Rat Development Stages

From Embryology

Witschi Rat Stages

Shown below are the Witschi standard stages of development[1] and the timing and specific features that identify each stage. See also the Rat Timeline which gives a day by day sequence and adds additional research findings on rat development.


Rat Links: rat | Rat Stages | Rat Timeline | Category:Rat
Historic Embryology - Rat 
1951 Albino Rat Development | 1921 Somitogenesis | 1933 Vaginal smear | 1938 Heart


Standard Stages (Witschi)
Age (days)
Size (mm)
Identification of Stages
Cleavage and Blastula
1 1 0.07 1 cell (in oviduct)
2 2 0.08 x 0.06 2 cells (in oviduct)
3 3 0.08 x 0.05 4 cells (in oviduct)
4 3.25 8-12 cells (in oviduct)
5 3.5 0.08 x 0.04 Morula (in uterus)
6 4 (0.08 x 0.03) Early blastocyst (in uterus)
7 5 (0.12 x 0.05) Free blastocyst (in uterus)
Gastrula
8 6 (0.28 x 0.07) Implanting blastocyst, with trophoblastic cone and inner cell mass; outgrowth of endoderm (hypoblast)
9 6.75 Diplotrophoblast; inner cell mass (pendant), covered with endoderm
10 7.25 (0.3 x 0.1) Near complete implantation; pendant begins differentiation into embryonic and extra-embryonic parts
11 7.75 (0.5 x 0.1) Completion of implantation; primary amniotic cyst; ectoplacental cone
Primitive Streak
12 8.5 (1.04 x 0.26) Connecting ectochorionic and amniotic cavities; rudiments of amniotic folds; primitive streak; start of 3rd layer formation; blastemas of heart and pericardium
Neurula
13 9 1.0 Presomite neurula; fusion of chorio-amniotic folds, chorio-amniotic stalk; neural plate; embryo bent dorsally; bud of allantoic stalk
14 9.5 1.5 Somites 1-4 (occipital); pendant with 3 cavities: ectochorionic cyst, exocoelom, and amniotic cavity; ectochorionic cyst collapsing; allantoic stalk projects into exocoelom; embryo bent dorsally
15 10 2 Somites 5-12 (cervical); 1st visceral arch; ectochorionic cyst fused with ectoplacenta and with allantoic stalk; regression of peripheral (distal) yolk sac and trophectoderm (diplotrophoblast); Reichert's membrane; gonia in endoderm; embryo bent dorsally
16 10.5 2.4 Somites 13-20 (upper thoracic); 2 visceral arches; disc and yolk sac placentas; appendicular folds; embryo reverses, curves ventrally
17 11 3.3 Somites 21-25 (lower thoracic); yolk stalk closes at level of 15th somite; primary gonia in mesentery; primitive streak disappears; tail bud becomes organized; arm and leg buds recognizable
Tail Bud Embryo
18 11.5 3.8 Somites 26-28 (upper lumbar); 3 visceral arches; arm buds recognizable
19 11.75 4.2 Somites 29-31 (lower lumbar); visceral arches I-IV; cervical folds; appendicular folds and buds
20 11.875 5 Somites 32-33 (upper sacral)
21 12 5.1 Somites 34-35 (lower sacral); deep cervical sinuses
22 12.125 5.2 Somite 36 (1st caudal); olfactory pits
23 12.25 5.6 Somites 37-38 (caudal); start of umbilical herniation
24 12.375 6 Somites 39-40 (caudal)
Complete Embryo
25 12.5 6.2 Somites 41-42 (caudal); occipital somites dispersing; 4 visceral arches; deep cervical sinuses; arm buds at somite levels 8-14, about as high as long; leg buds at somite levels 28-31, smaller; body forms a spiral of about 11/2 turns, the left face and trunk applied to yolk sac, the right side turned toward placenta; tail and allantoic stalk rise to the placenta
Metamorphosing Embryo
26 12.75 7 Somites 43-45 (caudal); mandibular, maxillary, and frontonasal processes; cervical sinuses closing; mammary welts; differentiaion of handplates; arm buds vascularized, brachial nerves entering; beginning of umbilical hernia
27 13 8 Somites 46-48 (caudal); prominent facial processes and clefts; nose-snout projecting; cervical sinuses closed; primordia of mammary glands; round handplates and footplates; larger umbilical hernia
28 13.5 8.5 Somites 49-51 (caudal); 1st visceral cleft transforms into external ear duct; precartilaginous condensations in handplates
29 14 9.5 Somites 52-55 (caudal); auricular hillocks on visceral arches I and II
30 14.5 10.5 Somites 56-60 (caudal); body uncoils; mandibular precartilage; nearly round opening of external ear duct; pleuroperitoneal canal has become very narrow
31 15 12 Somites 61-63 (caudal); facial clefts closed; pleuroperitoneal canal closed; complete diaphragm
32 15.5 14.2 Somite 64 (caudal); pinna turns forward; maximal size of umbilical hernia
33 16 15.5 Somite 65 (usually this is last caudal); snout lifts off chest; last stage of metamorphosis
Fetus
34 17-18 16-20

