Forty clones of Gonium pectorale M'uller were crossed in all combinations at 20°C, and the resultant zygotes examined to determine the degree of sexual compatibility within a single population. Clones isolated from the same site but in different years were incompatible, indicating a lack of gene flow between them. Two distinct groups were found within 31 clones isolated from a single mud sample, and all the clones in one were incompatible with all those in the other. However, members of both groups were compatible with those in a third group. The existence of at least two complementary pairs of mating types within a single G. pectorale population, sensu Stein (1958b), is considered in the context of other sexual compatibility results, and is proposed as a reason for the occasional inability to obtain opposite mating types from a mud sample from which only a few clones have been isolated. / Science, Faculty of / Botany, Department of / Graduate

The nature of the symbiotic association of the red alga Harveyella mirabilis (Reinsch) Schmitz and Reinke (Cryptonemiales) and its red algal hosts Odonthalia and Rhodomela (Ceremiales) was investigated. The distribution of H. mirabilis was revised to include additional host species as well as a greater range of occurrence in the northeast Pacific. A study of procarp development confirms that H. mirabilis should be retained in the order Cryptonemiales. Based only upon morphological criteria, H. mirabilis has been defined previously as parasitic on its red algal hosts. In the present study, a new definition of parasitism has been formulated to include physiological as well as morphological aspects of parasitism. Accordingly, a red algal parasite is defined as any red alga living temporarily or permanently within or on a host, deriving benefits from it and causing it harm. The association of Harveyella mirabilis and its hosts is considered with regard to (1) the reproductive and developmental dependence of H. mirabilis on a specific host, (2) the possibility of metabolite exchange between host and Harveyella, and (3) the effects of the presence of Harveyella on its host. A field and laboratory study of the development and reproduction of H. mirabilis has revealed that the completion of its life history is dependent on the presence of a suitable host and that reproduction and development are affected by seasonal changes in environmental parameters. Initial spore germination occurs in host wounds inflicted primarily by grazing isopods and amphipods. Rhizoidal cells penetrate the walls between host cells and establish secondary pit connections with host cells. Subsequent development is characterized by rapid proliferation of the rhizoidal cells within the host, a rupturing of the host's outer wall region and the final development of a colourless reproductive pustule. Morphological and cytological studies have shown that H. mirabilis conforms to a typical "Polysiphonia-type" life history. The effects of seasonal fluctuations in seawater salinity and temperature, and changes in the hours of bright sunshine (photoperiod) on the reproduction and development of H. mirabilis have been examined over a 20-month period. Gametogenesis occurred in northeast Pacific populations in the spring and fall between a seawater temperature range of 8.5-11 C whereas tetrasporogenesis occurred in the late winter as both photoperiod and water temperature increased. H. mirabilis is physiologically dependent upon the host 0. floccosa as a source of nutrients. Liquid scintillation analysis and light microscopic autoradiography have demonstrated that H¹⁴CO₃⁻ is photosynthetically assimilated by the host and subsequently transferred to H. mirabilis. The primary flow occurs from host medullary cells to adjacent rhizoidal cells of H. mirabilis. A secondary transfer occurs from host cells dispersed in the pustule to adjacent H. mirabilis cells. Ion exchange chromatography and chemical extraction techniques were employed to separate labeled fractions of 0. floccosa and H. mirabilis after various periods of ¹⁴C-translocation. The change in radioactivity in the alcohol-soluble neutral fraction most closely paralleled the total increase in radioactivity in H. mirabilis and the corresponding decrease in 0. floccosa. To identify translocated compounds, the labeled neutral fractions were separated by paper chromatography. An increase in radioactivity was associated with an unknown substance in Harveyella which had an R glucose value similar to glucuronic and galacturonic acids in both acidic and basic solvent systems. A concomitant decrease in radioactivity was associated with both a high R glucose unknown and mannitol in 0. floccosa neutral sugars separated in both basic and acidic solvents. Cortical, medullary, and rhizoidal cells of H. mirabilis were examined by light and electron microscopy to determine the structural mechanisms involved in nutrient transfer. A membrane system in the rhizoidal cells, consisting of the plasmalemma, pinocytotic vesicles, multivesicular and concentric bodies, ER, dictyosomes, microbodies and an extensive vacuolar system may be involved in the uptake, processing and distribution of nutrients throughout these cells. Histochemical identification was made of proteins, lipids and carbohydrates associated with this vacuolar/vesicle system. Light autoradiography, supported this proposed membrane uptake mechanism. Plasma-lemmal extensions (plasmalemmavilli) of H. mirabilis medullary cells in the pustule may also be involved in nutrient uptake. The effects of H. mirabilis on the host 0. floccosa were also examined by light and electron microscopy. In host medullary cells adjacent to rhizoidal cells, changes occur in vacuolation, plasmalemmal vesiculation, ER, plastids, nuclei, pit connections and walls. Direct penetration of host cells by rhizoidal cells of H. mirabilis occasionally occurs resulting in death of the host cells. Host medullary and cortical cells dispersed in the emergent pustule show few of the degenerative responses noted in host cells adjacent to H. mirabilis, rhizoidal cells. On the contrary, host cell division and photosynthetic assimilation of H¹⁴CO₃⁻ all increase. Spherical virus-like solitary bodies (S-bodies) occur in all cells of H. mirabilis and in host cells attached to H. mirabilis by secondary pit connections. The possibility that these structures may induce the infective host response is discussed. In the concluding discussion the possible evolution of H. mirabilis considered in relation to proposed theories of the origin of red algal parasites. / Science, Faculty of / Botany, Department of / Graduate

