Foregut structures of freshly moulted exuviae from Maja crispata,Cancer pagurus and Pseudosesarma moeschi (Decapoda: Brachyura)

Periodic moulting is vital for the growth of crustaceans. The process is characterized by a complete replacement of the mineralized exoskeleton, including eyestalks, legs, the pleon as well as the foregut and hindgut. In the present study a series of freshly moulted brachyuran exuviae Maja crispata Risso, 1827; Cancer pagurus Linnaeus, 1758 and Pseudosesarma moeschi (De Man, 1888)] were investigated concerning the remaining calcified foregut structures. All investigated exuviae show part or complete degradation of the lateral expanded ossicles of the gastric mill (e.g. ossicles II, V and IX). Most of the ossicles of the pyloric filter are unaffected by the degradation processes. Reduction of the calcium content and the increasing flexibility of the foregut ossicles enable the passage of the bigger “old” foregut through the smaller oesophagus of the newly formed foregut. The gastric teeth of the examined exuviae are not influenced by the moulting process.