Morphology and Histology of the Digestive System of Japanese Mantis Shrimp (Oratosquilla oratoria)

This study investigated the characteristics of the digestive system in adult Japanese mantis shrimp (Oratosquilla oratoria), which is a species of carnivorous crustacean, with a focus on morphological and histological analysis. The digestive system of O. oratoria includes the mouthparts, the esophagus, cardiac stomach, pyloric stomach, midgut, hindgut, anus and hepatopancreas. The histological structure of each organ is composed of the mucosal epithelial layer, submucous layer, muscularis, and outer membrane. Besides, the foregut is covered with a diverse chitinous layer. The labrum is densely populated with minor salivary glands. The mandibular-gastric mill apparatus and evenly arranged bifurcated setae are observed in the cardiac stomach. The secondary filter of the pyloric stomach is subtly intricate, with fine spicules and seta plate. The midgut, being the longest segment of the digestive tract and accounting for 59.39% of body length, has villi covered with dense microvilli. The hindgut also forms villi, but the height of the villi (695.96 μm) is 3.20 times that of the midgut (217.41 μm). The hepatopancreas encircles the entire pyloric stomach, midgut, and hindgut. The hepatosomatic index is approximately 3.83%.