Identification of Calmodulin in the Red Alga Susabi Laver (Porphyra yezoensis)

To test whether calmodulin is present in the red alga Susabi laver (Porphyra yezoensis), materials was concentrated from this alga, using hydrophobic chromatography. In this case, 0.25 m (NH₄)₂SO₄ should be added to bind the protein to the column in the presence of 5 mm CaCl₂. Calmodulin is present in the marine red alga, although at a very low concentration.     

Life History Traits of Two Chaetonotids (Gastrotricha) Under Different Experimental Conditions

Summary

A marine and a freshwater species of Chaetonotida (Gastrotricha) were reared under laboratory conditions. Their life tables and principal demographic parameters were determined at 2 different temperatures (20°and 25°C). At 25°C the data relative to the marine species were collected from 5 cohorts kept at 5 different salinity levels (15, 25, 35, 45, 55°/oo).

A higher temperature increases reproductive activity while shortening its duration in both species, whereas the length of the lifespan remains unaffected. Extreme salinity values (15 and 55°/oo) reduce the maximum longevity of the marine species and have opposite effects on reproductive activity, which is higher at low salinity and becomes lower at high salinity. The postparthenogenetic phase is remarkably long relative to the life cycle: this was observed in all experimental conditions and may be related to the existence of a second reproductive phase, which is hermaphroditic and follows the parthenogenetic one, as recently postulated from morphological data.     

Floridoside,L-Isofloridoside,and D-Isofloridoside in the Red Alga Porphyra columbina (Seasonal and Osmotic Effects)

The quantitative heteroside distribution in Porphyra columbina Montagne and Bangia atropurpurea (Roth) C. Agardh (Bangiales, Rhodophyta) has been measured using 13C-nuclear magnetic resonance spectroscopy and gas-liquid chromatography. In P. columbina, floridoside and both D- and L-isofloridoside were recorded, with concentrations of L-isofloridoside exceeding those of floridoside. All three compounds were also measured in B. atropurpurea. Marked changes in the relative amounts of the heterosides were recorded throughout the season. The role of L-isofloridoside in the osmotic acclimation of P. columbina has been demonstrated.     

Effects of Salinity on Primary Processes of Photosynthesis in the Red Alga Porphyra perforata

The effects of salinity on the primary processes of photosynthesis were studied in the red alga Porphyra perforata. The results show that there are at least three sites in the photosynthetic apparatus of this alga that were affected by increased salinity. The first site, photoactivation and dark-inactivation of electron flow on the reducing side of photosystem I, was completely inhibited at high salinity. The second site, electron flow on the oxidizing side (water side) of photosystem II, was inhibited as was the re-oxidation of Q in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The third site affected by high salinity was the transfer of light energy probably from pigment system II to I. High salinity reduced the amount of light energy that reached the reaction centers of photosystem II.

These effects are discussed in relation to the mechanisms available to this plant to avoid photoinhibition when it is exposed to stresses such as high light and high salinity which are conditions that are commonly found in the intertidal habitat.

     

The Effects of Salinity upon Cellular Volume of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in cell volume of the marine red alga Porphyra purpureahave been investigated using photomicroscopic and radioisotopictechniques. There is an inverse relationship between cell volumeand external salt content. The alga responds to changes in thewater potential of its bathing medium by rapid swelling in hyposalinemedia and shrinkage in hypersaline conditions. Cells P. purpureabehave as osmometers in concentrated sea-waters, obeying theBoyle-Van't Hoff law. A non-osmotic volume, 20–25% ofthe total cell volume in sea-water, can be predicted from thelinear plot of volume versus reciprocal pressure in concentratedsea-water media. In dilute sea-waters the presence of non-rigidcell walls serves to limit any increases in cell volume. Theprimary response to dilution stress is thus an increase in turgor.Cell volume is not returned to its original value followingprolonged immersion in either hyposaline or hypersaline media,showing that the alga does not ‘osmoregulate’ sensustricto.     

