A surface lipid may control the permeability slump associated with entry into anhydrobiosis in the plant parasitic nematode Ditylenchus dipsaci

Abstract

SUMMARYThe anhydrobiotic plant-parasitic nematode Ditylenchus dipsaci undergoes a decrease in permeability (the permeability slump) during the early stages of desiccation and this produces the slow rate of water loss necessary for its survival. There were no changes in annulation spacing, followed in individual nematodes by confocal microscopy, that would account for the permeability slump. Nile Red staining reveals that the surface of the nematode is coated with an extracuticular layer of lipid. This material can be seen in unstained desiccated nematodes where it forms an oil that adheres to the coverslip and to adjacent nematodes. The oily material leaves impressions on the coverslip (cuticle prints) after the nematode has detached upon rehydration. The presence of the surface lipid was confirmed using attenuated total reflection infrared spectroscopy. This material was shown to be a triglyceride and the proportion of fatty acids determined, using thin layer and gas chromatography. The production of the surface lipid material may be responsible for the permeability slump observed during the early phases of desiccation and its removal upon immersion in water may explain the paradox that cuticular permeability decreases during the permeability slump and yet desiccated nematodes are more permeable than are fully hydrated nematodes.

Predominantly Cytoplasmic Localization in Yeast of ASR1, a Non-Receptor Transcription Factor from Plants

“…In part because drought is currently a major agronomic problem [1], molecular responses to water loss have been extensively studied using a variety of biological models, such as dried bacteria, yeast, plants living in deserts and anhydrobiotic plants and invertebrate animals [2-8]. …”

Hygric stresses and strategies in maintaining the association between crayfish and ectosymbiotic worms across vastly different environments

“…Coiling with a water resurrection is a common response for an annelid, having been described in free-living annelids, oligochaetes, and leeches triggered by soil dryness (Valle et al 1999;Jiménez et al 2000;Díaz Cosín et al 2006) and it is associated with water conservation in soil nematodes (Wharton and Barclay 1993;Wharton 1996;Treonis and Wall 2005;Wharton et al 2008;Perry et al 2012). In fact, the water loss rate profile of C. mesochoreus fits the typical anhydrobiotic 'permeability slump' in nematodes (Wharton and Barclay 1993;Wharton 1996;Wharton et al 2008), which features a biphasic, two-component curve (discontinuous slope) as the worm shifts from vermiform (high water loss) to coiled form (low water loss) and back again to vermiform (high water loss). These shifts in water loss are likely due changes in respiratory water loss; i.e., active (high water loss) and immobile, inactive (low water loss).…”

“…These shifts in water loss are likely due changes in respiratory water loss; i.e., active (high water loss) and immobile, inactive (low water loss). Secretion of an excess waterproofing mucous covering the coiled worm that is removed when the worm is re-activated by addition of water like in nematodes (Wharton et al 2008) also cannot be ruled out; secretion of such a mucoid layer would restrict integumental water loss and lower the whole organism water loss rate. Branchiobdellidan aestivation can be entered and broken quickly (within minutes), it can be entered and broken multiple times (i.e., temporary), but it cannot last for extended periods (>~20 min).…”

The importance of feeding status and desiccation rate in successful anhydrobiosis of Panagrolaimus detritophagus

“…Starved worms will recover from drought more successfully if the period of starvation is followed by a smooth gradual drying period prior to undergoing desiccation. Fast dehydration strategists may have acquired adaptations that ensure the necessary slow rate of water loss (Wharton et al, 2008). The latter can be achieved via behavioural mechanisms, such as coiling, which lessens the rate of water loss by reducing the surface area exposed to the air.…”