Lock, stock and two different barrels: comparing the genetic composition of morphotypes of the Indo-Pacific sponge Xestospongia testudinaria

The giant barrel sponge Xestospongiatestudinaria is an ecologically important species that is widely distributed across the Indo-Pacific. Little is known, however, about the precise biogeographic distribution and the amount of morphological and genetic variation in this species. Here we provide the first detailed, fine-scaled (<200 km(2)) study of the morphological and genetic composition of X. testudinaria around Lembeh Island, Indonesia. Two mitochondrial (CO1 and ATP6 genes) and one nuclear (ATP synthase β intron) DNA markers were used to assess genetic variation. We identified four distinct morphotypes of X. testudinaria around Lembeh Island. These morphotypes were genetically differentiated with both mitochondrial and nuclear markers. Our results indicate that giant barrel sponges around Lembeh Island, which were all morphologically identified as X. testudinaria, consist of at least two different lineages that appear to be reproductively isolated. The first lineage is represented by individuals with a digitate surface area, CO1 haplotype C5, and is most abundant around the harbor area of Bitung city. The second lineage is represented by individuals with a predominantly smooth surface area, CO1 haplotype C1 and can be found all around Lembeh Island, though to a lesser extent around the harbor of Bitung city. Our findings of two additional unique genetic lineages suggests the presence of an even broader species complex possibly containing more than two reproductively isolated species. The existence of X. testudinaria as a species complex is a surprising result given the size, abundance and conspicuousness of the sponge.The project was supported by the Percy Sladen Memorial Fund of the Linnean Society of London and the Treub-Maatschappij Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank the Research Centre for Oceanography of the Indonesian Institute of Sciences (RCO-LIPI) for allowing us to use their research facilities and the University of Sam Ratulangi (UNSRAT) for logistic support. We thank Lin Dong, Peter Kuperus and Betsie Voetdijk for advice and help with molecular lab techniques. Hans Breeuwer provided valuable comments on the original manuscript.publishe

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Daily rhythmicity in coastal microbial mats

Cyanobacteria are major primary producers in coastal microbial mats and provide biochemical energy, organic carbon, and boundnitrogen to the mat community through oxygenic photosynthesis and dinitrogen fixation. In order to anticipate the specificrequirements to optimize their metabolism and growth during a day-and-night cycle, Cyanobacteria possess a unique moleculartiming mechanism known as the circadian clock that is well-studied under laboratory conditions but little is known about itsfunction in a natural complex community. Here, we investigated daily rhythmicity of gene expression in a coastal microbial matcommunity sampled at 6 time points during a 24-h period. In order to identify diel expressed genes, meta-transcriptome data wasfitted to periodic functions. Out of 24,035 conserved gene transcript clusters, approximately 7% revealed a significant rhythmicexpression pattern. These rhythmic genes were assigned to phototrophic micro-eukaryotes, Cyanobacteria but also toProteobacteria and Bacteroidetes. Analysis of MG-RAST annotated genes and mRNA recruitment analysis of two cyanobacterial andthree proteobacterial microbial mat members confirmed that homologs of the cyanobacterial circadian clock genes were alsofound in other bacterial members of the microbial mat community. These results suggest that various microbial mat membersother than Cyanobacteria have their own molecular clock, which can be entrained by a cocktail of Zeitgebers such as light,temperature or metabolites from neighboring species. Hence, microbial mats can be compared to a complex organism consistingof multiple sub-systems that have to be entrained in a cooperative way such that the corpus functions optimally