Hatching of the Anostracan Branchiopod Chirocephalus diaphanus Prévost I. Osmotic processes and the possible role of glycerol

Abstract

An osmotic hatching mechanism is proposed for the Anostracan Branchiopod Chirocephalus diaphanus, PREVOST . In this mechanism, glycerol is thought to accumulate in the egg as a result of the metabolism of the embryo . The osmotic pressure exerted by the egg, largely due to this glycerol accumulation, causes water to enter from the environment . Eventually the hydrostatic pressure thus generated is sufficient to cause rupture of the eggshell . It is recognised that hatching in this Anostracan is a two-staged phenomenon, a process of "breaking", in which glycerol is involved, preceding true "hatching", in which glycerol is not involved . The egg is described and the physiology and ecological significance of the proposed hatching mechanism are discussed .

Co-occurrence of free-swimming and quiescent nauplii in a spring hatching of two Chirocephalus diaphanus Prévost, 1803 (Anostraca) populations from mountain pasture pools

“…Finally, the 2-way ANOVA revealed a significant difference (F (1, 215) = 15.48, P < 0.000) in the frequencies obtained after the two treatments, with a higher proportion of quiescent nauplii (4.5%) after oven-drying. DISCUSSION Hall & MacDonald (1975) were the first to recognize that the hatching of Chirocephalus diaphanus is a two-stage process, in which "pre-breaking" of the tertiary shell precedes true "hatching". This developmental mechanism ensures that hatching cannot be achieved until two conditions are satisfied.…”

“…After deposition, some cysts remain in developmental pause for one or more years, while others resume metabolism as soon as favourable environmental conditions are restored. However, the timing of hatching seems to vary within the same season, since some cysts hatch immediately, producing free-swimming nauplii, while others remain in a quiescent state protected by the hatching membrane (Hall & MacDonald, 1975;Mossin, 1986;Eriksen & Belk, 1999;Merta, 2003). This outer shell is an extremely important structure, which also favours survival of the nauplius in adverse environmental conditions.…”

Cyst hatching in Anostraca accelerated by retinoic acid, amplified by Calcium Ionophore A23187, and inhibited by Calcium-channel blockers

“…RA is unsoluble in water, and is usually applied dissolved in DMSO or DMSO/ethanol (Eichele, 1989;Durston et al, 1989). Because of the possibility of toxic side effects and the circumstance that Anostraca cysts naturally contain sizeable concentrations of glycerol, derived from trehalose (Clegg, 1962(Clegg, , 1964Hall & MacDonald, 1975), we chose to dissolve RA in glycerol.…”

Terminating dormancy: hatching phenology of sympatric large branchiopods in Siangtian Pond, a temporary wetland in Taiwan

“…We conducted a total of 262 inundationdehydration replicates on 48 separate subsamples from May 2011 to April 2012. Since we aimed at hatching phenology, we neither measured the water parameters such as conductivity which has been demonstrated to be a good indicator of hatching occurrence (Brendonck et al, 2000;Vanschoenwinkel et al, 2010), nor monitored the chemical concentrations including glycerol and glycogen inside the eggs (Hall and MacDonald, 1975;Lavens and Sorgeloos, 1987;Murugan and Dumont, 1995), at the same time of experiment.…”