Browsing by Author "Meneses, I"

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    Assessment of populations of Gracilaria chilensis (Gracilariales, Rhodophyta) utilizing RAPDs
    (1996) Meneses, I
    Phenotypic variability and mixing of material due to massive cultivation for commercial purposes has contributed to the taxonomic confusion of Gracilaria in Chile. At least four species with cylindrical thalli and similar morphology have been recorded. However, since establishment of G. chilensis, most of the collected thalli have been attributed to this species despite the lack of diagnostic features. In an attempt to resolve whether Gracilaria from 3 localities where it grows in natural and artificial populations belongs to the same species, gametophytic samples were compared by applying RAPD-PCR to their total DNA. This was analysed using 25 different 10-mer primers from which 21 revealed polymorphism within and between populations. Similarity matrices and cluster analyses were performed based on the presence/absence of bands representing fragments of DNA generated by random amplification. Similarity values between two of the populations were equivalent to those detected within a third, indicating the mixing of genetic material due to transplant between the two former localities. Similarities between samples of Chilean Gracilaria and G. tenuistipitata from Sweden are considerably lower (0.45-0.53) than those between populations from Chile (0.74-0.88), confirming the existence of a single specific taxon, G. chilensis, in these three localities.
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    Differences in the early stages of development of gametophytes and tetrasporophytes of Chondracanthus chamissoi (CAg) Kutzing from Puerto Aldea, northern Chile
    (1996) Gonzalez, J; Meneses, I
    Gametophytes of Chondracanthus chamissoi are more abundant in the field than tetrasporophytes. This differential phase ratio is well known in the literature for other members of the Gigartinaceae and has been explained as the result of either stochastic events or differential reproductive or physiological capacities between the phases. The comparison of both phases of Chondracanthus chamissoi in their early stages of development under laboratory conditions were summarised. Despite the higher biomass of reproductive tetrasporophytes recorded in summer (the seasonal maxima), significantly more carpospores are released per gram than tetraspores. During the following processes of settlement and germination, tetraspores show higher average values mainly due to their persistence in time. These differences tend to disappear in winter when the capacity of spores to develop normally appears to be lower. On the other hand, sporophytic growth rates are higher than gametophytic growth rates for most conditions of day length, light intensity and temperature. With no other external factors considered, the higher abundance of gametophytes in the field appears to be a result of the higher capacities of tetraspores to settle and germinate after an extended period of time suspended in the water column.
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    Enhanced DNA extraction and PCR amplification of SSU ribosomal genes from crustose coralline algae
    (2002) Vidal, R; Meneses, I; Smith, M
    As crustose Corallinales on the coasts of Chile are usually flat, thin, strongly adherent to the rocks and with a high concentration of polysaccharides, there is a need to improve DNA extraction for molecular studies. The paper describes a protocol to achieve this, which includes steps for disruption of cell walls and precipitation of polysaccharides and proteins; this leads to a PCR-quality product. The DNA obtained permitted amplification of SSU and rbcL genes from small amounts of material (< 1 g) of several genera and species of Corallinales. Comparison of the sequences of small SSU fragments (approximately 500 bp), combined with morphological characters, together provide sufficient resolution to distinguish organisms at the genus and species levels.
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    Growth-related intraclonal genetic changes in Gracilaria chilensis (Gracilariales: Rhodophyta)
    (1999) Meneses, I; Santelices, B; Sánchez, P
    Gracilaria ia chilensis exhibits noticeable intraclonal variation, some of which is presumed to result from mitotic recombinations or other types of DNA turnover associated with replication activities during cellular division. To test this, genetic variability (determined by multilocus fingerprinting markers using the randomly amplified polymorphic DNA technique, RAPD) and total growth were simultaneously measured over time in clonal replicates of G. chilensis incubated under controlled laboratory conditions. The results suggest that genetic variability increases as growth occurs and biomass accumulates, supporting the hypothesis of growth-related increases in genetic heterogeneity. For species massively propagated by thallus fragmentation in either naturally or farmed populations, growth-dependent genetic changes may constitute a powerful means of generating intra-population variation without thalli becoming reproductively mature, and, as a, consequence, bypassing meiosis and/or sexual recombination.
