Pollinators of the sea: A discovery of animal-mediated fertilization in seaweed (original) (raw)
Related papers
Proceedings of The Royal Society B: Biological Sciences, 1999
In haploid^diploid red seaweeds, the dispersal of male gametes is presumed limited due to their lack of £agella. It has been suggested that this group su¡ers from sperm limitation and, consequently, that fertilization is relatively ine¤cient. Fertilization in most £oridean rhodophytes results in the formation a cystocarp, a swelling on the haploid female thallus housing the diploid zygote and its thousands of diploid daughter spores. To study the performance of non-motile male gametes in the sea, we evaluated both female and male fertilization success in a natural population of the red marine alga Gracilaria gracilis. Female fertilization success, estimated by cystocarp yield per unit female thallus, was evaluated with respect to the availability of male gametes. Male fertilization success, estimated by the individual contribution of di¡erent males to zygotes, was assessed by paternity analyses on 350 cystocarps produced in one reproductive season using two microsatellite loci. The results show that cystocarp yield is not sperm limited and that the large variation in male fertilization success cannot be solely explained by the distance travelled by the male gamete to ¢nd a mate. Taken together, the results suggest that, not only is fertilization e¤cient, but that male^male competition and/or female choice may play a role in shaping population mating patterns.
Gametogenesis, gametes and zygotes: An ecological perspective on sexual reproduction in the algae
British Phycological Journal, 1992
Ecological aspects of sexual reproduction in freshwater and marine algae are reviewed in the context of reproductive seasonality, gamete release, pheromones, fertilization success, polyspermy, parthenogenesis, and the dispersal of zygotes. Fertilization success in freshwater and marine macroalgae is higher than previously assumed, and the biological and physical variables that contribute to this are reviewed and analysed. These variables include synchronous release of gametes, plant architecture, immobilization of female gametes, cytological specializations (e.g., in the spermatia of some red algae), agglutinins, and a number of important aspects of water motion. Little is known about fertilization success in unicellular algae, but various aspects (gametogenesis, resting zygotes) of reproduction in such algae are considered. The review concludes with questions that should be addressed in future studies; a number of these require more attention to hydrodynamic variables.
Water-borne sperm trigger vitellogenic egg growth in two sessile marine invertebrates
Proceedings of the Royal Society B: Biological Sciences, 2000
A diverse array of sessile marine invertebrates mate by passive dispersal of sperm which fertilize the brooded eggs of neighbours. In two such species, a sea-mat (phylum Bryozoa) and an ascidian (phylum Chordata), vitellogenic egg growth is absent in reproductively isolated specimens, but is triggered by a water-borne factor released by conspeci¢cs. In both of these colonial, hermaphroditic species, the active factor can be removed from water by ¢ltration. The e¡ect involves self-/non-self-recognition: water conditioned by a separate subcolony of the same genetic individual does not prompt oocyte growth. In each species, allosperm move from the surrounding water to the ovary and are then stored in close association with the growing oocytes. We concluded that sperm themselves are the water-borne factor that triggers the major phase of female reproductive investment. This mechanism is, to our knowledge, previously undescribed in animals, but has parallels with the initiation of maternal investment in £owering plants following the receipt of compatible pollen. The species studied may be representative of many other aquatic invertebrates which mate in a similar way. The stimulation of egg growth by allosperm could lead to intersexual con£ict during oogenesis.
Integrative and Comparative Biology, 2006
In the marine environment, both external fertilization and settlement are critical processes linking adult and early juvenile life-history phases. The success of both processes can be tightly linked in organisms lacking a larval dispersive phase. This review focuses on synchronous gamete release (¼ spawning) in fucoid algae. These brown macroalgae are important components of temperate intertidal ecosystems in many parts of the world, and achieve synchronous gamete release by integrating various environmental signals. Photosynthesis-dependent sensing of boundary-layer inorganic carbon fluxes, as well as blue light and green light signals, possibly perceived via a chloroplast-located photoreceptor(s), are integrated into pathways that restrict gamete release to periods of low water motion. Avoidance of turbulent and/or high flow conditions in the intertidal zone allows high levels of fertilization success in this group. Temporal patterns and synchrony of spawning in natural populations are reviewed. Most species/populations have a more or less semilunar periodicity, although phase differences occur both between and within species at different geographical locations, raising the possibility that tidal and diurnal cues are more important than semilunar cues in entraining the response. The ecological and evolutionary role(s) of synchronous spawning in the intertidal zone are considered, particularly with regard to hybridization/reproductive isolation in species complexes, and reproductive versus recruitment assurance in the intertidal zone, where synchronous spawning during calm periods may be important for recruitment assurance in addition to fertilization success. Ways in which the roles of spawning synchrony could be tested in closely related species with contrasting mating systems (outcrossing versus selfing) are discussed.
