Embryonic staging series for the African House Snake (Lamprophis fuliginosus) using external

morphology

Eric Dichter and Scott Boback. Department of Biology, Dickinson College,

Carlisle, PA.

Outline

• The motivation

• The question

• African House staging series

• Continuing work

• Goals for future

Darwin’s finches – morphological variation of beaks

Bone morphogenetic protein (Bmp4)

Abzhanov et al. 2004

Bmp4

Is Bmp4 responsible for head shape differences between island

and mainland boas?

African House Snake staging series• oviparous• smaller size• shorter time of development• docile• VERY prolific reproduction

Staging criteria for Rock PythonStage External morphological characteristics

1 Mandibular process does not extend to eye, no scales, 5-6 body coils

2 Mandibular process extending rostral to eye

3 Mandibular process extends midway between eye and maxilla, scales visible on body, 3-4 body coils

4 Mandibular process lines up with maxilla, 3 coils

5 Cervical flexure > 90°, heart protrudes from body cavity

6 Scales on head, heart internalized, 2-3 coils

7 Fusion of eyelids in center of eye, 2 coils

8 Cervical flexure 120°, body wall closed, pigmentation beginning, 2 coils

9 Cervical flexure 180°, brain not visible through skin, pigmentation patter clear but pale, 1-2 coils

10 Resembles neonate, 1-2 body coils, egg tooth visible

Adapted from Boughner et al. 2007

Staging criteria for African House

• Mandibular length (relative to maxilla)• Brain development• Location of organs• Angle of cervical flexure• Weight• Length• Eye pigment• Scales

Adapted from Boughner et al. 2007

0-1 days

Mandible

Visible, protruding mesencephalon

External organs

6 days

Mandible

External organs

Visible, protruding mesencephalon

9 days

Mandible

External organs

Visible, protruding mesencephalon

13 days

Mandible

External heart

Visible, protruding mesencephalon

16 days

Mandible

Visible, protruding mesencephalon

Internalized heart (moved caudally)

13’ days

Mandible

Scales forming

Visible, protruding mesencephalon

16’ days

Mandible

Visible, flattening mesencephalon

27 days

Pigmentation pattern beginning

Visible, linearized skull

34 days

Pigmentation pattern darkening

Opaque, elongate skull

43 days

Pigmentation pattern darkening further

External hemipenes

54 days - hatched

Conclusions

• Rate of development variable – depends on environment, health of mother, genetics

• Comparable development at oviposition

• Development of L. fuliginosus similar to Python sebae – much shorter incubation

Continuing work• Mating snakes, incubating eggs, harvesting more

embryos

• Clearing and staining – location, timing of bone development in jaws

• In situ hybridizations – determine presence, location, timing of expression of certain growth factors (Bmp4, Bmp2, Fgf8, Shh)

Many thanks to…

• Prof. Boback• Prof. Mistry• Neil Ford• Ali Maksimak• Mike Montross• Chase Walling

Works cited

• Boughner, J.C., Buchtova, M., Fu, K., Diewert, V., Hallgrimsson, B., Richman, J.M. 2007. Embryonic development of Python sebae – I: Staging criteria and macroscopic skeletal morphogenesis of the head and limbs. Zoology 212-230.

• Abzhanov, A., Protas, P., Grant, B. R., Grant, P.R., Tabin, C.J. 2004. Bmp4 and Morphological Variation of Beaks in Darwin’s Finches