Morphological adaptations of digestive tract according to food and feeding habits of the lizardfish, Synodus variegatus, inhabiting Red Sea waters, Hurghada, Egypt

This study is concerned with the morphological adaptations of the digestive tract with respect to food and feeding habits of lizardfish Synodus variegatus. 75 fish specimens were seasonally collected from Hurghada, the Red Sea, Egypt. Results showed that the greatest value of feeding activity of S. variegatus was recorded in summer (82.26%) and the lowest value (24.14%) occurred in winter. While in autumn and spring, the feeding activity was moderate, with 44.50% and 47.26%, respectively. This species was proved to be a piscivorous and crepuscular feed, consuming a large variety of small fishes. Atherinomorus lacunosus, Herklotsichthys quadrimaculatus, Cephalopholis hemistiktos, Lethrinus mahsena, Parupeneus forsskali and Siganus rivulatus formed the major food items consumed.  S. variegatus has a reptile-like head to facilitate capturing the prey. Jaw's teeth are canine and slightly curved towards the inner part of the mouth. Buccal teeth are canine shaped and arranged in a line on vomerine and palatine in addition to five rows on ectopterygoid of both sides in the roof of the buccal cavity. They specialized in capturing and holding the prey and preventing its escape from the mouth cavity. The pharyngeal teeth are placed in rows and bent in shape. They are specialized in food cutting and masticating. Gill arch is V-shaped; it may be attributed to help in swallowing large prey. The front row gill rakers of the first-gill arch is short, straight, and ended by thin pointed spines adapted for food gathering and binding prey to the entry esophagus. Esophagus in S. variegatus is a short muscular narrow and distensible tube suitable for conducting food. Its stomach has a great distensibility giving a bag shape to allow catching relatively enormous prey. The intestine is a short, simple tube. In conclusion, the morphological features of the mouth, teeth, gill rakers, esophagus, stomach and intestine of lizardfish S. variegatus were subjected to various and significant modifications according to food and feeding habits to enrich the available data on the species.