A histological study of digestive tubules in intertidal and subtidal oysters, Crassostrea virginica, collected at high and low tides

Digestive tubules from intertidal and subtidal oysters, Crassostrea virginica, were histologically examined to gain a better understanding of their normal morphology during high and low tides and while being held out of water for up to 72 h. Intertidal and subtidal oysters from Bayou Texar, Pensacola, Florida, were collected from adjacent sites and processed for histological examination. A digestive tubule ratio for each oyster was determined by measuring the inside to outside tubule thickness from 20 tubules per animal. Digestive tubules with high tubule ratios (approaching 1.0) had low cuboidal epithelia, whereas tubules with low ratios (approaching 0.0) had columnar epithelia. In tidal studies, intertidal oysters sampled 13-15 h after emersion at low tides had no crystalline styles and high tubule ratios, whereas subtidal oysters collected at the same time exhibited crystalline styles and low tubule ratios. Intertidal oysters sampled 6-14 h after submersion at high tides had crystalline styles present and low tubule ratios, whereas subtidal oysters also possessed crystalline styles and low tubule ratios. These data indicate that intertidal C. virginica respond to tidal cycles with changes in tubule morphology, whereas subtidal oysters do not. In holding experiments, digestive tubule ratios in intertidal and most subtidal oysters held out of water did not significantly change over time, which may be a consequence of collection stress (quiescence and/or anaerobic metabolism).