Fertilization in the medusan, Spirocodon saltatrix.

Biological Bulletin (Impact Factor: 1.57). 01/1951; 99(3):412-5. DOI: 10.2307/1538471
Source: PubMed
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    ABSTRACT: Gelatinous Zooplankton reproduce in an environment inimical to fertilization success because of the high potential for gamete dilution and the often wide dispersion of reproductive adults. Organisms in this group that shed sperm externally but fertilize internally face additional barriers to high fertilization success. Special reproductive adaptations probably exist to counter this problem. However, most of the inferences made about fertilization success in marine organisms are based on results using benthic species, gelatinous Zooplankton being very difficult to capture and maintain in sexual condition. As a result, very little has been done to determine what sort of adaptations to enhance fertilization rates exist in gelatinous species. Furthermore, there is little direct evidence supporting mutual approach of the sexes that would bring the ripe gametes closer together. Close approach may be accomplished by a number of physical agencies, however, and possibly by gamete adaptations such as long‐lived sperm or special egg investments which trap sperm. Chance contact chemoreception (which leads to mutual spawning, sperm transfer during psuedocopulation, or true copulation) coordinates reproductive behavior in some species. Free‐spawned gametes may be mixed and more widely dispersed as the result of active spawningbehaviors which are temporally coordinated by environmental factors such as light and temperature. Sperm chemotaxis has been described in gelatinous Zooplankton, though its effect on fertilization rates is, at present, unknown. Except for sperm behavior in response to egg or tissue‐associated factors, other chemosensory interactions or adaptations that might increase fertilization rates in gelatinous Zooplankton have yet to be described.
    Marine and Freshwater Behaviour and Physiology 01/1996; 27(2-3):163-173. DOI:10.1080/10236249609378962 · 0.86 Impact Factor
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    ABSTRACT: Jellyfish eggs neither undergo apparent cortical reaction nor show any significant change in the membrane potential at fertilization, but nevertheless show monospermy. Utilizing the perfectly transparent eggs of the hydrozoan jellyfish Cytaeis uchidae, here we show that the polyspermy block is accomplished via a novel mechanism: a collaboration between Ca(2+) and mitogen-activated protein kinase (MAPK). In Cytaeis, adhesion of a sperm to the animal pole surface of an egg was immediately followed by sperm-egg fusion and initiation of an intracellular Ca(2+) rise from this site. The elevated Ca(2+) levels lasted for several minutes following the sperm-egg fusion. The Ca(2+) rise proved to be necessary and sufficient for a polyspermy block, as inhibiting a Ca(2+) rise with EGTA promoted polyspermy, and conversely, triggering a Ca(2+) rise by inositol 1,4,5-trisphosphate (IP3) or excess K(+) immediately abolished the egg's capacity for sperm-egg fusion. A Ca(2+) rise at fertilization or by artificial stimulations evoked dephosphorylation of MAPK in eggs. The eggs in which phosphorylated MAPK was maintained by injection of mRNA for MAPK kinase kinase (Mos), like intact eggs, exhibited a Ca(2+) rise at fertilization or by IP3 injection, and shut down the subsequent sperm-egg fusion. However, the Mos-expressing eggs became capable of accepting sperm following the arrest of Ca(2+) rise. In contrast, addition of inhibitors of MAPK kinase (MEK) to unfertilized eggs caused MAPK dephosphorylation without elevating Ca(2+) levels, and prevented sperm-egg fusion. Rephosphorylation of MAPK by injecting Mos mRNA after fertilization recovered sperm attraction, which is known to be another MAPK-dependent event, but did not permit subsequent sperm-egg fusion. Thus, it is possible that MAPK dephosphorylation irreversibly blocks sperm-egg fusion and reversibly suppresses sperm attraction. Collectively, our data suggest that both the fast and late mechanisms dependent on Ca(2+) and MAPK, respectively, ensure a polyspermy block in jellyfish eggs.
    Developmental Biology 05/2014; DOI:10.1016/j.ydbio.2014.04.020 · 3.64 Impact Factor
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    ABSTRACT: Egg-derived sperm-activating factors and attractants activate sperm motility and attract the sperm, respectively. These phenomena constitute the first communication signaling between males and females in the process of fertilization in many animals and plants, and in many cases, these are species-specific events. Thus, sperm motility activation and chemotaxis may act as a safety process for the authentication between conspecific egg and sperm, and help to prevent crossbreeding. Here, we examine species-specificity of sperm motility activation and chemotaxis in the ascidians belonging to the order Phlebobranchiata: Ciona intestinalis, Ciona savignyi, Phallusia mammillata, Phallusia nigra, and Ascidia sydneiensis. Cross-reactivity in both motility activation and chemotaxis of sperm was not observed between C. savignyi and P. mammillata, or between A. sydneiensis and Phallusia spp. However, there is a "one way" (no reciprocity) cross-reaction between P. mammillata and P. nigra in sperm activation, and between C. savignyi and A. sydneiensis in sperm chemotaxis. Furthermore, the level of activity is different, even when cross-reaction is observed. Thus, sperm motility activation and chemotaxis are neither "species-" nor "genus-" specific phenomena among the ascidian species. Moreover, the interaction between the sperm-activating and sperm-attracting factors (SAAFs) in the ascidian species and the SAAF receptors on the sperm cells are not all-or-none responses.
    Biological Bulletin 08/2013; 224(3):156-65. · 1.57 Impact Factor