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Fig. 2 | BMC Zoology

Fig. 2

From: Morphological and histological description of the midgut caeca in true crabs (Malacostraca: Decapoda: Brachyura): origin, development and potential role

Fig. 2

Maja brachydactyla. Larval stages (zoea I, zoea II, and megalopa). Tissue organization of the midgut caeca. General diagram of the larval midgut caeca (A). Anterior midgut caeca (B–C): zoea II 6 days post-hatching, PAS-Alcian Blue contrasted with Haematoxylin, longitudinal cross section (B); and megalopa 6 days post-hatching, Mallory’s Trichrome, transversal cross section (C). Transition between the posterior midgut caecum and the midgut tract, Haematoxylin-Eosin, longitudinal cross section of the specimen (D–E): megalopa 6 days post–hatching (D), and newly hatched zoea I (E). Posterior midgut caecum, zoea II 6 post-hatching old, Mallory’s Trichrome, transversal cross section of the specimen (F). Anterior midgut caeca, megalopa 10 days post-hatching, TEM (G–H): general view (G), and detail of the myofibrils-like filaments (H). Posterior midgut caeca, megalopa 10 days post-hatching, TEM (I–J): general view (I), and detail of the myofibrils-like filaments (J). Scale bars (nm): 500 (H, J); (μm): 2 (I), 5 (G), 20 (B–F). Abbreviations: AC, anterior midgut caecum; arrow, midgut- hindgut junction; asterisk, midgut-stomach junction; BF, basal folds; BL, basal lamina; CE, midgut caeca epithelium; CT, connective tissue; HE, hindgut tract epithelium; ME, midgut tract epithelium; MF, muscle fibres; MGG, midgut gland; Mt, mitochondria; Mv, microvilli; My, myofibrils-like filaments; RER, rough endoplasmic reticulum; SE, stomach epithelium; PC, posterior midgut caecum

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