中国水螅属一新种(螅形目,水螅科)

记述采自北京地区水螅属1新种：北京水螅Hydra beijingensis sp．nov．。新种的主要鉴别特征是出现体部与柄的分化;钩刺丝囊内刺丝缠绕具有2种形态：大部分钩刺丝囊(占2／3左右)内顶端基部刺丝呈4～5圈横向弹簧状缠绕,而占所观察刺丝囊总数1／3左右的囊内刺丝为不规则缠绕和纵向缠绕。标本保存在哈尔滨师范大学生命与环境科学学院生物学系无脊椎动物研究室。     

中国水螅属一新种(水螅纲,水螅科)

报道采自广东省肇庆市的淡水水螅1新种,多形水螅Hydra polymorphus sp.nov.,研究标本均来自1只水螅的单系繁殖群体,测量数据经生物统计学处理。新种的钩刺丝囊外形及内部刺丝盘旋均有多种形态,故新种名以此命名。所有研究标本保存于深圳大学生命科学学院。     

双头无基盘水螅的初步观察

自然形成的双头无基盘畸形体水螅极为罕见,为探索其形成原因,人工嫁接水螅14例,获得5例相同的双头水螅。对其分别进行连续观察发现:嫁接的双头水螅的双头可同时摄食,食物集聚于1个胃区。随个体生长其体柱延长,逐渐发育为2个胃区,在2个胃区间发生2~6个芽体,所有子代发育正常。出芽位置至触手环的距离同正常水螅。之后分化为2个出芽区,出芽区之间体柱较透明,同茎区组织。第21天开始发生基盘,发生过程异常缓慢。     

中国水螅属一新种(水螅虫纲:螅形目)

描述采自黑龙江省大庆、泰来和阿城地区的水螅属一新种：大庆水Ｈｙｄｒａ ｄａｑｉｎｇｅｎｓｉｓ ＦＡｎ,ｓｐ。ｎｏｖ．。新种的主要鉴别特征是：构刺丝囊内顶基部具有４．５～５．０圈横向弹簧状缠卷刺丝,较大型的构刺丝囊、粘刺丝囊和卷刺丝囊,生殖期,雄必个体形成数目较多的精巢（１２～１８个）和雌性个全产生较多的卵（４～１０枚）的遗传特性。标本保存在哈尔滨师范大学生物学系无脊椎动物教研室。     

水螅刺丝囊的分离与观察

水螅的刺丝囊依据其形态和功能,有穿刺丝囊、钩刺丝囊、粘刺丝囊和卷刺丝囊4种,是淡水水螅分类的主要依据之一.使用多种化学试剂探索分离刺丝囊的方法,实验发现利用10%的MgSO4或3%的NaCl处理离体触手5～6 min,用高纯水清洗后制作装片观察,可以获得最佳的显微图片和观察效果.最后初步探讨了不同体区刺丝囊的结构特点.     

水螅体色变化的实验观察

水螅体色变化的实验观察野生水螅（Ｈｙｄｒｏｉｄａｅ）体色一般呈褐色、灰色、绿色和乳白色４种,但有时能采到体呈红色、粉红色、深红色、暗红色和浅蓝色等个体。鉴定水螅,要依据外形特征、刺丝囊结构、雌雄生殖细胞特征和体细胞染色体分析等,而体色是次要的分类依据...     

水螅AChE和NPY类似物的定位

乙酰胆碱脂酶(AChE)组织化学定位方法常用于研究动物的神经系统,但迄今未见水螅AChE分布定位的相关报道。本文使用免疫细胞化学、组织化学和亚甲基蓝活染方法,探索AChE、NPY类似物在水螅上的连续分布状态,对阳性标本进行内胚层、外胚层人工分离手术,并与亚甲基蓝染色结果进行比较。本文首次成功地在水螅上定位出AChE,展示了AChE、NPY类似物在水螅上的分布特点。AChE定位在水螅体柱和触手基部外胚层的近外表,呈网状结构,正常水螅上没有发现明显的阳性神经细胞,外胚层表面受损部位内有阳性神经细胞,我们认为是一种临时的生理现象。成熟刺丝囊的刺针内有AChE 产物。NPY免疫组织化学反应(NPYIR)在水螅外胚层近外表处上均有分布,呈网状结构。垂唇和近基盘处NPYIR最强,NPYIR神经细胞仅存在于垂唇和近基盘处的外胚层基部。刺丝囊分化、发育初期NPYIR较强。随刺丝囊发育成熟而逐渐减弱。最后,进行了分析和比较,认为NPY、AChE来源于上皮细胞。水螅刺丝囊的分化和发育与NPY的作用密切相关;刺丝囊发射刺丝的机理与胆碱能的作用可能有联系     

