has accelerated, resulting in elevated levels of sedimentation on adjacent reefs. To understand the effects of this development on sponge community dynamics, we conducted surveys at three locations with varying degrees of adjacent coastal development to quantify species richness, abundance and diversity at two depths (8-10 m and 15-18 m). Sediment accumulation rate, total suspended solids and other water quality parameters were also quantified. The sponge community at the location with the least coastal development and anthropogenic influence was often significantly different from the other two locations, and exhibited higher sponge abundance, richness, and diversity. Sponge community composition and size distribution were statistically different among locations. This study provides correlative evidence that coastal development affects aspects of sponge community ecology, although the precise mechanisms are still unclear.

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Two species of Hamacantha with tylostyles are reported here for the Peruvian coast, namely H. desmacelloides sp.nov. and H. hyaloderma. The former is the first species in the genus with apically microspined sigmas, similar to those known to occur in Neofibularia, and recently reported from genera Biemna, Desmacella, Rhabderemia and Sigmaxinella. Hamacantha hyaloderma was previously known from Mexico to Canada, and is here reported for the first time from the south east Pacific. The finding of a second species with tylostyles led us to reinstate subgenus Hamacantha (Zygherpe). The possible phylogenetic significance of apically microspined sigmas is discussed in view of recent findings on the basis of molecular data.

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Marine sponges usually constitute the most diverse group of the benthic community in coral reefs. Although they are reasonably well studied at the northern Gulf of Mexico (GMx), the southern GMx is poorly known and lacks records from many major reef systems that lie off the Mexican coast. The present taxonomic study is the first sponge account from Alacranes reef, the largest coral reef system in the GMx, and from the shallow reef banks of Sisal, both in the northwest Yucatan Peninsula. The 19 species herein described represent the first sponge fauna records from these reefs. Among these, seven species represent new record for GMx: Erylus formosus, Cliona flavifodina, Spirastrella aff. mollis, Strongylacidon bermuda, Topsentia bahamensis, Agelas tubulata and Chelonaplysilla aff. erecta. Twelve species are new records for the Southern GMx: Erylus trisphaerus, Cliona amplicavata, Chondrilla caribensis, Halichondria lutea, Hymeniacidon caerulea, Axinella corrugata, Dragmacidon reticulatum, Chalinula molitba, Amphimedon caribica, A. complanata, Hyatella cavernosa and Dysidea variabilis. Additionally, a redescription of Erylus trisphaerus is presented which had not been reviewed since its original description in 1953 off Western Florida, except that it was listed for north La Habana, Cuba. 

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