SPORELING COALESCENCE AND INTRACLONAL VARIATION IN GRACILARIA CHILENSIS (GRACILARIALES,RHODOPHYTA)1

This study evaluates the hypothesis that spore coalescence may cause intraclonal variation. Spore coalescence might allow the occurrence of unitary thalli that in fact correspond to genetically different, coalesced individuals. Plant portions simultaneously derived from these chimeric individuals may exhibit dissimilar growth responses even when incubated under similar abiotic conditions. Testing of the hypothesis included various approaches. Transmission electron microscopy observations of early stages of sporeling coalescence indicated that polysporic plantlets were formed by groups of spores and their derivatives. Even though adjacent cells in two different groups may fuse, these groups maintained an independent capacity to grow and form uprights. Laboratory-grown plantlets showed a significant correlation between the initial number of spores and the total number of erect axes differentiated from the sporeling. Construction and growth of bicolor individuals indicated the chimeric nature of the coalesced individuals. Coalesced, bicolor holdfasts had green and red cells, which subsequently produced green and red uprights, respectively. Individuals fronds were also chimeric, as indicated by the production of green and red branchlets from single, red uprights. The existence of mixed tissues was further substantiated by random amplified polymorphic DNA analysis. The banding pattern produced by branchlets of a unisporic thallus was consistently monomorphic, whereas the patterns produced by the polysporic thallus were polymorphic. Growth rates of polysporic thalli had larger data dispersal and variation coefficients than oligosporic or monosporic thalli. Therefore, all results support the original hypothesis and suggest that coalescence might be ecologically more important than previously thought.     

QUANTIFICATION OF THE EFFECTS OF SPORELING COALESCENCE ON THE EARLY DEVELOPMENT OF GRACILARIA CHILENSIS (RHODOPHYTA)1

Sporeling coalescence in species of Gracilariales and Gigartinales is predicted to result in larger basal areas of growing disks as well as earlier initiation, increased abundance, and faster growth rates of erect shoots as compared to noncoalescent sporelings. These responses have been interpreted as providing mutual benefits for organisms living in aggregation, counterbalancing disadvantages associated with crowding. Quantitative evaluations of sporelings of Gracilaria chilensis failed to support several of these predictions. Sporelings were grown in the laboratory from a range of single sporelings to coalescent masses of 20 sporelings. Coalescent sporeling masses of G. chilensis exhibited larger basal areas than noncoalescent ones, but because the specific growth rates were inversely related to the original number of carpospores, no significant differences in actual area increments, during most of the experiment, were found among sporelings derived from one, two, or three to five coalescing sporelings. Initiation of erect shoots occurred at a similar time, regardless of their origin, i.e. coalescent or noncoalescent. Abundance of erect shoots was only loosely related to the number of coalescing sporelings. Even though by the end of the experiment (week 18), the total length of the longer erect shoots arising from coalescent sporeling masses was significantly greater than that of shoots arising from noncoalescent sporelings, total length was independent of the original number of coalescing sporelings. Furthermore, specific elongation rates between week 12 and week 18 were significantly greater for noncoalescent sporelings than for coalescent sporeling masses. Quantitative screening of other species seems necessary before generalizations on the ecological advantages of sporeling coalescence in seaweeds can be made.     

DIURNAL FLUCTUATION OF NITRATE REDUCTASE ACTIVITY IN THE MARINE RED ALGA GRACILARIA TENUISTIPITATA (RHODOPHYTA)1

The biochemical characteristics and diurnal changes in activity of the enzyme nitrate reductase (NR; EC 1.6.6.1) from the marine red alga Gracilaria tenuistipitata var. liui Zhang et Xia are described. Different assay conditions were tested to determine the stability of NR. The crude extract of G. tenuistipitata has a NR specific activity of 10.2 U.mg⁻¹, which is higher than the NR activities found for other algae, plants, and fungi. This NR is highly active at a slightly alkaline pH and is stable over a wide range of temperature, with an optimal activity at 20° C. The apical portions of the thallus contain 64.9 ± 6.6% of the total NR specific activity. The apparent Michaelis-Menten (K_m) constant found for KNO₃ was 197 μM, and it was 95 μM for NADH. The NR from G. tenuistipitata can be included in the NADH-specific group, because no activity was found when NADPH was used as an electron donor. In extracts of algae grown under either continuously dim light or a light-dark cycle, the activity of NR exhibits a daily rhythm, peaking at the middle of the light phase, when activity is 30-fold higher than during the night phase.     