A field, culture and cytological investigation has been made of the life histories of Porphyra gardneri (Smith et Bollenberg) Hawkes, P. nereocystis Anderson and P. thuretii Setchell et Dawson, three superficially similar epiphytic red algae (Bhodophyceae, Bangiales). Porphyra gardneri was found from February through November, but is basically a spring-early summer species, Porphyra nereocystis is an autumn-winter species and P. thuretii is a winter-early spring species. The reported number of host species and geographical distribution is increased for all three species. A light microscope study of spermatogenesis and carposporogenesis was undertaken to characterize the spermatangium and carpogonium and to follow their division sequence. The spermatangium in Porphyra gardneri and probably P. thuretii is formed by the production of a new wall layer around a transformed vegetative cell. In contrast, no new wall layer is formed by P. nereocystis spermatangia, making them difficult to distinguish from vegetative cells. The carpogonium of P. gardneri and P. thuretii is easily recognized because it differentiates bipolar prototrichogynes. In P. nereocystis the carpogonium does not form prctctrichogynes and can only be distinguished from vegetative cells by its elongate, rectangular shape. On the basis of these observations and reports in the literature I suggest that the species of Porphyra can be separated into at least two groups based on their spermatangial and carpogonial morphology; the more advanced group has carpogonia with prototrichogynes and clearly defined spermatangia due to the deposition of a new wall layer, whereas the more primitive group lacks these features. The first division in both spermatogenesis and carposporogenesis is periclinal. This is discussed with respect to the division sequences reported by other workers. The transfer of Porphyrella Gardneri Smith et Hollenberg to Porphyra gardneri is explained on the basis of the observed mode of carpogonium formation and carposporangial division. Of the three species studied, only Porphyra gardneri produces monospores. Under all photoperiod and temperature regimes tested monospores germinated into the foliose phase. At an ultrastructural level monosporogenesis in Porphyra gardneri is characterized by the production of abundant small and large fibrous vesicles. The economic implications of monospore production are discussed. Field observations of Porphyra gardneri suggest that photoperiod is an important factor involved in inducinq the formation of spermatangia and carpogonia. A conchocelis phase is reported for the first time for Porphyra gardneri and Porphyra thuretii. Under all photoperiod and temperature reqimes tested carpospores qerminated into the conchocelis phase. In P. sardneri and P. thuretii short days favoured conchosporanqial branch formation; however, no such photoperiodic effect was observed for P. nereocystis., Although my results were inconclusive, reports in the literature indicate that temperature is a critical factor in conchospore release. Amoeboid movement of conchospores is reported for E°I£J3J£§ thuretii and discussed with respect to the occurrence of this phenomenon in the Rhodophyta generally. The epiphyte-'host' attachment zone of Porphyra gardneri and P. nereocystis was examined with the light microscope. The basal rhizoids of P. gardneri penetrate deep into the medulla of the Laminaria blade, whereas the rhizoids of P. nereocystis make only a superficial penetration of the Nereocystis stipe. The spermatia of Porphyra gardneri and P. nereocystis were examined ultrastructurally and found to have many similarities with Florideophycidae spermatia. The occurrence of fertilization in the life history of Porphyra gardneri is documented with the light and electron microscopes. A diploid chromosome number 2n=8 is reported for the carpospores and vegetative cells of the conchocelis phase P. gardneri. This is the first unequivocal report of sexual reproduction in the genus Porphyra. Suspected spermatia attached to the carpogonia and linked to them via fertilization canals have been observed in P. nereocystis and P. thuretii suggesting that sexual reproduction also occurs in their life histories. Reports of sexual reproduction in other members of the Bangiophycidae are evaluated in light of my observations. / Science, Faculty of / Botany, Department of / Graduate

