Perkinsus marinus
Raghavendra Yadavalli,1
Kousuke Umeda,1,2
and José A. Fernández Robledo1,
*
1
Bigelow Laboratory for Ocean Sciences, Boothbay, ME, USA
2
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Filter
feeding
Some parasite
rejected
in pseudofeces
Parasite
released in feces
Rectum
Gills
Crassostrea virginica
Decaying oyster
Disease
progressing
Perkinsus
marinus
trophozoite
er
Extracellular palintomy
Host recognition and entry
Epithelium (e.g., gill, mantle)
Circulating
hemocyte
Hemocytes
transepithelial
migration
Hemocyte rupture
and parasite release
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Perkinsus marinus is a facultative intracellular marine protozoan parasite responsible for the Dermo disease in
Crassostrea virginica oysters. Associated with mass mortalities in the Gulf Coast and Chesapeake Bay (USA),
it remains one of the main hurdles for oyster reef restoration and aquaculture. Oysters take up the parasite by
filter-feeding; in the pallial cavity it can be phagocytosed by the hemocytes via CvGal1, gaining access to the
internal milieu. Inside the parasitophorous vacuole, the parasite resists oxidative stress and acquires nutrients.
Propagation strategies include binary fission, budding, palintomy, and schizogony. Although the effect on
humans upon consumption of raw infected oysters has not been studied, humanized HLA-DR4 mice fed with
P. marinus do not develop noticeable pathology but elicit systemic immunity. Parasite culture in host-free
media, and the use of genetic tools, make it a tractable genetic model and a heterologous expression and
vaccine-delivery system.
Surface moeity Crassostrea virginica
Galectin 1 (CvGal1)
Secret
Pallial cavity
Internal milieu
Promote
Involvement of CvGal1 and CvSI-1 in parasitemia
SP nhibitor (CvSI-1)
secreted in digestive gland
Serine rotease
PmSP
PmSP and CvSI-1 omplexParasite engulfment
(Infected hemocyte)
Circulating hemocyte
Perkinsus marinus
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KEY FACTS:
P. marinus is phylogenetically close to
dinoflagellates and apicomplexans.
Two genomes in the nucleus (86 Mb
encoding N23 600 proteins) and
mitochondrion, using mRNA trans-splicing
with a conserved 21–22 nt spliced leader.
With a direct life cycle, trophozoites are
released into the water with pseudofeces
and feces, or from decaying oysters.
It remains controversial whether
P. marinus produces zoospores as do
other Perkinsus spp.
Continuous culture in the absence of host
cells and transfection methodology
enable the study of physiology, cell biology,
and host–parasite interactions.
It offers a heterologous expression system
for human pathogen genes (e.g.,
Plasmodium falciparum, Toxoplasma gondii,
Cryptosporidium parvum, and Ebola virus).
DISEASE FACTS:
P. marinus infection is one of the World
Organization of Animal Health (OIE)-listed
diseases.
Once described in the Gulf of México, it is
now found in both North and South America.
High water temperature is the main
environmental clue associated with oyster
mass mortalities.
A protease inhibitor (CvSI-1) isolated from
the plasma of eastern oysters inhibits the
parasite's proliferation in vitro and
appears to be involved in the resistance
to Dermo disease.
With numerous chemical inhibitors of
in vitro propagation, treatment of
diseased oysters in the natural
environment remains unrealistic.
TAXONOMY AND CLASSIFICATION:
PHYLUM: Perkinsozoa
CLASS: Perkinsea
ORDER: Perkinsida
FAMILY: Perkinsidae
GENUS: Perkinsus
SPECIES: P. marinus
*Correspondence:
jfernandez-robledo@bigelow.org
(J.A. Fernández Robledo).
Trends in Parasitology, December 2020, Vol. 36, No. 12 © 2020 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.pt.2020.05.002 1013
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Acknowledgments
National Science Foundation (NSF) 1701480 (J.A.F.R.), National Oceanic and Atmospheric Administration (NOAA) NA15NMF4270303 (J.A.F.R.), and JSPS KAKENHI – Grant-in-Aid
for JSPS Fellows 19J00148 (K.U.).
Resources
www.dfo-mpo.gc.ca/science/aah-saa/diseases-maladies/pmdoy-eng.html
www.ncbi.nlm.nih.gov/genome/280
www.atcc.org
www.protocols.io
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1014 Trends in Parasitology, December 2020, Vol. 36, No. 12 © 2020 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.pt.2020.05.002
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