CHANGES IN CELL CHEMICAL COMPOSITION DURING THE LIFE CYCLE OF SCRIPPSIELLA TROCHOIDEA (DINOPHYCEAE)1

The cellular content of carbon, nitrogen, amino acids, polysaccharides, phosphorus and adenosine trtphosphate (ATP) was determined at several stages during the life cycle of the dinoflagellate Scrippsiella trochoidea (Stein) Loeblich. Carbon per cell decreased slightly between exponential and stationary phase growth in vegetative cells whereas nitrogen per cell did not change. Both of these cellular components increased markedly on encystment and then decreased to vegetative cell levels during dormancy and germination. C/N ratios increased gradually during cyst dormancy and activation, reflecting a more rapid decrease in N than in C pools, even though both decreased through time. Amino acid composition was relatively constant during the vegetative cell stages; glutamic acid was the dominant component. Arginine was notably higher in cysts than in vegetative cells but decreased significantly during germination, suggesting a role in nitrogen storage. The ratio of neutral ammo acids to total ammo acids (NAA/TAA) decreased as cysts were formed and then gradually increased during storage and germination. The ratio of basic ammo acids to total ammo acids (BAA/TAA) changed in the opposite direction of NAA/TAA, whereas the ratio of acidic acids to total amino adds (AAA/TAA) was generally invariant. Ammo acid pools were not static during the resting slate in the cysts: there was degradation or biosynthesis of certain, but not all, classes of these compounds. The monosacchande composition of cold and hot water extracted polysaccharides was quite different between cells and cysts. A high percentage of glucose in cysts suggests that the storage carbohydrate is probably in the form of glucan. Total cellular phosphorus was higher in all cyst stages than in vegetative cells. However, ATP-cell^?1 decreased as vegetative cells entered stationary phase and encysted, and continued to decrease in cysts during dark cold storage. ATP increased only as the cysts were activated at warm temperatures in the light and began to germinate. The above data demonstrate that dormancy and quiescence are not periods of inactive metabolism but instead are times when numerous biochemical transformations are occurring that permit prolonged survival in a resting state.     

THE CYST-THECA RELATIONSHIP IN CALCIODINELLUM OPEROSUM EMEND. (PERIDINIALES, DINOPHYCEAE) AND A NEW APPROACH FOR THE STUDY OF CALCAREOUS CYSTS

The paratabulate calcareous cyst of Calciodinellum operosum Deflandre was recorded in a sediment trap sample collected in the Bay of Naples (Tyrrhenian Sea, Italy). The germination of this resting stage produced a phototrophic vegetative cell that had the typical plate pattern of a Scrippsiella species. The cyst morphotypes, observed in a clonal culture of this species, ranged from cysts with well-developed paratabulation to cysts in which the paratabulation was barely visible, to cysts covered by irregularly shaped crystals. The analysis of thin sections of the calcareous cysts using the polarized light microscope equipped with crossed nicols and a gypsum plate showed that the optical orientation of the calcite crystals was tangential in all the morphotypes examined. We suggest that the crystallographic method we describe might provide insights for calcareous cyst taxonomy and phylogeny .     

浮游细菌群落变化对锥状斯氏藻藻华的影响

目的:本实验以大亚湾原发性锥状斯氏藻为例,采集野外样品,分析藻华不同时期主要菌群的结构和环境样品的硫化物与赋存形态。方法:应用末端限制性片段长度多态性技术和主成分分析方法,分析藻华发生过程中浮游细菌群落相似程度的情况,得到差异显著的浮游细菌类群。选出代表类群的样品进行16S r DNA高变区测序,获取浮游细菌的分类结果及相对丰度。采用Pearson相关性分析浮游细菌、藻、硫化物两两间的相互关系。结果:早期藻华以Enterobacteriaceae为主导,各优势菌群(Enterobacteriaceae:Alteromonadaceae:Rhodobacteraceae)的比例约为8:1:21,硫元素主要以DMS形式存在;而后期Alteromonadaceae成为优势物种,各优势菌群的比例转变为3:5:25,硫的赋存形态由DMS转变为DMSO;Rhodobacteraceae在藻华的前期与后期均以优势种存在。本实验还发现藻华不同时期4种与藻呈正向相关的细菌,以及8种对藻起负向调节作用的细菌,它们在藻华生消的过程中扮演着不同的角色。结论:菌群的组成性改变与藻华生消具有一定的相关性,并对藻类的硫代谢产生影响。结果的获得有助于认识藻华微生物学过程中硫代谢的生态学功能,拓展锥状斯氏藻藻华的理论认识。     