INFECTIOUS DISEASES OF MAZZAELLA LAMINARIOIDES (RHODOPHYTA): CHANGES IN INFECTION PREVALENCE AND DISEASE EXPRESSION ASSOCIATED WITH SEASON,LOCALITY, AND WITHIN-SITE LOCATION1

This study addresses the issues of infection prevalence and disease expression in two wild populations of the red algal host Mazzaella laminarioides and their variability associated with locality, season, and spatial location of the host in the intertidal zone. Our results demonstrated that Endophyton ramosum is the most frequent infective pathogen affecting M. laminarioides in Matanzas and Pucatrihue. This situation prevailed through the year and across the high-to-low intertidal gradient. Although there was a general trend for lower levels of infection in late winter and early spring, only in a few, cases was well-defined seasonality detected. Furthermore, clear seasonal patterns, as displayed by deformative disease in the high intertidal zone of Pucatrihue, were attenuated in the middle and lower intertidal zones. Differences in levels of infection in M. laminarioides between the high intertidal zones of Matanzas and Pucatrihue diminished toward the low intertidal zone. Thus, effects of seasonality and locality on infection prevalence may be influenced, at least in part, by the position of the hosts an the intertidal zone. Spatial distribution of the diseased individuals also varied along the beach. This pattern was consistent between the two sites and seemed related to wave exposure and the specific pathogen. Comparisons of the size distribution of noninfected fronds with their infected counterparts showed that infections by Endophyton ramosum and Pleurocapsa sp. more frequently affected medium-and large-sized fronds. This pattern was consistent temporally and similar in the two localities. Finally, a clear association between maturity and prevalence of infection was detected. This association resulted in most fronds of the noninfected segment of the host population being immature, whereas most mature fronds were infected. In conclusion, infectious diseases affecting the red alga Mazzaella laminarioides are a persistent phenomenon in wild populations of the host, although only a small segment of the infected populations displays the full expression of the disease. In spite of the suggested role of factors such as season, latitude, and spatial location of the host on disease prevalence and expression, additional studies are needed to understand fully the dynamics of infectious diseases in wild populations of algal hosts.     

STEROLS OF PORPHYRIDIUM(RHODOPHYTA)1,2

Species of the unicellular Porphyridium have been examined for their sterol content. Clones of 4 species maintained in axenic, chemically-defined culture were analyzed—these included P. sordidum Geitler, P. purpureum (Bory) Ross, P. aerugineum Geitler and P. violaceum Kormnann(P. griseum Geitler was not available to use for examination). The major sterol was 22-dehydrocholesterol in all except P. aerugineum in which there was a mixture of this sterol, cholesterol and higher sterols. Traces of C₂₈ and C₂₉ sterols were detected in most instances as well.     

LATITUDINAL TRENDS IN THE GROWTH AND REPRODUCTIVE SEASONALITY OF DELESSERIA SANGUINEA,MEMBRANOPTERA ALATA,AND PHYCODRYS RUBENS (RHODOPHYTA)1

The seasonality of Delesseria sanguinea, Membranoptera alata, and Phycodrys rubens (Rhodophyta) was studied at Helgoland (North Sea, Germany) and Roscoff (Brittany, France). Plants were collected at bimonthly intervals, and growth and reproduction were monitored. Growth of blades was observed mainly in spring, although small blades were found on plants of M. alata and P. rubens all year round. In summer, plants started to degenerate and in autumn they became fertile. The reproductive season of D. sanguinea lasted from October to February/April at both locations, whereas reproductive plants of M. alata and P. rubens were found until April at Helgoland and until June and August, respectively, in Roscoff_: Lower winter temperatures at Helgoland than at Rascoff may have caused these differences in the duration of the reproductive season. Using published data, the seasonal patterns at Helgoland and Roscoff were compared to those found at other locations (e.g. Barents Sea; Maine, USA; Isle of Man, UK) and local temperature/daylength conditions. Blade growth was synchronized across all populations and occurred in spring, when temperatures were usually still suboptimal for growth. Maximum reproduction was generally found in the colder half of the year but started earlier in autumn in the Barents Sea. Adaptive strategies in the seasonal control of growth and reproduction are discussed. Adequate timing of the history events (e.g. appearance of juveniles in spring) appears more important than maximal growth and reproduction of adults during the season with the most favorable temperatures.     

