A Morphological Study of Astrephomene Gubernaculifera and Volvulina Steinii

Stein, Janet R.

doi:10.2307/2439639

Cited by 32 publications

(20 citation statements)

References 4 publications

(9 reference statements)

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“…Time-lapse images of the anterior–lateral view (Additional file 1), lateral view (Additional file 2), posterior–lateral view (Additional file 3), and posterior view (Additional file 4) were obtained and analyzed as successive images and movies. During embryogenesis, each reproductive cell performed multiple divisions to form a spheroidal colony, as reported previously [24–26]. Moreover, cell divisions of all daughter protoplasts were synchronized, and six synchronous cell divisions resulted in the formation of 64-celled daughter colonies (Fig.…”

Section: Resultssupporting

confidence: 53%

“…Astrephomene has 32- or 64-celled spheroidal colonies resembling those of some volvocacean species, but there is a difference in the distribution of somatic cells; Astrephomene has two or four somatic cells distributed only in the posterior pole of the colony [24, 25] whereas volvocacean species lack somatic cells or have somatic cells distributed in the anterior pole of the colony. The feature of Astrephomene that distinguishes them from the Volvocaceae is the lack of inversion during embryogenesis; each reproductive cell in a colony divides successively to form a spheroidal daughter colony [24, 26]. The embryogenesis of Astrephomene has been visualized by light microscopy in previous studies [24–26].…”

Section: Introductionmentioning

confidence: 99%

“…The feature of Astrephomene that distinguishes them from the Volvocaceae is the lack of inversion during embryogenesis; each reproductive cell in a colony divides successively to form a spheroidal daughter colony [24, 26]. The embryogenesis of Astrephomene has been visualized by light microscopy in previous studies [24–26]. However, successive observations by light microscopy time-lapse imaging and cell-based studies of spheroidal colony formation in Astrephomene have not been performed; thus, the mechanism underlying the formation of a spheroidal colony without inversion is unclear.…”

Section: Introductionmentioning

confidence: 99%

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Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)

et al. 2016

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BackgroundVolvocine algae, which range from the unicellular Chlamydomonas to the multicellular Volvox with a germ–soma division of labor, are a model for the evolution of multicellularity. Within this group, the spheroidal colony might have evolved in two independent lineages: Volvocaceae and the goniacean Astrephomene. Astrephomene produces spheroidal colonies with posterior somatic cells. The feature that distinguishes Astrephomene from the volvocacean algae is lack of inversion during embryogenesis; the volvocacean embryo undergoes inversion after successive divisions to orient flagella toward the outside. The mechanisms of inversion at the molecular and cellular levels in volvocacean algae have been assessed in detail, particularly in Volvox carteri. However, embryogenesis in Astrephomene has not been subjected to such investigations.ResultsThis study relied on light microscopy time-lapse imaging using an actively growing culture of a newly established strain to conduct a developmental analysis of Astrephomene as well as to perform a comparison with the similar spheroidal volvocacean Eudorina. During the successive divisions involved in Astrephomene embryogenesis, gradual rotation of daughter protoplasts resulted in movement of their apical portions toward the embryonic posterior, forming a convex-to-spheroidal cell sheet with the apical ends of protoplasts on the outside. Differentiation of the posterior somatic cells from the embryo periphery was traced based on cell lineages during embryogenesis. In contrast, in Eudorina, the rotation of daughter protoplasts did not occur during successive cell divisions; however, inversion occurred after such divisions, and a spheroidal embryo was formed. Indirect immunofluorescence microscopy of basal bodies and nuclei verified this difference between Astrephomene and Eudorina in the movement of embryonic protoplasts.ConclusionsThese results suggest different tactics for spheroidal colony formation between the two lineages: rotation of daughter protoplasts during successive cell divisions in Astrephomene, and inversion after cell divisions in Eudorina. This study will facilitate further research into the molecular and genetic mechanisms of the parallel evolution of the spheroidal colony in volvocine algae.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0794-x) contains supplementary material, which is available to authorized users.

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Section: Resultssupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)

et al. 2016

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“…Thus, the evolution of a phototactic organ in microgametes appears to explain slight anisogamy in a manner consistent with the model. Interestingly, the isogametes of the multicellular A. gubernaculifera possess eyespots (Stein, 1958). also consider the case of a minimum volume for a gamete, required, for example, for chromosomes or a phototactic organ, but which does not contribute to the facultative volume affecting viability.…”

Section: Discussionmentioning

confidence: 99%

The evolution of sexes: A specific test of the disruptive selection theory

Silva

2017

Ecology and Evolution

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The disruptive selection theory of the evolution of anisogamy posits that the evolution of a larger body or greater organismal complexity selects for a larger zygote, which in turn selects for larger gametes. This may provide the opportunity for one mating type to produce more numerous, small gametes, forcing the other mating type to produce fewer, large gametes. Predictions common to this and related theories have been partially upheld. Here, a prediction specific to the disruptive selection theory is derived from a previously published game‐theoretic model that represents the most complete description of the theory. The prediction, that the ratio of macrogamete to microgamete size should be above three for anisogamous species, is supported for the volvocine algae. A fully population genetic implementation of the model, involving mutation, genetic drift, and selection, is used to verify the game‐theoretic approach and accurately simulates the evolution of gamete sizes in anisogamous species. This model was extended to include a locus for gamete motility and shows that oogamy should evolve whenever there is costly motility. The classic twofold cost of sex may be derived from the fitness functions of these models, showing that this cost is ultimately due to genetic conflict.

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“…Previous work on sexual isolation has employed Pringsheim's biphasic soil-water medium (21) with a p H near 6.8. The few studies concerned with the nutrition of G. pectorale have dealt with growth, not sexuality (18,29,22). Earlier studies were restricted to 3 clones which included only 2 populations.…”

Section: Introductionmentioning

confidence: 99%

GROWTH AND MATING OF GONZUM PECTORALE (VOLVOCALES) IN DEFINED MEDIA¹

Stein

1975

Journal of Phycology

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SUMMARY Growth in defined media of 32 populations of Gonium pectorale was studied to learn more about the sexual isolation reported for this species. The 23 populations containing both mating types (+ & ‐) were also studied for the ability to form zygotes in defined media. A preliminary study showed that some populations grew and reproduced sexually in a defined mineral medium, whereas others appeared to require exogenous organic materials for growth and/or zygote formation. The diverse reactions exhibited by the populations indicate physiological races which may explain, in part, the occurrence of sexual isolation.

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A Morphological Study of Astrephomene Gubernaculifera and Volvulina Steinii

Cited by 32 publications

References 4 publications

Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)

Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)

The evolution of sexes: A specific test of the disruptive selection theory

GROWTH AND MATING OF GONZUM PECTORALE (VOLVOCALES) IN DEFINED MEDIA¹

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A Morphological Study of Astrephomene Gubernaculifera and Volvulina Steinii

Cited by 32 publications

References 4 publications

Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)

Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)

The evolution of sexes: A specific test of the disruptive selection theory

GROWTH AND MATING OF GONZUM PECTORALE (VOLVOCALES) IN DEFINED MEDIA1

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GROWTH AND MATING OF GONZUM PECTORALE (VOLVOCALES) IN DEFINED MEDIA¹