| The species and distribution of Drupella margariticola collected from Sanya Coral Reef National Nature Reserve are investigated and studied in this paper. In order to clarify the gonad development, morphological structure features, and feeding mechanism of D.margariticola, the external features and internal structure of the D. margariticola are anatomized and observed systematically. In additon, consumption rates and digestibility of D. margariticola, and feeding behavior of D. margariticola were also studied. The main results are as follows:1 Species and dominant species of Drupa in Sanya Coral Reef National Nature ReserveWe researched the natural distribution and the main species of Drupa in Sanya Coral Reef National Nature Reserve by periodic sampling. The results showed that there are 7kinds of Drupa in Sanya Coral Reef National Nature Reserve inculding Drupa ricina,Drupella rugosa, Drupa fiscella, Drupa granulate, Drupa marginatra, Drupa uva, and the dominant species D. margariticola. The shell height of D. margariticolas ranged from12.92 mm to 31.74 mm, with an average of 26.17±4.31 mm. The shell width ranged from8.10 mm to 18.46 mm, with an average of 15.34±2.48 mm. And the weight of D.margariticolas ranged from 0.36 g to 5.30 g, with an average of 2.99±1.14 g. The shell height, width and weight of D. margariticolas between male and female groups’ difference is not significant(P>0.05). The liner model is fitted on the basis of shell height(H) and shell width(B) of D. margariticolas, the linear equation is: B=0.5533H+0.8673(R2=0.9225, n=300). The power function model is fitted on basis of shell height(H) and body weight(W) of D. margariticolas, the regression equation is: W=0.0002H2.8845(R2=0.948, n=300). The two equeations’ correlation coefficient is above 0.9 to mean between shell height and width, shell height and weiht have close correlation.2 Reproductive System and Gonadal Development of D. margariticolaThe reproductive system and gonadal development of D. margariticola were studied by using anatomical and tissue sectioning technique. The results showed that D.margariticola is gonochorism. The female reproductive system is composed of ovary,oviduct, albumen gland, nidamental gland, transfer capsule and vagina. The male reproductive system is composed of testis, prostate, seminal vesicle, vas deferens and penis.According to the size and shape of ovarian germ cell, ovarian development was divided into proliferating, growing maturing, spawning and resting stages. The development of spermary was divided into four stages, namely proliferating stage, growing stage, maturing stage and resting stage. The gonad occurred in Feb to Mar and developed over a 3-4month period. The peak reproduction of D. margariticola is from Jun to Aug in Sanya Coral Reef National Nature Reserve. The rate of sexual maturation is up from Jan, It has remained at a high level(70%) above from Apr to Sep. It has a sharp drop after Oct.3 Digestive system, consumption rates and digestibility of D. margariticolaThis study gives a detailed histological and anatomical account of the digestive system of D. margariticola. Consumption rates and digestibility of five food items(Goniopora stutchburyi, Decapterus Russell, Litopenaeus vannamei, Pinctada fucata martensii, Loligo chinensis) by D. margariticola were studied by ecology methods. The results showed that digestive system consists of digestive tract and digestive gland. The digestive tract is composed of mouth, proboscis, crop, esophagus, stomach, intestine,rectum and anus. The digestive gland is composed of salivary gland, esophagus gland and liver, and liver is the major digestive gland. The digestive tract tube wall, under a microscope view, is surrounded by a wall consisting of four principal layers: mucous membrane, submucosa, lamina muscularis and adventitia. Mucous membrane is composed of a single layer of columnar ciliated cells and a few goblet cells. Submucosa mainly is the connective tissue. Ring muscles and longitudinal muscle are the two types of muscle, the ring muscles is distributed in the inside while the longitudinal muscle is in the outside, and the adventitia is thinner than other tissue. The adults of D. margariticolas are carnivorous.There are always three teeth of each row symmetrically arrayed on the radula which is in the proboscis, and the pattern of radula is 1·1·1. During eating, the D. margariticola extends its proboscis and make the radula moving on the radula cartilage for cutting food.The food with greatest mean daily consumption in wet weight was G. stutchburyi with3.086±1.370 g, followed by L. chinensis(1.182±0.226g), L. vannamei(0.716±0.324g),Pinctada fucata martensii(0.615±0.249g) and D. Russell(0.303±0.453g). Absorption rate was higher when L. chinensis was consumed(21.19±4.36%, wet weight) followed by G.stutchburyi(9.12±2.18%), Pinctada fucata martensii(7.07±1.98%), L. vannamei(2.17±0.17%) and D. Russell(1.88±0.38%).4 Feeding behavior of D. margariticolaThe experiments about feeding behavior, prey selection of D. margariticola on three corals and one bivalve, and Turbinaria peltata bioerosion by different number of D.margariticola were conducted at laboratory. The results showed that D. margariticola preyed on three corals and one bivalve. Similarly, D. margariticola exhibited preference in the order Ruditapes philippinarum > Galaxea astreata > Turbinaria peltata > Goniopora stutchburyi. According to the tissue distruction of T. peltata, the feeding conditions can be divided into three types: not feeding(the food was not eaten at all), feeding is not obvious(less than half of the food was eaten or only biting traces), feeding obviously(the food was eaten up or almost). Placed 0, 20, 40, 60, 80, 100 D. margariticola in breeding boxes for feeding coral, respectively, in the order not feeding, feeding is not obvious, feeding is not obvious, feeding obviously, feeding obviously, feeding obviously. Results indicate that the more the number of D. margariticola, the greater the damage of coral. |
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