DIRECT ENUMERATION OF BACTERIA FROM MACROALGAE BY EPIFLUORESCENCE MICROSCOPY AS APPLIED TO THE FLESHY RED ALGAE KAPPAPHYCUS ALVAREZII AND GRACILARIA SPP. (RHODOPHYTA)1

This report describes a simplified method for direct counting of total bacteria associated with the fleshy red algae Kappaphycus alvarezii (Doty) Doty and Gracilaria spp. A Nuclepore® polycarbonate membrane (0.2–μm pore size) fitted to a vacuum filtration apparatus was used to filter algal tissue homogenate after serial dilution and staining with the fluorochrome 4′,6-diamidino-2-phenylindole. Using epifluorescence microscopy, it is possible to count bacteria without preseparating them from the algae. The technique requires homogenized algal tissue diluted with 0.2-μm-filtered, autoclaved seawater to a level appropriate for counting. Dilution reduces the amount of autofluorescent algal debris, which may interfere with Counting. The membrane filtration method yielded a bacterial count two orders of magnitude higher than that of the conventional agarspread plate technique. This method offers a more accurate approach to counting the total number of bacteria on macroalgae.     

CHARACTERIZATION OF SCHIZOSERIS CONDENSATA,SCHIZOSERIDEAE TRIB. NOV. (DELESSERIACEAE,RHODOPHYTA)1

The Myriogramme group of Kylin contains two distinct clusters of genera that merit recognition at the tribal level. We previously established the tribe Myriogrammeae, and in this paper we erect the Schizoserideae based on a study of the type species of Schizoseris, S. laciniata (=S. condensata), from the southern hemisphere. The Schizoserideae is characterized by 1) marginal and diffuse intercalary meristems; 2) nuclei initially arranged in a plate in the median plane in meristematic and mature cells; 3) chloroplasts one to few, lobed or dissected; 4) microscopic veins absent; 5) procarps scattered, formed singly on either side of the blade with cover cells absent and consisting of a one- to two-celled lateral sterile group, a one- to two-celled basal sterile group, and a four-celled carpogonial branch in which the trichogyne passes beneath the lateral sterile group and emerges anterior to it; 6) auxiliary cell diploidized by a connecting cell cut off posteriolaterally from the fertilized carpogonium; 7) gonimoblast initial cut off laterally from one side of the auxiliary cell and giving rise to unilaterally branched gonimoblast filaments bearing carposporangia in branched chains; 8) gonimoblast fusion cell highly branched, candelabra-like, incorporating all but the basalmost cells of the carposporangial chains and radiating through the central cells in the floor of the cystocarp; 9) spermatangial and tetrasporangial sori formed from surface cells in both monostromatic and polystromatic portions on both sides of the blade; and 10) tetrasporangia formed primarily from cortical rather than from central cells. The Schizoserideae presently includes Schizoseris Kylin, Neuroglossum Kützing, Abroteia J. Agardh, and Polycoryne Skottsberg in Kylin and Skottsberg.     

