Volume and morphology changes of a bdelloid rotifer species (Macrotrachela quadricornifera) during anhydrobiosis

Abstract

Following a study on the changes occurring in a bdelloid species (Macrotrachela quadricornifera, Rotifera, Bdelloidea) when entering anhydrobiosis, we investigated the changes in morphology, including weight and volume during the transition from the active hydrated to the dormant anhydrobiotic state by scanning electron microscopy, confocal microscopy and light microscopy. We compared sizes and morphologies of hydrated extended, hydrated contracted and anhydrobiotic specimens. Bdelloid musculature is defined: longitudinal muscles are contracted in the hydrated contracted animal (head and foot are retracted inside the trunk), but appear loose in the anhydrobiotic animal. When anhydrobiotic, M. quadricornifera appears much smaller in size, with a volume reduction of about 60% of the hydrated volume, and its internal organization undergoes remarkable modifications. Internal body cavities, clearly distinguishable in the hydrated extended and contracted specimens, are no longer visible in the anhydrobiotic specimen. Concomitantly, M. quadricornifera loses more than 95% of its weight when anhydrobiotic; this is more than expected from the volume reduction data and could indicate the presence of space-filling molecular species in the dehydrated animal. We estimate that the majority of body mass loss and volume reduction can be ascribed to the water loss from the body cavity during desiccation.

Universal behavior of the osmotically compressed cell and its analogy to the colloidal glass transition

“…However, filamentous networks typically cannot support appreciable compressive stress because filaments will lose their tension, perhaps even buckle, and thus weaken the network. Nevertheless, cellular compression occurs within tumors (9) and will always occur if the volume of the cell is decreased, as occurs in important physiological processes such as osmotic cell shrinkage, regulatory cell volume decreases (10), preservation of certain animal life forms during drought (anhydrobiosis) (11), and apoptosis (12,13).…”

Dry and survive: Morphological changes during anhydrobiosis in a bdelloid rotifer

“…Similar adaptations to control evaporative water loss are also present in other invertebrates, such as tardigrades (Wright et al, 1992;Wright, 2001;Womersley, 1988) and nematodes (Ellemby, 1969;Womersley and Ching, 1989). Indeed a slow rate of evaporation has been proposed to allow correct body contraction and rigorous packing of internal structures and thus, likely, prevents structural disorder (Ricci et al, 2003(Ricci et al, , 2008. The rate of water loss during desiccation affects the morphology of the dry rotifers, which assume an irregular shrunken appearance if dried very fast (Ricci et al, 2003).…”

“…4f). While in the hydrated rotifers the mitochondria have the usual appearance, in the anhydrobiotic M. quadricornifera they are surrounded by one or two rings Ricci et al (2008)); (e) sagittal section of a hydrated contracted specimen; (f) parafrontal section through a hydrated contracted specimen; (g) anhydrobiotic specimen at SEM; (h) sagittal section through an anhydrobiotic specimen; (i) frontal section through an anhydrobiont specimen. Abbreviations: f, foot; h, head; s, stomach; t, trunk; tr, trochi. of roundish electron-dense particles, with an average diameter of 200 Å, a value congruent with that of ribosome particles ( Fig.…”

“…During anhydrobiosis, bdelloids contract in a tun-shaped morphology, reducing the surface and controlling the evaporation rate. When dry, bdelloids show remarkable reduction of volume and size (Ricci et al, 2008).…”

Developmental stages in diapausing eggs: an investigation across monogonont rotifer species

“…Bdelloids can enter dormancy any time during their lives: when relative humidity decreases in the environment (e.g. for drying or freezing), the rotifer retracts head and foot and contracts into a compact shape halting metabolic expenditures (Ricci et al, 2003(Ricci et al, , 2007(Ricci et al, , 2008. In this condition, the dormant animal can resist severe stresses (Ricci et al, , 2007.…”