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- Legrand, Catherine, et al.
(författare)
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Allelopathy in phytoplankton – biochemical, ecological and evolutionary aspects
- 2003
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Ingår i: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 42:4, s. 406-419
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Tidskriftsartikel (refereegranskat)abstract
- It is considered self-evident that chemical interactions are a component of competition in terrestrial systems, but they are largely unknown in aquatic systems. In this review, we propose that chemical interactions, specifically allelopathy, are an important part of phytoplankton competition. Allelopathy, as defined here, applies only to the inhibitory effects of secondary metabolites produced by one species on the growth or physiological function of another phytoplankton species. A number of approaches are used to study allelopathy, but there is no standard methodology available. One of the methods used is cross-culturing, in which the cell-free filtrate of a donor alga is added to the medium of the target species. Another is to study the effect of cell extracts of unknown constituents, isolated exudates or purified allelochemicals on the growth of other algal species. There is a clear lack of controlled field experiments because few allelochemicals have been identified. Molecular methods will be important in future to study the expression and regulation of allelochemicals. Most of the identified allelochemicals have been described for cyanobacteria but some known toxins of marine dinoflagellates and freshwater cyanobacteria also have an allelochemical effect. The mode of action of allelochemicals spans a wide range. The most common effect is to cause cell lysis, blistering, or growth inhibition. The factors that affect allelochemical production have not been studied much, although nutrient limitation, pH, and temperature appear to have an effect. The evolutionary aspects of allelopathy remain largely unknown, but we hypothesize that the producers of allelochemicals should gain a competitive advantage over other phytoplankton. Finally, we discuss the possibility of using allelochemicals to combat harmful algal blooms (HABs). Allelopathic agents are used for biological control in agriculture, e.g. green manures to control soil diseases in Australia, but they have not yet been applied in the context of HABs. We suggest that phytoplankton allelochemicals have the potential for management of HABs in localized areas.
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- Alfonso, B., et al.
(författare)
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Tracing genetic variation of Gelidium canariense (Rhodophyta) based on new and historical collections
- 2023
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Ingår i: Phycologia. - 0031-8884. ; 62:4, s. 383-390
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Tidskriftsartikel (refereegranskat)abstract
- Genetic sequencing of herbarium specimens provides invaluable information on species genetic history. However, several factors hinder the extraction of high-quality DNA from long-term preserved specimens. Our goal was to study the genetic variability of the endemic and habitat-forming macroalga Gelidium canariense over the last 40 years using the mitochondrial intergenic marker cox2-3 spacer. We also studied the genetic diversity at the mesoscale (<100 km), i.e. between two localities on the north coast of Tenerife and at the macroscale (>100 km) using specimens collected on the island of La Palma. We found the presence of the same haplotype at the same location for the last 40 years. This haplotype also coincided within populations of Puerto de la Cruz and Garachico (Tenerife Island) and between populations of different islands (Tenerife and La Palma). This study provides a baseline (i.e. extraction method, PCR protocol for cox2-3 spacer molecular marker, level of DNA degradation of herbarium samples) of the genetic characterization of G. canariense that can be used in future molecular studies to better understand the distribution of genetic diversity in this vulnerable species.
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- Cronberg, Gertrud
(författare)
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The life cycle of Gonyostomum semen (Raphidophyceae)
- 2005
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Ingår i: Phycologia. - 0031-8884. ; 44:3, s. 285-293
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Tidskriftsartikel (refereegranskat)abstract
- Gonyostomum semen (Raphidophyceae) is today one of the most common flagellates in humic lakes ill Sweden and appears regularly in 30% of these lakes. The first mass development of this alga was recorded in 1948 in Lake Helgasjon, South Sweden. In this paper the life cycle of Gonyostomum is described for the first time. During the winter Gonyostomum survived as resting cysts on the surface of the bottom sediment. In spring (April to May) meiosis took place in the cysts, and on excystment two haploid gametes appeared. After a period of mobility, the gametes formed pairs. The gametes then fused, and a new diploid Gonyostomum cell developed. The vegetative stage of Gonyostomum, which was seen during the summer period (May-October), is thus the diploid phase. During this period normal, longitudinal cell division took place. Under unfavourable conditions, temporary cysts Could be formed. Cyst formation started from the centre of the cell, which swelled and became spherical. This was a thin-walled, temporary cyst, which was mobile and, like ordinary cells, had one flagellum protruding forward and one trailing behind. The temporary cysts could accumulate and settle in large clusters where the flagella were lost or had become invisible. When favourable conditions reappeared, the temporary cysts divided and formed two new gametes. In autumn, when the water temperature decreased to below about 10 degrees C, the temporary cysts went into dormancy and became resting cysts. The cyst wall thickened, and a brown body appeared within the cyst. Below 4-6 degrees C no vegetative cells were found.
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| 10. |
- Ellegaard, M., et al.
(författare)
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The species concept in a marine diatom: LSU rDNA-based phylogenetic differentiation in Skeletonema marinoi/dohrnii (Bacillariophyceae) is not reflected in morphology
- 2008
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Ingår i: Phycologia. - : Informa UK Limited. - 0031-8884. ; 47:2, s. 156-167
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Tidskriftsartikel (refereegranskat)abstract
- The ubiquitous marine diatom genus Skeletonema includes several newly described species. This paper presents a study of morphology and LSU sequence diversity of one of these new species, Skeletonema marinoi. The 15 monoclonal strains (from the Swedish west coast, the Swedish east coast, Portugal and Canada) included in the study showed differences in LSU rDNA sequence within the morphospecies, with differences seen even among clones established from a single plankton net sample. Morphologically, all clones were indistinguishable from each other and from the closely related species Skeletonema dohrnii. In the original description of these two species, they were differentiated by the structure of the girdle bands. However, the girdle band types of both species were found within single samples of almost all clones of S. marinoi in this study. The LSU-based phylogeny is consistent with the split into two species, and there may be a difference in their bioaeoszraphical distribution. We therefore do not at present suggest that the two species be merged. Questions regarding species delimitation and cryptic species within protists often arise from such studies that include data from both morphological and DNA sequence analysis, and such questions are addressed here.
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