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Table 1 Developmental staging table for P. vitticeps based on Sanger et al. [40] staging system for Anolis lizards

From: Sex determination mode does not affect body or genital development of the central bearded dragon (Pogona vitticeps)

Stage

Description

1. Late pre-limb bud

Limbs: Not yet present

Cranial: The neural tube is open, extending to the cranial margin of the metencephalon. The mesencephalon forms a conspicuous bulge, with little definition between it and the metencephalon

Eye: Optic cups are visible as round transparent protuberances with open choroid fissures

Thorax: The heart is present as a single, folded transparent endocardial tube enclosed within a membrane. Four pharyngeal clefts are open. The mesonephros is present, as are the otic vesicles

Somites: Approximately 35 somites are present with no obvious tail bud

2. Forelimb bud

Limbs: The forelimb buds are present. The hindlimbs are beginning to form as slight thickening of the mesoderm close to the caudal terminus of the embryo

Cranial: The neural tube remains open, extending to the caudal margin of the mesencephalon. Early meso-metencephalic constriction is apparent, and the metencephalon and mesencephalon become more distinct. The diencephalon becomes more prominent. The olfactory placodes are visible

Eye: The choroid fissure is obviously narrower, while the lens and optic cups become more defined and very faintly pigmented

Thorax: Three pharyngeal clefts are open. The mesonephros is larger, extending behind the presumptive liver, which has also increased in size from the previous stage. The margins of the otic vesicles become more defined. The tail bud begins to form

Somites: Have increased in number from the previous stage (approximately 46), extending past the thickening hindlimb mesoderm, but terminating before the tail bud

3. Hindlimb bud

Limbs: Both the fore and hindlimbs are becoming increasingly defined and are beginning to separate from the mesoderm. All limbs are approximately the same size

Cranial: Meso- and metencephalic constriction increases, giving the mesencephalon a more rounded appearance, and causing the metencephalon to appear more protuberant. The diencephalon becomes more apparent

Eye: The choroid fissure remains open, and the lens and optic cup become more distinct as pigmentation darkens on the lens

Thorax: Two pharyngeal clefts are open. All organs increase in size. The mesonephros extends higher in the body cavity. The endocardial tube (presumptive heart) constricts. The tail lengthens and begins to curl

Somites: Continue to increase in number as they are present past the hindlimb bud and into the developing tail (approximately 48)

4. Early limb bud

Limbs: Hind and forelimb buds are well defined and approximately the same size

Cranial: The margins of the mesencephalon are well defined, creating an obvious division between it and the metencephalon. The diencephalon increases in size. The neural tube narrows

Eye: Little change from previous stage

Thorax: All organs, aside from the embryonic kidney, are developing outside of the body cavity, but are beginning to become more enclosed within developing mesoderm

5. Late limb bud

Limbs: Both the hind and forelimb buds have increased in size and begin to show a slight pinching between the length of the limb and the developing hand

Cranial: The mesencephalon continues to develop as a large, translucent protuberance. The metencephalon reduces, while the diencephalon continues to increase in size

Eye: The eyes have become much larger and protuberant, taking on a uniform light brown colouration with diffuse black pigmentation surrounding the developing pupil

Thorax: The heart is internalised, while the intestines remain herniated

Genitalia: The cloaca begins to form as a small indentation between the hindlimb buds

6. Paddle-shaped limb bud

Limbs: Both the hind and forelimbs have a distinct paddle, or spade-like shape, but no delineated phalanges

Cranial: The mesencephalon becomes slightly less protuberant and translucent, while the diencephalon becomes less translucent and moves towards the mesencephalon

Eye: The eyes continue to increase in size, while the black pigmentation around the pupil becomes less diffuse

Thorax: The intestines are almost completely enclosed within the body cavity

Genitalia: The cloaca continues to become more defined as very small genital swellings begin to form on either side of the cloacal opening, between the hindlimbs

7. Digital plate

Limbs: Both the hind and forelimbs have become obviously proximodistally segmented, increase in width and become slightly pointed at the apex. Faint digit condensations are visible

Cranial: The mesencephalon reduces further and becomes less translucent. There is also some definition of the presumptive paired brain swellings as the diencephalon continues to move towards the mesencephalon

Eye: The eyes become more protuberant and the eyelid begins to form as a thin, translucent covering of skin around the ventral margin of the eye

Thorax: All organs have become completely internalised

Genitalia: The genital swellings increase in size and the anterior and posterior cloacal lips start to develop

8. Digital condensations

Limbs: The phalangeal bones have condensed, the interdigital webbing becomes slightly reduced, and the limb joints are more distinct

Cranial: The mesencephalic lobes become more obviously delineated

Eye: The overall appearance of the eye remains unchanged from the previous stage, but the eyelids continue to envelop more of the eye

Genitalia: The genital swellings increase in size and start to take on a slightly club-like shape. The anterior and posterior cloacal lips continue to become more defined

9. Early digital web reduction

Limbs: The interdigital webbing continues to reduce so that the distal tips are freed, while the elbow joint becomes more distinct, making the limbs flex at approximately 90 degrees

Cranial: Four mesencephalic lobes have become delineated, and the pineal eye is visible. The two posterior lobes are slightly more protuberant than the two anterior lobes

Eye: The eyelid now covers approximately three-quarters of the eye

Scales: Epidermal papillae first become visible, particularly along the dorsal surface

