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Developmental fates of the first four blastomeres of the chaetognath Paraspadella gotoi : Relationship to protostomes
Author(s) -
Shimotori Taishin,
Goto Taichiro
Publication year - 2001
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1046/j.1440-169x.2001.00583.x
Subject(s) - blastomere , biology , cleavage (geology) , embryo , hatchling , germ plasm , mitosis , developmental biology , cleavage furrow , blastoderm , cell , embryogenesis , evolutionary biology , genetics , microbiology and biotechnology , cell division , ecology , cytokinesis , paleontology , fracture (geology) , hatching
Experimental analysis of the development of chaetognaths is virtually lacking. To elucidate developmental fates, single blastomeres of the 2‐cell and 4‐cell embryos of Paraspadella gotoi were injected with a lineage‐tracing dye (Fluoro‐Ruby or DiI). The distribution of the labels was observed in the hatchlings. In a previous study, embryos were injected at the 2‐cell stage with Fluoro‐Ruby and two sets of complementary labeling patterns (DL and VR, and DR and VL) were found. The same results were obtained when DiI was used as a tracer dye. The 4‐cell embryo consists of the animal and vegetal cross‐furrow cells in a tetrahedral arrangement and one of the vegetal cross‐furrow cells typically contains the germ plasm. When single cells were injected at the 4‐cell stage, four labeling patterns were observed (D, V, L and R). These four patterns represent subsets of the four patterns observed in the hatchling injected at the 2‐cell stage. The V pattern is probably generated from the blastomere containing the germ plasm. It was found that the positions of the blastomeres at the 4‐cell stage corresponded to the future body axes, similar to classic spiralians and modified spiralians such as crustaceans. Furthermore, it was confirmed that second cleavage occurs in a leiotropic fashion, which is seen in the second cleavage of the classic spiralians. Chaetognaths may have some similarities to protostomes in their developmental program.