Two new species of Hemimycale from Southeastern Brazil are described in this study with the use of morphological and molecular data. Hemimycale oxeata sp. nov. is orange salmon colored in life and has unique oxeote like tornote spicules in addition to the typical (subtylo-)strongyles of the genus. Hemimycale ceadensis sp. nov. is reddish orange in life and has raised, tiny pore sieves, and subtylostrongyles with asymmetrical ends and raphides as microscleres. The diagnosis of the genus Hemimycale was slightly modified for the inclusion of the new species. Maximum-Likelihood analyses of 18S rRNA and COI sequences resulted in the clustering of both new species with the type species of the genus, thus confirming our morphological identification. The value of anatomical characters of pore sieves for diagnosing species and the genus is discussed. A key for species identification is also furnished. 

Sponges (Porifera) co-evolved with microorganisms in a well-established symbiotic relationship. Based on this characteristic, sponges can be separated into high microbial abundance (HMA) and low microbial abundance (LMA) species. Paraleucilla magna (Calcarea, Porifera) is an alien species of ecological importance in the Brazilian coastline. Little is known about the composition of its microbiota and that of other calcareous species, especially those inhabiting the Southwest Atlantic. Here, we describe the microbiota of P. magna and compare it to that of other calcareous sponge species for which such data exist. P. magna’s microbiota shows a lower diversity than that of Clathrina clathrus, C. coriacea, Leucosolenia sp., Leuconia sp. and Leucetta antarctica. P. magna microbiota is dominated by two bacterial OTUs of the Alphaproteobacteria class, that could not be classified beyond class (OTU001) and family levels (OTU002; Rhodospirillaceae). The Thaumarcheota was the predominant archaeal phylum in P. magna, with OTUs mainly affiliated to the genus candidatus Nitrosopumilus. The comparison with other calcareous species showed that microbiota composition correlated well with sponge phylogenetic affiliation. Metabolic prediction with PICRUSt software of P. magna bacterial microbiota indicated that membrane transport and carbohydrate, amino acid and energy metabolisms were most abundant while, for the archaeal domain, pathways related to translation, and energy metabolisms were predominant. Predicted metabolic features were compared between the different sponge species and seawater samples, showing that pathways related to cell motility, membrane transport, genetic information processing, xenobiotics metabolism and signal transduction are higher in the former while amino acid and nucleotide metabolism, translation, replication and repair, folding, sorting and degradation and glycan biosynthesis and metabolism are abundant in the latter. This study shows that P. magna’s microbiota is typical of an LMA sponge and that it differs from the microbiota of other calcareous sponges both in its composition and in predicted metabolic pathways.