First cleavages, preblastula and blastula in the parthenogenetic mite Archegozetes longisetosus (Acari, Oribatida) indicate holoblastic rather than superficial cleavage

摘要: The mode of cleavage in the Acari is generalized as superficial or intralecithal, with a preceding phase total (holoblastic) cleavage, but knowledge fragmentary and conclusions have been inconsistent, even when relating to same species. Since no data about early embryology available for speciose group Oribatida, we studied Archegozetes longisetosus using transmission electron microscopy. We focused on cleavages formation blastula, these are important controversial points Acari. expected, postulated other acarine eggs, be holoblastic followed by preblastoderm stage. A. blastomeres give rise yolk-free micromeres macromeres containing all yolk. In contrast expectations, do not form layer. They scattered along embryonic surface an external, monocellular layer that covers whole embryo. each existing TEM studies mites shows this pattern, since specialized seems unique Chelicerata, it may general However, question will require much more investigation, especially most relate Actinotrichida very few currently species major group, Anactinotrichida.