title: Eggs and embryos in Xenoturbella (phylum uncertain) are not ingested prey.
abstract: Xenoturbella is an enigmatic animal that has puzzled science for almost a century. The eggs and embryos found in Xenoturbella have recently been interpreted as ingested prey. However, PCR on individual eggs as well as in situ hybridisation and in situ PCR unambiguously show that they are Xenoturbella's own. The eggs and embryos are individually enclosed within follicles with the same ultrastructure. The cortical granules in oocytes and eggs from Xenoturbella but not Nucula stained positively with an antiserum against Reissner's substance. The embryos incorporated 5-bromodeoxyuridine in vivo, i.e. they replicate their genome and are living.
authors.affiliation: Museum of Evolution, Uppsala University, Norbyvägen 16, 752 36 Uppsala, Sweden. olle.israelsson@evolmuseum.uu.se
authors.forename: Olle
authors.initials: O
authors.lastname: Israelsson
authors.forename: Graham E
authors.initials: GE
authors.lastname: Budd
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002816:Chordata, Nonvertebrate / Q000196:embryology* / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D051545:Cyclooxygenase 1 / Q000235:genetics; D004032:Diet; D004625:Embryo, Nonmammalian; D005260:Female; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D050259:Genes, Mitochondrial; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008856:Microscopy, Fluorescence; D010063:Ovum / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D016133:Polymerase Chain Reaction; D011235:Predatory Behavior / Q000502:physiology*
chemical_list: D005456:Fluorescent Dyes; D051545:Cyclooxygenase 1; D016650:Fluorescein-5-isothiocyanate