Hypselodoris cf decorata (Risbec, 1928)

Here's another place where I break with what is generally believed. Many branchers consider this to be a variant of Hypselodoris maculosa. I have seen many H. maculosa and many of the animals pictured below, and I have to disagree. I think the species on this page has a more white-spotted red margin (as adults, anyway), a purplish tinge at the anterior end and the tip of the tail, and three orange bands on the rhinophores. Also, the mid-dorsal spots tend to be red rather than purple. In the Marshalls, H. maculosa has two bands on the rhinophores, the margins are more orange than red and have fewer white spots, and their dorsal spots are more purple than red. Of course there is enough variation in both that sometimes it is hard to be sure about a particular specimen. But what convinced me is that whenever I would find a pair, they would invariably be paired up with another of the same color form. I'd never find an obvious H. maculosa paired with an H. cf decorata, even though both could be found in the same habitat. But the real question is, if this species is indeed different, what do we call it? Risbec's (1928) drawing of "Chromodoris" decorata is similar, especially in the three orange bands on the rhinophores, but the drawing does not show the white-spotted marginal red band and the spots on the dorsum look more like short lines. Still, to help differentiate them from H. maculosa, we refer to this one as H. cf decorata.

Specimens of H. cf decorata are typically found under rocks along lagoon reefs and pinnacles at depths of about 5 to 15 meters, as well as on the seaward reef to as at least as deep as 40m. We often found them on the pilings under Medren Pier at Enewetak, and have seen one specimen at Pohnpei in the Caroline Islands.

Of course, after saying that H. cf decorata typically has wide red margins containing numerous white spots, here's one that doesn't. This is a young specimen, only about 15mm long. The larger ones have more red on the margins.

The specimen below was found on the Kwajalein Atoll seaward reef, under a rock at a depth of about 6m, on 7 March 2010.

The specimen below was found eating a purple sponge under a rock on a Kwajalein Atoll lagoon pinnacle at a depth of 8m on 18 October 2010.

Another on the same sponge.

The placement of this Kwajalein specimen is uncertain.

Created 19 December 2005
Updated 31 January 2016

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