Frontiers in Marine Science (Dec 2015)
Ontogenetic stomach development in catshark Scyliorhinus canicula.
Abstract
The gastrointestinal tract (GIT) of vertebrates develops from a simple undifferentiated tube into highly differentiated regions for the digestion and absorption of nutrients. Each region has a different histological structure and gene expression profile that enables the performance of their different functions. The stomach is the most highly derived GIT region and gastric glands are responsible for the secretion of HCl and pepsinogen that enables acid-peptic digestion, representing a functional innovation found exclusively in jawed vertebrates. The mechanisms of GIT organ specification are well studied in some vertebrates including mouse, Xenopus, chicken and some teleost fishes. General embryonic development has been studied in chondrichthyans but not GIT development. In this study we characterize the development of the stomach in the catshark Scyliorhinus canicula, an elasmobranch with a ~5 month development spanning 34 developmental stages. As a representative of basal jawed vertebrate for which genomic information is currently available, the catshark is a suitable model system to characterize the ancient expression and function developmental of physiologically relevant genes. Therefore, during this study we used embryos from a brood stock held in our fish facility to conduct gene expression, protein detection and histological analyses. Our aim was to characterize, at molecular and morphological levels, stomach development and the differentiation of its characteristic secreting glands. The differentiation of the stomach starts around stage 24. However, immunohistochemistry for the gastric proton pump indicates a delayed development of gastric gland that are only visible before hatching at stage 33-34. Supported by NSERC to JMW
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