• Sacculina called s Root headed barnacle.

• It is a parasite in crab.

• Body is indistinct.

• Sacculina is a fleshy lobe fixed to the abdomen of the crab by peduncle.

• There is a cloacal aperture or genital aperture at its posterior end.

• Appendages and alimentary canal are absent.

• Gonads and nerve ganglion are located inside the mantle.

• The peduncle gives off numerous roots like process which are distributed throughout the body of the crab.