Benthic fauna in the south-eastern part of the Pechora-sea: Current state and analysis of ecological quality.

In recent decades, economic activity has sharply increased in the Pechora Sea, one of the most hydrologically unique areas of the Barents Sea. Hence, the information about the current state of its ecosystems is quite important for assessing their possible changes in the future. The aim of the present study was to analyze the distribution of macrobenthos and assess its ecological quality in the southeastern part of the Pechora Sea at the beginning of the 21st century (based on data collected in 2012-2013). The results showed that since 1920s there have been no serious changes in the macrobenthos in the studied area. The weak shifts detected in the benthic fauna were either within the natural range of fluctuations in population of common species, or may be associated with differences in the methodological approaches of different researches. Heterogeneity in the macrobenthos distribution, the most significant abiotic factors identified in relation to it, quantitative indicators of biota, and species dominating in communities were similar to those revealed in previous studies. As of 2013, the characteristics of benthic communities in the southeastern part of the Pechora Sea, including their ecological quality, allow us to refer them as undisturbed biosystems.

FoxA expression pattern in two polychaete species, Alitta virens and Platynereis dumerilii: Examination of the conserved key regulator of the gut development from cleavage through larval life, postlarval growth, and regeneration.

BACKGROUND: foxA orthologs are involved in various processes from embryo patterning to regulation of metabolism. Since foxA conserved role in the development of the gut of errant annelids has never been thoroughly studied, we used a candidate gene approach to unravel the molecular profile of the alimentary canal in two closely related nereid worms with a trochophore-type lecithotrophic larva. RESULTS: The character of foxA expression in the two polychaetes was similar but not identical. The genes were successively activated first in blastoporal cells, then in the stomodeum, the midgut, and hindgut primordia, and in the cells of central and peripheral nervous system. Before the start of active feeding of nectochaetes, we observed a short phase of foxA expression in the entire digestive tract. After amputation of posterior segments, foxA expression was established de novo in the new terminal part of the intestine, and then in the developing hindgut and the anus. CONCLUSIONS: We discovered an early marker of endoderm formation previously unknown in errant annelids. Its expression dynamics provided valuable insights into the gut development. Comparative analysis of foxA activity suggests its primary role in gastrulation morphogenesis independently of its type and in midgut and foregut specification. Developmental Dynamics 248:728-743, 2019. © 2018 Wiley Periodicals, Inc.