It is known that specimens of Amphibolus can carry out both cryptobiosis (anhydrobiosis and cryobiosis) and encystment and that they produce two types of cysts (type 1 and type 2). In Amphibolus nebulosus from Greenland, the type 1 cyst is related to winter and the type 2 to summer. In Amphibolus volubilis, found in Apennines (Monte Rondinaio, Italy), a detailed description of the encystment processes has been done, but not of the relationships between climatic factors and dynamics of the cyst 1 and cyst 2. Therefore, a study on seasonal dynamics of the A. volubilis cysts has been carried out with monthly samplings, from March 2003 up to March 2005. For each sampling, all specimens present in five-six replicates of 0.5 g of moss have been collected and analyzed.In all samplings, non-encysted and encysted animals (type 1 or type 2 cysts) have been found. The cyst trends are similar in the two considered years. Type 1 cysts have been found from November to March-April, but they were present in a very low percentage with respect to the total animals. Type 2 cysts have been found from June to October and are often more abundant than the non-encysted tardigrades. The two types of cysts never overlap. Correlation tests have evidenced that dynamics of type 2 cyst is positively related to the air temperature (T) and negatively related to the relative humidity (RH) of the air. The trend of type 1 cyst is negatively related to T, while no relationship to RH has been evidenced. The presence of non-encysted animals is negatively related to T and positively related to RH. Experiments of encystment induction have been performed in laboratory. In the same experimental conditions (same temperature, photoperiod, food and oxygen availability), non-encysted animals collected in April form type 2 cysts, whereas animals collected in November form type 1 cysts. The number of days to enter each type of cyst is related to experimental temperature. At the same temperature, the animals spent less time to enter in type 1 cyst than in type 2 cyst. In lab, the animals come out from type 2 cyst, if do not die, soon or later encyst again and enter always type 1 cyst.The data from nature and those from laboratory lead to conclude that, differently from what happens in anhydrobiosis and cryobiosis, climatic conditions do not directly affect encystment; but seasonal changing induces still unknown endogenous factors responsible of that kind of dormant stage.
Cysts of Amphibolus volubilis (Eutardigrada, Eohypsibiidae): seasonal dynamics and laboratory induction / Guidetti, Roberto; Boschini, Deborah; Bertolani, Roberto; Rebecchi, Lorena. - STAMPA. - Volume unico:(2006), pp. 45-45. (Intervento presentato al convegno Tenth International Symposium on Tardigrada tenutosi a Catania nel 18-23 giugno 2006).
Cysts of Amphibolus volubilis (Eutardigrada, Eohypsibiidae): seasonal dynamics and laboratory induction.
GUIDETTI, Roberto;BOSCHINI, Deborah;BERTOLANI, Roberto;REBECCHI, Lorena
2006
Abstract
It is known that specimens of Amphibolus can carry out both cryptobiosis (anhydrobiosis and cryobiosis) and encystment and that they produce two types of cysts (type 1 and type 2). In Amphibolus nebulosus from Greenland, the type 1 cyst is related to winter and the type 2 to summer. In Amphibolus volubilis, found in Apennines (Monte Rondinaio, Italy), a detailed description of the encystment processes has been done, but not of the relationships between climatic factors and dynamics of the cyst 1 and cyst 2. Therefore, a study on seasonal dynamics of the A. volubilis cysts has been carried out with monthly samplings, from March 2003 up to March 2005. For each sampling, all specimens present in five-six replicates of 0.5 g of moss have been collected and analyzed.In all samplings, non-encysted and encysted animals (type 1 or type 2 cysts) have been found. The cyst trends are similar in the two considered years. Type 1 cysts have been found from November to March-April, but they were present in a very low percentage with respect to the total animals. Type 2 cysts have been found from June to October and are often more abundant than the non-encysted tardigrades. The two types of cysts never overlap. Correlation tests have evidenced that dynamics of type 2 cyst is positively related to the air temperature (T) and negatively related to the relative humidity (RH) of the air. The trend of type 1 cyst is negatively related to T, while no relationship to RH has been evidenced. The presence of non-encysted animals is negatively related to T and positively related to RH. Experiments of encystment induction have been performed in laboratory. In the same experimental conditions (same temperature, photoperiod, food and oxygen availability), non-encysted animals collected in April form type 2 cysts, whereas animals collected in November form type 1 cysts. The number of days to enter each type of cyst is related to experimental temperature. At the same temperature, the animals spent less time to enter in type 1 cyst than in type 2 cyst. In lab, the animals come out from type 2 cyst, if do not die, soon or later encyst again and enter always type 1 cyst.The data from nature and those from laboratory lead to conclude that, differently from what happens in anhydrobiosis and cryobiosis, climatic conditions do not directly affect encystment; but seasonal changing induces still unknown endogenous factors responsible of that kind of dormant stage.
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