About 5mm in length, quite a direct and agile mover. It had a round transleceunt head. I could make out what looked like a notochord, it looked a lot like a fossil Pikaia!
No interactions present.
It will not have been a notochord, which is the precursor of the vertebral column and is found in vertebrates and lower chordates only. Perhaps you saw the line of the gut.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
Sorry, I didn't make myself clear. I know what a notochord is, I was just using it for descriptive purposes hence the ref to a pikaia. This is the first time I've ever studied invertebrates. Just wanted to give as much detail as possible to help the identification.
Lat/Lng: 51.4413, -2.5946
OS grid ref: ST587715
Fast flowing, rocky, shallow river (the Malago) about 1 foot deep.