Biological Study Of Carcinoscorpius Rotundicauda And Tachypleus Tridentatus In Coastal Areas Of Beibu Gilf In Guangxi

In this paper, we aged136individuals of Carcinoscorpius rotundicauda and264individuals of Tachypleus tridentatus in coastal areas of Beibu Gulf in Guangxi and determinated their sex by phenotypic observation and size measurement. On the basis of that, the statistical analysis of morphometry parameters in different ages, instars and sex as well as the relationship between prosomal width and body weight were carried out to identify the morphological variation and allometry characteristic of C. rotundicauda and T. tridentatus. At the same time we investigated the morphology and histology of fhe digestive tract of C. rotundicauda and T. tridentatus by the methods of anatomy, conventional paraffin tissue sections and optical microscopy. We redefined the division of the digestive tract of C. rotundicauda and T. tridentatus, and discussed the adaptive relationship of digestive tract and their omnivorous habit. The main results of this thesis were summarized as follows:1. Based on the size-frequency distribution of prosomal width, we aged the instars of136individuals of C. rotundicauda were7-16th instar,264individuals of T. tridentatus were6-15th instar, and estimated the range in prosomal width of each instar. Prosomal width of7-15th instar of C. rotundicauda ranged as follows:22.0-28.0mm,28.1-36.0mm,36.1-42.0mm,42.1-56.0mm,56.1-72.0mm,72.1-92.5mm,92.6-112.5mm,112.6-142.5mm,142.5-182.5mm. The range in prosomal width of6-15th instar of T. tridentatus were as follows:20.0-25.0mm,25.1-31.0mm,31.1-38.0mm,38.1-48.0mm,48.1-60.0mm,60.1-76.0mm,76.1-94.0mm,94.1-120.5mm,120.6-151.4mm,154.6-196mm.2. All morphological parameters of C. rotundicauda and T. tridentatus were increased along with the growth of age, and there were significant differences in the morphological ratios of different ages. Significant differences between juveniles and adults of C. rotundicauda and T. tridentatus were detected for the ratios of prosomal length and opisthosomal length (a/b), dorsal prosomal length and telson length (c/d), length of1st opisthosomal spine and length of4th opisthosomal spine (S1/S4), the ratio values were comparatively lower for the adults than juveniles. The ratio of opisthosomal width and opisthosomal length (k1/b) of two horseshoe crab species was gradually reduced with the increase of age, while ratio value of length of1st opisthosomal spine and length of6th opisthosomal (s1/s6) of T. tridentatus turned to be increased with age.3. Significant differences between sex of C. rotundicauda and T. tridentatus were obtained for the ratios of S1/S4, S1/S6, prosomal width and prosomal length(g/a), distance between the two compound eyes and prosomal width(f/g), a/b, k1/b and c/d. Females of the two species showed significantly higher body ratios of S1/S4, S1/S6, but lower ratios of g/a. For the two sexes, body ratios of a/b, k1/b, c/d and f/g of C. rotundicauda were significantly lower, while S1/S6was higher than T. tridentatus. For females of the two species, ratio of S1/S4was not different significantly, while for males S1/S4of C. rotundicauda was significantly higher than T. tridentatus.4. C. rotundicauda and T. tridentatus in different ages, instars and sex generally exhibited positive allometry between prosomal width and body weight with a very high degree of correlation(R2>0.81). Regression coefficient (relationship between log prosomal width and log body weight) were all greater than1. Overall performance showed that the carapace width and total body weight were increased with age of C. rotundicauda and T. tridentatus, and female horseshoe crabs showed better growth than males.5. The morphology and histology characteristics of the digestive tract of C. rotundicauda and T. tridentatus were basically similar. We divided the digestive tract into foregut (cavum buccale, oesophagus, proventriculus, pylorus), midgut and hindgut (midgut and rectum). The wall epithelium of the digestive tract except midgut was covered by periostracum, and all the digestive tract included mucosa, submucosa, muscular layer and adventitia. And it proved that the morphologic and structure of the digestive tract was adapted to their omnivorous habit.