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Takashi Nakada - One of the best experts on this subject based on the ideXlab platform.
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New "missing link" genus of the colonial volvocine green algae gives insights into the evolution of oogamy.
BMC Evolutionary Biology, 2014Co-Authors: Hisayoshi Nozaki, Ryo Matsuzaki, Toshihiro Yamada, Fumio Takahashi, Takashi NakadaAbstract:Background The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (External Fertilization during isogamy) and Fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal Fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified.
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New “missing link” genus of the colonial volvocine green algae gives insights into the evolution of oogamy
BMC Evolutionary Biology, 2014Co-Authors: Hisayoshi Nozaki, Toshihiro K Yamada, Ryo Matsuzaki, Fumio Takahashi, Takashi NakadaAbstract:Background The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (External Fertilization during isogamy) and Fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal Fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified. Results We identified a novel colonial volvocine genus, Colemanosphaera , which produces bundles of spindle-shaped male gametes through successive divisions of colonial cells. Obligately anisogamous conjugation between male and female motile gametes occurred outside the female colony (External Fertilization during anisogamy). This new genus contains 16- or 32-celled spheroidal colonies similar to those of the volvocine genera Yamagishiella and Eudorina . However, Colemanosphaera can be clearly distinguished from these two genera based on its sister phylogenetic position to the enigmatic flattened colonial volvocine Platydorina and External Fertilization during anisogamy. Two species of Colemanosphaera were found in a Japanese lake; these species are also distributed in European freshwaters based on a published sequence of an Austrian strain and the original description of Pandorina charkowiensis from Ukraine. Conclusions Based on phylogeny and morphological data, this novel genus exhibits a missing link between Platydorina and the typical spheroidal colonial volvocine members such as Pandorina or Yamagishiella . Considering the External obligate anisogamy, oogamy evolution may have been preceded by the transition from External to internal Fertilization during anisogamy within the volvocine green algae.
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New "missing link" genus of the colonial volvocine green algae gives insights into the evolution of oogamy.
BMC evolutionary biology, 2014Co-Authors: Hisayoshi Nozaki, Ryo Matsuzaki, Toshihiro Yamada, Fumio Takahashi, Takashi NakadaAbstract:The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (External Fertilization during isogamy) and Fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal Fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified. We identified a novel colonial volvocine genus, Colemanosphaera, which produces bundles of spindle-shaped male gametes through successive divisions of colonial cells. Obligately anisogamous conjugation between male and female motile gametes occurred outside the female colony (External Fertilization during anisogamy). This new genus contains 16- or 32-celled spheroidal colonies similar to those of the volvocine genera Yamagishiella and Eudorina. However, Colemanosphaera can be clearly distinguished from these two genera based on its sister phylogenetic position to the enigmatic flattened colonial volvocine Platydorina and External Fertilization during anisogamy. Two species of Colemanosphaera were found in a Japanese lake; these species are also distributed in European freshwaters based on a published sequence of an Austrian strain and the original description of Pandorina charkowiensis from Ukraine. Based on phylogeny and morphological data, this novel genus exhibits a missing link between Platydorina and the typical spheroidal colonial volvocine members such as Pandorina or Yamagishiella. Considering the External obligate anisogamy, oogamy evolution may have been preceded by the transition from External to internal Fertilization during anisogamy within the volvocine green algae.
Geoff A. Parker - One of the best experts on this subject based on the ideXlab platform.
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Sperm Competition Games: Inter- and Intra-species Results of a Continuous External Fertilization Model
Journal of theoretical biology, 1997Co-Authors: M.a. Ball, Geoff A. ParkerAbstract:Abstract We investigate the relationship between sperm competition intensity and sperm expenditure, both across species and within a species, using two sperm competition models. In model 1, the males cannot assess the number of competitors, and their ejaculate effort is shaped by the average number 〈N〉 of competitors. In model 2, males can assess the numberNiof competitors at each spawning exactly. Males can vary the massmof their sperm and the numbersiat a spawning. The aim is to find the evolutionarily stable strategies and hence the way thatmandsivary withNi. A continuous Fertilization model in which the sperm have to swim in order to fertilize an egg is described. This is used to find simultaneous equations describingm* andsi*. These are solved numerically.
