PHYLOGENETIC SYSTEMATICS OF THE ULVACEAE (ULVALES,ULVOPHYCEAE) USING CHLOROPLAST AND NUCLEAR DNA SEQUENCES1

Systematic hypotheses for the Ulvaceae were tested using phylogenetic analysis of sequences for the gene encoding the large subunit of RUBISCO, small subunit rDNA and a combined data matrix. Representatives of eight putative ulvaceous genera and twelve additional taxa from the Ulvophyceae and Trebouxiophyceae were included in analyses using maximum parsimony and maximum likelihood criteria. Molecular data supported hypotheses for the Ulvaceae that are based on the early development of vegetative thalli and motile cell ultrastructure. Ulvaceae sensu Floyd and O'Kelly, including Percursaria Bory de Saint‐Vincent, Ulvaria Ruprecht and a complex of closely related species of Chloropelta Tanner, Enteromorpha Link and Ulva L. was supported; however, monophyly of Enteromorpha and Ulva was not supported. The Ulvales and Ulotrichales sensu Floyd and O'Kelly were monophyletic. Blidingia Kylin and Kornmannia Bliding were allied with the former and Capsosiphon Gobi with the latter, although relationships among these and other taxa in these orders remain uncertain. The Ulvales are characterized by an isomorphic life history pattern, gametangia and sporangia that are identical in structure and development, motile cells with bilobed terminal caps and proximal sheaths consisting of two equal subunits. Method of motile cell release and the gross morphology of vegetative thalli are not systematically reliable characters.     

EFFECTS OF LIGHT ON GROWTH,RuBPCase ACTIVITY AND CHEMICAL COMPOSITION OF ULVA SPECIES (CHLOROPHYTA)1

The effects of light on growth, RuBPCase activity, and chemical composition of Ulva curvata (Kütz.) De Toni and U.Lactuca L. were examined at a range of temperatures and N-supply levels. Groeth of Ulva speices becomes more light-dependent with increasing temperature and N. The effect of light on RuBPcase is N-dependent, with a positive correlation under N-sufficient and a negative correlation under N-limited conditions. Light effects on pigment levels and ratios may be independent of effects on growth rate. These interactions uncouple growth rate from RuBPCase and pigments, and thus from tissue%N. The limits of variability of the growth-%N relationship can be described by a parabola. Under relative light or temperature-limitation, %N is negatively, growth increase with increasing %N. Tight coupling of seaweed wrowth and chemical composition may therefor be relatively rare in natural waters where growth can be simultaneously limited by light, temperature, and N.     

METABOLIC REGULATION OF AMMONIUM UPTAKE BY ULVA RIGIDA (CHLOROPHYTA): A COMPARTMENTAL ANALYSIS OF THE RATE-LIMITING STEP FOR UPTAKE1

Non-linear time courses of ammonium (NH₄⁺) depletion from the medium and internal accumulation of soluble nitrogen (N) in macroalgae imply that the rate-limiting step for ammonium uptake changes over time. We tested this hypothesis by measuring the time course of N accumulation in N-limited Ulva rigida C. Agardh. Total uptake was measured as removal of NH₄⁺ from medium. Rates for the component processes (transport of NH₄⁺ across the membrane = R_v assimilation of tissure NH₄⁺ into soluble N compounds = R_a, assimilation of tissue NH₄⁺ into soluble N compounds = R_a and incorporation of soluble N compounds into macromolecules = R₁) were determined by measuring the rate of labelling of the major tissue N pools after the addition of ¹⁵N-ammonium. The results indicate that nitrogen-specific rates (mass N taken up / mass N present / unit time) are ranked in the order of R_t < R_a < R₁ Absolute uptake rates (μmol N. mg dry wt^?1. h^?1) showed a different relationship. Membrane transport appears to be inhibited when NH₄⁺ accumulates in the tissue. Maximum uptake rates occur when assimilation of NH₄⁺ into soluble N compounds begins. Assimilation of NH₄⁺ into soluble N compounds was initially faster than incorporation of soluble N compounds into macromolecules. Implications of rate limitations caused by differences in maximal rates and maximal pool sizes are discussed.     