大乳头水螅在中国的首次发现

淡水水螅有效物种已记述36种。史新柏等(1987)对哈尔滨的强壮水螅Hydra robustaIto,1947作过报道;范学铭报道了中国水螅4个新种,即哈尔滨水螅Hydra harbinensisFan、漠河水螅Hydra mohensisFan,1999、大庆水螅Hydra daqin-gensisFan,2000和北京水螅Hydra beijingensisFan,2003,     

五种水螅基因组DNA的RAPD多态性研究

利用RAPD技术对水螅科2属5种水螅进行了基因组DNA多态性研究.80个随机引物筛选出18个引物,共扩增出303个清晰稳定的DNA片段,分子量在0.3～3.0kb之间.以UPGMA聚类法构建树状图,阐明水螅属种的分类关系:大庆水螅Hydra daqingensis、北京水螅H.beijingensis和强壮水螅H.robusta 3种分成两组并聚在一起;不同属的漠河水螅H.mohensis和绿水螅Chlorohydra sp.聚为一支;由此2属5种水螅分为两个支系.     

秋季降温期水温和饵料量对沙蜇无性繁殖的影响

20世纪末以来,沙蜇在东亚水域频繁暴发,不仅影响正常的渔业生产活动,也给海洋生态系统健康带来极大危害。在室内模拟秋季降温条件,研究了不同水温（4种降温条件）与饵料量（0.42、1.25、和4.2 μg C螅状体^-1d^-1）对沙蜇螅状体足囊繁殖与横裂生殖的影响。结果显示：1）秋季降温速度快慢导致的积温差异对沙蜇螅状体生成足囊数有显著影响（P < 0.001）,积温越大,螅状体生成的足囊数量越多,发现两者具有较好的线性关系（y=142.59x+208.39;R²=0.967）,低积温条件下的足囊萌发也较少;2）饵料量对螅状体无性繁殖的影响是有一定阈值范围的,在一定饵料量范围内,螅状体生成的足囊数量随饵料量的增加而增加,而超过一定阈值范围,过剩的饵料影响水质对沙蜇螅状体反而产生负面影响。3）秋季新繁育出来的当龄沙蜇螅状体可在越冬前发生横裂生殖,但横裂生殖的螅状体比例和放碟数量均较少。试验结果说明,全球变化背景下,积温升高、饵料量小幅增加均可能导致沙蜇秋季有性繁殖的当龄螅状体在越冬前生成更多的足囊,促进诱发翌年水母暴发。     

光周期对中国水螅种群增长、无性出芽生殖及抗氧化酶活力的影响

单细胞真核绿藻在中国水螅(Hydra sinensis)内胚层皮肌细胞中共生是有较高科研价值的特殊生物学现象。水螅宿主细胞为共生藻提供CO2、氮源及矿物质,而共生藻通过光合作用可能为宿主提供碳水化合物等有机物营养,因此水螅与共生藻间代谢流是以共生藻光合作用为中心,但基于代谢流二者间的互作机制目前尚未阐明。水螅通过营养积累进行出芽生殖,从母体脱落的芽体数量间接反映水螅营养积累的相对量。而光暴露时长能影响共生绿藻光合作用,如果共生藻的确能向水螅细胞转移光合作用产物,那光暴露时长应该能间接影响水螅的营养积累、从而进一步影响水螅无性出芽生殖。为证实该假说,本研究应用种群累积培养法,观察了光周期对中国水螅种群增长、无性出芽生殖及抗氧化酶(SOD和CAT)活力的影响。结果显示,光周期对中国水螅种群增长具有明显的影响。培养15 d后,所有实验组水螅的种群密度均为正增长,其中8L∶16D(在一个24h周期内光暴露8 h、黑暗16 h)实验组种群密度最大、而0L∶24D(持续黑暗)实验组种群密度最小。另外,随着光暴露时长的增加,中国水螅SOD及CAT活力整体均呈下降趋势。结果表明,从光周期对中国水螅无性出芽生殖及两种抗氧化酶活力的影响来看,中国水螅对光周期的生理学响应较为敏感,这个现象可能源于共生绿藻能通过向宿主细胞转移光合作用产物的方式为水螅提供营养补充。     

