Physiological and molecular responses of the Antarctic harpacticoid copepod Tigriopus kingsejongensis to salinity fluctuations - A multigenerational study.

Since Antarctica and the surrounding Southern Ocean are facing global climate change, biota inhabiting those coastal regions is now challenged by environmental fluctuations including coastal freshening. In this study, the effects of salinity range of 0-75 (practical salinity unit, PSU) on the Antarctic harpacticoid copepod Tigriopus kingsejongensis was investigated by measurement of 96 h survival rate, lifespan, and sex ratio with further analysis of multigenerational growth parameters and mRNA expressions under salinity of 15-45. Different stages of the copepods (i.e., nauplius, male, and female) generally showed tolerance to hypo- and hypersalinity, wherein female copepods were more tolerant than males when exposed to salinity fluctuations. Lifespan was significantly shortened by hypo- and hypersalinity compared to control salinity (34), but there was no significant difference in the sex ratio between salinity treatments. Multigenerational experiments across five generations revealed that exposure to salinities of 15 and 45 reduced body length compared to that in control salinity and the first generation of each salinity group. Our results provide evidence regarding T. kingsejongensis on their preferred salinity ranges, physiological limit to salinity fluctuations, and population dynamics in future salinity.

Validation of Direct Boiling Method for Simple and Efficient Genomic DNA Extraction and PCR-based Macroalgal Species Determination.

A rapid, simple, and cost-effective total DNA extraction method referred to as a direct boiling method for PCR-based algal species determination was validated using representative species of green, brown, and red algae. Each sample was briefly minced in two buffers, Tris-EDTA (TE) or PCR buffer, and transferred to a heat block for boiling at 98°C for 5 min. No detergent was used in this experiment. The entire DNA isolation procedure was completed within 10 min. After brief centrifugation, the supernatant was directly used as a template for PCR. As a result, all genomic DNA markers were successfully amplified and sequenced from each algal taxon. Regardless of DNA quality, the direct boiling method is very suitable to identify unknown species of algae from a large amount of samples in a limited time and can be applied broadly to routine seasonal or annual monitoring of algae. DNA from an Undaria pinnatifida sporophyte, however, was not successfully extracted by this direct boiling method, probably due to a high concentration of polysaccharides.

The complete mitochondrial genome of the terebellid polychaete Neoamphitrite affinis (Polychaeta; Terebellidae).

Here, we sequenced and annotated the complete mitochondrial genome for the terebellid polychaete, Neoamphitrite affinis (Malmgren 1866). The complete mitogenome of N. affinis is 15,823 bp, with 33.4% A, 18.2% C, 11.5% G, and 37.0% T. The circular N. affinis mitochondrial genome comprises 13 protein-coding genes (PCGs), 23 transfer RNA (tRNA) genes including 2 methionine tRNA genes, 2 ribosomal RNA (rRNA) genes, and a non-coding region. Phylogenomic analysis based on 26 in-group taxa belonging to the two main clades, Sedentaria and Errantia, is congruent with published phylogenetic relationship for annelids, which N. affinis was grouped with Pista cristata (Terebellida; Terebellidae). This mitogenome resource will be useful for future phylogenetic studies of families belonging to Sedentaria.