CHANGES IN NITROGEN POOLS IN ULVA FENESTRATA (CHLOROPHYTA) AND GRACILARIA PACIFICA (RHODOPHYTA) UNDER NITRATE AND AMMONIUM ENRICHMENT

The accumulation of nitrogen in different cellular pools by the macroalgae Ulva fenestrata (Postels and Ruprecht) (Chlorophyta) and Gracilaria pacifica (Abbott) (Rhodophyta) was studied in a laboratory experiment. After 8 or 9 days of nitrogen enrichment, nitrate, ammonium, free amino acid (FAA), protein, chlorophyll (chl), phycoerythrin (PE), and insoluble nitrogen pools were extracted and analyzed, and their relative contribution to total nitrogen (TN) was assessed. In U. fenestrata, the nitrate and ammonium enrichments resulted in a significant increase of TN from 2.41% dry weight (dw) to 4.19% and 4.71% dw, respectively. All the extracted N pools increased significantly. In G. pacifica, TN increased more under ammonium enrichment than under nitrate enrichment. In both macroalgae, proteins and FAA were the most important N storage pools. Protein-N ranged from 700 to 2300 μmol N·g dw⁻¹ (43%–66% of TN) and contributed the most to TN increase (41%–89%). The FAA pool was always larger in G. pacifica than in U. fenestrata. In both species, the FAA pool accounted for 4%–17% of TN (70–600 μmol N·g dw⁻¹). In U. fenestrata, nitrate can represent a temporary storage pool: it accumulated up to 200 μmol N·g dw⁻¹ (7% of TN) and contributed more than FAA to overall increase in cellular nitrogen. In contrast, G. pacifica had a small nitrate pool. The PE pool in G. pacifica increased with TN but was never more than 9% of total protein-N or 6% of TN, and it was less important than FAA as a storage pool. All TN was recovered in the extracted and insoluble N pools at the end of the experiment in U. fenestrata. In G. pacifica, the extracted and insoluble N pools accounted on average for 83%–90% of TN.     

Dynamics of total surface bacteria and bacterial species counts during desiccation in the Malaysian sea lettuce, Ulva reticulata (Ulvales, Chlorophyta)

The present study illustrates the dynamics of surface bacteria during post‐harvest desiccation of Ulva reticulata Forsskal. Algal fronds were subjected to desiccation for 31 days. The total surface bacteria and bacterial species counts were monitored for moisture content and water activity index (a_w). There was an 86% decrease in total algal moisture content. However, a_w showed a more gradual decrease. The total bacterial count increased in the first week, reaching a maximum on day 7. After this, there was a drastic drop in the total bacterial count until day 14, and then a more gradual decline towards the end of the process. Six species of bacteria were isolated throughout this process: Azomonas sp., Aeromonas hydrophila, Vibrio alginolyti‐cus, Escherichia coli, Proteus vulgaris and Vibrio para‐haemolyticus. The dynamics of each of these bacterial species exhibited trends similar to the total bacterial count. Based on these findings, the drastic decrease in the total bacterial count after seventh day of desiccation could not be attributed to the a_w or salinity. Therefore, the possible exposure of these bacteria to the algal internal fluid upon the rupture of the thallus cells was seen as the most likely reason for the drop in the bacterial population. Scanning electron microscope micrographs taken after the tenth day of desiccation showed the presence of cracks and areas where the bacteria were exposed to the algal internal fluid. In vitro antibacterial tests of three different solvent extracts of Ulva reticulata were also carried out against these surface bacteria to verify the antibacterial potential of its internal fluid. It was apparent that all these surface bacteria were inhibited by at least one of the three extracts, and there were indications of the possible presence of multicompound antibacterial potential, since extracts of different polarity showed bacteria‐specific activity. Hence, it is possible that Ulva reticulata has the potential to protect itself against the opportunistic bacteria present on its surface and in its environment.     

Resolving the identity of commercially cultivated Ulva (Ulvaceae,Chlorophyta) in integrated seaweed-abalone aquaculture farms in South Africa

Species of Ulva have a wide range of commercial applications and are increasingly being recognized as promising candidates for integrated aquaculture. In South Africa, Ulva has been commercially cultivated in integrated seaweed-abalone aquaculture farms since 2002, with more than 2000 tonnes of biomass cultivated per annum in land-based paddle raceways. However, the identity of the species of Ulva grown on these farms remains uncertain. We therefore characterized samples of Ulva cultivated in five integrated multi-trophic aquaculture farms (IMTA) across a wide geographical range and compared them with foliose Ulva specimens from neighboring seashores. The molecular markers employed for this study were the chloroplast-encoded Ribulose-1,5-bisphosphate carboxylase oxygenase (rbcL), the Internal Transcribed Spacer (ITS) of the nuclear, and the chloroplast elongation factor tufA. All currently cultivated specimens of Ulva were molecularly resolved as a single species, U. lacinulata. The same species has been cultivated for over a decade, although a few specimens of two other species were also present in early South African IMTA systems. The name Ulva uncialis is adopted for the Ulva “Species A” by Fort et al. (2021), Molecular Ecology Resources, 22, 86) significantly extending the distribution range for this species. A comparison with wild Ulva on seashores close to the farms resulted in five new distribution records for South Africa (U. lacinulata, U. ohnoi, U. australis, U. stenophylloides, and U. aragoënsis), the first report of a foliose form of U. compressa in the region, and one new distribution record for Namibia (U. australis). This study reiterates the need for DNA confirmation, especially when identifying morphologically simple macroalgae with potential commercial applications.     

