Stuck on you!

Lynne Tuck (@scubalynne) recently made a very cool observation. She watched a flatworm slide over a Bigbelly Seahorse. When she first noticed the flatworm it was on the seahorse's 'shoulder'. While she watched it moved across the seahorse's head, at one stage covering both of its eyes, then along the snout and finally onto the belly. The seahorse tried to dislodge the flatworm a number of times. To view photos of the flatfish's journey, click on the left image above.

Spotting this interaction was pretty cool, but I'm super impressed that Lynne was able to take photos and video of the action. You can watch the video on the Australasian Fishes Project YouTube channel.

I asked flatworm expert Jorge Rodriguez if it was possible to identify the flatworm. He stated, "The flatworm in this picture is most likely Thysanozoon brocchii. It was probably crawling on the rocks and continued moving on top of the seahorse as if it were part of the substrate. You can discover more about this species in the paper (pages 50 to 51 and plate 21) I published last year about southeastern Australian marine flatworms: https://drive.google.com/file/d/1AFiy9JeZlZIOVI68dmrHTyilgGsFCDgT/view?usp=sharing"

This isn't the first observation that shows a fish being 'slid over' by another organism. The following three observations show nudibranchs on fishes.
https://www.inaturalist.org/observations/62871126
https://www.inaturalist.org/observations/94036335
https://www.inaturalist.org/observations/14626334

The two observations below show a seahorse and scorpionfish with invertebrate eggs attached to them - evidence of previous 'visitations'.
https://www.inaturalist.org/observations/73089275
https://www.inaturalist.org/observations/14436670

And just to turn the tables, here is a small fish on a nudibranch.
https://www.inaturalist.org/observations/17092421