Embryo mortality in a captive-bred, Critically Endangered amphibian

Area of Science:

• Amphibian conservation biology
• Veterinary pathology
• Microbiology

Background:

• The critically endangered southern corroboree frog (Pseudophryne corroboree) relies on captive assurance colonies for survival.
• High embryonic mortality (40-90%) in captive breeding programs hinders conservation efforts.

Purpose of the Study:

• Investigate the causes of embryonic mortality in captive southern corroboree frogs.
• Determine the impact of infections and anatomical deformities on embryo survival.

Main Methods:

• Examined 108 abnormal embryos from Melbourne Zoo's 2021 breeding season.
• Utilized culture and molecular methods (Sanger sequencing of ITS region) for microbial identification.
• Assessed fungal growth patterns and presence of anatomical deformities.

Main Results:

• 100% of abnormal embryos exhibited fungal infections.
• 41.6% of infected embryos also had anatomical deformities.
• Identified fungal genera Ilyonectria (new vertebrate host record) and Plectosphaerella (new embryo infection record).
• Dominant bacteria genera: Herbaspirillum and Flavobacterium (role in mortality unknown).
• No significant difference in survival based on fungal growth patterns or deformities.

Conclusions:

• Fungal infections and deformities significantly impact captive southern corroboree frog embryo survival.
• Understanding and mitigating embryonic mortality is vital for successful conservation breeding and reintroduction.