Between November 2022 and February 2023, Te Papa Natural History interns Tobia Dale and Ben Carson assisted with the curation of three major donations of New Zealand frogs and lizards. In this third blog about their work, Tobia describes her attempt to track down the first evidence of a deadly fungus in Aotearoa New Zealand.

How a sticky note led me down a rabbit hole

With Ben off on university fieldwork, I was tasked with sorting through microscope histology slides that were donated as part of the Phil Bishop acquisition. The tissue samples on the slides had been prepared by zoologist Bruce Waldman and his co-workers. I began with nearly 1,000 slides and several photocopied lab books full of cryptic notes and started trying to piece the puzzle together. What I thought would be an afternoon project turned into a 5-day mission, after finding an intriguing sticky note attached to one of the slides.

A deadly fungus

Many of the microscope slides were prepared as part of a study into the presence and distribution of chytrid fungus in New Zealand frogs. The name ‘chytrid fungus’ is used as shorthand for the pathogen Batrachochytrium dendrobatidis, which causes the disease chytridiomycosis. This disease has had a devastating impact on frog populations all around the world, including causing several species to become extinct.

Chytrid fungus was first detected in New Zealand in 1999 (by Bruce Waldman and his research students). The full impact of chytrid on New Zealand’s endemic frogs / pepeketua is not well understood, but it is thought to have driven the decline of Coromandel populations of the endangered Archey’s frog (Leiopelma archeyi).

Slow progress

My first hurdle was deciphering the etched codes on the bottom of the glass slides, which seemingly disappeared when the slides were lying flat. The next two hours were spent tracing over these etches in permanent marker. I then tried to match these codes to the corresponding notes in the lab books.

This was a lot harder than I’d anticipated, as multiple projects that used tissue from a single frog each had a different coding system. For example, the tissue from slide BW84 was from the same specimen as #E39 1 and 02LR19, KR 36, B40 and 35. Confusing!

My eureka moment

On day two I struck gold! One of the laboratory notebooks contained a sticky note stating “1st location of chytrid fungus in NZ”. This led me to a research paper by Bruce Waldman, published in the journal Surveillance, detailing the first case of the deadly chytrid fungus being found in New Zealand. The fungus was found on five sick southern bell frogs collected at Godley Head, Christchurch, in late 1999.

The article contained an image of a chytrid zoosporangium filled with disease-causing zoospores (a tiny bubble filled with little fungi spores in the top layer of skin).

My supervisor, vertebrate curator Colin Miskelly, challenged me to find the exact zoosporangium cluster that was illustrated in the article, by examining the microscope slides. We hoped that we could identify this historically significant slide, so that it could be kept track of, to allow future researchers to examine it.

Stymied by a needle in a haystack

With the challenge set, I started searching for this infamous slide. By the end of day three, I had managed to decipher the master codes, align what letter of the alphabet went with which year, and had narrowed the number of slides that I needed to view through the microscope down to 18.

Over the next 2 days, I learnt how to recognise evidence of chytrid fungus on the microscope slides, and confirmed several slides with chytrid from samples collected at Godley Head in late 1999.

However, after searching each slide carefully, I had to admit defeat. None of them appeared to match the published image. We don’t know if this is because the slide that was photographed is not among those acquired by Te Papa, or whether it is there but is unrecognisable.

This might be possible if the tissue section has deteriorated or become distorted over time, so that it no longer matches the photograph taken of it more than 20 years ago – or maybe I need to further develop my self-taught chytrid ID skills!

Related blogs

• Processing pickled pepeketua – how many frogs can you fit in a jar?
• Wanted dead or alive – Our Natural History interns’ work with Wellington lizards

Further reading

• Berger, L.; Speare, R.; Kent, A. 1999. Diagnosis of chytridiomycosis in amphibians by histologic examination. https://researchonline.jcu.edu.au/13062/
• Bishop, P.J.; Speare, R.; Poulter, R.; Butler, M.; Speare, B.J.; Hyatt, A.; Olsen, V.; Haigh, A. 2009. Elimination of the amphibian chytrid fungus Batrachochytrium dendrobatidis by Archey’s frog Leiopelma archeyi. Diseases of Aquatic Organisms 84: 9–15
• Waldman, B.; van de Wolfshaar, K.E.; Klena, J.D.; Andjic, V.; Bishop, P.J.; Norman, R.J.de B. 2001. Chytridiomycosis in New Zealand frogs. Surveillance 28: 9–11.