Re: Doriopsis pecten and egg ribbon from Japan

Thanks Gary,

This is a nice example of why knowing something about a species' food and egg ribbons is just as valuable as lots of anatomy. If you look at the Fact Sheets on Doriopsis granulosa and D. pecten and my comments in many of the attached messages, you will see I think there are two widespread speices in the tropical Indo-West Pacific. One of these is the dark blue D. pecten which apprears to feed exclusively on a dark blue sponge of the genus Terpios. Its egg ribbon, as illustrated in Nishina Masayoshi's recent message [#9368] is white with a frilly edge, and quite small and delicate. The other species, D. granulosa, is usually considered to be yellow, but as I discuss on the Forum [#9351], I am pretty sure it is variable in colour sometimes being a dark green. It feeds on another sponge, which has been indentified as Prianos phlox. This sponge is usually yellow or yellowish orange, but I suspect from your middle photo can also be greenish yellow. The egg ribbon of this species [#9329] is much larger, sturdier, and yellow.

Both these sponges can be found in close proximity to each other. My interpretation of your photos is that the blue one in the upper photo is D. pecten, but the dark greenish one in the middle photo is D. granulosa. Both yellow egg ribbons appear to be those of D. granulosa, but I can't get any feel for the height of the ribbon in the middle photo. In the middle photo, the dark blue sponge on the left is Terpios, while the greenish sponge on the right is almost certainly what I am calling Prianos phlox. It is possible the blue animal in your upper photo is also D. granulosa but I think it would be a bit unfair on us if bit D. granulosa also has a colour form identical to that of D. pecten.

I guess what you should watch out for is the white frilly ribbon of D. pecten, and whether blue animals are always on the blue sponge while all other coloured animals - even dark green - are on yellow to yellow-green sponges.

Best wishes,
Bill Rudman