Over several years Harry ten Hove and I have been observing species of
Hydroides that have 2 different 2-tiered opercula. One of these opercuka
has 2 simple tiers, and the other has a much more developed operculum.
For example, one a typical Hydroides minax operculum and the other a
more simple one. -- Both of these opercula are present on a single
individual. We described this in a discussion section in Ben-Eliahu & ten
Hove, 1989, page 393.
The simpler of these forms has been found in several different Indo-
Pacific species together with the mature form.
If you have come accross the phenomenon of more than one kind of 2-
tiered opercula in a single specimen of Hydroides we would welcome
your additions to this list.
Thanks in anticipation of your kind attention.
Nechama Ben-Eliahu and Harry A. ten Hove
<nbenelia at cc.huji.ac.il>
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