Reversible arrest of Artemia development by cadmium

Abstract

Under normal conditions, an encysted Artemia embryo undergoes a developmental process that culminates in the gradual, uninterrupted emergence of the prenauplius from the cyst. The hatching membrane surrounding the emerged organism is then ruptured, usually beginning at the posterior end, and a motile nauplius is released. We have observed this process microscopically in the presence and absence of cadmium and report that cadmium disrupts Artemia development in a dose–dependent manner. At 0.1 μM, cadmium slows emergence but nauplii eventually resume rellatively normal development. Emergence and hatching are either delayed considerably or almost entirely prevented at 1 μM cadmium. Cadmium at 10 μM, completely arrests emergence but development continues at a reduced rate, eventually resulting in hatching of some organisms without need for complete emergence. If organisms exposed to 10 μM cadmium are washed, abnormally shaped emerged forms are released and many of these eventually hatch, although in an unusual manner. Cadmium at 10 μM causes complete, rapid precipitation of purified Artemia tubulin at 0 °C but cadmium at the lower concentrations tested has no apparent inhibitory effect on microtubule assembly. Although we do not know the actual cadmium–induced physiological changes that result in abnormal development of Artemia, our results indicate that we can now examine the interdependence of morphological and molecular aspects of Artemia development in a way not previously possible.

Pesticide exposure impacts not only hatching of dormant eggs, but also hatchling survival and performance in the water flea Daphnia magna

“…Our findings are in agreement with the results of Raikow et al (2006Raikow et al ( , 2007, who observed that the biocide SeaKlean had significant negative effects on hatching of D. mendotae dormant eggs, but with a ten times lower sensitivity compared to neonate mortality (Song et al 2011). Studies using dormant eggs of other zooplankton species (mainly rotifers and Artemia) gave variable results; ranging from no significant adverse effects on hatching rates (Sarabia et al 2003(Sarabia et al , 2008Varó et al 2006;Marcial and Hagiwara 2007), to effects on unhatched embryos at concentrations below effect levels for hatched individuals Rafiee et al 1986). This indicates that effects of chemicals on dormant stages differ among and within species as well as among toxicants, depending on their mode of action.…”

“…Varó et al (2006) and Sarabia et al (2003Sarabia et al ( , 2008 reported no adverse effects of metal and pesticide exposure on hatching of Artemia cysts. Bagshaw et al (1986) and Rafiee et al (1986), on the contrary, reported that hatching of dormant eggs was more sensitive to heavy metal exposure than hatched individuals.…”

Diapause termination and development of encystedArtemiaembryos: roles for nitric oxide and hydrogen peroxide

“…To quantify larval emergence and hatching ( Fig. 1) (Go et al, 1990;Rafiee et al, 1986), which served as measures of cyst development, 6 samples of 250 ml from each of three 50 ml tubes were mixed individually with 250 ml of sea water and 2 drops of Lugol's solution (Van Stappen, 1996) prior to counting with the aid of a dissecting microscope. Two drops of NaOCl [14% (technical) active chlorine] and NaOH (32% w/v) were then added to dissolve cyst shells, revealing non-hatched embryos for counting.…”

Shell-bound iron dependant nitric oxide synthesis in encysted Artemia parthenogenetica embryos during hydrogen peroxide exposure

“…To maintain a successful cryptobiotic state during diapause, the dormant embryos synthesize a barrier made of thick shell (hematin as major component) as well as copious amount of intracellular molecular chaperones, such as p26, HSPs, and Artemin (Clegg et al 2000;Liang and MacRae 1999;Warner et al 2004;Zhou et al 2008). Although proteins involved in the protection of embryos (pre and post-diapause conditions) are well documented, the role of maternally provided shell on the survival of dormant embryos and its role in diapause deactivation are not clearly understood (Rafiee et al 1986). Subtractive hybridization of mRNA during encystment process in A. parthenogenetica revealed the involvement of a special gene, shell gland-expressed gene (SGEG), in regulating the formation of hard shells during diapause.…”