虾夷扇贝Patinopecten yessoensis (Jay)和仿刺参Apostichopus japonicus (Seienka)多倍体诱导研究

本文采用化学方法诱导了虾夷扇贝Patinopecten yessoensis (Jay)和仿刺参Apostichopus japonicus (Selenka)的多倍体。采用6－二甲基氨基嘌呤（6－dimethylaminopurine）抑制虾夷扇贝极体释放，研究了诱导三倍体的实验条件、技术工艺以及三倍体虾夷扇贝幼虫的生长和培育方法。结果表明，使用6－二甲基氨基嘌呤（6－DMAP）可诱导17.3%-100.0%的三倍体虾夷扇贝面盘幼虫。筛选并优化了生产中操作简便、高效、成活率高的诱导条件，并研究出在扇贝三倍体诱导中批量获得受精卵、处理及培育的技术工艺，对扇贝三倍体的规模化诱导及培育等生产性应用具有较高的参考价值。报道了采用细胞松弛素B（cytochalasin B）、秋水仙素（colchicine）、6－DMAP以及咖啡因（coffeine）等药物抑制虾夷扇贝第一极体（PB_1）释放、PB_1和第二极体（PB_2）释放以及抑制第一次卵裂等方法诱导四倍体的结果。结果表明，CB、6－DMAP和秋水仙素抑制扇贝第一次有丝分裂诱发四倍体的比例低于25%，而采用CB抑制PB_1可有效地诱导产生四倍体，从授精后42min提前到15-22min开始处理，抑制PB_1的放出有助于提高四倍体的比例，在12 ℃，处理开始和终上时间分别在授精后20－22min和60－62min时，面盘幼虫四倍体率最高，为56.5%。对CB处理抑制受精卵PB_1释放的处理组胚胎的染色体分离状况进行了观察研究。对照组受精卵具有19条四分体染色体，经过减数分裂I期（meiosis I）和减数分裂II期（meiosis II），放出PB_1和PB_2，受精卵的发育具有不同步性。处理组受精卵在第二次减数分裂中出现了“三级分离“、“联合二级分离“和“独立二级分离“等特殊的分离类型，初步分析了CB抑制第一极体放出的机理。对三倍体虾夷扇贝的繁殖潜力和卵子的大小进行了观察研究，三倍体扇贝具一定的繁殖能力，三倍体雌贝平均产卵3.26 * 10~6个，而相同壳长二倍体贝为1.45 * 10~7，三倍体产卵量仅为二倍体产卵量的22.5%。三倍体卵子产出后，形状不规则，卵子平均直径为87.25μm，比二倍体大11.7%，卵子体积比二倍体大39.4%。利用CB抑制第一极体释放诱导了虾夷扇贝的四倍体，诱导率为41.5%。首次报道了仿刺参Apostichopus japanicus (Selenka)多倍体诱导的结果。采用紫外线照射的海水成功地使海参分别单独产卵、排精，从而准确地控制了海参的人工授精后处理的时间。采用0.2、0.4mg/L CB 抑制受精卵第一极体释放以及10、20、30和40mg/L 的6－DMAP 分别抑制PB_1、PB_2放出的方法诱导了仿刺参的多倍体。研究了诱导的药物浓度、处理时间以及处理开始时间等，同时对幼体的成活率等进行了探讨。结果表明，2种药物均可诱导仿刺参产生三倍体和四倍体，从效果上看，采用CB抑制PB_1诱导，到达小耳幼体时，可产生9.7%-21.3%的四倍体。6－DMAP抑制PB_2放出诱导三倍体，三倍体诱导率介于7.5%-25.8%之间。

Divergent selection and realized heritability for growth in the Japanese scallop, Patinopecten yessoensis Jay

In order to improve the production and accurately estimate response to selection, divergent selection for growth in shell height was conducted in a cultured population of the Japanese scallop Patinopecten yessoensis. Applying the same selection intensity +/- 1.756 in upward and downward directions, three groups including two selected groups of Fast and Slow and one non-selected Control group were created, which were reared under the same environmental conditions at any stage. Differences always significantly existed among the three groups (P < 0.05), except for larvae at day 1 and at day 5, and in the order of Fast > Control > Slow. The average standardized response to selection (SR), realized heritability (h(R)2) and genetic gain (GG) was 0.473%, 0.269% and 7.85% for the Fast group and 0.381%, 0.217% and 6.60% for the Slow group respectively. Moreover, significant differences (P < 0.05) were detected between the fast and the slow lines in both SR and h(R)2, providing evidence for an asymmetric response in two directions. Performance in shell height is improved by 7.85% in the fast line after one generation selection, suggesting that mass selection for faster growth in a cultured population of the Japanese scallop is effective.

