Shoshana Goldenberg

Heat shock proteins and resistance to desiccation in congeneric land snails

Land snails are subject to daily and seasonal variations in temperature and in water availability and depend on a range of behavioral and physiological adaptations for coping with problems of maintaining water, ionic, and thermal balance. Heat shock proteins (HSPs) are a multigene family of proteins whose expression is induced by a variety of stress agents. We used experimental desiccation to test whether adaptation to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desiccation-resistant, desert species Sphincterochila zonata, and a Mediterranean-type, desiccation-sensitive species Sphincterochila cariosa. We examined the HSP response in the foot, hepatopancreas, and kidney tissues of snails exposed to normothermic desiccation. Our findings show variations in the HSP response in both timing and magnitude between the two species. The levels of endogenous Hsp72 in S. cariosa were higher in all the examined tissues, and the induction of Hsp72, Hsp74, and Hsp90 developed earlier than in S. zonata. In contrary, the induction of sHSPs (Hsp25 and Hsp30) was more pronounced in S. zonata compared to S. cariosa. Our results suggest that land snails use HSPs as part of their survival strategy during desiccation and as important components of the aestivation mechanism in the transition from activity to dormancy. Our study underscores the distinct strategy of HSP expression in response to desiccation, namely the delayed induction of Hsp70 and Hsp90 together with enhanced induction of sHSPs in the desert-dwelling species, and suggests that evolution in harsh environments will result in selection for reduced Hsp70 expression.

Natural annual cycle of heat shock protein expression in land snails: desert versus Mediterranean species of Sphincterochila.

SUMMARY Land snails are subject to daily and seasonal variations in temperature and in water availability, and have evolved annual cycles of activity and aestivation as part of their survival strategy. We tested in the field whether adaptation to different habitats affects the endogenous levels of heat shock proteins (HSPs) in two closely related Sphincterochila snail species, a desiccation-resistant desert species, Sphincterochila zonata, and a Mediterranean-type, desiccation-sensitive species, S. cariosa. We examined HSP levels in various tissues of snails during aestivation and after resumption of activity. Our study shows that, during aestivation, S. cariosa had higher standing stocks of Hsp70 in the foot and the hepatopancreas, and of small HSPs (sHSPs) in all the examined tissues, whereas S. zonata had higher stocks of Hsp70 in the kidney and of Hsp90 in the kidney and in the hepatopancreas. Arousal induced a general upregulation of HSPs, except for Hsp90, the expression of which in the foot was higher during aestivation. We suggest that the stress protein machinery is upregulated during arousal in anticipation of possible oxidative stress ensuing from the accelerating metabolic rate and the exit from the deep hypometabolic state. Our findings support the concept that, in land snails, aestivation and activity represent two distinct physiological states, and suggest that land snails use HSPs as important components of the aestivation mechanism, and as part of their survival strategy during and after arousal. Our study also indicates that adaptation to different habitats results in the development of distinct strategies of HSP expression with likely consequences for the ecology and distribution of land snails.

Cannibalistic phenomena in salamandra salamandra larvae in certain water bodies and under experimental conditions

Salamandra salamandra larvae originating from a single batch (layed by one female) were raised at different temperatures and on ion-rich or distilled water. Temperature, but not the presence or absence of ions affected growth. Larvae originating from one batch or from several batches born on the same day, were kept without food for long periods of several months in order to observe cannibalistic predation under such conditions. This phenomenon is known in natural populations of salamanders inhabitating either rain pools in rocks or permanent springs poor in aquatic life. It was found that cannibalism increased under experimental conditions proportionally to the increase in size between the larvae.

Thermal effect on evaporative water loss and haemolymph osmolarity in scorpions at low and high humidities

Abstract 1. 1. Evaporative water loss and haemolymph osmolarity were studied in four scorpion species: two from mesic habitats, Scorpio maurus fuscus ( Scorpionidae ) and Nebo hierochonticus (Diplocentridae); and two from xeric habitats, Buthotus judaicus and Leiurus quinquestriatus (both Buthidae). 2. 2. Low humidity and high temperatures increased both the percentage and the rate of water loss. This effect was more pronounced in the two mesic species. 3. 3. Haemolymph osmolarity increased at high temperature and low humidity. In humid air osmolarity dropped only in the mesic species but remained high in the xeric species. 4. 4. Haemolymph osmolarity was low in winter and high in summer.

