中国鲎微卫星引物扩增圆尾鲎DNA的PCR反应体系优化

采用正交设计法,从dNTPs浓度、引物浓度、Mg2＋浓度、Taq DNA聚合酶用量4个因素3个水平出发,优化设计圆尾鲎DNA的PCR反应体系（引物为中国鲎微卫星引物）.并采用直观分析方法分析正交试验结果,最终建立了圆尾鲎SSR-PCR最佳反应体系：总体积20μL,Taq DNA聚合酶1.5 U、dNTPs 0.16 mmol/L、引物0.2μmol/L、Mg2＋2.0 mmol/L;并通过PCR梯度实验进一步优化模板DNA质量浓度、退火温度及退火时间,获得最佳反应条件：模板DNA质量浓度为30 ng/μL,退火温度为48℃,退火时间为20～25 s.对最佳反应体系和反应条件进行了检验,结果显示该反应体系稳定性高、重复性好.     

圆尾鲎消化道形态及组织学观察

对圆尾鲎消化道进行形态学和组织学观察。消化道分为前肠(口腔、食道、嗉囊、砂囊)、中肠和后肠(直肠、肛门)。各部位上皮均为单层柱状上皮,除中肠外,均有几丁质层覆盖于腔面。口腔环肌为横纹肌,有大量腺体分布;食道环肌层不连续,纵肌数量少;嗉囊有腺体分布;砂囊环肌层连续,纵肌成束分散排列,有放射肌分布;肠道肌肉为横纹肌,肠腺发达,具2对肝胰腺导管;直肠环肌连续;肛门几丁质层中有许多腺体导管,在其表皮层之下的结缔组织中充满皮肤腺。     

Frequent occurrence of the tetrodotoxin-bearing horseshoe crab <Emphasis Type="Italic">Carcinoscorpius rotundicauda</Emphasis> in Vietnam

Tetrodotoxin (TTX) was detected by HPLC and LC-MS/MS in specimens of the horseshoe crab Carcinoscorpius rotundicauda collected from Tan Hai village, Vung Tau province, Vietnam, where cases of poisoning due to the consumption of horseshoe crab have frequently been reported. The soft tissue from 10 out of the 12 specimens analyzed showed considerable levels of TTX, making them unsafe for human consumption (81.2 ± 50.3 MU/g). Paralytic shellfish poisoning (PSP) toxins were also detected in all of the specimens, but the levels were low. These findings show that the frequency of occurrence of C. rotundicauda specimens with a high level of TTX is significantly high, and that the TTX is responsible for the food poisonings caused by the consumption of C. rotundicauda in this area.     

圆尾鲎与中国鲎消化道形态学与组织学观察

比较分析圆尾鲎和中国鲎消化道组织学和形态学特征,为其发育生物学的研究和健康繁育提供理论依据。中国鲎与圆尾鲎均来自于广西合浦县西场镇邻近海域,10龄和14龄均各5只,平均头胸甲宽:圆尾鲎46.78~52.42 mm、中国鲎46.09~55.44 mm。通过形态解剖、组织切片和光镜技术等对消化道的形态学与组织学特征进行研究。结果表明:圆尾鲎与中国鲎消化道外部及解剖形态基本相似;它们的消化道可划分为前肠(口道、食道、前胃、幽门)、中肠和后肠(直肠、肛门);前肠、中肠和后肠都由几丁质层、粘膜层、粘膜下层、肌层及外膜组成,但是中肠不含几丁质层。10龄中国鲎和圆尾鲎的消化道总长以及中肠长度差异显著,消化道其余各部分的长度差异不显著。不同龄同种鲎以及同龄不同种鲎间的所有测量指数差异显著。消化道各部分的结构、组织形态均与其杂食性密切相关。     

10龄及14龄中国鲎和圆尾鲎头胸甲宽度与体重的回归分析

为了研究鲎形体与体重之间的关系,进一步探讨其生长特性,分别测定了中国鲎(Tachypleus tridentatus)和圆尾鲎(Carcinoscorpius rotundicauda)14龄成鲎和10龄幼鲎及不同性别的形态参数(头胸甲宽度及体重)。结果表明,中国鲎和圆尾鲎14龄成鲎和10龄幼鲎以及雌、雄的头胸甲宽度与体重均表现为正相关(R20.88);10龄中国鲎和圆尾鲎异速生长曲线的斜率-回归系数b分别为2.2263和2.1883,而14龄成鲎的回归系数b分别为3.1551和2.6501;10龄和14龄雌、雄中国鲎的b值分别为2.2314(♀)、1.9626(♂)和3.2295(♀)、2.8674(♂),10龄和14龄雌、雄圆尾鲎的b值分别为2.5342(♀)、1.9547(♂)和2.7791(♀)、2.1803(♂),b值均大于1,表明体重增长率大于头胸甲宽度的增长率,处于正生长期,且雌鲎的异速生长率均大于雄鲎;F检验表明,中国鲎和圆尾鲎10龄及14龄不同性别的头胸甲宽度与体重存在极显著的线性关系(P0.01)。     

Nursery habitat for Asian horseshoe crabs along the northern Beibu Gulf,China: Implications for conservation management under baseline gaps

1. Identification, protection and enhancement of essential habitats are priority issues for management and restoration of exploited species. The shores utilized by Asian horseshoe crabs as nurseries were surveyed and the coastal habitat characteristics were described in the northern Beibu Gulf of China. Regression models were applied to explore species‐habitat relationships.
2. Fourteen and ten nursery sites were identified for Tachypleus tridentatus and Carcinoscorpius rotundicauda populations, respectively. Xiacun and Jinhaiwan in the eastern region of the northern Beibu Gulf were the essential nurseries for T. tridentatus, whereas Shanxin and Jiaodong in the western part were the primary nursery shores for C. rotundicauda. These shores supported high densities (4–6 individuals/100 m²) of juvenile horseshoe crab populations.
3. Mangrove and seagrass coverage area, coupled with sediment physico‐chemical parameters, particularly grain size, and the environmental heterogeneity of nursery habitats explained the distribution pattern of juvenile populations. Most juvenile populations were found along the outer fringe of mangroves in the small shallow estuary, particularly near outflows of tidal creeks with generally higher chlorophyll a and organic carbon contents. The distribution of high‐density juvenile populations of both species also overlapped with areas of seagrass patches.
4. These findings highlight the importance of mangroves and seagrasses in the nursery habitat use of Asian horseshoe crabs. Preserving the estuarine habitats with these vegetation types and identifying the high‐use nursery sites should be prioritised in China and other Asian places to conserve the declining Asian horseshoe crab populations.