Hypselodoris 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 H. decorata 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 more red. 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 a H. decorata, even though both could be found in the same habitat.

Specimens of H. decorata are typically found under rocks along lagoon reefs and pinnacles at depths of about 5 to 15 meters. We've also found them on the pilings under Medren Pier at Enewetak.

Of course, after saying that H. 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.

Created 19 December 2005
Updated 12 January 2007