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 | 1925 Neural Folds and Cranial Ganglia | 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.


Somite Timeline

Table III - Showing Means and Variation for Each Rat Age
Maximum Variation
Age
Days-Hrs.
Number of
Litters
Number of
Embryos
Counted
Means All Embryos One Litter Standard
Deviation
Coefficient of
Variation %
10-12 1 4 8.7 6-11 6-11 2.8 32
10-13 1 6 1 0. 2 8-13 8-13 1.9 19
10-16 2 12 12.4 6-26 6-26 5.8 47
10-17 6 48 12.9 4-26 7-26 3 .3 26
10-18 4 23 14.1 6-18 9-18 3.1 22
10-19 1 6 14 .3 12-17 12-17 1.2 8
10-22 3 16 13.1 6-19 6-14 3.9 30
10-23 3 17 15.2 8-18 8-18 2.4 16
11-00 2 0 14.6 10-17 10-17 1.9 13
11-02 2 15 20 . 9 17-22 17-22 1. 3 6
11-04 1 10 25. 3 23-26 23-26 1.2 5
11-06 1 2 18.0 18-18 18-18 .0 0
11-08 1 8 25 0 23-28 23-28 1.9 8
11-09 1 3 22 .0 20-25 20-25 2 . 2 10
11-10 2 18 26.2 21-31 21-31 2.9 11
11-11 3 26 25.6 14-29 14-27 3.2 12
11-12 1 3 26. 7 25-28 25-28 1.2 4
11-14 1 3 21.3 21-22 21-22 .6 2
11-15 1 8 23.1 17-28 17-28 4 . 0 17
11-16 1 7 26.7 24-28 24-28 1.3 5
11-17 1 7 26.1 25-28 25-28 1.1 4
11-18 3 25 25 .4 19-28 19-28 1.9 7
11-20 2 16 27.2 25-29 25-29 1.2 4
23 Ages 44 292 Av 2.2 Av 13%
Data Reference[2]   Links: rat | somitogenesis


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.
  2. Landacre FL. and Amstutz MM. Data on the number of somites compared with age in the white rat. (1929) Ohio J. Science. 29(6): 253-259.


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Cite this page: Hill, M.A. (2018, December 13) Embryology Rat Development Stages. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Rat_Development_Stages

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© Dr Mark Hill 2018, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G