 

1st fetal stage: rapid growth of eyelids (eyes entirely covered at end of 18th day); palate complete; pinna covers ear duct; umbilical hernia withdraws
35

ante-natal

19-22 20-40

 

2nd fetal stage: sealed eyelids; fetal membranes and placentas reach peak of development; tail grows to 10mm;

Birth occurs (22nd day in rat, 19th day in mouse)

35

post-natal

1-16 post-partum 40-1001 After birth, fetus becomes a breathing and suckling nestling2; during 1st 16 days (22 to 38 days total age), eyelids remain sealed and external ear ducts plugged with periderm
36

post-natal

17+ post-partum 100+1 Periderm seals of ears and eyelids vanish; active feeding begins within next 3 days and weaning after 1 week (total weaning age, 45-48 days for rats and mice)

 

* Age (days)- days after fertilization

* Size (mm)- largest and smallest dimensions

Table Data

The main table data is modified from [1] and other sources as listed within the table.

Species Stages Comparison

The table below gives an approximate comparison of human, mouse and rat embryos based upon Carnegie staging.

Species Embryonic Comparison Timeline
Carnegie Stage
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Human Days 1 2-3 4-5 5-6 7-12 13-15 15-17 17-19 20 22 24 28 30 33 36 40 42 44 48 52 54 55 58
Mouse Days 1 2 3 E4.5 E5.0 E6.0 E7.0 E8.0 E9.0 E9.5 E10 E10.5 E11 E11.5 E12 E12.5 E13 E13.5 E14 E14.5 E15 E15.5 E16
Rat Days 1 3.5 4-5 5 6 7.5 8.5 9 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17 17.5
Note these Carnegie stages are only approximate day timings for average of embryos. Links: Carnegie Stage Comparison
Table References  
Human

O'Rahilly R. (1979). Early human development and the chief sources of information on staged human embryos. Eur. J. Obstet. Gynecol. Reprod. Biol. , 9, 273-80. PMID: 400868
Otis EM and Brent R. Equivalent ages in mouse and human embryos. (1954) Anat Rec. 120(1):33-63. PMID 13207763

Mouse
Theiler K. The House Mouse: Atlas of Mouse Development (1972, 1989) Springer-Verlag, NY. Online
OTIS EM & BRENT R. (1954). Equivalent ages in mouse and human embryos. Anat. Rec. , 120, 33-63. PMID: 13207763

Rat
Witschi E. Rat Development. In: Growth Including Reproduction and Morphological Development. (1962) Altman PL. and Dittmer DS. ed. Fed. Am. Soc. Exp. Biol., Washington DC, pp. 304-314.
Pérez-Cano FJ, Franch À, Castellote C & Castell M. (2012). The suckling rat as a model for immunonutrition studies in early life. Clin. Dev. Immunol. , 2012, 537310. PMID: 22899949 DOI.

References

  1. 1.0 1.1 Witschi, E. (1962) Development: Rat. In: Growth Including Reproduction and Morphological Development. Altman, P. L. , and D. S. Dittmer, ed. Fed. Am. Soc. Exp. Biol., Washington DC, pp. 304-314.



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Cite this page: Hill, M.A. (2018, September 24) Embryology Rat Development Stages. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Rat_Development_Stages

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