title: The embryogenesis of the tick Rhipicephalus (Boophilus) microplus: the establishment of a new chelicerate model system.
abstract: Chelicerates, which include spiders, ticks, mites, scorpions, and horseshoe crabs, are members of the phylum Arthropoda. In recent years, several molecular experimental studies of chelicerates have examined the embryology of spiders; however, the embryology of other groups, such as ticks (Acari: Parasitiformes), has been largely neglected. Ticks and mites are believed to constitute a monophyletic group, the Acari. Due to their blood-sucking activities, ticks are also known to be vectors of several diseases. In this study, we analyzed the embryonic development of the cattle tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). First, we developed an embryonic staging system consisting of 14 embryonic stages. Second, histological analysis and antibody staining unexpectedly revealed the presence of a population of tick cells with similar characteristics to the spider cumulus. Cumulus cell populations also exist in other chelicerates; these cells are responsible for the breaking of radial symmetry through bone morphogenetic protein signaling. Third, it was determined that the posterior (opisthosomal) embryonic region of R. microplus is segmented. Finally, we identified the presence of a transient ventral midline furrow and the formation and regression of a fourth leg pair; these features may be regarded as hallmarks of late tick embryogenesis. Importantly, most of the aforementioned features are absent from mite embryos, suggesting that mites and ticks do not constitute a monophyletic group or that mites have lost these features. Taken together, our findings provide fundamental common ground for improving knowledge regarding tick embryonic development, thereby facilitating the establishment of a new chelicerate model system.
authors.affiliation: Laboratório Integrado de Bioquímica Hatisaburo Masuda (LIBHM), 1 - Núcleo em Ecologia e Desenvolvimento Sócio Ambiental de Macaé NUPEM, Universidade Federal do Rio de Janeiro (UFRJ-Campus Macaé), Brazil.
authors.forename: Vitória Tobias
authors.initials: VT
authors.lastname: Santos
authors.forename: Lupis
authors.initials: L
authors.lastname: Ribeiro
authors.forename: Amanda
authors.initials: A
authors.lastname: Fraga
authors.forename: Cíntia Monteiro
authors.initials: CM
authors.lastname: de Barros
authors.forename: Eldo
authors.initials: E
authors.lastname: Campos
authors.forename: Jorge
authors.initials: J
authors.lastname: Moraes
authors.forename: Marcio Ribeiro
authors.initials: MR
authors.lastname: Fontenele
authors.forename: Helena Marcolla
authors.initials: HM
authors.lastname: Araújo
authors.forename: Natalia Martins
authors.initials: NM
authors.lastname: Feitosa
authors.forename: Carlos
authors.initials: C
authors.lastname: Logullo
authors.forename: Rodrigo Nunes
authors.initials: RN
authors.lastname: da Fonseca
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002417:Cattle; D054885:Cumulus Cells / Q000166:cytology; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D047108:Embryonic Development; D005260:Female; D023421:Models, Animal; D010802:Phylogeny; D048494:Rhipicephalus / Q000166:cytology / Q000196:embryology*
keywords: BMP/Dpp; Toll; cellularization; development; evo-devo; evolution