Development and staging of the water flea Daphnia magna (Straus, 1820; Cladocera, Daphniidae) based on morphological landmarks

Abstract

BackgroundCrustaceans of the genus Daphnia are one of the oldest model organisms in ecotoxicology, ecology and evolutionary biology. The publication of the Daphnia pulex genome has facilitated the development of genetic tools to answer long-standing questions in these research fields (Science 331: 555-561, 2011). A particular focus is laid on understanding the genetic basis of the striking ability of daphnids to change their phenotype in response to environmental stressors. Furthermore, Daphnia have recently been developed into crustacean model organisms for EvoDevo research, contributing to the ongoing attempt to resolve arthropod phylogeny. These problems require the comparative analyses of gene expression and functional data, which in turn require a standardized developmental staging system for Daphnia.ResultsHere we provide a detailed staging system of the embryonic development of Daphnia magna based on morphological landmarks. The staging system does not rely on developmental hours and is therefore suitable for functional and ecological experiments, which often cause developmental delays in affected embryos and thus shifts in time reference points. We provide a detailed description of each stage and include schematic drawings of all stages showing relevant morphological landmarks in order to facilitate the application of this staging scheme.ConclusionWe present here a staging system for Daphnia magna, which is based on morphological landmarks. The staging system can be adopted for other daphnids with minor variations since the sequence of development is highly conserved during early stages and only minor heterochronic shifts occur in late embryonic stages.

Brood pouch-mediated polystyrene nanoparticle uptake during Daphnia magna embryogenesis

“…A more thorough understanding of the exact localization of PSNPs in or on lipid droplets, respectively, might be of interest for future studies. Here, we observed that the eggs start to internalize PSNP after being in the brood pouch from stage 2 onwards, thus in early embryogenesis while the embryos are still in the chorion shell (Mittmann et al 2014;Giardini, Yan, and Heyland 2015). This suggests that, in contrast to the observed protective role of chorion in fish (Fent et al 2010), the chorion of crustacean embryos does not play a protective role for NP exposure.…”

Effect of age on acute toxicity of cadmium, copper, nickel, and zinc in individual‐metal exposures to Daphnia magna neonates

“…In contrast, the oldest neonates had a 3.8‐fold shallower concentration–response curve (as indicated by the slope) and a 4‐fold greater variability around the average Cd EC50 (as indicated by the CV ) within a 4‐h age window. These results may suggest that the daphnids were released from the parent daphnid with a physiological defense mechanism ; however, such a mechanism might have waned as they aged and the neonates became susceptible to a variety of external factors that may have led to increased variability in the susceptibility to some metals. Alternatively, Cd (and to some extent Zn) might have interfered with important age‐dependent developmental/physiological processes that occur between 48 h and 72 h postbirth (i.e., after a test started with daphnids 0–4 h old had ended, when the daphnids were 48–52 h old, but before a test started with daphnids 20–24 h old had ended, when the daphnids were 68–72 h old).…”

“Crustacea”: Comparative Aspects of Early Development

“…The studies on the cell division patterns of some Dendrobranchiata, Caridea, Euphausiacea, and Branchiopoda have used whole mounts Scholtz 2004 , 2014 ;Hertzler 2005 ;Biffi s et al 2009 ;Klann and Scholtz 2014 ), while for The branchiopod crustaceans undergo a direct development which results in juveniles that are morphologically similar to their adults. The left column illustrates major events of embryonic development which takes place in the dorsal brood pouch of the mother (Based on Mittmann et al ( 2014 )). Scale bars: 100 μm.…”