Microbiology and storage life of fresh edible seaweeds

Samples of two edible seaweeds, Palmaria palmata and Ulva rigida, were stored at 4 °C after harvesting, and their microbial flora were measured over a period of two weeks, using food control methods. The results showed a low level of mesophilic aerobes, fungi and yeasts throughout the storage period, whether the seaweeds were unwashed, or washed with seawater, and there was a satisfactory retention of physical characteristics. Seaweeds washed with tap water degraded in less than one week.     

高温对环带锦斑蛾幼虫滞育的抑制作用

本文报道了高温（31℃）对环带锦斑蛾幼虫滞育发生的抑制作用。当幼虫暴露于31℃ 时,所有个体都继续发育,与光周期无关。在诱导滞育的光周期条件(L12∶D12)下,光期的高温配合不同的暗期低温（15～28℃）,导致几乎所有个体滞育,但当暗期为5℃时,滞育率反而下降;相反,当光期的低温配合不同持续时间的暗期高温（31℃）时,则几乎所有的个体都继续发育,这说明高温在暗期发挥着重要的作用。在暗期给予不同时间长度（2、4、 6、8、10、12 h）的高温处理,结果表明一个2 h的高温处理就能有效地抑制滞育的发生。在暗期的不同时间给予4 h高温处理,显示了幼虫在暗期开始后的第一个4 h (18:00～22:00 )对高温最敏感,完全抑制了滞育的发生。最后讨论了高温调节滞育机制在该虫生活史上的适应意义。     

SEXUALITY AND UNIPARENTAL INHERITANCE OF CHLOROPLAST DNA IN THE ISOGAMOUS GREEN ALGA ULVA COMPRESSA (ULVOPHYCEAE)1

Ulva compressa L. is a heterothallic macroalga considered to be in the early evolutionary stage between isogamy and anisogamy. Two genetic lines of this species, each consisting of gametophytes with opposite mating types, were collected on the coasts of Ehime and Iwate prefectures: MGEC‐1 (mt⁺) and MGEC‐2 (mt^?) from Ehime, and MGEC‐5 (mt⁺) and MGEC‐6 (mt^?) from Iwate. Their relative gamete sizes (i.e., cell volumes) do not correspond to their mating types: MGEC‐6 (19.8 μm³) > MGEC‐1 (18.6 μm³) > MGEC‐5 (17.0 μm³) > MGEC‐2 (10.1 μm³). The pattern of organelle inheritance is an important sexual characteristic in many eukaryotes. We therefore investigated the relationship between gamete size and the inheritance of chloroplast DNA (cpDNA). Polymorphisms between the cpDNA of the two lines were used as markers. We found a 24 bp insertion between psbF and psbL, and the substitution of a StyI site (from C CAAGG to T CAAGG) in the intergenic region between petD and accD. Two interline crosses (MGEC‐1 × MGEC‐6 and MGEC‐2 × MGEC‐5) produced 42 and 38 zygotes, respectively. PCR and PCR–RFLP analyses showed that the cpDNA of the mt⁺ gametes was consistently inherited in both crosses. The cpDNA is inherited from one parent only, and it depends not on gamete size but on being mt⁺. The cpDNA was observed during crossing and in the zygotes 6 h after mating. In 6% of the zygotes, the cpDNA derived from the mt^? gametes disappeared 3–4 h after mating. Preferential digestion of the cpDNA in the zygote’s mt^? gamete may form the basis for uniparental inheritance of cpDNA.     

Use of the green alga Ulva rigida C. Agardh as an indicator species to reassess metal pollution in the Thermaikos Gulf, Greece, after 13 years

The concentrations of metals (Mn, Pb, Fe, Zn, Cu, Cd,Co, Ni, Cr, Na, K, Ca, Mg) were determined in thegreen alga Ulva rigida, in the sediment andseawater of Thermaikos Gulf (Greece) during monthlysamplings in 1994–1995. This Gulf is the recipientof domestic and industrial effluents. Pb, Fe, Cu, Coand Cr concentrations in U. rigida at the studyarea were higher than those 13 years earlier andapparently came from different sources than those forZn, Cd and Ni. The relative abundance of metals inthe alga decreased in the order: Mg > Na > K >Ca > Pb > Fe > Mn > Zn > Cr, Cu > Ni >Co > Cd. Only Cu concentrations in the alga fromKalochori and Cd ones from Viamyl showed significantseasonal changes. Cu and Cd concentrations ingeneral followed the same pattern of variation, withminimum values in winter-spring. This pattern isdiscussed in relation to growth dynamics and tissueage. Only Pb concentrations in the alga showed asignificant positive correlation with concentrationsin the seawater. There were both positive andnegative correlations among some metals in the alga. It is concluded that U. rigida can be used as anindicator species, especially for Pb.