Unprecedented frequency of mitochondrial introns in colonial bilaterians.

Animal mitogenomes are typically devoid of introns. Here, we report the largest number of mitochondrial introns ever recorded from bilaterian animals. Mitochondrial introns were identified for the first time from the phylum Bryozoa. They were found in four species from three families (Order Cheilostomatida). A total of eight introns were found in the complete mitogenome of Exechonella vieirai, and five, 17 and 18 introns were found in the partial mitogenomes of Parantropora penelope, Discoporella cookae and Cupuladria biporosa, respectively. Intron-encoded protein domains reverse transcriptase and intron maturase (RVT-IM) were identified in all species. Introns in E. vieirai and P. penelope had conserved Group II intron ribozyme domains V and VI. Conserved domains were lacking from introns in D. cookae and C. biporosa, preventing their further categorization. Putative origins of metazoan introns were explored in a phylogenetic context, using an up-to-date alignment of mitochondrial RVT-IM domains. Results confirmed previous findings of multiple origins of annelid, placozoan and sponge RVT-IM domains and provided evidence for common intron donor sources across metazoan phyla. Our results corroborate growing evidence that some metazoans with regenerative abilities (i.e. placozoans, sponges, annelids and bryozoans) are susceptible to intron integration, most likely via horizontal gene transfer.

A new species of Diadema (Echinodermata: Echinoidea: Diadematidae) from the eastern Atlantic Ocean and a neotype designation of Diadema antillarum (Philippi, 1845).

Diadenia africanum sp. nov. Rodríguez et al. 2013 occurs in the eastern Atlantic Ocean at depths of 1-80 meters off Ma- deira Islands, Salvage Islands, Canary Islands, Cape Verde Islands, Sâo Tome Islands and at the continental coast off Sen- egal and Ghana. This species was previously considered an eastern Atlantic population of D. antillarum. Genetic distances between the holotype of D. africanum and the neotype of D. antillarun herein designated, measured 3.34% in Cytochrome oxidase I, 3.80% in ATPase-8 and 2.31% in ATPase-6. Such divergence is similar to that already highlighted between other accepted species of Diadena. Morphometric analysis of test, spine and pedicellarial characters also separated D. africanum from D. antillartn and reveals that this new species is morphologically similar to D. antillarum ascensionis from the mid Atlantic. The tridentate pedicellariae, which have been shown to have diagnostic characters which discriminate among species of Diadema, occur as both broad and narrow valved forms in D. antillarumn from the western Atlantic. In D. africanum the tridentate pedicellariae occur only as a single form which is characterized by moderately broad and curved valves, with an expanded distal gripping region. This form of tridentate pedicellaria is very similar to that of D. antillarum ascensionis from the central Atlantic, with only slight variations in valve serration and valve curvature differ- entiating the two forms.