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First published online June 6, 2005
Journal of Experimental Biology 208, 2433-2445 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01629
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The anhydrobiotic potential and molecular phylogenetics of species and strains of Panagrolaimus (Nematoda, Panagrolaimidae)

Adam J. Shannon*, John A. Browne*, Jacqueline Boyd, David A. Fitzpatrick and Ann M. Burnell{dagger}

Institute of Bioengineering and Agroecology, Department of Biology, National University of Ireland Maynooth, Maynooth, Co Kildare, Ireland



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  		Fig. 1. The effect of preconditioning time at 98% RH (relative humidity) on the survival of 10 strains of Panagrolaimus. Treated nematodes were preconditioned at 98% RH at 20°C for 0–96 h, desiccated for 48 h over activated silica gel, `prehydrated' at 100% RH for 24 h and rehydrated in S Basal buffer for 24 h before survival was determined. Survival values are the mean of five replicates ± S.E.M. Mixed stage populations were used for all strains. For each preconditioning time means designated with the same letter are not significantly different (ANOVA, P<0.05). The full names of the Panagrolaimus species and strains used in this experiment are as follows: Panagrolaimus sp. (PS1732); Panagrolaimus rigidus (AF40); Panagrolaimus detritophagus (P. det; BSS8); Panagrolaimus sp. (BW287); Panagrolaimus sp. (PS443); Panagrolaimus sp. (PS1579); Panagrolaimus rigidus (AF36); Panagrolaimus sp. (P. WS94); Panagrolaimus sp. (PS1159) and Panagrolaimus superbus (P. sup; DF5050).

 


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  		Fig. 2. The length–frequency distribution of nematodes that survived anhydrobiosis compared with a matched control. Treated nematodes were preconditioned at 98% RH (relative humidity) for 48 h, desiccated for 24 h over activated silica gel, `prehydrated' at 100% RH for 24 h and rehydrated in M9 buffer for 24 h before survivors were isolated and measured. The control samples were maintained at 98% RH for 96 h and rehydrated in S Basal buffer for 24 h before survivors were isolated and their lengths determined.

 


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  		Fig. 3. The effect of preconditioning at 98% RH (relative humidity) on the levels of trehalose, glucose and glycerol in P. superbus, a `fast dehydration strategist' and five `slow dehydration strategist' strains of Panagrolaimus. Nematodes were exposed to 98% RH for various time periods (0–96 h) before carbohydrates were extracted. Carbohydrate levels are expressed as percentage dry mass. (A) P. superbus DF5050; (B) P. rigidus AF36; (C) Panagrolaimus sp. PS1159; (D) Panagrolaimus sp. PS1579; (E) Panagrolaimus sp. WS94; (F) Panagrolaimus sp. PS443.

 


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  		Fig. 4. The effect of preconditioning at 98% RH (relative humidity) on the levels of trehalose, glucose and glycerol in four strains of Panagrolaimus sp. classified as `poor desiccators'. Nematodes were exposed to 98% RH for various time periods (0–96 h) before carbohydrates were extracted. Carbohydrate levels are expressed as percentage dry mass. (A) Panagrolaimus sp. BW287; (B) P. detritophagus BSS8; (C) Panagrolaimus rigidus AF40; (D) Panagrolaimus sp. PS1732.

 


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  		Fig. 5. Scanning electron micrographs of desiccated Panagrolaimus following exposure to dried silica gel (<10% RH; relative humidity) for 48 h. (A) Panagrolaimus superbus DF5050 exposed directly to silica gel without preconditioning; (B) Panagrolaimus sp. PS1159 exposed to silica gel following preconditioning at 98% RH for 72 h; (C) Panagrolaimus sp. BW287 exposed to silica gel following preconditioning at 98% RH for 72 h; (D) Panagrolaimus sp. PS1732 exposed to silica gel following preconditioning at 98% RH for 72 h. Scale bars, 15 µm (A–C), 10 µm (D).

 


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  		Fig. 6. Hypotheses of phylogenetic relationships among isolates and species of Panagrolaimus derived from alignments of the rDNA ITS1, ITS2 and D3 DNA sequences. (A) The phylogenetic tree obtained using maximum parsimony (MP) and neighbor-joining (NJ) algorithms. NJ bootstrap values (1000 replicates) are indicated on the internal branches. MP bootstrap analysis retrieves scores nearly identical to those displayed. (B). The phylogenetic tree obtained using maximum likelihood (ML) and Bayesian methods. ML bootstrap values (100 replicates) are indicated. The scale bar represents 0.1 substitutions per site.

 

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© The Company of Biologists Ltd 2005