A "Dancing" Marine Flatworm off of Hong Kong - Observation of the Week, 4/5/22

Our Observation of the Week is this Pseudobiceros bedfordi flatworm, seen in Hong Kong by @josylai!

A scuba instructor living in Hong Kong, Josy Lai tells me that early in her career she focused on teaching skills and general marine knowledge, 

but then, there had always been times that we saw mysterious marine organisms and I didn’t quite know what they were. Having no background in biology or ecology, I have spent time reading marine guides and browsing the internet. The more I study, the more I am amazed by nature; the more I learn, the more I realize that I don’t understand much and would love to know more.

One of the amazing creatures she recently encountered was the flatworm documented in the observation of the week, which Josy saw when she was exploring a remote dive site off of Hong Kong island.

In general, underwater visibility in Hong Kong varies from 0.5 meters to 5 meters. During that dive, visibility was surprisingly good and visibility hit up to 10 meters. Remotely, I saw something “floating” in mid-water. At one point I thought that was a broken piece of plastic bag, and wanted to grab it. When I swam closer, I noticed immediately that it was a beautiful Pseudobiceros bedfordi “dancing in the air”! I spent five minutes watching its beautiful movement and almost forgot to photograph it. I was lucky enough to take a few pictures of this gorgeous marine flatworm until it finally landed on a rock.

Known colloquially as the Persian carpet flatworm or Bedford’s flatworm, Pseudobiceros bedfordi’s dorsal side is intricately patterned with both large stripes and many, many tiny spots. Ranging from the Maldives to Fiji, these 8-10cm long worms feed on tunicates and crustaceans and, yes, undulate beautifully when they swim. 

When it comes to reproduction, these hermaphroditic invertebrates engage in behavior known as “penis fencing,” as do many other flatworms. Generally, each individual tries to use one of its two penises to stab and inseminate the other without in turn getting inseminated. The inseminated individual usually takes on a greater physiological burden, which we believe is why they try to avoid being inseminated. However, in some species both individuals often inseminate each other. 

“As I spend most of my time scuba diving now,” says Josy (above, with a sea fan), “my current nature interest is marine animals. I also conduct marine conservation workshops in Hong Kong, and organize underwater and beach clean-ups on a regular basis.”

She joined iNat just over a year ago and tells me it’s

an important platform for me to learn more about marine life. Biologists and citizen scientists have helped me a lot in suggesting IDs of the animals I see. From iNaturalist, I learn about what other divers in the Indo-Pacific region have observed; I learn about the characteristics and sometimes habitats of the animals. When I dive now, I have a clearer idea of what to look for in a certain environment and I look more into details. I enjoy sharing my observations on the platform, and just can’t wait to receive responses or ID suggestions from other users after uploading a new observation. 

I like the way that iNaturalist has created an active community for professionals and citizen scientists to exchange ideas and knowledge. I am so glad to be part of your community.

(Some quotes have been lightly edited for clarity.)

- You can follow Josy on Facebook and Instagram.

- And you can check out her diving videos and watch her sing on her YouTube channel!

- David Attenborough and the BBC show us these worms in action.

- See the diversity and beauty of iNat’s flatworm observations!

Posted on April 5, 2022 09:09 PM by tiwane