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    Seasonal and spatial monitoring of productivity and of reproduction of Chondrus canaliculatus (Gigartinales, Rhodophyta) from Chile
    (2001) Vega, JMA; Meneses, I
    Chondrus canaliculatus (C. Agardh) Greville used to cover extensive areas at Puerto Aldea 30 degrees 16' S, 71 degrees 30' W), Tongoy Bay, Chile. The exploitation of this commercially-valuable alga without knowledge of its production behavior and reproductive characteristics led to its severe reduction in the area. Seasonal monitoring of biomass, reproductive capacity and reproductive potential of an intertidal and a subtidal population of C. canaliculatus from this locality was performed in order to gather information on how to manage this resource. Total and fertile frond biomass both have a maximum (4 and 2.5 Kg per m(2) respectively) in spring-summer and a minimum (2.4 and 1.8 Kg per m(2) respectively) during winter. Both were also higher in the subtidal (maxima of 4.2 and 2.6 Kg per m(2)) than in the intertidal population (maxima of 4.0 and 2.6 Kg per m(2)) and carposporic fronds were always more abundant than tetrasporic fronds. Reproductive capacity (based on the number of spores per sorus, the number of sori per frond and the fertile biomass per area unit) followed a similar seasonal pattern reaching a maximum of 5.5 x 10(9) spores per m(2) and was higher in the intertidal than in the subtidal and in tetrasporic rather than carposporic plants. Laboratory studies of spore settlement and survival indicated that the reproductive potential was not different between reproductive phases and between habitats. This potential, close to 30% in relative terms, is similar to those evaluated in other members of the Gigartinaceae. Maxima of total and reproductive biomass, spore production, spore settlement and juvenile survival occurred one to two months earlier in the intertidal than in the subtidal. The data available at this point suggests that the harvesting of the fronds should be done in different periods for the intertidal (early and mid-summer) and the subtidal (mid- to late summer) and approximately a month after the spore productivity peak when these have already been released, assuming that the recovery of biomass is through the growth of new individuals. Further studies on vegetative means of growth and maintenance of the populations should be added to this information in order to propose an adequate management of this resource.
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    Sources of morphological variation in populations of Gracilaria chilensis Bird, McLachlan & Oliveira of Chile
    (1996) Meneses, I
    Gracilaria chilensis Bird, McLachlan & Oliveira is generally recognized as a variable species whose morphological changes are the result of the environmental conditions under which it grows. However, no experimental evaluation has ever been done and few descriptive studies have focused on matching particular morphologies with distinct populations. Five localities with G. chilensis populations along Chilean coasts were sampled. The posterior analysis of vegetative characters indicated that populations from Lenga are easily segregated from other localities. Meanwhile, localities such as Maullin, Coquimbo and Niebla can be grouped apparently due to their similar growth habit, i.e. plants originated from spores, and not due to characteristics of their habitat. Results also showed that variability of most characters within populations, originated through vegetative propagation, is not significantly different from that of populations of sporic origin where higher genetic variability is expected. Finally, other variables such as reproductive stage and life history phase of the plants exhibited differences in few characters.
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    Strain selection and genetic variation in Gracilaria chilensis (Gracilariales, Rhodophyta)
    (1999) Meneses, I; Santelices, B
    Strain selection processes in seaweed often have assumed that sterile clones could be maintained for long periods in a diversity of environments without major genetic changes. However, clonal species such as Gracilaria chilensis exhibit intra-clonal variation in performance and ongoing studies suggest such changes may be due to rapid changes in DNA composition associated with growth, via mitotic recombinations. Therefore performance of a given ramet in this type of seaweed should be understood as the dynamic outcome of rapid reactions between the environment and the changing genotype of the selected strain. To evaluate this idea, we measured changes in genetic variability, as detected by DNA-fragment polymorphism using RAPDs-PCR, exhibited by clones of G. chilensis after two transfers to different environmental conditions (from field to controlled laboratory conditions and from the laboratory to large-scale tank culture). The transfer to laboratory conditions reduced the frequency of low similarity values and increased the frequency of intermediate similarity values in DNA banding patterns, suggesting the branchlets produced under controlled laboratory conditions have less genetic variability (evaluated as total DNA polymorphism) than plants recently collected in the field. Tank incubation reduced the total range of similarity and significantly increased the frequency of high similarity values. Results thus suggest the dynamic of genetic changes in vegetative clones of Gracilaria chilensis that is fast and strongly affected by the external environment.