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We combine published and new mineralogical data on most major taxa of brachiopods from all over the world, to investigate patterns and controls on brachiopod carbonate mineralogy. Measurements of 1726 specimens in 162 species (including 56 fossil species) ranged from 79°N to 74°S and from intertidal to almost 4000 m deep. Calcareous brachiopods mostly create strong resilient valves of very low-Mg calcite ($\bar{\chi }$ χ ¯ = 1.3 wt% MgCO3). The substrate-cemented Craniida ($\bar{\chi }$ χ ¯ = 8.9 wt% MgCO3) and Thecideida ($\bar{\chi }$ χ ¯ = 6.5 wt% MgCO3) are unusual in precipitating calcite with higher Mg content. This is the first study to find bimineralic brachiopods; a few species show a combination of low-Mg ($\bar{\chi }$ χ ¯ = 0.8 wt% MgCO3) and intermediate-Mg calcite ($\bar{\chi }$ χ ¯ = 7.2 wt% MgCO3) (sensu Smith AM, Key MM Jr, Gordon DP. 2006. Skeletal mineralogy of bryozoans: taxonomic and temporal patterns. Earth-Science Reviews. 78:287–306.). While Mg in calcite varies systematically among valve layers and sometimes along the growth axis, we found no consistent difference between valves of the same individual. A weak latitudinal signal indicates some overall temperature control of Mg, but in general, brachiopods are active calcifiers, precipitating low-Mg calcite even when Mg:Ca ratio in seawater is high. The drivers on brachiopod mineralogy are individual, environmental, and phylogenetic – resulting in complex variability. [ABSTRACT FROM AUTHOR]

One of the most salient features of marine bryozoans is their well-calcified skeleton, and many species in this phylum are important reef-builders. To date, the molecular machinery responsible for skeletal formation in these key animals remains unknown. In this study we performed de novo transcriptome assembly from RNA from Cellaria immersa colonies collected in New Zealand, the first from the family Cellariidae. The assembly resulted in a set of 125,750 transcripts and was estimated to be 97.2% complete when compared to BUSCO core gene sets. A function was predicted for 61,442 (48.8%) of the translated proteins, using similarity searches against a range of databases using BLAST and InterProScan. Cellaria species form erect, heavily calcified arborescent colonies, which when abundant can create micro-forests or meadows on the ocean floor. RNA was extracted separately from younger distal and older proximal parts of the colonies, aiming to identify the key genes involved in biomineralization as the young zooids (at the distal growth margin) of the colony are more likely to be actively growing and calcifying compared to the old zooids of the proximal parts of the colony. Differential expression analysis was carried out to identify differential expression between the distal and proximal parts of the colonies. This showed that 506 (2.2%) of the transcripts were expressed more highly in the young zooids and 4,676 (20.4%) were expressed more highly in the old zooids. Over 50 protein families were identified as candidates involved in biomineralization in C. immersa based on the functional annotation, their expression pattern and literature. Transcripts encoding 24 such protein families were more highly expressed in the young zooids. This is the first such study on a heavily calcified species from the phylum Bryozoa, increasing the amount of 'omics' data available for C. immersa and the phylum. These data provide a resource for current and future studies of heavily calcified bryozoans, shedding a light on the biomineralization process in this phylum. [ABSTRACT FROM AUTHOR]

Ctenostomes are a group of gymnolaemate bryozoans with an uncalcified chitinous body wall having few external, skeletal characters. Hence, species identification is challenging and their systematics remain poorly understood, even more so when they exhibit an endolithic (boring) lifestyle. Currently, there are four Recent families of endolithic bryozoans that live inside mineralized substrates like mollusk shells. In particular, Penetrantiidae Silén, 1946 has received considerable attention and its systematic affinity to either cheilostomes or ctenostomes has been debated. Species delimitation of penetrantiids remains difficult, owing to a high degree of colonial and zooidal plasticity. Consequently, an additional molecular approach is essential to unravel the systematics of penetrantiids, their phylogenetic placement and their species diversity. We therefore sequenced the mitochondrial (mt) genomes and two nuclear markers of 27 ctenostome species including nine penetrantiids. Our phylogeny supports the Penetrantiidae as a monophyletic group placed as sister taxon to the remaining ctenostomes alongside paludicellids, arachnidioids and terebriporids. The boring family Terebriporidae d'Orbigny, 1847 were previously considered to be among vesicularioids, but our results suggest an arachnidioid affinity instead. Ctenostome paraphyly is supported by our data, as the cheilostomes nest within them. A Multiporata clade is also well supported, including the former victorelloid genus Sundanella. Altogether, this study provides new insights into ctenostome systematics, assists with species delimitation and contributes to our understanding of the bryozoan tree of life. [ABSTRACT FROM AUTHOR]