BETA/KAPPA-CARRAGEENANS AS EVIDENCE FOR CONTINUED SEPARATION OF THE FAMILIES DICRANEMATACEAE AND SARCODIACEAE (GIGARTINALES,RHODOPHYTA)1

The Dicranemataceae consists of five species in four genera of macroscopic red algae endemic to the southern half of Australia plus a single species from southern Japan. Investigations of the nonfibrillar wall components of five of the six species show that all are composed mainly of hybrid (or mixed) beta (β)/kappa(κ)-type carrageenans. Detailed studies of Tylotus obtusatus (Sonder) J. Agardh show that it produces the largest dry-weight percentage of β-carrageenan yet recorded. Monosaccharide composition, total sulfate content, sulfation pattern revealed by infrared and ¹³C-nuclear magnetic resonance spectroscopy and a positive specific optical rotation ([α]_D+ 54°) are indicative of a low-sulfate-containing carrageenan with gelling properties similar to those of agar and furcellaran. β-carrageenan is recorded in only five other red algal species belonging to relatively unrelated families, and we conclude that its uniform occurrence in the highly specialized family Dicranemataceae has phylogenetic significance. Chemical and anatomical examination of the genus Sarcodia, which produce lambda-type carrageenan in both its gametophytic and tetrasporophytic phases, suggests that, despite the recent proposal to incorporate the Dicranemataceae into the Sarcodiaceae, the two families should continue to be separated.     

SEASONAL PATTERNS OF PHOTOSYNTHESIS AND LIGHT-INDEPENDENT CARBON FIXATION IN MARINE MACROPHYTES1

The contribution of light-independent carbon fixation (LICF) to the overall carbon gain and the seasonal patterns of maximum photosynthesis (P_max and LICF were characterized in a broad taxonomic range of macrophytes from Monterey Bay, California. P_max and LICF rates (nmol C.g filtered seawater^?1.min^?1) varied among species and taxonomic groups examined, and as a function of tissue type in the phaeophyte Laminaria setchellii Silva (Phaeophyceae). On average, P_max values were higher in the Rhodophyta, whereas LICF rates were greater in the Phaeophyceae. LICF rates were generally less than 5% of P_max in the marine macrophytes studied and, as a consequence, cannot fully compensate for respiratory carbon losses, which usually are greater than 10% of P_max. All species studied possessed the highest P_max and LICF rates when irradiance levels were highest and decreased during periods of low incident irradiance. Seasonal patterns of P_max and LICF in most of the macrophytes from the stenothermal environment of Monterey Bay were strongly correlated with photosynthetic photon flux rather than seawater temperature. The concomitant decrease of LICF and P_max rates in all species examined argues against LICF playing a major role in carbon acquisition under light-limiting conditions as suggested previously. Rather, the strong positive correlation of P_max and LICF indicates the direct coupling of photosynthate (e.g. 3-phosphoglyceric acid) generation with production of substrates for LICF reactions. Our results also suggest that LICF might be a useful indicator of photosynthetic metabolism in marine macrophytes.     

DIVERSITY OF HALOGENATED SECONDARY METABOLITES IN THE RED ALGA LAURENCIA NIPPONICA (RHODOMELACEAE,CERAMIALES)1,2

Many morphologically similar, but chemically distinct, populations have been found in the marine red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) growing in Japan. Each chemical type is characterized by a specific end-product of halogenated secondaly metabolite synthesis: chamigrane-type sesquiterpenoids such as prepacifenol and halochamigrene epoxide and C₁₅ bromoethers such as laurencin, laureatin, isoprelaurefucin, epilaurallene, and kumausallene. These seven types of secondary metabolite syntheses remained the same in the wild and under various culture conditions. Because bromoethers and terpenoids are probably synthesized by different metabolic pathways, it is virtually certain that different sets of enzymes participate in their synthesis. Prepacifenol- and laureatin-producing populations were selected as representatives of terpenoid and bromoether groups, respectively. F₁ tetrasporophytes derived from crosses between reciprocal, female and male gametophytes of prepacifenol- and laureatin-producing strains bore both types of metabolites, suggesting that the genes Producing these enzyme systems are encoded by nuclear genomes. The F₁ gametophytes resulting from the reciprocal crosses produced either prepacifenol or laureatin, and the four individuals derived from spore tetrads (a set of tetraspores derived from a single tetrasporangium) produced either prepacifenol or laureatin in a 1:1 ratio, indicating that genes participating in terpenoid synthsis and those participating in bromoether synthesis are on different loci of homologous chromosomes and are segregated at meiosis (tetrasporogenesis). One individual of this interpopulational F₁ gamtophyte produced both parental types of metabolite, perhaps indicating the occurrence of a recombination type. Natural hybrid individuals, including such recombination-type gametophytes, were found in a sympatric locality at which these two chemical types occur. F₁ tetrasporophytes derived from crosses between respective prepacifenol- and laureatin-producing strains and their F₁ gametohytes produced only parental-type metabolite-producing plants. These results indicate that the diverse chemical types can be referred to as races (chemical races).     

