Observation of the Week, 7/27/16

This parasitic Isopod seen by @oryzias outside of Hong Kong is our Observation of the Week!

Like many of us, Hung-Tsun Cheng became infatuated with animals and nature after learning about dinosaurs. As a child, his father took him on weekend hikes “if I finished my homework,” bringing along a net to look for fish in the streams. He was especially fascinated by fish that had developed sucker-like fins on their bellies that allowed them to stay put in fast-flowing streams.

While recently moving some Sumatran silverside fish (Hypoatherina valenciennei) from a drying-out tidepool, Hung-Tsun noticed one that was unhealthy. And on closer inspection, he found a parasitic isopod attached to it!

While it’s tough to ID, this isopod most likely belongs to the Cymothoidae family of isopods, which are parasitic, mainly on fish, and found in both marine and freshwater environments. There are about 380 described species in the family, and they feed on blood. Interestingly, these isopods are protandrous hermaphrodites, meaning they are all males when they are juveniles, but become female when they attach to their species-specific host. Perhaps the most well-known member of this family is Cymothoa exigua, which feeds on the tongues of snapper fish. Eventually, the fish’s tongue withers and dies, but the fish will actually use the isopod as a prosthetic tongue! The isopod presumably stays in there as it is a safe place for its young to develop.

The Hong Kong area has quite a thriving iNaturalist community, with over 15,000 observations of 2,999 (so close to 3,000!) species made by 257 observers. @sunnetchan has over 4,000 of those observations and has written a passionate journal entry about documenting every living thing he can. @hkmoths has started a Hong Kong Moths project to document moth species and abundance. Keep up the awesome work, Hong Kong iNatters!

- by Tony Iwane

- A nice write-up in Wired about Cymothoa exigua, and some videos showing them. Not for the squeamish!

- It’s National Moth Week! Roger Kendrick (@hkmoths) has a nice article about moths and citizen science on their website. Get out and find some moths!

Posted by tiwane tiwane, July 27, 2016 05:10


Thank you Tony (@tiwane). I also want to thank the people who bring us iNaturalist, which has opened my mind.

Not only I learn so much from the database, it also give us a new better purpose in life.
To be honest, my observations are nothing but legwork and cut a paste. With the power of the iNat, I really hope that my observation can attract more true experts and naturalists can join force to complete the citizens' database for the Flora and fauna of Hong Kong one day. :-)

Posted by sunnetchan over 4 years ago (Flag)

Thank you for the kind words, @sunnetchan, and thank your for your great contributions to iNat!

Posted by tiwane over 4 years ago (Flag)

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