The Effects of Salinity upon Galactosyl-Glycerol Content and Concentration of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in the major alcohol-soluble, low molecular weight carbohydratesof P. purpurea, O--D-galactopyranosyl-(1-2)-glycerol (‘floridoside’)and O--D-galactopyranosyl-(1-1)-glycerol (‘isofloridoside’),have been examined in response to salinity variation. ‘Floridoside’is shown to vary in absolute amount, increasing in hypersalineand decreasing in hyposaline media. ‘Isofloridoside’content per cell does not change in a similar manner. Responsesare almost identical under light or dark conditions, ‘floridoside’changes being complete within 24 h. Decreasing the externalwater potential using ionic and non-ionic solutes has the sameeffect upon galactosyl-glycerol content. The amount of ‘floridoside’synthesized, and degraded under hypersaline and hyposaline conditionsrespectively is shown to be insufficient to restore cell volumeto its original value. It is therefore suggested that the primaryfunction of ‘floridoside’ increases in concentratedsea-waters is that of a compatible solute, serving to protectthe cell during periods when the external salt content is increaseddramatically.     

Effects of Environmental Factors and Metal Ions on Growth of the Red Alga Gracilaria Chorda Holmes (Gracilariales, Rhodophyta)

Gracilaria is a potentially valuable source of marine biopolymers such as proteins and polysaccharides. In order to select suitable culture conditions, growth and tolerance of Gracilaria chorda Holmes from Shikoku Island in southwest Japan were investigated under variations of temperature (5–30 ^∘C), photon irradiance (20–120 μmol photons m⁻² s⁻¹), and photoperiod (12:12 h, 14:10 h light:dark regime) in a unialgal culture. Gracilaria chorda showed wide tolerances for all factors investigated, which is characteristic of eurythermal species. Maximum growth was observed at 18–24 ^∘C. The optimum photon irradiance for the algal growth was 60–120 μmol photons m⁻²s⁻¹. Instead of using ordinary sea salt (NaCl) to prepare artificial seawater, ultra pure salt was adopted. Gracilaria chorda grew faster in artificial seawater made with ultra-pure salt than that made with ordinary sea salt, probably because the former medium was clear, while the latter was milky. Effects of some metal ions on the growth were tested with artificial seawater. Iron ions affected algal growth, but cobalt ions did not. This study enables us to determine suitable culture conditions for G. chorda. A scaled-up 30 l culture of G. chorda under such conditions was successful.     

Life Cycle of the Tick Haemaphysalis Leporis-palustris (Acari: Ixodidae) Under Laboratory Conditions

The life cycles of two separate populations (colonies A and B) of the rabbit tick, Haemaphysalis leporis-palustris, were studied under laboratory conditions. Domestic New Zealand rabbits, Oryctolagus cuniculus, and wild rabbits, Sylvilagus brasiliensis, were used as hosts for ticks from colony B and only O. cuniculus rabbits were used as hosts for ticks from colony A. Developmental periods were observed in an incubator at 27±1°C and RH 90±5%. Larvae from colonies A and B fed for 8.0±3.7 days and 8.5±1.3 days, respectively, on O. cuniculus. On S. brasiliensis larvae from colony B fed for 7.2±1.3 days. Nymphs from colony A fed for 8.1±1.4 days on O. cuniculus and nymphs from colony B fed for 8.1±1.0 days on S. brasiliensis. Only one engorged nymph from colony B was recovered from O. cuniculus. Females from colony A fed for 20.9±5.9 days on O. cuniculus and females from colony B fed for 18.6±2.4 days on O. cuniculus and 18.7±3.7 days on S. brasiliensis. Engorged larvae from colony A required 13.7±3.7 days to molt while engorged larvae from colony B required 11.8±3.0 and 11.5±1.8 days to molt, after having fed on O. cuniculus and S. brasiliensis, respectively. Engorged nymphs from colonies A and B required 16.3±1.9 days and 14.7±1.4 days to molt, respectively. Engorged females from colonies A and B required 4–7 and 3–5 days, respectively, to start oviposition. Mean egg incubation periods lasted for 33–34 days. For ticks from colony B, host species accounted for significant differences (p<0.05) in larval and nymphal feeding periods, oviposition weights and CEIs. Significant differences (p<0.05) between the two colonies when ticks fed on O. cuniculus were observed for larval and nymphal feeding and premolt periods, engorged female and oviposition weights and conversion efficiency indexes (CEI). S. brasiliensis were always a more suitable host for H. leporis-palustris than O. cuniculus. Significantly more larvae and nymphs engorged and molted when fed on S. brasiliensis (p<0.001). Females fed S. brasiliensis were more successful to lay fertile eggs and showed the highest engorged and egg mass weights, and the highest CEIs. Data of H. leporis-palustris fed on wild rabbits (one of its natural host species) are reported for the first time.     