REGULATION OF A GLUCOSE TRANSPORT SYSTEM IN STICHOCOCCUS BACILLARIS1

Glucose and related non-metabolizable analogs were transported into cells of Stichococcus bacillaris Naeg. By a specific and active transport system. Glucose transport capacity was stimulated eight-fold by incubation in medium of low osmotic potential (0.09 osM). Stimulation occurred over 24 h in the dark and over 72 h in low osmotic medium. Inhibition of protein synthesis prevented any transport, stimulation from occurring. Kinetic studies revealed that the stimulation caused an increase in Ike maximal velocity of transport and did not affect the half-saturation constant for transport. It was concluded that incubation of cells in the dark or in low osmolar medium induces a synthesis of the transport system. The glucose analog 2-deoxy-D-glucose was only phosphorylated to a limited extent upon entry into the cells, and the free sugar accumulated linearly in dark pre-incubated tells for a period of at least six minutes to reach an intracellular/extracellular concentration ratio of almost 300. Glucose, in contrast, was rapid h converted to sucrose and other cell constituents. Cells incubated 24 h with, glucose or 6-deoxy-D-glucose did not exhibit any altered transport system activity. Cells incubated 24 h with 7 mM dibutyryl cAMP exhibited a 2.5-fold stimulation of transport activity. No stimulation was observed in cells treated only 30 min with dibutyryl cAMP.     

RECENT APPEARANCE OF CYLINDROSPEMOPSIS (CYANOBACTEIUA) IN FIVE HYPEREUTROPHIC FLORIDA LAKES1

Observations of historical and recent phytoplankton samples from five hypereutrophic Florida lakes indicate that nitrogen-fixing cyanobacteria in the genus Cylindrospermopsis Seenayya et Subba Raju have entered these water-bodies sometime in the last 30 years. Cylindrospermopsis forms a year-round bloom in one of the five lakes, dominates seasonally in another, and is at least at times an important component of the phytoplankton community in the remaining three. The increase in abundance of Cylindrospermopsis in Florida lakes could have implications for water management.     

PHACOTUS LENTICULARIS (CHLAMYDOMONADALES,PHACOTACEAE) ZOOSPORES REQUIRE EXTERNAL SUPERSATURATION OF CALCIUM CARBONATE FOR CALCIFICATION IN CULTURE1,2

In nature, zoospores of the chlamydophycean genus Phacotus Perty usually have a calcified lorica. The only cultured species, Phacotus lenticularis (Ehrenberg) Stein, did not readily calcify in artificial media. To overcome this deficiency, we developed an artificial culture medium (N-HS) in which Phacotus lenticularis formed mineralized loricae, as under natural conditions. Calcification of Phacotus (strain Krienitz 91/1) was achieved in a medium containing the ionic concentrations found in natural habitats (i.e. Lake Haussee and Lake Stechlin), hard-water lakes of the Baltic Lake District (Germany). The N-HS medium contained extremely low phosphate concentrations and high calcium and magnesium concentrations compared with common culture media, but the concentrations were similar to those in the lakes. Calcium carbonate in N-HS medium was dissolved up to the saturation concentration (saturation index = 1). Supersaturation was achieved by the addition of ultra-alkaline compounds (Na₂S_iO₃ or NaOH). The medium with the highest super-saturation had a saturation index of 118 and was extremely supersaturated with respect to calcium carbonate. In that medium and in modified media with less of the sodium compounds (lower supersaturations), calcification of zoospores was observed. To determine the effects of sodium and silicon compounds on calcification, various other silicon and sodium compounds were tested but were shown to be ineffective. In conclusion, calcification of Phacotus lenticularis depends directly on the degree of calcium carbonate supersaturation of the medium, but the fundamental mineralization pattern does not. Our study shows that calcification in Phacotus lenticularis can be triggered and controlled by supersaturation of calcium carbonate.     

