Screen for the presence of Paramarteilia in Echinogammarus marinus after feeding or injection by Paramarteilia only infected, Paramarteilia - Dictyocoela duebenum co-infected or uninfected E. marinus tissue. Ld – DNA ladder, NTC – No Template Control, +Cont – Paramarteilia positive control sample. Controls = Cf - Control fed with infected tissue (n = 7), Ci - Control injected with uninfected tissue (n = 4). Paramarteilia only = Pf - Fed with tissue infected by Paramarteilia only (n = 7), Pi – Injected with tissue infected by Paramarteilia only (n = 4). Co-infected by D. duebenum and Paramartielia = Cof - Co-infection fed (n = 11). Coi1-Coi5 – Represents co-infection injected individuals. Brood (Coi2) - Brood harvested from an ovigerous female (Coi2) four months after injection by co-infected tissue.