Ultrastructure of Carposporogenesis in the Red Alga Caulacanthus ustulatus (Gigartinales, Caulacanthaceae)

Carposporangium differentiation in Caulacanthus ustulatus (Turner)Ktzing proceeds through four developmental stages. The youngestcarposporangia are embedded within confluent mucilage and containa nucleus, a few small starch granules, concentric membranebodies and proplastids without a peripheral thylakoid. The intermediate-agedcarposporangia are characterized by the formation of fibrousvacuoles by a fibrous vacuole associated organelle (FVAO). Plastidsalso start to develop their internal thylakoid system. In nearlymature carposporangia, highly active, curved dictyosomes producecored vesicles, while fibrous vacuoles increase in number anddisplay a perinuclear arrangement. Abundant starch granulesare present, some of which exhibit a degenerating appearance.A carposporangium wall is formed and plastids complete theirinternal thylakoid system. Carposporangium maturation is signalledby the presence of adhesive vesicles. Fully developed and peripherallyarranged plastids, centrally located fibrous vacuoles, fewerstarch granules and a monolayered wall are the features of maturecarposporangia. Carposporogenesis, Caulacanthus ustulatus (Turner) Kützing, red algae, ultrastructure     

An Investigation of Tetrasporogenesis in the Marine Red Alga Gastroclonium clavatum (Roth) Ardissone (Rhodymeniales)

Gastroclonium clavatum tetrasporogenesis have been studied usinglight and electron microscopy. They are spherical bodies whichdifferentiate early and 50–70 per branch segment havebeen recorded. The developing sporangia expand into the largethallus cavity. The plastids become dispersed evenly throughthe cytoplasm at this stage. Thylakoids become arranged as parallelarrays and sporadically a single peripheral thylakoid enclosesall the others; the matrices contain globules reaching a maximumdiameter of 270 nm. Plastid multiplication occurs through binaryor multiple fission. The starch occurs in bowl-shaped grains.The mitochondria are always rich in cristae and often providedwith small opaque inclusions. The Golgi apparatus is markedby pleomorphic dictyosome features. Dictyosome-mitochondrionassociations are frequent. The different kinds of cytoplasmicinclusion are described. Gastroclonium clavatum, Rhodophyta, tetrasporogenesis, ultrastructure     

Purification and Characterization of Mannitol-l-Phosphatase in the Red Alga Caloglossa continua (Ceramiales, Rhodophyta)

Purification of mannitol-l-phosphatase, an enzyme catalyzing the final step of mannitol biosynthesis, was first achieved in the mannitol-accumulating red alga Caloglossa continua (Okamura) King et Puttock. The enzyme was shown to be a monomer, since gel filtration and sodium dodecyl sulfate–polyacrylamide gel electrophoresis gave close values of apparent molecular weights of 28,500 and 30,200, respectively. The protein exhibited an isoelectric point of 4.8. The substrate specificity for mannitol-l-phosphate (MIP) was very high, and that for K _m(MIP) was 0.41 mM. The catalytic activity was optimal at pH 7.4. The enzyme was activated by Mg²⁺, but was strongly inhibited by Ca²⁺, NaF, N-ethylmaleimide, and p-hydroxymercuribenzoic acid. Seawater levels of NaCl and physiological levels of mannitol also inhibited the activity by 50% or more. Changes in the concentrations of those ions and metabolites may regulate the biosynthesis of mannitol as an osmoregulant in vivo. Received May 7, 2001; accepted June 15, 2001.     

Life History Studies on the Genus Trillium (Liliaceae) I. Reproductive Biology of Four Japanese Species

Abstract Four Japanese Trillium (Liliaceae) species which are representative perennial herbs of the temperate deciduous forests— Trillium kamtschaticum (2x), T. apetalon (4x), T. tschonoskii (4x) and T. smallii (6x)—were studied for their reproductive characteristics, e.g., patterns of reproductive resource allocation and reproductive output.
In spite of the differences in ploidy levels (from 2x to 6x), all four species showed very similar reproductive traits. It became evident that in response to the increase in reproductive allocation to total reproductive organs (RA), the number of seeds produced per plant (P_N) clearly increased. This trend is well in accord with the relationship found in four North American species and also several temperate woodland perennial herbs which occur in closed, stable and predictable environments, and possess typical xenogamous breeding systems. Although there is no conspicuous trend between ploidy levels and P_N, one of the significant differences noted in this study was in seed weight, which ranged from 2.93 mg in diploids, to 3.42–3.45 mg in tetraploids, and to 4.47 mg in hexaploids.     