THE CYTOSKELETON OF THE NAKED GREEN FLAGELLATE SPERMATOZOPSZS SIMILIS (CHLOROPHYTA): ANALYSIS OF ISOLATED BASAL APPARATUSES IN THE PARALLEL CONFIGURATION1,2

The biflagellate green alga Spermatozopsis similis is demonstrated to be a model organism for the biochemical and functional analysis of the basal apparatus. Basal apparatuses were isolated in the presence of 10⁻⁶ M Ca²⁺, which induces the reorientation of the basal bodies into the parallel state. Serial thin sectioning of enriched basal apparatuses stained with tannic acid reveals several novel details of the structure of the basal bodies, the distal connecting fiber, and the striated microtubule-associated fibers. We observed a pronounced difference in size of a striated fiber connecting the basal bodies to the five-stranded microtubular roots depending on its association with the developmentally older or younger basal body. Instead of a proximal connecting fiber, the proximal end of each basal body is associated with a striated triangular plate; these plates appear to serve as spacers for the basal bodies in the parallel and antiparallel configurations. We suggest that the plates play a role in maintaining basal body orientation during forward and backward swimming. The results are summarized in representative drawings of the basal apparatus.     

FIVE NEW GOMPHONEMA SPECIES (BACILLARIOPHYCEAE) FROM RIVERS IN SOUTH AFRICA AND SWAZILAND1

Diatom material from South Africa and Swaziland was examined with light and scanning electron microscopy. Five new taxa are proposed: Gomphonema crocodilei, G. quasicrocodilei, G. venusta, G. latistigmata, and G. cholnokyi. Gomphonema venusta has been previously misidentified as Gomphonema clevei Fricke and G. cholnokyi as G. subclavatum (Grunow) Grunow. All of the species possess biseriate striae, areolae with external vela, a true stigma, and marginal laminae underlying the valve margin and mantle. Compared to the other members of gomphonemoid lineage, the five new species show greatest similarity to Gomphoneis mesta Passy-Tolar & Lowe, G. magna Kociolek & Stoermer, and G. rhombica (Fricke) Merino, García, Hernández-Mariné, & Fernández and to the Herculeana lineage of Gomphoneis sensu Kociolek and Stoermer. The most recent phylogenetic analysis of the genus Gomphoneis showed that the two lineages of the genus. Herculeana and Elegans, are not monophyletic. The Herculeana lineage is more closely allied to Gomphonema than to the Elegans lineage. Since the Elegans lineage contains the generitype of Gomphoneis (G. elegans (Grunow) Cheve), and the species described here are more closely related to the Herculeana lineage, we have assigned them to Gomphonema.     

COORDINATNE NUCLEAR AND CHLOROPLAST DIVISION IN UNILOCULAR SPORANGIA OF LAMINARIA ANGUSTATA (LAMINARIALES,PHAEOPHYCEAE)1

Changes in the number of nuclei and chloroplasts were examined during the process of unispore formation in unilocular sporangia of Laminaria angustata. Just before meiosis, eight chloroplasts were always present in unilocular sporangial mother cells. The number of chloroplasts remained constant through meiosis. After the resulting four nuclei divided again (third nuclear division), a close association between a nucleus and a chloroplast developed among each of the eight nuclei and eight chloroplasts. The eight chloroplasts divided ahost synchronously before the synchronous division of the eight nuclei. Following the 16 nucleate stage with 16 chloroplasts and the final 32 nucleate stage with 32 chloroplasts, 32 unispores, each with a nucleus and a chloroplast, were fomd in unilocular sporangza of L. angustata. Immunofluorescence microscopy using an anti-centrin antibody showed that two anticentrin-stained structures (as future mitotic poles) occurred adjacent to each of the premitotic four nuclei, and each spot was located near a chloroplast. Therefore, after the third division, each of the eight nuclei established close contact with a chloroplast presumably mediated by the centrosomes.