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Sperm Competition Games: External Fertilization and “Adapative” Infertility
Journal of theoretical biology, 1996Co-Authors: M.a. Ball, Geoff A. ParkerAbstract:Abstract We develop a model of a continuous Fertilization process in which eggs and sperm are shed simultaneously, and in which the eggs are fertilized at a rate proportional to sperm density surrounding the egg mass. The model derives the ESS size and number of sperm in an ejaculate of an Externally-fertilizing animal such as a fish species, in which the probability or intensity of sperm competition varies. It also predicts the ESS level of infertility (eggs remaining unfertilized after all sperm have died). Sperm size is assumed to increase sperm competitive ability (e.g. by increasing speed) and is also assumed to affect sperm longevity (either positively or negatively). Ejaculate expenditure is traded off against expenditure on obtaining further spawnings, and size and number of sperm can vary independently. The model predicts that the ESS ejaculate expenditure (product of sperm size and number) should increase, and that the ESS infertility should decrease with sperm competition intensity measured across species. Other results depend on the way that sperm size affects longevity. The available biological evidence suggests that longevity decreases with sperm size, probably because the main increase is in tail length which increases sperm energy expenditure. In this case, sperm size should increase with sperm competition intensity from an optimum at zero competition which maximizes the total distance travelled by the entire ejaculate in its lifetime, to an optimum for maximum sperm competition which maximizes the product of speed and sperm number. However, if longevity increases with sperm size, then the non-competitive optimal sperm size is greater than that for maximum competition, so that sperm size decreases with sperm competition intensity. Sperm numbers typically increase with sperm competition intensity, and always so if sperm competition is high enough, though decreases are possible over a range of low sperm competition intensity if (i) sperm longevity decreases with sperm size, and (ii) infertility is high enough.
Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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New "missing link" genus of the colonial volvocine green algae gives insights into the evolution of oogamy.
BMC Evolutionary Biology, 2014Co-Authors: Hisayoshi Nozaki, Ryo Matsuzaki, Toshihiro Yamada, Fumio Takahashi, Takashi NakadaAbstract:Background The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (External Fertilization during isogamy) and Fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal Fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified.
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New “missing link” genus of the colonial volvocine green algae gives insights into the evolution of oogamy
BMC Evolutionary Biology, 2014Co-Authors: Hisayoshi Nozaki, Toshihiro K Yamada, Ryo Matsuzaki, Fumio Takahashi, Takashi NakadaAbstract:Background The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (External Fertilization during isogamy) and Fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal Fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified. Results We identified a novel colonial volvocine genus, Colemanosphaera , which produces bundles of spindle-shaped male gametes through successive divisions of colonial cells. Obligately anisogamous conjugation between male and female motile gametes occurred outside the female colony (External Fertilization during anisogamy). This new genus contains 16- or 32-celled spheroidal colonies similar to those of the volvocine genera Yamagishiella and Eudorina . However, Colemanosphaera can be clearly distinguished from these two genera based on its sister phylogenetic position to the enigmatic flattened colonial volvocine Platydorina and External Fertilization during anisogamy. Two species of Colemanosphaera were found in a Japanese lake; these species are also distributed in European freshwaters based on a published sequence of an Austrian strain and the original description of Pandorina charkowiensis from Ukraine. Conclusions Based on phylogeny and morphological data, this novel genus exhibits a missing link between Platydorina and the typical spheroidal colonial volvocine members such as Pandorina or Yamagishiella . Considering the External obligate anisogamy, oogamy evolution may have been preceded by the transition from External to internal Fertilization during anisogamy within the volvocine green algae.
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New "missing link" genus of the colonial volvocine green algae gives insights into the evolution of oogamy.
BMC evolutionary biology, 2014Co-Authors: Hisayoshi Nozaki, Ryo Matsuzaki, Toshihiro Yamada, Fumio Takahashi, Takashi NakadaAbstract:The evolution of oogamy from isogamy, an important biological event, can be summarized as follows: morphologically similar gametes (isogametes) differentiated into small “male” and large “female” motile gametes during anisogamy, from which immotile female gametes (eggs) evolved. The volvocine green algae represent a model lineage to study this type of sex evolution and show two types of gametic unions: conjugation between isogametes outside the parental colonies (External Fertilization during isogamy) and Fertilization between small motile gametes (sperm) and large gametes (eggs) inside the female colony (internal Fertilization during anisogamy and oogamy). Although recent cultural studies on volvocine algae revealed morphological diversity and molecular genetic data of sexual reproduction, an intermediate type of union between these two gametic unions has not been identified. We identified a novel colonial volvocine genus, Colemanosphaera, which produces bundles of spindle-shaped male gametes through successive divisions of colonial cells. Obligately anisogamous conjugation between male and female motile gametes occurred outside the female colony (External Fertilization during anisogamy). This new genus contains 16- or 32-celled spheroidal colonies similar to those of the volvocine genera Yamagishiella and Eudorina. However, Colemanosphaera can be clearly distinguished from these two genera based on its sister phylogenetic position to the enigmatic flattened colonial volvocine Platydorina and External Fertilization during anisogamy. Two species of Colemanosphaera were found in a Japanese lake; these species are also distributed in European freshwaters based on a published sequence of an Austrian strain and the original description of Pandorina charkowiensis from Ukraine. Based on phylogeny and morphological data, this novel genus exhibits a missing link between Platydorina and the typical spheroidal colonial volvocine members such as Pandorina or Yamagishiella. Considering the External obligate anisogamy, oogamy evolution may have been preceded by the transition from External to internal Fertilization during anisogamy within the volvocine green algae.
