Eggshell formation during prolonged gravidity of the tuataraSphenodon punctatus

Cree, Alison; Guillette, Louis J.; Reader, Karen L

doi:10.1002/(sici)1097-4687(199611)230:2<129::aid-jmor2>3.0.co;2-c

Cited by 13 publications

(10 citation statements)

References 38 publications

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“…[48] The tauatara lay eggs, like their common ancestors, snakes and lizards of the Squamata order. However, the eggs laid by the tuatara are unique-they are not laid until after 7 months of pregnancy and the shells surrounding the eggs are flexible, yet are largely inorganic with a small organic component [49][50][51] .…”

Section: Tuatara Egg Shellsmentioning

confidence: 99%

“…[52] While the egg is not laid until the 7 th month of pregnancy, it takes an additional 5 months for the young to emerge. [49][50][51]53] From the start of development to hatching, the egg mass increases by 2-3 times. [54] The tuatara eggshell consists of a mixture of calcite crystals and organic molecules [49][50][51]55] .…”

Section: Tuatara Egg Shellsmentioning

confidence: 99%

“…[49][50][51]53] From the start of development to hatching, the egg mass increases by 2-3 times. [54] The tuatara eggshell consists of a mixture of calcite crystals and organic molecules [49][50][51]55] . The organic component of the eggshell is of unidentified composition, though consists of a mixture of ribbon-like fibers of varying diameter and an amorphous matrix [49][50][51]55] .…”

Section: Tuatara Egg Shellsmentioning

confidence: 99%

“…[54] The tuatara eggshell consists of a mixture of calcite crystals and organic molecules [49][50][51]55] . The organic component of the eggshell is of unidentified composition, though consists of a mixture of ribbon-like fibers of varying diameter and an amorphous matrix [49][50][51]55] . The calcite component may have trace amounts of magnesium, as detected by XRF and XES, though trace amounts of phosphorous, silicon, and iron were also detected, with the authors concluding the silicon and iron came from ground contamination [50] .…”

Section: Tuatara Egg Shellsmentioning

confidence: 99%

“…When laid, the fibrous organic membrane and calcite crystals are thoroughly intermixed throughout the ENTIRETY of the shell with variation in density of the two components. [49][50][51] At the exterior of the eggshell, the calcite crystals are more dense and of random shape, size, and orientation. [49][50][51] Moving toward the shell interior, shown in Figure 3D and 3E, the calcite forms rough columns that gradually becomes less dense as the organic matrix becomes more dense.…”

Section: Tuatara Egg Shellsmentioning

confidence: 99%

See 4 more Smart Citations

Disordered Structures in Biology Can Provide Material Properties not Obtained with Precise Hierarchy

Metzler

Barthelat

Wilker

2018

Adv Funct Materials

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Biological organisms exist in an astounding array of habitats. The materials produced by these organisms correspondingly exhibit significant diversity in function and form. Highly ordered and structured biological materials have been the subject of intense scientific investigation, especially in the context of exploring possible models for functional materials. Biological materials lacking in organized structure, on the other hand, such as barnacle exoskeletons, have largely been ignored. Here disordered biological materials falling into four different classes are discussed: soft and organic, hard and organic, soft and a composite of organic and inorganic, and

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Section: Tuatara Egg Shellsmentioning

confidence: 99%

Section: Tuatara Egg Shellsmentioning

confidence: 99%

Section: Tuatara Egg Shellsmentioning

confidence: 99%

Section: Tuatara Egg Shellsmentioning

confidence: 99%

Section: Tuatara Egg Shellsmentioning

confidence: 99%

See 3 more Smart Citations

Disordered Structures in Biology Can Provide Material Properties not Obtained with Precise Hierarchy

Metzler

Barthelat

Wilker

2018

Adv Funct Materials

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Structure, function, and evolution of the oviducts of squamate reptiles, with special reference to viviparity and placentation

Blackburn

1998

J. Exp. Zool.

169

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In lizards and snakes, the oviducts function in fertilization, sperm storage, egg transport, eggshell deposition, maintenance of the early embryo, and expulsion of the egg or fetus. In viviparous forms they also contribute to placentae responsible for gas exchange and nutrient provision to the fetus. Dissections of species of 30 genera coupled with data from the literature indicate that squamate oviducts vary interspecifically in seven macroscopic features, including the extent and nature of regional differentiation, vascular supply, topographic asymmetry, number of oviducts, vaginal pouches, and relationship to the cloaca. The uterus, infundibulum, and vagina differ histologically in their epithelia, glands, and myometrial layers. Seasonal cyclicity occurs in all three oviductal regions, most prominently in the uterus, and is under endocrinological control. Regional and cytological specializations reflect the diverse functions performed by the oviduct. Definitive evidence for oviductal albumen production and egg resorption is lacking. In viviparous squamates, three uterine specializations may facilitate maternal-fetal gas exchange: an attenuated epithelium, reduced uterine glands (and a reduced shell membrane), and increased vascularization. Contrary to previous reports, pregnant uteri show no epithelial erosion or capillary exposure. Specializations for nutrient provision to the fetus include mucosal hypertrophy, enlarged glandular epithelia, and multicellular glands whose secretions are absorbed by the chorioallantois. Comparisons with other amniotes indicate that squamates inherited the oviduct as an organ with capabilities for egg uptake and transport, fertilization, eggshell deposition, and oviposition. Other features have evolved convergently among squamates: infundibular sperm receptacles, unilateral oviduct loss, uterine gestation, placentation, and specializations for placentotrophy. Cladistic analysis indicates that oviductal features associated with deposition of tertiary egg investments in reptiles reflect evolutionary convergence as well as secondary simplification, rather than a unidirectional trend towards increased specialization.

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Morphological changes in the corpus luteum of tuatara (Sphenodon punctatus) during gravidity

Guillette

Cree

1997

J. Morphol.

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Tuatara (Sphenodon spp.) are rare reptiles, members of the reptilian order Sphenodontida, inhabiting small offshore islands of New Zealand. Females usually require about three years to yolk a clutch of eggs followed by an 8‐month period of in utero egg shelling. As in other vertebrates, the post‐ovulatory follicle forms a transitory endocrine structure, the corpus luteum. The tuatara Sphenodon punctatus exhibits a corpus luteum having several unusual morphological features as compared to turtles and squamate reptiles. Like the crocodilians, the tuatara has a corpus luteum in which the luteal cell mass never fills the central cavity and in which the thecal fibroblasts do not close the ovulation aperture. As in all oviparous reptiles examined, however, the corpus luteum appears to persist throughout gravidity based on its histological appearance. During gravidity, plasma progesterone concentrations are detectable, even though gravidity lasts an exceptionally long time (8 months) for an oviparous species. Luteolysis is initiated within two months following oviposition. The initial stages of luteolysis appear rapid, but luteal scar tissue is apparent in the ovaries of all adult females we examined and probably persists for many years post‐oviposition. J Morphol 232:79–91, 1997. © 1997 Wiley‐Liss, Inc.

show abstract

Eggshell formation during prolonged gravidity of the tuataraSphenodon punctatus

Cited by 13 publications

References 38 publications

Disordered Structures in Biology Can Provide Material Properties not Obtained with Precise Hierarchy

Disordered Structures in Biology Can Provide Material Properties not Obtained with Precise Hierarchy

Structure, function, and evolution of the oviducts of squamate reptiles, with special reference to viviparity and placentation

Morphological changes in the corpus luteum of tuatara (Sphenodon punctatus) during gravidity

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