Phrixocephalus cincinnatus begin their life as free-swimming larvae (called a nauplii) (1). After developing to their next larval stage (copepodids), they seek an unknown intermediate fish or invertebrate host, where they mate (2). The mated females then seek the eye of a flatfish host. They enter the eye and elongate to produce an elaborate “holdfast” organ (1, 2). This organ consists of intertwined rootlets that embed into the host eye, causing a large area of blood and necrotic host cells to accumulate around the organ (2). The holdfast both anchors the parasite to the host eye and allows the parasite to ingest host blood and body fluids (1). The parasite then extends its egg sacs back through the cornea (1). The damage caused to the eye can cause the host to go blind, especially in heavy infections where both eyes are affected (1).
Phrixocephalus cincinnatus is found off the west coast of North America (2). It is known to infect at least 8 host species as its final host [Atherestes stomias (arrowtooth flounder), C. sordidus, C. xanthostigma (longfin sanddab), Hippoglossus stenolepis (Pacific halibut), Lepidogobius lepidus (bay goby), Parophrys vetulus (English sole), Pleuronichthys decurrens (curlfin sole), and Zalembius rosaceus (pink seaperch)] (1).
1. https://digitalcommons.unl.edu/parasitologyfacpubs/458
2. 10.2307/3283261
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Dr. Chenhua Li (Lead, Ideas), Dr. Þórey Jónsdóttir (Illustrator, Ideas), Stephen Pollo (Writer, Researcher), Yuanzhe Wang (Digital Consultant).