Abstract
We provide an alternative interpretation for the “whitish film” that covered the young white shark observed with an aerial drone in a paper published recently (Gauna and Sternes, Environ Biol Fish 107:249–254, 2024). The paper claimed that this whitish film was a leftover intrauterine substance (e.g., uterine milk, which is a maternal secretion to nourish embryos), thus suggesting that the individual was a newborn. However, we are skeptical of this interpretation for the following reasons: (1) our previous studies showed that the secretion of intrauterine substances in white sharks ceases in mid-gestation and, (2) even if the secretion continues until birth, the substance is unlikely to be retained on the skin for a long time after birth. Based on data from Lamna ditropis, a close relative of the white shark, we hypothesize that the whitish film is an embryonic epithelium that covers the surface of skin denticles. This reinterpretation does not alter but reinforces the major conclusion of (Gauna and Sternes, Environ Biol Fish 107:249–254, 2024) that the individual sighted is a newborn.
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Data is available upon request.
References
Gauna C, Sternes PC (2024) Novel aerial observations of a possible newborn white shark (Carcharodon carcharias) in Southern California. Environ Biol Fish 107:249–254
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Acknowledgements
We thank the following for providing access to the salmon shark specimen at the Kesennuma Fish Market: the Kesennuma Fishery Cooperative and Yoji Niinuma and other staff at the Kesennuma Shark Museum. We also thank Ryo Nozu (Hiroshima University) for helping to collect the salmon shark specimens. This study was supported by JSPS KAKENHI (grant number 17K18451).
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TT, KeM, MN, KiM, MT, and KS conducted the necropsy of pregnant white shark specimens. TT and KeM performed the necropsy of a pregnant salmon shark specimen. MN conducted a histological analysis of the embryonic skin of salmon sharks. TT wrote the manuscript. TT, KeM, MN, KiM, MT, and KS reviewed and edited the manuscript.
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Dr. Keiichi Sato is on the Editorial Board of this journal, but he had no involvement in the peer review of this article and had no access to information regarding its peer review.
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Tomita, T., Miyamoto, K., Nakamura, M. et al. Whitish film covering a newborn white shark was not intrauterine material but embryonic epithelium. Environ Biol Fish 107, 719–722 (2024). https://doi.org/10.1007/s10641-024-01560-z
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DOI: https://doi.org/10.1007/s10641-024-01560-z
