Aldona Dobrzycka-Krahel

THE EFFECT OF HYPOXIA AND ANOXIA ON OSMOTIC AND IONIC REGULATION IN THE BRACKISH WATER ISOPOD SADURIA ENTOMON (LINNAEUS) FROM THE GULF OF GDANSK (SOUTHERN BALTIC)

Abstract The experimental material for the investigations was collected from the deep zones of the Gulf of Gdañsk. The experiments were performed at salinities of 3.0 PSU (96.87 mmol/kg), 7.3 PSU (235.73 mmol/kg), 15 practical salinity unit (PSU) (484.39 mmol/kg) and 25 PSU (807.32 mmol/kg) in conditions of hypoxia (saturation = 15% O2), anoxia (saturation <1% O2) and control conditions in aerated water (saturation = 100% O2), at a constant temperature of 10°C. Hypoxia (saturation = 15% O2) had no statistically significant effect (P > 0.05) on the osmoregulation of S. entomon in comparison with the control samples. Anoxia (saturation <1% O2) decreased the osmotic concentration of hemolymph in S.entomon. After 6 h only at salinity 3 PSU there was a statistically significant difference between the anoxic and control samples (P < 0.05). After 96 h there was a statistically significant tendency (P < 0.05) for the osmotic concentrations to decrease in anoxic conditions at all the salinities tested except 25 PSU. A tendency was observed for the Na+ concentrations in the hemolymph to decrease in anoxic conditions, which was statistically significant at salinity 7.3 PSU (P < 0.05) after 96 h but not statistically significant at the other salinities tested. The results show a low concentration of K+ in the hemolymph of S. entomon and slight fluctuations of K+ concentrations, but at environmental salinities the K+ concentration decreases under anoxic conditions but not to a statistically significant extent (P > 0.05).

Range extension of Dikerogammarus villosus (Sowinsky, 1894) in Poland (the Baltic Sea basin) and its ability to osmoregulate in different environmental salinities

Abstract The paper reports the range extension of the Ponto- Caspian gammarid Dikerogammarus villosus (Sowinsky, 1894) and the first occurrence of this species in new areas of the Polish part of the Baltic Sea basin: the Śmiała Vistula and the Vistula Lagoon. The studies additionally determine the osmoregulatory ability of the species under laboratory conditions within the salinity range of 2-22 PSU. Determination of the osmoregulation of the species shows that D. villosus is a hyperregulator at given experimental salinities and can function in a wide range of external salinities so it is potentially able to colonize various water bodies. Osmoregulatory capacity, which is an indicator of organism’s efforts to regulate the concentration of its body fluids, shows that for individuals from the Gulf of Gdańsk, 6 PSU is the best tolerated salinity. Osmoregulatory capacity is the lowest at this salinity value. The range extension and potential osmoregulatory abilities of the species to spread to other waters are discussed in the context of pollution levels given in the literature with reference to the habitat and sensitivity of the species to e.g. fluoride and cadmium toxicity.

Laboratory study of the effect of salinity and ionic composition of water on the mortality and osmoregulation of the gammarid amphipod Dikerogammarus haemobaphes (Eichwald, 1841): implications for understanding its invasive distribution pattern

The effect of salinity and ionic composition of ambient water on the mortality of the Ponto-Caspian gammarid amphipod Dikerogammarus haemobaphes (Eichwald, 1841) was measured in the laboratory and an osmoregulatory curve plotted. A three-day experiment showed that salinities both higher (15, 20 PSU) and lower (0.1, 3.5 PSU) than 7 PSU reduced survival. Salinity levels of 0.1 and 20 PSU were lethal after 20 and 55 h of exposure, respectively. Among the ions analysed (Cl−, , Na+, K+, Ca2+, Mg2+), Cl− and K+, and the ratios of Na+/K+ and Na+/Cl− had the greatest influence on the mortality of D. haemobaphes. Mortality was zero in waters where the concentrations and ratios of these ions most closely resembled those prevailing in the Caspian Sea. The osmoregulatory curve shows that D. haemobaphes is a eurytopic species i.e. osmoregulation is hyperosmotic within the salinity range of 0.1–20 PSU. The results of this study indicate ways in which inherent physiological capabilities affect the ability of an organism to tolerate environmental conditions outside its historical range. The results suggest some ways in which anthropogenic changes may have affected the spread of this species beyond its original range.

A laboratory-based comparison of osmoregulatory ability at different water temperatures and salinities in the stenothermic isopod Saduria entomon (Linnaeus, 1758) and the eurythermic amphipod Corophium volutator (Pallas, 1766) from the Baltic Sea

The aim of the investigation was a comparison of osmoregulatory ability at different water temperatures and salinities by the stenothermic isopod Saduria entomon (Linnaeus, 1758) and the eurythermic amphipod Corophium volutator (Pallas, 1766) from the Baltic Sea. The experiments were performed under laboratory conditions at different water temperatures (5, 10 and 15 °C) and salinities (3, 6.6, 15 and 25 PSU for S. entomon and 3, 6.3, 15 and 25 PSU for C. volutator). The osmotic concentrations of the crustaceans’ haemolymph were determined using the melting point method. Temperature had a statistically significant effect on the osmoregulation in S. entomon, but had generally no statistical influence on the osmoregulation in C. volutator. This physiological information regarding adaptation provides a basis for predicting the distribution of these species in changing environments. The implications of the results for the comparative adaptability of the two species are considered.