Organelle survival in a foreign organism: Hydra nematocysts in the flatworm Microstomum lineare

Nematocysts are characteristic organelles of the phylum cnidaria. They are designated kleptocnidae when sequestered in animals that feed on cnidaria. Kleptocnidae are known for more than a century. Nevertheless it is still enigmatic how selected nematocyst types survive in the predator and how they reach their final destination in the foreign body. In the free-living Platyhelminth Microstomum lineare the fate of nematocysts of the prey Hydra oligactis was analyzed at the ultrastructural level and by fluorescence microscopy using hydra polyps that had been stained in vivo with the fluorescent dyes TROMI and TRITC. M. lineare digested hydra tissue in its intestine within 30?min and all nematocyst types were phagocytosed without adherent cytoplasm by intestinal cnidophagocytes. Desmoneme and isorhiza nematocysts were digested whereas cnidophagocytes containing the venom-loaded stenotele nematocysts started to migrate out of the intestinal epithelia through the parenchyma to the epidermis thereby traversing the subintestinal and subepidermal muscle layer. Within one to two days, M. lineare began to form a muscle layer basolateral around epidermal cnidophagocytes. Epidermal stenoteles survived in M. lineare for at least four weeks. The ability of epidermal stenotele nematocysts to discharge suggest that this hydra organelle preserved its physiological properties in the new host.     

Interference of asexual and sexual reproduction in the green hydra

The green hydra, Hydra viridissima, has three sexes: hermaphrodite, male, and female. I investigated the reproductive strategies of the green hydra and the relationship between asexual budding and sexual reproduction. The proportion of mature individuals in the asexually reproducing population increased with increasing temperature. Sexual reproduction did not interrupt asexual budding in hermaphrodites or males; sexual reproduction did interrupt asexual budding in females. Sexual reproduction also resulted in exponential population growth during the reproductive season. The number of asexual buds on each parental individual was positively correlated with the parental individual size in asexual individuals and in males. The same positive correlation was found between the number of testicles and the size of males. These correlations reflect a common tendency in asexual and sexual reproduction: larger parental individuals have a greater number of propagules or gametes. No correlation was found between size and buds or size and gonads in hermaphrodites; hermaphrodites had at most one asexual bud and were significantly larger than males, females, and asexual individuals. The larger size of hermaphrodites supports the hypothesis that producing both female and male gonads is more energetically costly than producing only one type of gamete (gonochorism).     

Hydra of Hawaii: phylogenetic relationships with continental species

The presence of freshwater hydra in the Hawaiian Islands, over 3,700 km from the nearest continental margin, provokes the question of how these animals could reach the islands. We examined three islands for hydra and found two species (the brown hydra, Hydra vulgaris Pallas 1766, and green hydra, H. viridissima Pallas 1766) present at multiple locations on Oahu and Kauai, and at a single site on Hawaii. Phylogenetic analysis based on the internal transcribed spacer (ITS1 and ITS2) regions of ribosomal DNA indicates that all collected strains of brown hydra were closely related to each other—consistent with a single introduced origin. The analysis also shows that all sampled Hawaiian brown hydra fall within a specific clade of H. vulgaris. This clade is sister to a North American clade and nested within a deeper North/Central America clade. The clade with all the Hawaiian brown hydra includes also individuals from Southern California, suggesting a Californian origin for the brown Hawaiian hydra. Hawaiian hydra were probably transported to the islands by man.     

Morphological features and isoenzyme characterization of endosymbiotic algae from green hydra

Symbiotic associations are of a wide significance in evolution and biodiversity. Green hydra is a typical example of endosymbiosis. In its gastrodermal myoepithelial cells, it harbors individuals of unicellular green algae. Morphological characteristics of isolated algae determined by light and electron microscopy are presented. Cytological morphometric parameters (cell area, cell radius, chloroplast area) of isolated algae from green hydra (Cx), as well as from reference species Chlorella kessleri (Ck) and Chlorella vulgaris (Cv), revealed similarity between the isolated endosymbiont and C. kessleri. Isoenzyme patterns of esterase (EST), peroxidase (POX), and catalase (CAT) were used for the investigation of genetic variability in endosymbiotic algae isolated from green hydra. Out of 14 EST isoenzymes observed in Cx species, 9 were expressed in the Cx sample. Results of the EST isoenzyme analysis indicated a higher degree of similarity between Cx and Cv than between Cx and Ck. Due to much higher heterogeneity, EST isoenzymes seem to be more suitable genetic markers for identification of different Chlorella species than CAT and POX isoenzymes. Results obtained suggest that symbiogenesis in green hydra has probably not been terminated yet.     