Water balance and resistance to desiccation in rock-dwelling snails

We have examined the resistance to desiccation among rock-dwelling land snails of various phylogenetic groups:Cristataria genezarethana (Clausiliidae),Rupestrella rhodia (Chondrinidae) andLevantina caesareana (Helicidae), all from the same location in Israel.L. caesareana was the most resistant andR. rhodia the least resistant to desiccation andC. genezarethana was of intermediate resistance. Differences in the rates of water loss during desiccation were determined mainly by rate of water loss during the first 2 days of desiccation. The high rates of water loss in rock-dwelling species exceed those of other snails in the Mediterranean habitat of Israel. However, snails collected in the field at the end of aestivation were in only a mild state of dehydration, suggesting that the rocky habitat protects its occupants against desiccation. We also suggest that among the rock-dwelling species, the protective role of the rock is more important in the more evolutionarily primitive genera (the chondrinidRupestrella and the clausiliidCristataria) and that physiological capacities are more effective in the more highly evolved helicidLevantina.

Intraspecific variation in resistance to desiccation in the land snailTheba pisana

Theba pisana is a bush-dwelling snail with a circum-Mediterranean distribution. In Israel it is limited to a narrow coastal strip, along which there is a north-to-south gradient in mean annual rainfall (700–300 mm per year). In this study we found significant intraspecific differences among populations ofT. pisana in resistance to desiccation along this gradient, and in a population from Greece, which may be grossly correlated with the climatic gradient. The Greek population was the least resistant to desiccation with an extremely high rate of water loss. The differences in total mass loss were mainly determined by the rate of water loss during the first 4 days of desiccation. A general phenomenon during desiccation was the close regulation of the soft body water content at the expense of the extra-pallial fluid compartment.

Heat shock proteins and survival strategies in congeneric land snails (Sphincterochila) from different habitats

Polmunate land snails are subject to stress conditions in their terrestrial habitat, and depend on a range of behavioural, physiological and biochemical adaptations for coping with problems of maintaining water, ionic and thermal balance. The involvement of the heat shock protein (HSP) machinery in land snails was demonstrated following short-term experimental aestivation and heat stress, suggesting that land snails use HSPs as part of their survival strategy. As climatic variation was found to be associated with HSP expression, we tested whether adaptation of land snails to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desert species Sphincterochila zonata and a Mediterranean-type species Sphincterochila cariosa. Our study suggests that Sphincterochila species use HSPs as part of their survival strategy following desiccation and heat stress, and as part of the natural annual cycle of activity and aestivation. Our studies also indicate that adaptation to different habitats results in the development of distinct strategies of HSP expression in response to stress, namely the reduced expression of HSPs in the desert-inhabiting species. We suggest that these different strategies reflect the difference in heat and aridity encountered in the natural habitats, and that the desert species S. zonata relies on mechanisms and adaptations other than HSP induction thus avoiding the fitness consequences of continuous HSP upregulation.

Water loss and haemolymph osmolarity of Potamon potamios, an aquatic land crab, under stress of dehydration and salinity

Abstract 1. 1. Small crabs survived over 18% water loss and large crabs 21% when in dry air. Size, temperature and relative humidity affected this rate. 2. 2. Haemolymph osmolarity of newly collected crabs ranged from 530 to 630 mOsm/kg, depending on their size and the season. 3. 3. When dehydrated, haemolymph osmolarity rose to over 700 mOsm/kg, and ion concentration increased by over 10%. 4. 4. Crabs survived in sea-water for at least two weeks. Haemolymph osmolarity rose and ion concentration increased. The acclimation pattern affected the haemolymph osmolarity.

The heat shock response in congeneric land snails (Sphincterochila) from different habitats

Land snails are subject to daily and seasonal variations in temperature and in water availability, and use heat shock proteins (HSPs) as part of their survival strategy. We used experimental heat stress to test whether adaptation to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desert species, Sphincterochila zonata, and a Mediterranean-type species, Sphincterochila cariosa. Our findings show that in S. cariosa, heat stress caused rapid induction of Hsp70 proteins and Hsp90 in the foot and kidney tissues, whereas the desert-inhabiting species S. zonata displayed delayed induction of Hsp70 proteins in the foot and upregulation of Hsp90 alone in the kidney. Our study suggests that Sphincterochila species use HSPs as part of their survival strategy following heat stress and that adaptation to different habitats results in the development of distinct strategies of HSP expression in response to heat, namely the reduced induction of HSPs in the desert-dwelling species. We suggest that the desert species S. zonata relies on mechanisms and adaptations other than HSP induction, thus avoiding the fitness consequences of continuous HSP upregulation.

Osmotic and ionic regulation in two Pachygrapsus crabs, under varying salinities and dehydration

Abstract 1. 1. Haemolymph osmolality and ion (Cl − ) concentration were studied in 2 intertidal crabs, Pachygrapsus marmoratus and P. transversus . 2. 2. The haemolymph osmolality hardly changed throughout the year. 3. 3. Both crabs were hyper-osmotic at salinities less concentrated than sea water, and hypo-osmotic at salinities of 125, 150, 175 and 200% sea water. 4. 4. Low (Cl − ) concentration changed with the ambient salinities. It rose steeply at 200% sea water. 5. 5. Dehydration caused a rise in haemolymph osmolalities in both species but more significantly in P. transversus .