Isogamy: Asexual Reproduction & Differentiating Gametes

[jaumzaum]

I was looking for a type of organism in which the was no differentiation between the gametes, both are 100% identical (of course, there could be mutations, but no allele differentiation in matching-type regions, like the positive + and negative - mathing types in some algaes), and with a sexual reproduction. In isogamous organisms we have a small genetic differentiation between the gametes, as the + and - one I said. Is there an organism like this in nature? Also, is there any isogamous organism in which the gametes are produced in the same organ or region?

 

[Greg Bernhardt]

Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?

 

[Torbjorn_L]

The closest to a response I can come is with this recent reference [from Wikipedia]:

"Author Summary

Sexual differentiation in eukaryotes is manifested in two fundamentally different ways. Unicellular species may have mating types where gametes are morphologically identical but can only mate with those expressing a different mating type than their own, while multicellular species such as plants and animals have male and female sexes or separate reproductive structures that produce sperm and eggs.

The relationship between mating types and sexes and whether or how an ancestral mating-type system could have evolved into a sexually dimorphic system are unknown.

In this study we investigated sex determination in the multicellular green alga Volvox carteri, a species with genetic sex determination; we established the relationship of V. carteri sexes to the mating types of its unicellular relative, Chlamydomonas reinhardtii. Theoretical work has suggested that sexual dimorphism could be acquired by linkage of gamete size-regulatory genes to an ancestral mating-type locus. Instead, we found that a single ancestral mating locus gene, MID, evolved from its role in determining mating type in C. reinhardtii to determine either spermatogenesis or oogenesis in V. carteri. Our findings establish genetic and evolutionary continuity between the mating-type specification and sex determination pathways of unicellular and multicellular volvocine algae, and will enable a greater understanding of how a transcriptional regulator, MID, acquired control over a complex developmental pathway."

[ http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001904 ; my bold]

As I understand it, the question only applies to eukaryotes, since prokaryote sexual reproduction is not certain to involve full reproduction, mating types or (duh) organs. [ http://en.wikipedia.org/wiki/Sexual_reproduction ]

Given that, the referenced work "establish genetic and evolutionary continuity between the mating-type specification and sex determination pathways" and hence a deep root to "sexes or separate reproductive structures that produce sperm and eggs".

Maybe there are lineages that have evolved later exceptions, but those seem to be rare to say the least. That in itself may point to a difficulty, but I would like to see more research on the MID system to possibly tell us more.

Seems no one understand sex yet; it just happens. oo)