An ulvophycean marine green alga produces large parthenogenetic isogametes as predicted by the gamete dynamics model for the evolution of anisogamy

In eukaryotes, the gamete size difference between the two sexes (anisogamy) evolved from gametes of equal size in both mating types (isogamy). The gamete dynamics (GD) model for anisogamy evolution combines gamete limitation and competition and predicts that, if gametes of both mating types can develop parthenogenetically (i.e. without fusing with the opposite mating type), large isogamy can evolve under gamete-limited conditions. Ulvophycean marine green algae that have been claimed to exhibit various gametic systems from isogamy to anisogamy are important models for testing such theories. However, in most previous papers, whether a species is isogamous or anisogamous has not been examined statistically. Caution is necessary regarding claims of slight anisogamy because of gamete size variation. We reveal (i) that the gametic system of Struvea okamurae is large isogamy using a generalized linear mixed model (GLMM), which accounted for the variation of gamete size among individual gameto..., We collected gametophytes and sporophytes of Struvea okamurae in early spring (March 2020) at a depth of about 3 m off the coast of Ginoza, Okinawa, Japan (26°47’N, 127°78’E) (figure 1), and established the uni-algal culture strains of these gametophytes (So-4, So-6, So-14, So-21, and So-27) and sporophyte (So-1) using a protoplast-formation method. Protoplasts were cultured in 1/4 concentration Provasoli’s enriched seawater (PES) medium [20] at 22°C under a long day condition (14 h: 10 h = light: dark) and ca. 15 μmol photons ·m-2 · s-1 in a culture chamber (LH-220S; NK system, Osaka, Japan). We isolated gametophyte/sporophyte Struvea plants developed from a protoplast individually into 12 well plastic plates (IWAKI, Tokyo, Japan) and induced gametogenesis/zoosporogenesis under an eutrophic condition by changing the medium.
We estimated the volume of S. okamurae gametes more accurately than previous studies on other ulvophycean species by eliminating the error due to discrepancies betw..., , # An ulvophycean marine green alga produces large parthenogenetic isogametes as predicted by the gamete dynamics model for the evolution of anisogamy

[https://doi.org/10.5061/dryad.w9ghx3fxf](https://doi.org/10.5061/dryad.w9ghx3fxf)

The data set includes the time until gamete release and the volume of gametes with the genotype and sex of gametophytes.

The uploaded Excel file consists of two sheets for the time until gamete release and the volume of gametes.

From our crossing tests, we determined that strains with So-4, So-27, So-1.1.1c1, and So-1.1.2b1 genotypes have one mating type (labelled type A) and that strains with So-6, So-14, So-21, So-1.1.4a3, and So-1.1.4b4 genotypes have the other mating type (labelled type B).

The unit of the time until gamete release and that of the gamete volume is \"hour (h)\" and \"cubic micrometer (um^3)\", respectively.

### Change log

**27-Sept-2024:** We uploaded the R script file that we used to analyze the data. The data on the time until gamete...