Dear  Andy and Kay,

I greatly appreciate your postings about the donacids, as I have been
working
on their populations in Okinawa, mainland Japan and some overseas areas.

In Okinawa, where typhoons are frequent, causing much disturbance on
the beach sediments, donacids survive well with several ecological traits,
that work as bet-hedging against unpredictable disturbance events.
For example, they reproduce repeatedly during the warmer months and
recruitment of juveniles occur throughout the year.

I got specimens of both D. gouldii and D. variavilis and after watching
and comparing them, I wonder what happened to them between the
two sides of American continent, perhaps they shared the same
ancestral population before the isolation of the two oceans several
million years ago. On the east side, the population developed so much
color variation of the shell, while the other side it did not.

Cheers,

Masashi Yamaguchi
Faculty of Science
Univ. of the Ryukyus
Nishihara, Okinawa
903-0213 Japan

http://www.cc.u-ryukyu.ac.jp/~coral/