bend boat colorful colourful connection cord cords gordian hold knot knots maritime node plaited rope ropes strength strong tight twisted alliance bond bowline bowline knot fastener fastening fixation fusion security stable adult alien alpine alps aquaticus Austria biology environment europe Gordiacea Gordius hairworm horsehair host hydrostatic long Nematoida nematomorph Nematomorpha parasite parasitic pressure primitive Saitenwurm sceleton science slim strange string thin under violin Vitulus aquaticus Wasserkalb water worm