Hypselodoris maritima? from Western Australia

Dear Jean-Paul,
I am glad you like the site and find it useful.

I am pretty sure this is a colour form of Hypselodoris maritima. One important feature is that the gills seem to be white with orange edges. Western Australia seems to have an interesting fauna which includes a number of what seem to be unique colour forms of Western Pacific species. In the Western Pacific, Hypselodoris maritima does not usually have such obliquely arranged black lines, and the mantle does not have such a brownish yellow appearance.

We can surmise that a population has established itself in Western Australia since the relatively recent opening of the Timor Sea across the top of Australia. Only further collecting and observations will allow us to determine whether these Western Australian 'colour forms' should be considered separate species.

There is a similarly coloured species from the Western Indian Ocean, Hypselodoris nigrolineata but that differs considerably in colour including having the gills all orange, not lined as in H. maritima.
Best wishes,
Bill Rudman.