Consumers are concerned about antibiotic and ractopamine usage; therefore, alternatives need to be found. Objectives of this study were to investigate the effects of using seaweed as an alternative feed supplement and comparing performance, carcass, pork quality, and immune traits in pigs fed seaweed, control, and ractopamine diets. Pigs were allocated to one of three treatments (CON, SWE, RAC) at weaning (n = 40/treatment). Pigs were weighed every two weeks. Carcass characteristics, pork quality, and immune data were collected post-mortem. No differences were found between treatments for feed intake, growth, or feed efficiency. Pigs on RAC treatment had greater hot carcass weight and dressing percentage (P < 0.05). Chops from RAC pigs were lighter (P = 0.05), less red (P < 0.05), and tougher (P = 0.08). There were no differences between treatments for FABP2 gene expression, cell proliferation percentages, or crypt depths. Therefore, no negative effects of feeding seaweed to pigs were found in this study.

El alga roja agarófita Gracilaria gracilis (Stackhouse) M. Steentoft, L.M. Irvine & W.F. Farnham crece en Bahía Busta-mante, (Chubut, Argentina). El objetivo general de este estudio fue conocer el estado reproductivo actual de esta pradera natural, como así también los epífitos de G. gracilis y la estructura y propiedades físicas del agar. Información de base indispensable para un futuro desarrollo de esporocultivos. Los muestreos y las mediciones de campo se realizaron men-sualmente entre marzo de 2006 y febrero de 2008. Se evalua-ron las variaciones temporales de la biomasa y los estados reproductivos, poniendo especial atención en la presencia de carposporofitos, por su potencial utilidad en esporocultivos. En ambos años se observó la mayor biomasa a fines de prima-vera y verano, y en el invierno de cada año se registraron los valores más bajos. Se encontró la coexistencia de las tres fases del ciclo de vida durante los dos años, con predominio de tetrasporofitos. Dos conjuntos de datos de individuos se analizaron por separado, los provenientes de la reproducción sexual (tetrasporas y carposporas) y de la reproducción asexual por fragmentación del talo. En la fracción de fragmen-tación, las frecuencias de tetrasporofitos fueron superiores a las de gametofitos. Sin embargo, en la fracción originada a partir de esporas, se observó una tasa de ploidía cercana a 0,5. Los carposporofitos estuvieron siempre presentes, con sus valores máximos en verano y en otoño. Los datos biológi-cos se relacionaron con factores ambientales por medio de un análisis canónico de correspondencias (ACC). El primer año se caracterizó por valores mayores de biomasa de G. gracilis y Undaria pinnatifida, menor epifitismo, talos de Gracilaria más grandes y una mayor proporción de tetrasporofitos y gameto-fitos maduros. El segundo año se caracterizó por una alta proporción de talos vegetativos de Gracilaria y alta densidad de epífitos. El mejor momento para obtener esporas de talos cistocárpicos sería en verano y principios del otoño.También se estudió la diversidad de epífitos creciendo sobre G. gracilis, su variación temporal de abundancia y la estructura anatómi-ca de la interfase hospedante - epífito. Veintinueve especies de algas se registraron como epifitas. La densidad total tuvo valores altos durante todo el segundo año de muestreo.Las infecciones halladas fueron clasificadas teniendo en cuenta la fuerza de adhesión y el grado de invasión de los epífitos, y el grado de daño que causó al hospedante. El tipo I de in-fección, que se caracteriza por epífitos débilmente unidos a la superficie del hospedante y sin dañar sus tejidos, se debió principalmente a la cianófita Calothrix confervicola, una de las especies más abundantes. Ceramium rubrum, junto con Polysi-phonia abscisa y otras Ceramiales, fueron las especies que causaron más daño al hospedante, debido a que sus rizoides penetraron en la porción cortical, llegando a veces al tejido medular (tipo V de infección). Estas especies fueron