Hypselodoris tryoni is found occasionally at Enewetak and Kwajalein Atolls. The best place for them was on the pilings under Medren Island pier at Enewetak until the summer storm of 1982, when the southwesterly swell generated by the storm washed them all away. It took about 8 months, but they finally started to show up under the pier again in March of 1983. Aside from the pier, they can be found occasionally on lagoon pinnacles and along the interisland subtidal reefs at depths of about 2 to 12 meters. It is one of the few chromodorid species here usually found exposed during the day rather than hiding under rocks. Specimens we've seen have ranged from 5 to 70mm in length. Hypselodoris tryoni was first reported in the Marshalls from Enewetak and Kwajalein Atolls as Chromodoris tryoni by Johnson & Boucher (1984).
This species was formerly considered in the genus Risbecia, and like other former Risbecia species, will often queue up to move along the reef. Most commonly, this is referred to as trailing behavior, although I kind of like an alternate term, "queuing behavior." In queuing, the following individual crawls along immediately after the leader, with the anterior edge of its foot on the leader's tail. Although usually paired, occasionally you can see three in a line as shown in the lower photo below.
The single animal below was found on a shallow lagoon reef on 30 July 2012.
Created 3 January 2006
Updated 6 October 2012