by Christoph — In this blog, we don't usu­ally con­sider big, mul­ti­cel­lu­lar an­i­mals, say, arthro­pods like Drosophila, ne­matodes like C. el­e­gans, or tardi­grades like Hypsi­bius du­jar­dini. We do make ex­cep­tions for the hosts of mi­cro­bial en­dosym­bionts. Why al­low the 'wa­ter bears' (tardi­grades)? With body lengths of 0.5‒1 mm, they are a bit too big to be hon­orary mi­crobes but...