las más abundantes durante la mayor parte del estudio. Se realizó un estudio comparativo de las propiedades, composición y ren-dimiento del agar de G. gracilis obtenido en las cuatro estaciones del año, relacionándolo con factores ambientales y biológicos de la población. Se realizaron extracciones a diferentes temperaturas, obteniéndose el mayor porcentaje de carbohidratos a 70 C, independientemente de la estación de cosecha. En el material de otoño-invierno, se incrementó el contenido de proteínas. La agarosa de muestras de primavera-verano fue la que presentó mayor fuerza de gel. Se concluye que se puede obtener a partir de G. gracilis de Bahía Busta-mante una agarosa de mejores propiedades gelificantes y de excelente rendimiento extrayendo a temperaturas más bajas de las habituales. / The agarophyte Gracilaria gracilis (Stackhouse) M. Steentoft, L.M. Irvine & W.F. Farnham grows in Bahía Bustamante, Chubut province, Argentina. The biomass variation and the reproduction of the natural Gracilaria gracilis bed in Bahía Bustamante (Argentina) were analyzed during two years, aiming at: knowing the present situation of the population in order to get an updated status overview; establishing the relevant features of the temporal variations in both biomass and reproductive states in relation to three aspects: envi-ronmental factors, epiphytes and associated algae; and assessing the carpospore availability for future spore-culture development. Field measurements and sampling were perfor-med monthly between March 2006 and February 2008. In both years G. gracilis biomass presented marked seasonal varia-tions, with a minimum in winter and a maximum in late spring and in summer. During both years coexistence of the three life-cycle phases was found, with dominance of tetrasporo-phytes. Two data sets from individuals originated from sexual reproduction (tetraspores and carpospores) and from asexual reproduction by thallus fragmentation were analyzed separa-tely. In the fragmentation fraction, tetrasporophyte frequen-cies remained higher than those for gametophytes. However, in the spore- originated fraction, a generation ratio close to 0.5 was observed. Female gametophytes bearing cystocarps were always present, with their maximum values in summer and in autumn. Biological data were related to environmental factors by means of a canonical correspondence analysis (CCA). The first year was characterized by higher biomass values of G. gracilis and Undaria pinnatifida, lower epiphytism, larger Gracilaria thalli and greater proportion of mature tetras-porophytes and gametophytes. The second year was charac-terized by high Gracilarias vegetative thalli proportion and high epiphyte density. The best time to obtain spores from cystocarpic thalli would be in summer and early autumn. In this paper the diversity of epiphytes growing on G. gracilis, their temporal variation of abundance, and the anatomical structure of host-epiphyte interfaces were studied. Twenty-nine algal species were recorded as epiphytes during two years of monthly sampling (March 2006 - February 2008). Total epiphyte density ranged between 0.037 ind.cm-2 (November 2006) and 35.27 ind.cm-2 (April 2007), with high density values during all the second sampling year. The different infections were analyzed taking into account the epiphyte attachment strength and invasiveness, and the degree of damage that it caused to the host. The Infection type I, characterized by epiphytes weakly attached to the host surface and without host tissue damage, was mainly caused by the cyanophycean Calothrix confervicola, one of the most abundant species. Ceramium rubrum, together with Polysiphonia abscissa and other Ceramiales were the most abundant species during most of the study. They were the species that caused more damage to the host because their rhizoids penetrated the cortical portion, reaching sometimes the medullary tissue (Infection Type V). This is the first study of epiphytism in a Gracilaria species of Southwest Atlantic coast.

