Diagnostic features
Multiple filaments within a common sheath, forming "branching" tufts. Filaments are falsely branched, initiated at heterocytes. Heterocytes usually ellipsoidal rather than spherical, and may be absent. Filaments do not taper. Terminal cells hemispherical to almost spherical. Blue or blue-green in colour.
![[Coleodesmium], Kakanui River, X9. Photo: Otago Regional Council & Manaaki Whenua Image](/assets/Tools-And-Resources/Identification/algae/coleodesmium3__ScaleWidthWzEwMjRd.jpg)
![[Coleodesmium], Kakanui River, X640. Photo: Otago Regional Council & Manaaki Whenua Image](/assets/Tools-And-Resources/Identification/algae/coleodesmiumb__ScaleWidthWzEwMjRd.jpg)