The embryonic development of Schistosoma mansoni eggs: proposal for a new staging system.
Schistosomiasis is a water-borne parasitic illness caused by neoophoran trematodes of the genus Schistosoma. Using classical histological techniques and whole-mount preparations, the present work describes the embryonic development of Schistosoma mansoni eggs in the murine host and compares it with eggs maintained under in vitro conditions. Two pre-embryonic stages occur inside the female worm: the prezygotic stage is characterized by the release of mature oocytes from the female ovary until its fertilization. The zygotic stage encompasses the migration of the zygote through the ootype, where the eggshell is formed, to the uterus. Fully formed eggs are laid still undeveloped, without having suffered any cleavage. In the outside environment, eight embryonic stages can be defined: stage 1 refers to early cleavages and the beginning of yolk fusion. Stage 2 represents late cleavage, with the formation of a stereoblastula and the onset of outer envelope differentiation. Stage 3 is defined by the elongation of the embryonic primordium and the onset of inner envelope formation. At stage 4, the first organ primordia arise. During stages 5 to 7, tissue and organ differentiation occurs (neural mass, epidermis, terebratorium, musculature, and miracidial glands). Stage 7 is characterized by the nuclear condensation of neurons of the central neural mass. Stage 8 refers to the fully formed larva, presenting muscular contraction, cilia, and flame-cell beating. This staging system was compared to a previous classification and could underlie further studies on egg histoproteomics (morphological localizome). The differentiation of embryonic structures and their probable roles in granulomatogenesis are discussed herein.
Laboratório de Patologia, Instituto Oswaldo Cruz/Fundação Oswaldo Cruz, Pavilhão Gomes de Faria. Av. Brasil, 4365-Manguinhos, Rio de Janeiro 21040-900, RJ, Brazil. ajurberg@igc.gulbenkian.pt
Arnon D
AD
Jurberg
Tiana
T
Gonçalves
Tatiane A
TA
Costa
Ana Carolina A
AC
de Mattos
Bernardo M
BM
Pascarelli
Pedro Paulo A
PP
de Manso
Marcelo
M
Ribeiro-Alves
Marcelo
M
Pelajo-Machado
José M
JM
Peralta
Paulo Marcos Z
PM
Coelho
Henrique L
HL
Lenzi
D000818:Animals; D047108:Embryonic Development; D005260:Female; D051379:Mice; D009865:Oocytes; D012550:Schistosoma mansoni / Q000196:embryology*; D012555:Schistosomiasis mansoni / Q000469:parasitology*