Skeletogenesis is a key morphogenetic event in the life of marineinvertebrates. Marine calcifiers secrete their calcareous skeletonstaking up ions from seawater.Marine biominerals include aragonite and calcite, the latter ofwhich in some taxa (e.g. echinoderms, coralline algae) can havea substantial magnesium (Mg) component.Echinoderms have an extensive endoskeleton composed of highmagnesian calcite and occluded matrix proteins1. As biomineralizationin sea urchin larvae is sensitive to theMagnesium:Calcium ratio of sea water, we investigated theeffects of magnesium deprivation on development and skeletogenesisin the Mediterranean sea urchin Arbacia lixula.Microscopic inspection revealed that embryos reared in Mg-freeseawater exhibited developmental delay from 6 hours post-fertilization,complete lack of skeleton formation at 24 hours, andsevere skeleton malformations in larvae (48-72 hours). We subsequentlyfocused on the localization of the skeletogenic cells(primary mesenchyme cells) and the spatial expression of associatedgenes. Immunocytochemistry revealed abnormal ectopiclocation of the primary mesenchyme cells (PMCs) and of thedeveloping skeleton of treated embryos. Expression of msp130,an important skeleton matrix protein gene expressed only inPMCs, detected by in situ hybridization, was normal at 24 hours,but this gene was not down-regulated at 48 hours, as in controls2.Strikingly, development of the pigment cells, immune cellsthat, like the skeleton, are mesodermal derivatives, was alsoimpaired. These results suggest the essential role of Mg in skeletonformation in sea urchin embryos with an indication that thiselement is also generally important for development of mesoderm.1. Smith AM et al. Mar Ecol Prog Ser 2016, 561:1–162. Martino C et al. Aq tox 2018, 194:57-66.
Original languageEnglish
Pages (from-to)4-4
Number of pages1
Publication statusPublished - 2018


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