Mehregan Ebrahimi - One of the best experts on this subject based on the ideXlab platform.
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embryonic and early development of the zagros tooth carp aphanius vladykovi actinopterygii cyprinodontidae
Journal of Morphology, 2018Co-Authors: Nafiseh Sanjarani Vahed, Hamid Reza Esmaeili, Mojtaba Masoudi, Mehregan EbrahimiAbstract:The embryonic and early larval development of laboratory reared Zagros tooth-carp, Aphanius vladykovi Coad, 1988, are described and illustrated. Development and embryogenesis start with the External Fertilization of sticky, transparent and spherical telolecithal/macrolecithal eggs with a mean diameter of 1.61± 0.12 mm and it continues with meroblastic/radial cleavage, blastulation/blastula formation, epibolic cell migration during gastrulation and organogenesis resulting in a newly hatched larvae of 5.23 ± 0.09 mm in length with attached yolk sac at about 164 hr (at 24 ± 1°C) after Fertilization.
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Embryonic and early development of the Zagros tooth‐carp, Aphanius vladykovi (Actinopterygii: Cyprinodontidae)
Journal of morphology, 2018Co-Authors: Nafiseh Sanjarani Vahed, Hamid Reza Esmaeili, Mojtaba Masoudi, Mehregan EbrahimiAbstract:The embryonic and early larval development of laboratory reared Zagros tooth-carp, Aphanius vladykovi Coad, 1988, are described and illustrated. Development and embryogenesis start with the External Fertilization of sticky, transparent and spherical telolecithal/macrolecithal eggs with a mean diameter of 1.61± 0.12 mm and it continues with meroblastic/radial cleavage, blastulation/blastula formation, epibolic cell migration during gastrulation and organogenesis resulting in a newly hatched larvae of 5.23 ± 0.09 mm in length with attached yolk sac at about 164 hr (at 24 ± 1°C) after Fertilization.
M.a. Ball - One of the best experts on this subject based on the ideXlab platform.
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Sperm Competition Games: Inter- and Intra-species Results of a Continuous External Fertilization Model
Journal of theoretical biology, 1997Co-Authors: M.a. Ball, Geoff A. ParkerAbstract:Abstract We investigate the relationship between sperm competition intensity and sperm expenditure, both across species and within a species, using two sperm competition models. In model 1, the males cannot assess the number of competitors, and their ejaculate effort is shaped by the average number 〈N〉 of competitors. In model 2, males can assess the numberNiof competitors at each spawning exactly. Males can vary the massmof their sperm and the numbersiat a spawning. The aim is to find the evolutionarily stable strategies and hence the way thatmandsivary withNi. A continuous Fertilization model in which the sperm have to swim in order to fertilize an egg is described. This is used to find simultaneous equations describingm* andsi*. These are solved numerically.
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Sperm Competition Games: External Fertilization and “Adapative” Infertility
Journal of theoretical biology, 1996Co-Authors: M.a. Ball, Geoff A. ParkerAbstract:Abstract We develop a model of a continuous Fertilization process in which eggs and sperm are shed simultaneously, and in which the eggs are fertilized at a rate proportional to sperm density surrounding the egg mass. The model derives the ESS size and number of sperm in an ejaculate of an Externally-fertilizing animal such as a fish species, in which the probability or intensity of sperm competition varies. It also predicts the ESS level of infertility (eggs remaining unfertilized after all sperm have died). Sperm size is assumed to increase sperm competitive ability (e.g. by increasing speed) and is also assumed to affect sperm longevity (either positively or negatively). Ejaculate expenditure is traded off against expenditure on obtaining further spawnings, and size and number of sperm can vary independently. The model predicts that the ESS ejaculate expenditure (product of sperm size and number) should increase, and that the ESS infertility should decrease with sperm competition intensity measured across species. Other results depend on the way that sperm size affects longevity. The available biological evidence suggests that longevity decreases with sperm size, probably because the main increase is in tail length which increases sperm energy expenditure. In this case, sperm size should increase with sperm competition intensity from an optimum at zero competition which maximizes the total distance travelled by the entire ejaculate in its lifetime, to an optimum for maximum sperm competition which maximizes the product of speed and sperm number. However, if longevity increases with sperm size, then the non-competitive optimal sperm size is greater than that for maximum competition, so that sperm size decreases with sperm competition intensity. Sperm numbers typically increase with sperm competition intensity, and always so if sperm competition is high enough, though decreases are possible over a range of low sperm competition intensity if (i) sperm longevity decreases with sperm size, and (ii) infertility is high enough.