Diets of Introduced Predators Using Stable Isotopes and Stomach Contents

ABSTRACT In a study of predation on ground-nesting birds at South San Francisco Bay (South Bay), California, USA, we analyzed stomach contents and stable isotopes of carbon and nitrogen to identify commonly consumed prey. We obtained the stomach contents from 206 nonnative red foxes (Vulpes vulpes regalis) collected in the South Bay area and Monterey County during 1995–2001 and from 68 feral cats (Felis silvestris) from the South Bay area during 2001–2002. We determined prey identity, biomass, and frequency, described seasonal diet trends, and derived an Index of Relative Importance. Avian species were the most frequent prey we found in the stomachs of red foxes from South Bay (61%), whereas small rodents were most frequent for red foxes from Monterey County (62%). Small rodents were the most frequent prey we found in feral cats (63%). Carbon and nitrogen isotopic signatures for foxes supported stomach content findings. However, isotope results indicated that cats received a majority of their energy from a source other than rodents and outside the natural system, which differed from the stomach content analysis. We demonstrated the utility of both stable isotope and stomach content analyses to establish a more complete understanding of predators' diets. This information aids natural resource managers in planning and evaluating future predator-removal programs and increases our understanding of the impacts of nonnative foxes and cats on native species.     

THE FATTY ACID AND STEROL COMPOSITION OF FIVE MARINE DINOFLAGELLATES

The fatty acid and sterol compositions of five species of marine dinoflagellates (Scrippsiella sp. Symbiodinium microadriaticum Freud, Gymnodinium sp., Gymnodinium sanguineum Hirasaki, and Fragilidium sp.) are reported. All contained the major fatty acids that are considered common in dinoflagellates, but the proportions were quite variable, and some species contained low contents of some polyunsaturated fatty acids. Concentration ranges for the major fatty acids were: 16:0 (9.0%–24.8%), 18:4(n-3) (2.5%–11.5%), 18:5(n-3) (7.0%–43.1%), 20:5(n-3) (EPA) (1.8%–20.9%), and 22:6(n-3) (DHA) (9.9%– 26.3%). Small amounts of novel very-long-chain highly unsaturated C₂₈ fatty acids occurred in all species. Each dinoflagellate contained a complex mixture of 4-methyl sterols and 4-desmethyl sterols. Four species contained cholesterol, although the amounts were highly variable (from 0.2% of total sterols in Scrippsiella sp. to 45.6% in Fragilidium sp.). All but G. sanguineum contained the 4-methyl sterol dinosterol, and all species contained sterols lacking a double bond in the ring system (i.e. stanols); in Scrippsiella sp. cholestanol composed 24.3% of the total sterols. Other common features of the 4-methylsterol profiles were the presence of 23,24-dimethyl alkylation and unsaturation at Δ²² in the side chain. In Scrippsiella sp., four steroidal ketones were identified: cholestanone, dinosterone, 4α,23,24-trimethyl-5α-cholest-8(14)-en-3-one, and dinostanone. The structures of these corresponded to the major sterols in this species, suggesting that the sterols and steroidal ketones are biosynthetically linked. Steroidal ketones were not detected in the other species. Although fatty acid profiles can be used to distinguish among algal classes, they were not useful for differentiating among dinoflagellate species. In contrast, whereas some taxonomic groupings of dinoflagellates display similar sterol patterns, others, such as the gymnodinoids studied here, clearly do not. The combination of fatty acid, sterol, and steroidal ketone profiles may be useful complementary chemotaxonomic tools for distinguishing morphologically similar species. The identification of steroidal ketones supports earlier suggestions that certain dinoflagellates might be a significant source of such components in marine environments.     

Validation of bysmatrum arenicola horiguchi et pienaar, sp. nov. (dinophyceae)(Note)

Validation here of the name Bysmatrum arenicola Horiguchi et Pienaar sp. nov. rather than Scrippsiella arenicola for this sand-dwelling dinoflagellate from South Africa also corrects the inadvertently invalid basionym publication.     