Is larger better in sit-and-wait predators? Competitive superiority in Hydra

Contrary to a generalisation arising from many studies, a larger body size is not always the key to competitive superiority amongst animals. An analysis of competition between pairs of Hydra oligactis, Hydra vulgaris and Hydra circumcincta, that simultaneously encountered a single prey item, showed that competitive success in these sessile predators depended on species and clone in inter- and intraspecific competition, respectively. H. oligactis appeared to be competitively superior, even to the larger H. vulgaris individuals. Phenotypic traits important for prey capture, such as the fraction of the nematocyst that penetrates the prey (penetrants), were positively related to success in intraspecific competition. Body size appeared to be a positive key factor in determining foraging success in the competition between pairs of conspecifics from single or different clones. In contrast to the results of the intraspecific competition, body size was not significantly related to the foraging success of competing heterospecifics.     

A Non-sulfated Chondroitin Stabilizes Membrane Tubulation in Cnidarian Organelles

Membrane tubulation is generally associated with rearrangements of the cytoskeleton and other cytoplasmic factors. Little is known about the contribution of extracellular matrix components to this process. Here, we demonstrate an essential role of proteoglycans in the tubulation of the cnidarian nematocyst vesicle. The morphogenesis of this extrusive organelle takes place inside a giant post-Golgi vesicle, which topologically represents extracellular space. This process includes the formation of a complex collagenous capsule structure that elongates into a long tubule, which invaginates after its completion. We show that a non-sulfated chondroitin appears as a scaffold in early morphogenesis of all nematocyst types in Hydra and Nematostella. It accompanies the tubulation of the vesicle membrane forming a provisional tubule structure, which after invagination matures by collagen incorporation. Inhibition of chondroitin synthesis by β-xylosides arrests nematocyst morphogenesis at different stages of tubule outgrowth resulting in retention of tubule material and a depletion of mature capsules in the tentacles of hydra. Our data suggest a conserved role of proteoglycans in the stabilization of a membrane protrusion as an essential step in organelle morphogenesis.     

Prey selection and predatory impact of four major sea stars on a soft bottom subtidal community

We dived at regular intervals (8-, 12- or 24-h) over periods up to 24 days to quantify the feeding activities of identified sea stars along permanent transects in the upper sediment bottom zone (8-11 m deep). In this habitat, large individuals of four sea stars predominated. The diet of Asterias vulgaris (molluscs and echinoderms) was intermediate between that of Leptasterias polaris (mainly molluscs) and that of Crossaster papposus (mainly echinoderms), whereas the diet of Solaster endeca strongly differed from the other sea stars, as it only fed on holothuroids. Calculation of the Ivlev electivity index indicated little or no selection for many abundant prey species, whereas some rare prey in this zone (e.g., Mytilus edulis) were strongly selected. We quantified prey size selection, and observed evidence of selection on smaller individuals when feeding on infaunal bivalves (possibly the deeper burying of larger individuals limited attacks) and selection of larger individuals when feeding on epifaunal prey (possibly to maximize energetic intake). We observed A. vulgaris feeding on Mya truncata, which had been captured by L. polaris (kleptoparasitism) and this bivalve disappeared from the diet of A. vulgaris in areas where we experimentally removed L. polaris. Estimations of foraging rates over 100 days relative to prey availability indicated strong interactions among the sea stars themselves. C. papposus likely have a strong impact on conspecifics, L. polaris and A. vulgaris, and A. vulgaris on L. polaris. In contrast, <1% of total biomass of the most abundant prey of L. polaris (M. truncata) and C. papposus (Strongylocentrotus droebachiensis) was consumed in 100 days.     

