Sequence Comparison of Mitochondrial 16S rRNA Gene between Two Sesarma Species

Partial sequences of the mitochondrial 16S rRNA gene were determined for two Sesarma species （S. haematocheir and S. pficata）, and the length of sequence of S. haematocheir and S. plicata was the same. Of the 533 nucleotides obtained, the A, T, G and C contents were similar, which were 198 bp （37.1%）, 206 bp （38.6%）, 84 bp （15.8%）, 45 bp （8.4%） and 200 bp （37.5%）, 205 bp （38.5%）, 81 bp （15.2%）, 47 bp （8.8%） respectively. There were 49 different sites between the two species, including 21 transition sites, 22 transversion sites and 6 deletion/insertion sites. Furthermore, 361 bp homologous fragment was analyzed to discuss the phylogenetic relationship of 20 Sesarma species. The results showed that AT content （78.6% - 82.9%） was higher than GC content and there were 91 vadable positions of 16S rRNA sequences among the 20 species. Among 3 Sesarma species in China, S. dehaani and S. haematocheir were closely related （d=0.0151）; and there were greater genetic distances between S. pficata and S. dehaani I S. haematocheir （d=0.0924/0.0923）. The average genetic distances of S. plicata , S. dehaani and S. haematocheir with the North American crabs of genus Sesarma were respectively 0.103 2 ± 0.008 9, 0.0783±0.0105 and 0.072 0± 0.011, which indicated that there were greater genetic differences between China and North American Sesarma crabs and they were monophyletic each other.

Infestation and morphological identification of the stalked epizoic barnacle Octolasmis on the blue crab Portunus pelagicus from the Red Sea

The intensity of infestation of the epizoic stalked barnacle Octolasmis on the blue crab was calculated for a total of 180 individuals collected around Jeddah, the western Red Sea Saudi coast. More than 90% of the crabs were found bearing the Octolasmis at a prevalence rate of 92% and mean intensity of 18.5 ? 18.6(0–127 epibiont per host). The intensity of infestation increased with host size in the range 90–135 mm. Generally, females were more infested(69%) than the males(31%). Octolasmis angulata occurred mostly on the gills, and the lower side of the gill chambers was more infested(84%) than the upper side(16%) and the left side of gills was also more infested than the right side in both males and females. Further studies are still needed to examine the commensal relationship and its impact on the fishery market of the Red Sea blue crab populations.

Screening of Lectins in Crab and Shrimp from Fujian Coast of China

Twelve species of crustacean from Fujian coast were examined for lectins with different animal erythrocytes. Serum extracts froma ll of 12 species showed agglutinating activity against at least two types of the erythrocytes used, which revealed the existence of lectins in these species. There were five species ( Penaeus japonicus , Lophosquilla costata, Charybdis feriatus, Portunus pelagicus, Scylla serrata ) whose serums could agglutinate all the erythrocytes tested. The lowest serum protein concentration required to produce erythrocytes agglutination varied remarkably, ranging from 0.7μ g/mL to 8 080μ g/mL. The strongest activity was shown in the agglutination of rabbit erythrocyte by serum of Penaeus vanaminas. Inhibition assays performed with seven mono- and bisaccharides showed that agglutination of quail erythrocytes by serums of three species (Portunus pelagicus, Scylla serrata and Sesarma sp. ) were not inhibited by any sugars, while others were inhibited by at least three types of sugars. The assay of temperature influence on agglutinating activity showed that only Penaeus japonicus retained activity when the serum was heated to 90 ℃, and other serums lost their activity at 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃ for 10 minutes, respectively.