Experimental evidence of pollination in marine flowers by invertebrate fauna
Nature Communications, 2016
Pollen transport by water-flow (hydrophily) is a typical, and almost exclusive, adaptation of plants to life in the marine environment. It is thought that, unlike terrestrial environments, animals are not involved in pollination in the sea. The male flowers of the tropical marine angiosperm Thalassia testudinum open-up and release pollen in mucilage at night when invertebrate fauna is active. Here we present experimental evidence that, in the absence of water-flow, these invertebrates visit the flowers, carry and transfer mucilage mass with embedded pollen from the male flowers to the stigmas of the female flowers. Pollen tubes are formed on the stigmas, indicating that pollination is successful. Thus, T. testudinum has mixed abiotic-biotic pollination. We propose a zoobenthophilous pollination syndrome (pollen transfer in the benthic zone by invertebrate animals) which shares many characteristics with hydrophily, but flowers are expected to open-up during the night.
Marine Ecology-progress Series, 2003
Near its southern limit in the Northeastern Atlantic, the dioecious brown alga Fucus vesiculosus is absent from the exposed coast yet it is abundant in estuaries and coastal lagoons. In contrast, the phylogenetically and ecologically related hermaphroditic species F. spiralis occurs along the open coast, though often in low abundance. We hypothesized that the absence of F. vesiculosus from exposed shores near its southern limit was due to reduced external fertilization success, as its gametes may be diluted beyond the level required for successful fertilization, in contrast with its hermaphroditic, self-compatible congener. To test this hypothesis, individuals of both species were transplanted to 3 exposed sites near their southern limit in the Northeastern Atlantic. Egg settlement and fertilization success (% of eggs fertilized) were evaluated daily during the main reproductive season. Recruitment was evaluated at the end of the reproductive season, and recruit mortality was evaluated using outplants of laboratory-cultured embryos. On the exposed shores near their southern limit, transplanted adults of both species survived and released eggs, and fertilization success was unexpectedly high. However, recruitment and recruit survivorship of F. vesiculosus was significantly lower than F. spiralis. Our results suggest that F. vesiculosus is restricted to low water-motion environments because of recruitment failure and recruit mortality on exposed bare shores near its southern limit, and not because of inability to fertilize eggs in turbulent environments. This study does not support our hypothesis of a role for dioecy/hermaphroditism in explaining the distribution of externally fertilizing marine organisms in high water-motion environments.
Journal of the Marine Biological Association of the UK, 2002
Patterns of in situ fertilization success with respect to high and low tide periods are reported for the intertidal red seaweed Gracilaria gracilis which inhabits rock pools. Cystocarp (zygote) production was experimentally compared at high tide and low tide in both high-and low-shore tide pools at two sites using ten virgin female plants. High-and low-shore pools showed di¡erent patterns with respect to tide period. High-shore pools showed signi¢cantly greater numbers of cystocarps at low tide than at high tide whereas cystocarp production did not di¡er between high and low tide periods in low shore pools. The possible mechanisms of gamete release are discussed in light of these results.
Seaweed reproductive biology: environmental and genetic controls
Botanica Marina, 2017
Knowledge of life cycle progression and reproduction of seaweeds transcends pure academic interest. Successful and sustainable seaweed exploitation and domestication will indeed require excellent control of the factors controlling growth and reproduction. The relative dominance of the ploidy-phases and their respective morphologies, however, display tremendous diversity. Consequently, the ecological and endogenous factors controlling life cycles are likely to be equally varied. A vast number of research papers addressing theoretical, ecological and physiological aspects of reproduction have been published over the years. Here, we review the current knowledge on reproductive strategies, trade-offs of reproductive effort in natural populations, and the environmental and endogenous factors controlling reproduction. Given that the majority of ecophysiological studies predate the “-omics” era, we examine the extent to which this knowledge of reproduction has been, or can be, applied to f...