A timetable of embryonic development, and ovarian and uterine changes during pregnancy, in the stripe-faced dunnart, Sminthopsis macroura (Marsupialia: Dasyuridae)
in ReproductionSearch for other papers by Lynne Selwood in
Current site
Google Scholar
PubMed
Search for other papers by P. A. Woolley in
Current site
Google Scholar
PubMed
Summary. Aged stages (63) were available for establishment of a timetable of embryonic development of the stripe-faced dunnart. On Day 0 oocytes reaching maturity were found in the ovary. Within ± 24 h of time 0 (time of minimum morning weight) polymorphonuclear leucocytes appeared and spermatozoa were last detected in the urine of 70% of females. Embryos were collected at intervals during pregnancy by hemihysterectomy and the embryos in the contralateral uterus either were examined at a later stage of pregnancy or allowed to develop to term.
Cleavage to the unilaminar blastocyst stage with around 32 cells took 3 days with a cleavage arrest of 24 h at the 4-cell stage. Expansion of the unilaminar blastocyst occurred over the next 3 days. Primitive endoderm cells appeared on Day 6, fully bilaminar blastocysts by the end of Day 7 and trilaminar blastocysts on Day 8. Shell loss and implantation of 13–15-somite stage embryos occurred on Day 8 and organogenesis over the next 2–3 days. The gestation period was 9·5–12·0 days with most births occurring between 10·5 and 11·0 days.
Major steps in embryonic development were correlated with stages in the development of the corpora lutea, which were maximal in size, and possibly in secretory activity, when the embryos were at the bilaminar blastocyst stage. Regression commenced when the embryos were at the primitive streak stage. At the time the corpora lutea were maximal the uterine epithelium reached its greatest height and the endometrium was thick and folded. Later in pregnancy villous-like projections of the epithelium formed, and the luminal epithelial cells became rounded.
Two cell populations, a tier of 8 smaller cells above the yolk mass and a tier of 8 larger cells around the sides of the yolk mass appeared at the 16-cell stage. From the 16-cell stage to the blastocyst stage, with 150–200 cells, two cell populations distinguished by size, cell cycle time, cytoplasmic appearance and position relative to the yolk mass were present. The two populations were indistinguishable in blastocysts with > 200 and < 2000 cells. They reappeared in blastocysts with > 2000 cells, as the darker cells of the embryoblast, and as the paler cells of the trophoblast. The darker cells lay in the yolky hemisphere and the paler cells in the non-yolky hemisphere.
Keywords: embryo; development; uterus; corpus luteum; marsupial
Reproduction is committed to supporting researchers in demonstrating the impact of their articles published in the journal.
The two types of article metrics we measure are (i) more traditional full-text views and pdf downloads, and (ii) Altmetric data, which shows the wider impact of articles in a range of non-traditional sources, such as social media.
More information is on the Reasons to publish page.
| Sept 2018 onwards | Past Year | Past 30 Days | |
|---|---|---|---|
| Full Text Views | 336 | 108 | 4 |
| PDF Downloads | 490 | 152 | 11 |
Online ISSN: 1741-7899
Print ISSN: 1470-1626
Strengthening biomedical communities
to advance science and health
CONTACT US
Bioscientifica Ltd | Starling House | 1600 Bristol Parkway North | Bristol BS34 8YU | UK
Bioscientifica Ltd | Registered in England no 3190519