Uncovering the Microbial Diversity of Two Exotic Calcareous Sponges.

Sponges-associated microorganisms play important roles in their health and ecology; consequently, they may be crucial in the successful adaptation of exotic species to novel environments. However, few studies have focused on the microbial diversity of exotic sponges, especially those with calcium carbonate spicules (class Calcarea). Therefore, this is the first in situ characterization of the microbiota of the exotic calcareous sponges Sycettusa hastifera and Paraleucilla magna. Our results suggest that S. hastifera has a more stable microbiota than P. magna, as there were no differences in its beta diversity among sampling sites. Conversely, P. magna showed significant differences in its microbial communities, perhaps related to its adhesion to artificial substrate and/or shellfish mariculture activities. Each sponge species presented a single dominant proteobacterial OTU potentially active in the nitrogen cycle, which could help sponge detoxification, especially in polluted areas where exotic species usually establish. Our results show the importance of assessing the microbial diversity to unveil host-microorganism relationships and suggest that these associated nitrogen-cycling microorganisms could favor the success of exotic sponges in new environments.

Calcareous sponges (Porifera, Calcarea) from Florida: new species, new records and biogeographical affinities.

Florida is among important marine biodiversity areas with high richness and endemism of marine taxa. Despite the economic and scientific importance of the region, knowledge on the diversity and distribution of some groups, such as calcareous sponges, is still reduced and scattered in old literature. In the present work, sponges collected in the Florida Keys were studied under an integrative perspective (traditional morphology and DNA: ITS). Three calcinean species were found: Clathrina smaragda sp. nov., C. lutea, and Ernstia rocasensis. Clathrina smaragda sp. nov. is the first Clathrina described with a green cormus. The occurrence of C. lutea in Florida was confirmed, and E. rocasensis had its geographical distribution widened from the Northeastern Brazilian waters to Florida, although Floridian individuals of this species have presented differences in morphological characters that resulted in the proposition of a new diagnosis and a discussion on morphological plasticity in Clathrinidae. A complete list of the calcareous sponges from Florida is presented and their distributional patterns are discussed.

Fragmentation, Fusion, and Genetic Homogeneity in a Calcareous Sponge (Porifera, Calcarea).

Sessile marine invertebrates living on hard substrata usually present strategies such as size variations, longer life spans, fragmentation and fusion to occupy and compete for space. Calcareous sponges are usually small and short-lived, and some species are known to undergo frequent fragmentation and fusion events. However, whether fusion occurs only between genetically identical individuals remains unclear. We investigated the occurrence of chimaeras in the calcareous sponge Clathrina aurea by following the dynamics of fragmentation and fusion of 66 individuals in the field for up to 18 months and determined size variations and the life span of each individual. Microsatellites were used to determine whether fusion events occur among genetically different individuals. Growth and shrinkage of individuals were frequently observed, showing that size cannot be associated with age in C. aurea. The life span of the species ranged from 1 to 16 months (mean: 4.7 months). Short life spans and variable growth rates have been observed in other species of the class Calcarea. Fragmentation and fusion events were observed, but fusion events always occurred between genetically identical individuals, as has been suggested by graft experiments in adult Demospongiae and other Calcarea. These results suggest that at least C. aurea adults may have some mechanism to avoid chimaerism.