辽东栎天然更新

在北京东灵山地区对辽东栎的天然更新进行研究。辽东栎的结实具有大年现象（masting），大年现象十分复杂，在种群水平、个体之间都存在差异。 动物对辽东栎的天然更新有重要的影响。捕食和传播辽东栎坚果的脊椎动物至少包括小型啮齿目动物中的岩松鼠、花鼠、大仓鼠、社鼠、大林姬鼠和棕背鼠平，鸟类中的松鸦。岩松鼠、花鼠和大仓鼠有发达的颊囊，能够将坚果暂时放在颊囊中进行传播，岩松鼠有分散埋藏坚果的习性;松鸦能够将坚果放在素囊中进行长距离传播。成熟坚果在森林地表的消失非常快，少部分被脊椎动物就地消耗，大部分被传播到巢穴中或分散埋藏。成熟坚果的丢失存在时空差异。无脊椎动物中的昆虫对辽东栎去叶有重要影响。去叶与昆虫幼虫的密度以及长度显著相关。幼树去叶在辽东栎种群大树密度最高的地点最高，而在密度最低的地点最低。大树去叶在辽东栎种群总胸径面积最大的地点最大。 辽东栎实生苗在野外十分匮乏，可能是由于东灵山地区小型啮齿目动物缺乏天敌，使它们的活动十分强烈。它们有异常强大的捕食和搬运辽东栎坚果的能力，使能够逃逸捕食的坚果数量很少。现阶段辽东栎的更新几乎完全靠萌生苗进行，大树的生长大多弯曲不直。实生幼苗在小的林窗中的生长比在树冠下的生长好。综合考虑实生个体和萌生个体，50 龄林中种群大小结构稳定，能够长时间生存发展下去;30 龄林种群中个体间的竞争激烈，种群处于衰退状态。 研究结果建议：对辽东栎林的天然更新，应该采取综合治理的方法，充分考虑各种生物和非生物因素的影响，处理好生物因素的非生物因素的关系;人为进行适当干扰，例如在森林中创建适当大小的林窗，以更好地促进辽东栎的天然更新。

Abundance and conservation status of the Yangtze finless porpoise in the Yangtze River, China

middle and lower reaches of the Yangtze River, China. It is the only freshwater population of porpoises in the world and is currently listed as Endangered by IUCN. In November and December 2006 we used two boats and line transect methods to survey the entire current range of the population, except for two lakes (Poyang and Dongting). Sighting results were similar for both boats, so we pooled all data and analyzed them using two line transect models and a strip transect model. All models produced similar estimates of abundance (1111, 1225 and 1000). We then added independent estimates of the number of porpoises from the two lakes for a total estimate of approximately 1800 porpoises. Our findings indicate that the population continues to decline and that its distribution is becoming more fragmented. Our current estimate in the main river is slightly less than half the estimate from surveys between 1984 and 1991 (which was probably an underestimate). We also found an apparent gap in the distribution of porpoises between Yueyang and Shishou (similar to 150 km), where sightings had previously been common. Continued threats to Yangtze finless porpoises include bycatch in unregulated and unselective fishing, habitat degradation through dredging, pollution and noise, vessel strikes and water development. Immediate protective measures are urgently needed to ensure the persistence of finless porpoises in the Yangtze River. The survey design and analytical methods developed in this study might be appropriate for surveys of cetaceans in other river systems. (c) 2008 Elsevier Ltd. All rights reserved.

First human-caused extinction of a cetacean species?

The Yangtze River dolphin or baiji ( Lipotes vexillifer), an obligate freshwater odontocete known only from the middle-lower Yangtze River system and neighbouring Qiantang River in eastern China, has long been recognized as one of the world's rarest and most threatened mammal species. The status of the baiji has not been investigated since the late 1990s, when the surviving population was estimated to be as low as 13 individuals. An intensive six-week multivessel visual and acoustic survey carried out in November-December 2006, covering the entire historical range of the baiji in the main Yangtze channel, failed to find any evidence that the species survives. We are forced to conclude that the baiji is now likely to be extinct, probably due to unsustainable by-catch in local fisheries. This represents the first global extinction of a large vertebrate for over 50 years, only the fourth disappearance of an entire mammal family since AD 1500, and the first cetacean species to be driven to extinction by human activity. Immediate and extreme measures may be necessary to prevent the extinction of other endangered cetaceans, including the sympatric Yangtze finless porpoise ( Neophocaena phocaenoides asiaeorientalis).