pa4210844 live transparent freshwater triclad flatworms, girardia tigrina, on black, cecp 2023

2023 america animal aquatic backlit benthic black branches bright british brown cecp close closeup columbia creeks darkfield detail dugesiidae eyes eyespots fauna flat flatworm flatworms freshwater girardia gut invasive invertebrate isolated live macro midline natural nature north pa4210844 pharynx planaria planarian platyhelminthes predator red spings streams tigrina transparent triclad tricladida turbellaria uncommon unusual visible water white wild worm