Thoracican barnacles are common in hydrothermal vent fields. Here, we characterized the first mitogenome of a hydrothermal vent barnacle. The mitogenome of Eochionelasmus ohtai was 15,585 bp in length and had the typical pancrustacean gene arrangement. Its protein-coding genes (PCGs) were very similar in terms of length, AT content, and start and stop codons to those of other thoracican species. The phylogenetic tree constructed with 13 PCGs divided balanomorph barnacles, including E . ohtai , into two clades. This will further our understanding of the evolution of hydrothermal vent barnacles using mitogenomes, although further mitogenomic analysis of undetermined taxa is required.

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Non-monophyletic Poecilasmatids are deep-water epibiotic barnacles and are classified as five-capitular-plate members of the Lepadiformes. Here, we offer the first characterization of the mitogenome of a Poecilasmatid barnacle (Glyptelasma annandalei). The mitogenome was 16,107 bp long, with 72.3% AT content. Its gene arrangement was identical to that of the lepadids Lepas anserifera and L. australis, except for the location of the tRNA Ser gene. On the mitogenomic tree, two Lepadiformes families (Poecilasmatidae and Lepadidae) were monophyletic, which concurs with the findings of previous studies. Further mitogenomic analysis of undetermined Lepadiformes taxa is required to deepen our understanding of their phylogeny and evolution.

To develop a brackish water flea as a promising model for marine monitoring, Diaphanosoma celebensis were exposed to two pollutants, cadmium (Cd) and benzo[a]pyrene (BaP), which have different chemical characteristics and distinct modes of metabolic action on aquatic animals. Twenty-four hours after exposure to Cd (2 mg/L) or BaP (25 μg/L), whole body transcriptomes were analyzed. In total, 99.6 Mbp were assembled from nine libraries, resulting in 98,458 transcripts with an N50 of 1883 bp and an average contig length of 968 bp. Functional gene annotations were performed using Gene Ontology, Eukaryotic Orthologous Groups, and Kyoto Encyclopedia of Genes and Genomes pathway analyses. Cd significantly modulated endocrine and digestive enzyme system. Following BaP treatment, DNA repair and circadian rhythm related metabolisms were significantly modulated. Both the chemicals induced stress response and detoxification metabolism. This brackish water flea genomic information will be useful to monitor estuaries and coastal regions, as water fleas have been confirmed as promising sentinel models in freshwater ecosystems.Electronic supplementary materialThe online version of this article (10.1186/s41065-018-0075-3) contains supplementary material, which is available to authorized users.

Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), a primary approach for evaluating gene expression, requires an appropriate normalization strategy to confirm relative gene expression levels by comparison, and rule out variations that might occur in analytical procedures. The best option is to use a reference gene whose expression level is stable across various experimental conditions to compare the mRNA levels of a target gene. However, there is limited information on how the reference gene is differentially expressed at different ages (growth) in small invertebrates with notable changes such as molting. In this study, expression profiles of nine candidate reference genes from the brackish water flea, Diaphanosoma celebensis, were evaluated under diverse exposure to toxicants and according to growth. As a result, four different algorithms showed similar stabilities of genes for chemical exposures in the case of limited conditions using the same developmental stage (H2A was stable, whereas Act was fairly unstable in adults), while the results according to age showed a significantly different pattern in suite of candidate reference genes. This affected the results of genes EcRA and GST, which are involved in development and detoxification mechanisms, respectively. Our finding is the first step towards establishing a standardized real-time qRT-PCR analysis of this environmentally important invertebrate that has potential for aquatic ecotoxicology, particularly in estuarine environments.