Try adding the option SaveDefinitions -> True to Manipulate, so that all the definitions of Shroud and Spikes are embedded into the output cell.

I think that a single ParametricPlot3D cannot mix surfaces and lines. You can do it with two separate plots combined with Show:

M3 = Manipulate[
  Show[ParametricPlot3D[{Shroud}, {\[Theta], -\[Pi]/2, \[Pi]/
      2}, {\[Lambda], 0, \[Pi]/2}, 
    PlotStyle -> {{Blue, Opacity[opacity]}, {Blue, Thick}}, 
    PlotRange -> All, ViewPoint -> {3, 4, 2.5}, Axes -> True, 
    Boxed -> False, FaceGrids -> None, AxesOrigin -> {0, 0, 0}, 
    AxesLabel -> {None, None, None}, ViewPoint -> {10, 5, 10}],
   ParametricPlot3D[{Spikes}, {\[Lambda], 0, \[Pi]/2}, 
    PlotStyle -> {{Blue, Thick}, {Blue, Opacity[opacity]}}, 
    PlotRange -> All, ViewPoint -> {3, 4, 2.5}, Axes -> True, 
    Boxed -> False, FaceGrids -> None, AxesOrigin -> {0, 0, 0}, 
    AxesLabel -> {None, None, None}, 
    ViewPoint -> {10, 5, 10}]], {opacity, .3, 1}]