Life History Studies on the Genus Trillium (Liliaceae) V. Reproductive Biology and Survivorship of Three Declinate-flowered Species

Absract Three pedicellate-declinate-flowered species of Trillium (Liliaceae), T. vaseyi and T. flexipes , were studied for their life history characteristics, e.g., stage class structures of natural populations and reproductive features, including energy allocation to reproductive activities. The populations structures of all three species showed similar depletion structures characterized by a conspicuous decrease of individuals in the small juvenile stages, as was also observed in pedicellate-erect-flowered Trillium species However, with respect to reproductive characteristics, these three declinate-flowered species showed different features from erect-flowered species, although they belong to the same pedicellate-flowered group. That is, these declinate-flowered Trillium species exhibited low seed setting rates of 30% in T. catesbaei , 45% in T. vaseyi and 34% in T. flexipes , suggesting that they possess different mating systems from erect-flowered species which showed high seed setting rates of 50–90%.     

Response of Phytoplankton Photophysiology to Varying Environmental Conditions in the Sub-Antarctic and Polar Frontal Zone

Climate-driven changes are expected to alter the hydrography of the Sub-Antarctic Zone (SAZ) and Polar Frontal Zone (PFZ) south of Australia, in which distinct regional environments are believed to be responsible for the differences in phytoplankton biomass in these regions. Here, we report how the dynamic influences of light, iron and temperature, which are responsible for the photophysiological differences between phytoplankton in the SAZ and PFZ, contribute to the biomass differences in these regions. High effective photochemical efficiency of photosystem II (/ 0.4), maximum photosynthesis rate (), light-saturation intensity (), maximum rate of photosynthetic electron transport (1/), and low photoprotective pigment concentrations observed in the SAZ correspond to high chlorophyll and iron concentrations. In contrast, phytoplankton in the PFZ exhibits low / ( 0.2) and high concentrations of photoprotective pigments under low light environment. Strong negative relationships between iron, temperature, and photoprotective pigments demonstrate that cells were producing more photoprotective pigments under low temperature and iron conditions, and are responsible for the low biomass and low productivity measured in the PFZ. As warming and enhanced iron input is expected in this region, this could probably increase phytoplankton photosynthesis in this region. However, complex interactions between the biogeochemical processes (e.g. stratification caused by warming could prevent mixing of nutrients), which control phytoplankton biomass and productivity, remain uncertain.     

UV-Absorbing Substance in the Red Alga <Emphasis Type="Italic">Porphyra yezoensis</Emphasis> (Bangiales,Rhodophyta) Block Thymine Photodimer Production

The effect of the water-soluble UV-absorbing substance (UVAS) extracted from the marine red alga Porphyra yezoensis Ueda on UV-dependent thymine photodimer production was investigated. The T<>T pyrimidine-pyrimidone 6-4 dimer and the cyclobutane cis-syn T<>T 5-6 dimer produced by UV irradiation with a xenon lamp were analyzed by reverse-phase high-performance liquid chromatography. Although the dimer production was reduced when the irradiation was filtered through a UVAS solution, it decreased more when thymine was mixed with UVAS. Furthermore, UVAS inhibited the degradation of UV-irradiated thymine. The inhibitory effect of UVAS was significantly greater than that of exogenously added adenine or guanine, which forms complementary base pairs with thymine. These data suggest that in addition to its filtering effect against UV radiation, UVAS also protects thymine by a direct molecule-to-molecule energy transfer process. The protective function of UVAS against UV irradiation is advantageous for this alga under strong UV irradiation.     

氮、硅限制对赤潮藻扁面角毛藻休眠孢子形成的影响

休眠孢子的形成对于赤潮藻种群的保存、延续以及分布扩散等均具有重要的意义。通过单因子营养限制研究氮、硅对赤潮藻扁面角毛藻（Chaetoceros compressus）休眠孢子形成的影响,结果表明：培养基中氮的初始浓度对休眠孢子的出现时间有一定影响。氮的初始浓度越低,休眠孢子出现的时间越早：反之,氮的初始浓度越高,休眠孢子出现的时间越晚。氮缺乏是硅藻形成休眠孢子的必需条件之一,当培养基中氮含量低于10μmol·L^-1时,扁面角毛藻可以形成休眠孢子。氮缺乏诱发的休眠孢子的形成需要大量的硅,当培养基中硅含量低于23μmol·L^-1时,即使氮缺乏,扁面角毛藻也几乎不再继续形成休眠孢子。这说明硅藻休眠孢子的形成不仅受氮浓度的影响,还与硅浓度有关。