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Diseases of Aquatic Organisms

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DAO 152:73-83 (2022)  -  DOI:

Embryo mortality in a captive-bred, Critically Endangered amphibian

M. J. Davidson1,*, R. Bushell1, R. Ploeg1, M. Marenda1, C. Halliday2, D. Goodall3, D. Gilbert3, T. A. Kosch1, L. F. Skerratt1, L. Berger1

1Faculty of Veterinary and Agricultural Science, University of Melbourne, Werribee, Victoria 3030, Australia
2Centre for Infectious Diseases and Microbiology Laboratory Services, NSW Health Pathology—Institute of Clinical Pathology and Medical Research, Westmead, New South Wales 2145, Australia
3Wildlife Conservation and Science, Zoos Victoria, Parkville, Victoria 3052, Australia
*Corresponding author:

ABSTRACT: The Critically Endangered southern corroboree frog Pseudophryne corroboree is dependent upon captive assurance colonies for its continued survival. Although the captive breeding programme for this species has largely been successful, embryonic mortality remains high (40-90% per year). This study aimed to investigate the causes of mortality in P. corroboree embryos in the captive collection at Melbourne Zoo. During the 2021 breeding season, we investigated 108 abnormal embryos to determine the impact of infections and anatomical deformities on survival and used culture and molecular methods to identify microbes. Overall, 100% of abnormal embryos had fungal infections, and of these, 41.6% also had anatomical deformities. The mortality rate in abnormal embryos was 89.8%; however, we detected no difference in survival in any of the 3 observed fungal growth patterns or between deformed and non-deformed embryos. Sanger sequencing of the ITS region identified fungal isolates belonging to the genus Ilyonectria, the first record in a vertebrate host, and another as a Plectosphaerella sp., which is the first record of infection in an embryo. Dominant bacteria identified were of the genera Herbaspirillum and Flavobacterium; however, their role in the mortality is unknown. Fungal infection and deformities have a significant impact on embryo survival in captive-bred P. corroboree. In a species which relies on captive breeding, identifying and reducing the impacts of embryonic mortality can inform conservation efforts and improve reintroduction outcomes.

KEY WORDS: Southern Corroboree frog · Pseudophryne corroboree · Fungi · Infection · Deformities · Assurance colony

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Cite this article as: Davidson MJ, Bushell R, Ploeg R, Marenda M and others (2022) Embryo mortality in a captive-bred, Critically Endangered amphibian. Dis Aquat Org 152:73-83.

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