Ontogeny of the post-gastric tract of the spider crab Maja brachydactyla (Brachyura): morphology and ultrastructure

The Crustacean Society (TCS) Mid-Year Meeting, 9-22 June 2017, BarcelonaThe post-gastric tract of brachyurans includes the midgut tract, the associated caeca (a pair of anterior caeca and a single posterior caecum), and the hindgut tract. These organs were studied in all the larval (zoea I, zoea II and megalopa), first juvenile and adult stages of the spider crab Maja brachydactyla Balss, 1922 employing stereo, light, and electron microscopy techniques. The midgut tract is a short tube that enlarges proportionally with the body length during the development. It is lined by a simple columnar and microvillous epithelium involved in the synthesis of the peritrophic membrane from hatching. The subjacent connective tissue contains inner bands of circular muscles and outer bands of longitudinal muscles. The larval midgut caeca are small buds that enlarges during the development to reach the enlarged and coiled blind end tubules in adults. The caeca are lined by a simple columnar and microvillous epithelium with an important apocrine secretory activity: big vesicles released from the cell apex and tiny vesicles released from the microvilli. The hindgut tract is a large tube with five internal longitudinal folds, the epithelium changes from squamous in larvae to columnar in adults; it is lined by a cuticle. The hindgut cuticle is rich in microspines distributed in bands along the longitudinal folds. In the subjacent connective abundant rosette glands, inner bands of longitudinal muscles and outer bands of circular muscles are presentPeer Reviewe