Genitalia: The genitalia continue to grow and develop an increasingly club-like shape, and the cloacal lips continue to thicken

10. Digital webbing partially reduced

Limbs: The digital webbing continues to reduce to approximately half the length of the phalanges

Scales: Epidermal papillae develop along the dorsal surface and margin of the presumptive beard. The epaulettes also start to form

Genitalia: The genitalia now have a club-shaped appearance, but are not yet bilobed

11. Digital webbing completely reduced

Limbs: The phalanges are no longer joined by any interdigital webbing, and there is a slight pinching at the distal tips of each phalange

Cranial: The posterior mesencephalic bulges become more protuberant

Eye: The eyelid thickens, creating an almond-like shape around the eye. The pigmentation darkens, and the black pigmentation condenses around the pupil

Scales: The epidermal papillae become more prominent along the dorsal surface and margins of the presumptive beard. Very faint pigmentation is visible on the developing epaulettes

Genitalia: Both sexes now exhibit bilobed hemipenes

12. Eyelid margin (digital pad)

Limbs: The phalanges become more elongated with some joint definition and increased pinching at the distal tips, but the claws remain transparent

Eye: They eyelid now covers the eye up to around the margins of the black pigmentation around the pupil

Scales: Scale anlagen are present along the margins of beard and side of body, and dorsal surface. Some epidermal papillae develop on the dorsal surface along with faint, scattered pigmentation on the developing epaulettes

Genitalia: Bilobed hemipenes continue to develop in both sexes

13. Dorsal patterning (toe lamellae)

Limbs: The claws are well defined and are no longer transparent. All limb joints become well defined

Eye: The eyelid surrounds the pupil and beings to thicken at its anterior margins, but remains transparent, underneath which the eyes’ darkening pigmentation is still visible

Scales: Epidermal papillae are now evident across the entire body. Scale anlagen increase in number and become more defined along the beard margins, sides of body and dorsal surface. Very faint, scattered melanophores appear on the developing epaulettes, extending caudally from the margins of the eye and ear hole. Patterning develops along the dorsal surface and the pigmentation slightly darkens

Genitalia: Bilobed hemipenes continue to develop; however, in some females they begin to reduce in length but retain their bilobed appearance

14. Mesencephalic bulge reduction (scale anlagen)

Limbs: The limbs no longer change in shape

Cranial: The mesencephalic bulges begin to reduce, and the area of the presumptive parietal bone becomes less translucent

Eye: The anterior margins of the eyelid continue to thicken

Scales and Pigmentation: Scale anlagen now cover most of the body, and light pigmentation appears on limbs, tail and cranium, while the dorsal patterning continues to slightly darken

Genitalia: The hemipenes continue to regress in females and remain unchanged in males

15. Full dorsal scales (first full scales)

Cranial: The mesencephalic lobes continue to reduce so that the head has an even dome shape in profile. The presumptive parietal bones continue to develop, further reducing the transparency of the skull

Eye: The eyelids’ anterior margins thicken further, more closely enclosing the pupil, but remains transparent. The whole eye darkens so there is no delineation between pigmentation around the pupil and the rest of the eye

Scales and Pigmentation: Pigmentation has darkened considerably from pervious stage, and distinct patterns cover the entire dorsal surface. The claws also darken. Overlapping scales cover most of the dorsal surface, including the tail and limbs. Presumptive spines develop along the beard and sides of body

Genitalia: In females, the genitalia continue to regress so that either the bilobed appearance is retained, or has disappeared so that the genitalia resemble small, even swellings characteristic of hemiclitores

16. Fully developed scales

Cranial: The parietal bone continues to develop so that the mesencephalic lobes are less visible

Eye: The eyelids continue to thicken over the whole eye and have a well-defined almond shape around the pupil

Scales and Pigmentation: Fully developed scales are now common across the body, particularly along the beard and dorsal surface. Scales begin to become more prominent on the phalanges and eyelids. Pigmentation continues to darken over the whole body, so that distinct patterns are now obvious

Genitalia: In females, the genitalia generally continue to regress to hemiclitores, however, there are still some specimens that retain bilobed hemipenes or regressed hemipenes

17. Eye reduction (pigmentation)

Cranial: The parietal bone is well developed so that the cranium has a smooth dome-like appearance in profile and the mesencephalic lobes are barely visible

Eye: The eyes become less protuberant, but the pigmentation and eyelid morphology remains unchanged

Scales and Pigmentation: Scales continue to develop across the body and are now commonly found to be overlapping. Pigmentation darkens across all dorsal surfaces

Genitalia: Most female specimens now exhibit either regressed hemipenes or hemiclitores

18. Near-hatching

Cranial: The partial bone has formed and is now covered in scales and darkly pigmented. The pineal eye is still visible

Eye: The eyes are significantly less protuberant, but there is still some dark pigmentation visible under the eyelid

Scales and Pigmentation: The scales are almost completely developed, and the pigmentation patterns look much like those seen in hatchlings

Genitalia: The genitalia have completely regressed in females so that only the genital ridge is present within the vent. Males possess large bilobed hemipenes

  1. More detail is provided for morphological traits that are not described for Anolis, as well as a general characterisation of genital development. Where applicable, stages that were named after diagnostic characters in Anolis that are not present in P. vitticeps, were renamed with the original name in brackets