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by: Ilya Vasey

Mathematics Major at Skyline College

Mentor: Susanne Schubert

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Identification of Parasitic Protozoa in a Bay Area Leopard Shark

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Leopard Sharks

  • Triakis semifasciata
  • Feed on worms, clams, and small species of fish
  • Pupping season and die-offs both happen in the Spring Months

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Miamiensis avidus

  • Parasitic Protozoa(Jung, 2007, p.73)
  • Linked to leopard shark die-off events(Okihiro, 2019, 55)
  • Enter through the nares and infect sensory organs and brain

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Background

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Objective

  • To conduct a necropsy on a leopard shark stranded in SF Bay.
  • To discern the presence of Miamiensis avidus in tissue samples of the olfactory organs.

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Image Courtesy of Mark Okihiro

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Methodology

  • Measurements
  • Cleaning and sanitizing shark
  • External Exam for trauma and parasites
  • Dissection of the head
  • A peek at the GI tract
  • Sampling of tissue observation under microscope: wet mount cytology

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Specimen’s Location of Stranding

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Specimen Details

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External Analysis Summary

No Signs of Trauma

No External Parasites

Date of Necropsy: 4.26.2023

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Specimen Sex and Details

  • Mass: 7.5 kg
  • Total Length: 95.5 cm
  • Sex: Male

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My Specimen

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Dissection of the Head

Olfactory Bulb (R)

Cerebrum

Location of Olfactory Lamellae

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Observations under a Microscope

Image Courtesy of Mark Okihiro

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Observations under a Microscope

Image Courtesy of Mark Okihiro

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Results and Analysis

  • Larger cell anomalies in tissue samples resemble protozoa structures
  • No other apparent cause of death.
  • Location and timing of stranding coincides with die-off event

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Possible Protozoan

Image Courtesy of Mark Okihrio

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Further Research and Investigation

  • M. Avidus is a future candidate for die-off culpability of marine species
  • Effects of ingestion by humans is unknown
  • The next step in my research is to locate a specimen and conduct a PCR test on tissues from olfactory organs and the brain.

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Acknowledgements

This research was made possible with the mentorship and motivation from Professor Susanne Schubert, who assured me that research is open to anyone.

Ben Mingoa previously researched leopard sharks at Skyline College and provided me with great data on die-off events.

Scout Kessler brought my tissue samples into excellent focus under a microscope. The microscopic images in this presentation are thanks to her.

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References

  1. Retallack, H., Okihiro, M. S., Britton, E., Sommeran, S. V., & DeRisi, J. L. (2019). Metagenomic next-generation sequencing reveals Miamiensis Avidus (Ciliophora: Scuticociliatida) in the 2017 epizootic of leopard sharks (triakis semifasciata) in San Francisco Bay, California, USA. Journal of Wildlife Diseases, 55(2), 375. https://doi.org/10.7589/2018-04-097
  2. Rauch, K. D. (2023, February 16). Leopard Sharks and bat rays are dying in Berkeley’s Aquatic Park. Berkeleyside. https://www.berkeleyside.org/2023/02/14/leopard-sharks-bat-rays-dying-aquatic-park-berkeley
  3. Jung, S.-J., Kitamura, S.-I., Song, J.-Y., & Oh, M.-J. (2007). Miamiensis Avidus (Ciliophora: Scuticociliatida) causes systemic infection of olive flounder paralichthys olivaceus and is a senior synonym of philasterides dicentrarchi. Diseases of Aquatic Organisms, 73, 227–234. https://doi.org/10.3354/dao073227

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