Spirogyra conjugation tubes and spores

[jc maccagno]

pond water 40X Meiji MX5000

[Ernst Hippe]

Hello,
the second picture is remarkable: there are two conjugation tubes to one cell, but only one zygote. Where is the second one??
Regards Ernst

[uaalgae]

This is a very strange occurrence. I have observed Spirogyra sexual reproduction in many species. Usually if the two filaments (+/-) have slightly shorter or longer cells, this will often cause two adjacent male cells to try and form an association with the same female cell (one accepting the male gamete). Since there is one zygote in the female cell, would this mean that this is a 3N instead of 2N zygote? Very interesting.