Study On The Feeding Selection And The Adaptability Of Digestive System Structure And Function Of Three Common Sea Cucumbers In Tropical Coral Reefs

Holothuria atra,Holothuria edulis,and Stichopus chloronotus are common species in the large benthic community of tropical coral reefs,and their feeding activities play an important role in the recycling and reuse of organic matter in coral reef habitat.In this paper,the selection characteristics of the sediments and the adaptability of the tentacles and digestive system structure of wild H.atra,H.edulis,and S.chloronotus in the typical tropical coral reefs of Wuzhizhou Island in Sanya were studied.The results showed that Holothuria edulis,and Stichopus chloronotus had flat and large mastoids(H.atra mastoid diameter 74.56±16.38?m,H.edulis mastoid diameter 73.39±14.78?m)suitable for ingesting large particle sediments,S.chloronotus spherical The tentacles of the tentacles(65.43±14.84?m in diameter)are suitable for the sedimentation of fine particles;in the intestinal contents of H.atra,the proportion of gravel,very coarse sand and coarse sand is greater than or close to the sediment,and the S.chloronotus is in the In the intestinal contents,the proportion of fine sand,very fine sand and silt is greater than that of sediment,gravel and very coarse sand.The intestinal content is always smaller than the sediment.The H.edulis is always in the silt granular intestine.Larger than sediment,indicating that the three sea cucumbers have the ability to choose independently,and it is proved that H.atra actively chooses coarse grain feeding,and S.chloronotus actively selects fine particles to feed;The content of organic matter in the stomach contents of the three sea cucumbers is nearly twice that of sediments,indicating that sea cucumbers can actively ingest sediments with higher organic content than in the environment;the organic matter in sediments and stomach contents is mainly concentrated in medium sand and fine The sand particle size,organic matter content and organic matter amount gradually decrease along the stomach,foregut,and middle and hindgut.The foregut,middle and hindgut have a large absorption capacity,and the main particle size to be digested and absorbed is in medium sand and fine sand.The three kinds of sea cucumbers in the selected intake of sediment organic matter and the digestion and absorption of organic matter in the intestine formed an adaptive compatibility;histological quantitative analysis showed that the thickness of the foregut mucosa of the three sea cucumbers was the largest,close to the total thickness of 60%,which is highly efficient digestion It is compatible with the function of absorbing organic matter;the total thickness of the intestinal wall and the thickness of the submucosa layer and muscle layer of the hindgut are significantly higher than that of the foregut,especially the submucosa layer,which accounts for about 80%of the total thickness,indicating that it has a relatively better Elastic and shrinking capacity,suitable for efficient delivery and discharge of large particulate organic matter.In the seasonal changes,the intestines are developed in the spring and summer,and the intestines are atrophied in the autumn and winter.The sediments corresponding to the winter intake are fine,and the sediments in the summer are relatively thick,indicating that the coarse particles can be ingested when the digestive tract is developed.Sediment and efficient absorption.The results confirmed that the unique structure and function of the three sea cucumber feeding organs and digestive tract ensured the efficient intake of organic matter in the coarse grain habitat of coral sand.