Histochemistry of goblet cells and micro-computed tomography to study the digestive system in the long-snouted seahorse Hippocampus guttulatus

Sygnathids are agastric teleosts (no stomach), relying on a digestive tract using different mechanisms to process and absorb nutrients. This results in a low digestion efficiency at early stages, forming a mayor bottleneck in the rearing of these fish. In agastric species, the numerous goblet cells present in the oesophagus could be considered as a morphological adaptation that replaces a functional stomach, although the specialization and number of these cells is species-specific and vary throughout the development and intestinal region. The present study aim to characterize the biochemical composition of goblet cells and investigate the morphology of the digestive system during the ontogeny of Hippocampus guttulatus seahorses (from 0 to 60 days post-partum, dpp) in order to understand the mechanisms of nutrient digestion in a species that lacks gastric glands.