A citation and a certified copy of the third party petition shall be served on the third party defendant in the manner prescribed by Articles 1231 through 1293. Unless previously served on or filed by the third party defendant, certified copies of the following pleadings shall also be served on him in the same manner: the petition in the principal demand; the petition in the reconventional demand, if any; and the answers to the principal and reconventional demands filed prior to the issuance of citation in the third party action.