Conservation ecology of endangered species Paphiopedilum armeniacum (Orchidaceae)

Paphiopedilum armeniacum is an endangered orchid species, endemic to China. During the period of April 2000 to October 2005, 66 observation sites were selected in Luoshapo of Nushan Mountains in Yunnan, China, to carry out the conservation ecological research on P. armeniacum. A total of 443 genets (1302 ramets in total) of P. armeniacum were sampled, their biological characteristics such as reproductive pattern, phenology, and life cycle were observed, and the ecological habits of the species such as the habitat and the structure of communities were studied. Experiments on ex-situ conservation were conducted, and the cloned ramets were replanted to their original habitat after ex-situ reproduction in Shenzhen, Guangdong, China. The relationships between P. armeniacum and climate, vegetation, other environmental factors in the original habitat, and the biological characteristics of asexual offsprings of P. armeniacum, which were replanted to the original habitat after ex-situ cultivation and reproduction, were investigated. The studies show that P. armeniacum in Luoshapo grows very well in secondary shrub boskets or in tussocks on limestone hills. It has both sexual and asexual reproduction. Asexual reproduction serves to complete the sexual reproduction and to extend the lifetime of genets, while it does not reduce sexual reproduction. There are two modes of asexual reproduction-by tillering or by producing rhizomes. The litter of shrub boskets or tussocks provides P. armeniacum with humus, and the rhizome reproduction of P. armeniacum is an adaptation to the litter-covered condition, i.e. to escape from the unfavorable environment. Blooming rate of ramets is 7.39% 1.02%, and fruit set rate from the blooming ramets is 32.23% 12.08%. P. armeniacum is able to invade the moderately destroyed forests and those in early restoring but is unable to grow in large dense forests. P. armeniacum also grows very well in artificial spare woods in Shenzhen and can reproduce many cloned ramets, which can normally bloom and yield fruits after being replanted to the original habitat. The results of this study show that P. armeniacum can be conserved by ex-situ conservation and by replanting the ex-situ reproduced ramets to original habitat. On the basis of the analysis of endangered mechanisms of P. armeniacum, it can be concluded that P. armeniacum has strong capability of both asexual and sexual reproductions, and an emergency mechanism consisted of massive production of rhizomes to cope with damage. Because highly effective pollinating insects that facilitate pollination in P. armeniacum are present in the habitat, flowering ramets produce fruits with large quantity of seeds, many of which in turn grow into new genets that can reproduce many cloned ramets. P. armeniacum makes very effective use of its environment and has distinct characteristics of enduring harsh environmental conditions; therefore, rather than its own inherent biological defects, the main threats facing this species are the destruction of its survival space and the wipe-out collecting of the plants as a result of trading. Based on the analysis mentioned above, certain appropriate strategies have been proposed for the conservation of P. armeniacum.     

The influence of population density on fission and growth of Holothuria atra in natural mesocosms

Investigation of the population dynamics, asexual reproduction (fission) and growth of holothuroids has been impeded by the difficulty of tagging individuals. We conducted the first tests on the interactions between population density, fission and growth of holothuroids in experimental populations placed in natural mesocosms (microatolls) at One Tree Reef (OTR), Great Barrier Reef. Similarly sized Holothuria atra were translocated to the microatolls in low (LDT) and high (HDT) density treatments. We hypothesised that holothuroids in lower density treatments would have more resources per individual and that this would promote higher frequencies of asexual reproduction and smaller individuals. The seasonal pattern of fission was similar in natural (unmanipulated) and experimental populations, with the maximum number of fission products occurring in winter and spring. The overall density of the LDT (0.19 ind. m^- 2) and HDT (0.59 ind. m^- 2) did not vary over time. This ‘steady state’ suggested that some fission products died and that asexual reproduction compensated for overall mortality and emigration. There was no difference in sediment chlorophyll pigments between treatments indicating that the different densities of H. atra did not affect benthic microalgal biomass. The percentage of fission products was greater in the LDT than the HDT but this difference was not statistically significant, providing some support for the hypothesis that H. atra in the LDT exhibit a higher fission rates. At the end of the experiment H. atra in LDT were significantly longer and heavier than in HDT. H. atra surpassed their initial deployment weight and length after 13 months in the LDT by 115.2% and 45.2% respectively and in the HDT 86.9% and 24.6% respectively, changing from the small to the large phenotype known for this species. This differential growth may be linked to habitat stability and high benthic productivity and demonstrates the phenotypic plasticity of holothuroids and potential to achieve ‘Optimum Individual Size’ with respect to environmental conditions. Our results will assist in finetuning conceptual models on asexual reproduction and future experimental studies on the phenomena of fission and plastic growth in holothuroids.