Structure and permeability of the egg capsule of the placental Australian sharpnose shark, Rhizoprionodon taylori

Buddle, Alice L., Van Dyke, James U., Thompson, Michael B., Simpfendorfer, Colin A., Murphy, Christopher R., Day, Margot L., and Whittington, Camilla M. (2022) Structure and permeability of the egg capsule of the placental Australian sharpnose shark, Rhizoprionodon taylori. Journal of Comparative Physiology B: Biochemical Systemic and Environmental Physiology, 192. pp. 263-273.

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Shark placentae are derived from modifications to the fetal yolk sac and the maternal uterine mucosa. In almost all placental sharks, embryonic development occurs in an egg capsule that remains intact for the entire pregnancy, separating the fetal tissues from the maternal tissues at the placental interface. Here, we investigate the structure and permeability of the egg capsules that surround developing embryos of the placental Australian sharpnose shark (Rhizoprionodon taylori) during late pregnancy. The egg capsule is an acellular fibrous structure that is 0.42 ± 0.04 μm thick at the placental interface between the yolk sac and uterine tissues, and 0.67 ± 0.08 μm thick in the paraplacental regions. This is the thinnest egg capsule of any placental shark measured so far, which may increase the diffusion rate of respiratory gases, fetal wastes, water and nutrients between maternal and fetal tissues. Molecules smaller than or equal to ~ 1000 Da can diffuse through the egg capsule, but larger proteins (~ 3000–26,000 Da) cannot. Similar permeability characteristics between the egg capsule of R. taylori and other placental sharks suggest that molecular size is an important determinant of the molecules that can be exchanged between the mother and her embryos during pregnancy.

Item ID: 72465
Item Type: Article (Research - C1)
ISSN: 1432-136X
Keywords: Chondrichthyan, Pregnancy, Electron microscopy, Ussing chamber, Viviparity
Copyright Information: © The Author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit
Funders: Australian Research Council (ARC)
Projects and Grants: ARC DP1801103370
Date Deposited: 16 Feb 2022 07:47
FoR Codes: 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310404 Evolution of developmental systems @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310903 Animal developmental and reproductive biology @ 50%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180502 Assessment and management of pelagic marine ecosystems @ 100%
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