Effect of salinity on the distribution of Ponto-Caspian gammarids in a non-native area – environmental and experimental study

ABSTRACT The native area of gammarids from the so-called ‘Caspian complex’, Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and D. villosus (Sowinsky, 1894), is associated with brackish waters. Over the last several decades they have colonized the European inland waters and part of the brackish Baltic Sea. It is believed that anthropogenic increase in the salinity of inland waters facilitated their expansion. However, the influence of salinity on the dispersal of gammarid species outside their native area is not fully understood. We tested the hypothesis that salinity was a major factor in determining distribution, based on the abundance of Gammaridae in three coastal areas of low salinity (brackish Baltic), i.e. 0.3, 3.4 and 7.3 PSU, successfully inhabited by them. Additionally, for the first time, the effect of water salinity on the osmoregulatory capacity of O. crassus was examined under laboratory conditions, for the salinities given above. The experiments showed that similarly as in the case of other Caspian complex species, salinity values of about 7 PSU create better conditions for osmoregulation in O. crassus than lower salinities (i.e. 0.3 and 3.4 PSU). In the environmental part of the study, we observed that only D. villosus achieved a significantly higher abundance in the area of 7.3 PSU. Thus, we concluded that in the range of 0.3–7.3 PSU, salinity is not a key factor governing the distribution of Ponto-Caspian gammarids.

The Signal Crayfish Pacifastacus leniusculus — Distribution and Invasion in the Southern Baltic Coastal River

ABSTRACT The signal crayfish Pacifastacus leniusculus (Dana, 1852) of North American origin was introduced to Europe (to Scandinavia) in the 1960s. Since that time due to translocation to many countries, biological features and ecological plasticity, it became widespread, invasive and displaced native species. The paper reports first multi- point colonization of P. leniusculus in the Polish rivers. The aim of the study was to determine the current distribution of the signal crayfish in the coastal Baltic tributary (the River Wieprza) after 20 years of deliberate releases in its drainage area. During sampling at 28 sites with use of the “Pirate” crayfish traps and hand collection methods in spring and summer 2014, 127 P. leniusculus individuals were found at 8 sites in the Wieprza and its two tributaries, both away from and close to known sites of their introduction in 1995 and 1996 in the Wieprza River drainage area. The species spreads via the Wieprza River towards the Baltic brackish waters. With such expansion of this species, it is expected to be found in Polish coastal waters of the Baltic Sea and in other coastal rivers in the near future. The conflict between legal aspects of the signal crayfish farming, colonization by the species of the natural aquatic ecosystems and the expectations of consumers is discussed.

Spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) on its way to the open coastal waters of the Baltic Sea

Abstract The aim of this work was to assess the adaptive capabilities of the spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) in the open coastal waters of the Baltic Sea. The results could help to predict the likely further expansion of this species and its colonization of brackish waters. The following aspects were discussed in the paper: the occurrence of the species in the Polish coastal zone of the Baltic Sea, the plasticity demonstrated in the body size of individual crayfishes, food preferences, hemolymph osmolality and reproduction in waters of different salinities, which enable the species to colonize brackish waters. In the Vistula Lagoon (salinity 2-3 PSU), where the population of O. limosus is stable, the length of individuals ranged from 77 to 118 mm. These crayfish mostly fed on fodder; the second and the third food preferences were crayfish abdominal muscle and green algae. O. limosus is a hyper-regulator in freshwaters and at low salinities (up to 13 PSU), and a hyporegulator at higher salinities (14, 21, 28, 35 PSU). Laboratory studies showed that the embryonic development of O. limosus at salinities of 3 and 7 PSU was normal and a high level of reproductive success was achieved. Salinity of 3 PSU is more favorable for the development of juveniles than 7 PSU. It seems to be just a matter of time before this crayfish starts to form populations in the brackish, coastal waters of the Baltic Sea.

Length-weight relationships of Ponto-Caspian gammarids that have overcome the salinity barrier of the southern Baltic Sea coastal waters

Abstract Gammarids from the Caspian complex have invaded many European waters along the rivers and canals of the inland migration corridors. The species examined in this work are well known as invaders of European freshwater environments, so the colonization of brackish habitats is a phenomenon inviting more detailed investigation. The aim of this study was to determine the condition of the Ponto-Caspian gammarids Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and Dikerogammarus villosus (Sowinsky, 1894) as expressed by the relationship between total length and the wet weight of specimens in the brackish waters of the Gulf of Gdansk (Poland). The relationships can be regarded as responses to a newly expanded habitat after they overcome the salinity barrier of the southern Baltic Sea coastal waters. All these Ponto-Caspian gammarids demonstrated an increase in weight with increasing total length: P. robustoides (b = 2.852), O. crassus (b = 3.3477), D. haemobaphes (b = 3.7855) and D. villosus (b = 2.6917). The results are an indicator of the relatively good condition of the organisms and indicate that the brackish environment of the Gulf of Gdansk affords them excellent possibilities for growth.