Temporal and Spatial Variation of Benthic Intertidal Community of a Sandstone Reef in Pernambuco—Brazil as a Tool to Evaluate Bioinvasion

In this study,the superior and inferior intertidal areas of hard substrate were sampled during the rainy season(June and August)and dry season(October and December)of 2015 at Piedade Beach.The percent cover of Chthamalus bisinuatus,Brachidontes solisianus,Isognomon bicolor,Ulva spp.and filamentous green algae were measured with a 20×20 cm quadrat with one hundred intersections.The quadrats were placed randomly at the sampling sites of Piedade reef.One-way ANOVAs(Analyses of Variance)were used to test the temporal variation of the studied organisms.Chthamalus bisinuatus occurred only in the superior mesolitoral where they had an increase in percent cover during the dry season,which wasn’t statistically significant.Brachidontes solisianus occurred in both superior and inferior levels and had a significant decrease in the superior intertidal during the dry season.Isognomon bicolor occurred only in the inferior level and decreased to almost zero in the December.Ulva spp.and green filamentous algae had an opposite pattern in the inferior intertidal although only the filamentous algae showed a significant decrease in the dry season.Organisms such as Chthamalus bisinuatus resists better the heat and are dominant in the superior intertidal levels of reefs and rocky coasts.Brachidontes solisianus didn’t change much in the lower intertidal and showed that can coexist with the invasive Isognomon bicolor.While the filamentous green showed a decrease in the dry season probably more affected by desiccation than Ulva spp.at Piedade reef.

扁平钳蛤性腺发育的组织学研究

通过石蜡切片对扁平钳蛤进行性腺发育组织学观察,结果表明,扁平钳蛤雌雄性腺的发育都可分为增殖期、生长期、成熟期、排放期和休止期5个时期。增殖期为滤泡形成期,出现了精原细胞和卵原细胞,贴近滤泡壁分布;在生长期,性腺面积、滤泡数目和生殖细胞数目都明显增大,卵母细胞和精母细胞形成;成熟期雌性滤泡内充满卵细胞,其生发泡透亮,核仁清晰可见,雄性滤泡内充满着蓝紫色的精子,精子尾部聚集在滤泡中央,呈鲜红色;排放期滤泡破损,卵细胞和精子排放,性腺面积减小;休止期滤泡腔萎缩,基本无生殖细胞残留。扁平钳蛤生殖周期为一年,5—6月处于性腺发育增殖期;7—10月性腺进入繁殖期,包括生长期、成熟期和排放期;11月进入休止期;其他月份性腺基本不发育。

吊养和底播两种养殖方式对扁平钳蛤生长的影响

扁平钳蛤具有蓝褐色珍珠层,是培育色泽特异珍珠的潜能品种,不同养殖方式的选择对扁平钳蛤的生长和存活具有重要的影响。本研究采用锥形笼吊养和底播养殖两种方式对扁平钳蛤进行为期半年的养殖,探讨两种养殖方式对扁平钳蛤壳长、壳宽、壳高和体重等生长性状以及其存活率的影响,以摸索一种适合扁平钳蛤的养殖方式。结果表明,养殖半年后,吊养扁平钳蛤(以小贝为例)的壳长、壳高、壳宽和体重的增长率分别为137.95%、143.84%、152.63%和92.68%,而底播贝则分别为110.30%、113.02%、115.85%和68.97%,吊养贝和底播贝之间存在显著差异(p<0.05)。吊养贝在6个月的养殖期内总存活率分别为100%、75.56%、82.22%、91.11%、98.89%和82.22%,而底播贝总存活率则分别为100%、66.67%、74.44%、88.89%、100%和91.11%。在5、6、7、8四个月内吊养贝的存活率都显著高于底播贝(p<0.05);9月份两者无显著差异(p>0.05),在10月份因受台风影响则表现为底播贝的存活率高于吊养贝(p<0.05)。这从生长性状和存活率两方面表明,锥形笼吊养与底播相比更适合于扁平钳蛤的养殖。