Changes in transcriptomic response to salinity stress induce the brackish water adaptation in a freshwater snail

Studying the mechanisms of the establishment of a population in a novel environment allows us to examine the process of local adaptations and subsequent range expansion. In a river system, detecting genetic or phenotypic differences between a freshwater and brackish water population could contribute to our understanding of the initial process of brackish water adaptation. Here, we investigated behavioural and gene expression responses to salt water in a freshwater and brackish water population of the freshwater snail, Semisulcospira reiniana. Although the individuals in brackish water exhibited significantly higher activity in saltwater than freshwater individuals just after sampling, the activity of freshwater individuals had increased in the second observation after rearing, suggesting that their salinity tolerance was plastic rather than genetic. We found 476 and 1002 differentially expressed genes across salinity conditions in the freshwater and brackish water populations, respectively. The major biological process involved in the salinity response of the freshwater population was the biosynthesis and metabolic processing of nitrogen-containing compounds, but that of the brackish water population was influenced by the chitin metabolic process. These results suggest that phenotypic plasticity induces adaptation to brackish water in the freshwater snail by modifying its physiological response to salinity.

Freshwater population of the Atlantic salmon (Salmo salar Linnaeus, 1758) of the Svir River (the Ladoga Lake basin): abundance, structure and conservation

Until the early 1930s the Svir River freshwater population of Atlantic salmon (Salmo salar Linnaeus, 1758) was the largest in the Ladoga Lake basin. A catastrophic decrease in the salmon abundance took place due to loss of spawning grounds after the dam construction in the riverbed and a long-time timber rafting in the main tributaries. Over-fishery in the 1950s and a poaching also contributed to this negative trend. The Svirsky hatchery was put in action in 1933 to support the salmon population. In course of 30-year monitoring the size characteristics of smolts, lake-living individuals and spawners were determined, as well as the state of gonads in males and females at different stages of the life cycle were evaluated. The “autumnal” form was described. It was found that all salmon spawners caught near the dam of the hydroelectric power station over the last decades were of hatchery origin and belonged to the same age classes as in the previous period. The present-day scale of hatchery propagation is too small for conservation of the Svir River salmon population. The population will be lost soon, if an artificial reproduction will not expanded and effective actions of fishery control inspection will not restored.

Parenting behaviour is highly heritable in male stickleback

Parental care is critical for fitness, yet little is known about its genetic basis. Here, we estimate the heritability of parenting behaviour in a species famous for its diversity and its behavioural repertoire: three-spined stickleback ( Gasterosteus aculeatus ). Male three-spined stickleback are the sole providers of parental care that is necessary for offspring survival; therefore, this system offers the opportunity to study the inheritance of parental behaviour when selection is primarily acting on males. Fanning behaviour is a conspicuous parental behaviour that is readily quantified in this species. We show that the heritability of fanning behaviour is ≥0.9 and significantly different from zero within a freshwater population. Moreover, there was abundant genetic variation for fanning behaviour, indicating that it could readily evolve. These results suggest that parenting behaviour is tractable for further genetic dissection in this system.

Salinity-induced phenotypic plasticity in threespine stickleback sperm activation

Phenotypic expression may be and often is influenced by an organism's developmental environment, referred to as phenotypic plasticity. The sperm cells of teleosts have been found to be inactive in the seminal plasma and are activated by osmotic shock for most fish species, through release in either hypertonic (for marine fish) or hypotonic (for freshwater fish) water. If this is the case, the regulatory system of sperm mobility should be reversed in salt- and freshwater fish. We tested this hypothesis by first activating sperm of salt- and freshwater populations of threespine stickleback in salt- and freshwater. The sperm from saltwater stickleback could be activated in either salinity, which matches the freshwater colonization history of the species, whereas the sperm from the freshwater population acted as predicted by the osmotic shock theory and was activated in freshwater only. As the freshwater population used here was calculated to be thousands of years old, we went on to test whether the trait(s) were plastic and sperm from freshwater males still could be activated in saltwater after individuals were exposed to saltwater. After raising freshwater stickleback in saltwater, we found the mature males to have active sperm in both saltwater and freshwater. Further, we also found the sperm of wild-caught freshwater stickleback to be active in saltwater after exposing those mature males to saltwater for only 2 days. This illustrates that the ability for stickleback sperm to be activated in a range of water qualities is an environmentally induced plastic trait.

Salinity modulates thermotolerance, energy metabolism and stress response in amphipodsGammarus lacustris

Temperature and salinity are important abiotic factors for aquatic invertebrates. We investigated the influence of different salinity regimes on thermotolerance, energy metabolism and cellular stress defense mechanisms in amphipodsGammarus lacustrisSars from two populations. We exposed amphipods to different thermal scenarios and determined their survival as well as activity of major antioxidant enzymes (peroxidase, catalase, glutathione S-transferase) and parameters of energy metabolism (content of glucose, glycogen, ATP, ADP, AMP and lactate). Amphipods from a freshwater population were more sensitive to the thermal challenge, showing higher mortality during acute and gradual temperature change compared to their counterparts from a saline lake. A more thermotolerant population from a saline lake had high activity of antioxidant enzymes. The energy limitations of the freshwater population (indicated by low baseline glucose levels, downward shift of the critical temperature of aerobic metabolism and inability to maintain steady-state ATP levels during warming) was observed, possibly reflecting a trade-off between the energy demands for osmoregulation under the hypo-osmotic condition of a freshwater environment and protection against temperature stress.

Resdescription of two synhymeniid ciliates, Chilodontopsis simplex Ozaki & Yagiu, 1941 and Zosterodasys transverses (Kahl, 1928) Foissner et al., 1994 (Alveolata, Ciliophora, Phyllopharyngea)

The morphology and infraciliature of two synhymeniid ciliates, Chilodontopsis simplex Ozaki & Yagiu, 1941 and Zoster-odasys transverses (Kahl, 1928) Foissner et al., 1994, collected from coasts of Qingdao, China, and Incheon, South Korea,respectively, have been investigated using live observation and protargol impregnation method. Chilodontopsis. simplexis characterized by: cell size 90–160 × 45–95 µm in vivo, oval to long elliptical in outline; 59–78 somatic kineties, 11–13nematodesmal rods; synhymenium constricted to ventral side, composed of 45–90 dikinetids, running across cell width;single contractile vacuole located in posterior cell end. The marine population of Zosterodasys transverses is briefly de-scribed, linked to the previously reported 18S ribosomal RNA gene (Genbank accession number EU286812), and compared to the freshwater population.