Biological and nutritional aspects involved in fern multiplication

Gametophytes of several species of ferns were mechanically triturated and the resulting homogenates cultured in vitro for propagation purposes. Differences in the time period from spore culture to sporophyte development were perceivable between species. For those species with a fast life cycle and high sporophyte production such as Woodwardia virginica and Dryopteris affinis sp. affinis, homogenization of gametophytes can be considered to be excellent method for propagation, yielding hundreds of sporophytes in a short period of time. Sporophyte formation was inhibited in O. regalis by the succesive application of homogenization to gametophytes regenerated by this technique. The effect of the culture medium composition on fern production was also studied in O. regalis and P. ensiformis gametophytes. In these species, sporophyte formation increased when the gametophytes were cultured in a medium containing water+0.7% agar. Addition of sucrose inhibited gametophyte development and induced their necrosis. The 1/2 dilution of Murashige and Skoog basal medium, without sucrose, favoured leaf expansion in P. ensiformis sporophytes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Coupled effects of irradiance and iron on the growth of a harmful algal bloom-causing microalga Scrippsiella trochoidea

Effects of irradiance and iron on the growth of a typical harmful algal blooms (HABs) causative dinoflagellate, Scrippsiella trochoidea, were investigated under various irradiances (high light: 70 μmol m^?2 s^?1 and low light: 4 μmol m^?2 s^?1) and iron concentrations (low iron: 0.063 mg L^?1, medium iron: 0.63 mg L^?1 and high iron: 6.3 mg L^?1), and evaluated by the parameters of algal cell density, specific growth rate, optical density and chlorophyll a content. The results indicated that there was significant difference in the cell density of dinoflagellate S. trochoidea between high light and low light intensity treatments across the entire experiments, 7-fold higher at high irradiance as compared with low irradiance, which was further enhanced by the iron concentration. It was found that the maximum cell density of 25 × 10⁴ cell mL^?1 occurred under the combination of high light intensity and high iron concentration, followed by 23 × 10⁴ cell mL^?1 in the combination of high light and medium iron, and 20 × 10⁴ cell mL^?1 in the combination of high light and low iron. There was no significant effect of iron concentration on the cell density under low light intensity. The cell density maintained about 3 × 10⁴ cell mL^?1 across all combinations of iron concentrations and low light in the end of experiments. Such interactive effects of light intensity and iron level dependent were also observed for the specific growth rate, OD₆₈₀ and chlorophyll a content of S. trochoidea. The maximum values of specific growth rate, OD₆₈₀ and chlorophyll a content peaked at the condition of high irradiance and high iron, which were 0.22 d^?1, 0.282 and 0.673 mg L^?1, respectively. In general, their values increased significantly with the increasing of iron concentration at high irradiance, whereas no significant difference was observed among three iron concentrations at low irradiance, all remaining approximately 0.06 d^?1, 0.03 and 0.050 mg L^?1, respectively. Those results suggest that there may be a strong interactive effect between irradiance and iron on microalgal growth and their physiological characteristics. The combination of high light and high iron concentration may accelerate algal cell growth and pigment biosynthesis, thus leading to massive occurrence of HABs.     

温度、光照和pH值对锥状斯氏藻和塔玛亚历山大藻光合作用的影响及光暗周期对其生长速率和生物量的影响

用测定净光合放氧速率的方法研究了温度、光照和pH对锥状斯氏藻(Scrippsiella trochoidea)和塔玛亚历山大藻(Alexandrium tamarense)光合作用的影响.在不同光暗周期(L∶D)条件下培养锥状斯氏藻和塔玛亚历山大藻,研究了光暗周期对生长繁殖速率和生物量的影响.2种藻对温度的变化敏感,适宜的温度范围是17～25℃,最适温度20～22℃,低于10℃和高于30℃不能生长;锥状斯氏藻的光饱和点是400 μmol·m-2·s-1,塔玛亚历山大藻的光饱和点是650 μmol·m-2·s-1, 都属于喜高光强的微藻;2种藻对pH值的变化极其敏感,适宜的pH值范围很小,为7.0～9.0, 最适pH值7.5～8.0, 与其生活的海洋环境一致,pH值高于9.5时, 不能进行有效的光合作用,pH值10.0可致全部细胞死亡;在一定范围内,2种藻的生长速率(μ)和生物量随着光照时间的延长呈比例增加.