No description available.

Pseudendoclonium was established in 1900 by N. Wille to include a crust-forming green microalga occurring near the high water line on jetties in Drobak, Norway. Ordinal and familial affiliation of the genus have remained uncertain due to a lack of distinguishing morphological characteristics and because molecular phylogenetic data have not been generated for the type species. Ribosomal SSU rDNA sequence data for Pseudendoclonium submarinum, the type species, are presented. Phylogenetic analysis of these data place Pseudendoclonium within the Ulvales. SSU rDNA sequence data from three additional species, Pseudendoclonium basiliense, Pseudendoclonium akinetum and Pseudendoclonium fucicola are included in the analyses and clearly support the hypothesis that Pseudendoclonium is polyphyletic. Based on the sequence data, P. submarinum and P. fucicola share ulvalean lineage, but these algae are not congeneric and P. fucicola must be removed from Pseudendoclonium. Sequence data support the classification of P. basiliense and P. akinetum as distinct species of a single genus. The close affiliation of these two species with Ulothrix and other Ulotrichalean genera, however, reveals their ordinal separation from P. submarinum. P. basiliense and P. akinetum must also be removed from Pseudendoclonium and require generic reassignment within the Ulotrichales.

Temporal variability in nutrient supply has not generally been considered to be a factor controlling macroalgal community structure. Frequent sampling in environments with multiple nitrogen (N) inputs reveals that N supply varies greatly on scales of hours, days and weeks. This thesis describes studies of the adaptations of macroalgae to variability in N supply and the effects of this variability on the species composition of a macroalgal community. A study was made of the efficacy of using N flux (water flow rate X N concentration) to predict the growth rate of Gracilaria tikvahiae (Rhodophyta). The relationship between growth rate and flow rate was affected by concentration and the relationship between growth rate and N concentration was affected by flow rate such that growth was a linear function of N flux. Thus, N flux proved to be a better predictor of growth rate than water flow rate or N concentration taken alone. Increased N flux during a period of high N concentration increased both the maximum photosynthetic rate and photosynthetic rates at low irradiances of G. tikvahiae and Enteromorpha clathrata. Storage of N taken up during N pulses (relatively short episodes of high N availability) as photosynthetic pigment protein complexes would thus allow macroalgae to fix carbon rapidly to supply carbohydrates necessary for growth during N-limitation and for rapid N uptake during the next N pulse. The effects of nutritional history on NH⁺₄ uptake by Ulva lactuca, Gracilaria tikvahiae and Enteromorpha spp. were investigated. Algae grown at low N fluxes or in N-free medium took up NH⁺₄ much more rapidly than algae grown at high N fluxes. Enteromorpha spp. took up NH⁺₄ more rapidly than the other species. Rapid uptake by algae immediately after collection from the field, after growth at low N fluxes or after growth in N-free medium suggests that N-limited or starved algae in the field can take up pulses of N rapidly (in excess of immediate requirements). G. tikvahiae, Enteromorpha spp., and filva lactuca grew in N-free medium at rates similar to those observed at the high and low N fluxes for 14, 10 and 9 days (respectively), indicating that N taken up during periods of high N availability can support growth in the absence of N. Experimental manipulation of the frequency with which N pulses occurred in the field showed that the frequency with which N pulses occur in nature may be important in regulating the species composition and productivity of macroalgal communities.

No description available.

No description available.