Goniobranchus preciosus was found occasionally at Enewetak Atoll, where it lived on lagoon interisland reefs under dead coral at depths of 4 to 5 meters. Several were also found under corrugated aluminum sheets blown into the lagoon off Enewetak Island by typhoon Pamela in 1982. At Kwajalein, it has been only rarely found under dead coral but is occasionally found in lagoon Halimeda patches in 7 to 30m. Sizes ranged up to about 35mm but most specimens were smaller. As currently understood, G. preciosus shows considerable variation in color. The dorsum ranges from pure white to yellowish white scattered sometimes densely with orange spots or even blotches. The margin is white to bluish white at the very edge, followed by reddish purple and orange submarginal bands, but the bluish white edge can be either very thin--so thin that it almost disappears, which if it did would make these identical to Goniobranchus verrieri--or thicker or even broken up into spots. This page shows some of the variations, and others can be seen on our Bali, Anilao and Lembeh Strait pages. The variations of this species and others in the same color group are ripe for a thorough comparison of molecular data.
The one below had a very thin but distinct white line along the edge of its margin.
Most Enewetak specimens were nearly all white dorsally, except for the marginal bands. Many Kwajalein specimens have had varying amounts of orange speckling scattered over the dorsum. The three shots below are of a Kwajalein specimen that had a particularly vivid mantle margin.
The 20mm specimen in the two photos below from Kwajalein had not only a vivid margin but also numerous orange spots over the dorsum.
The specimens in the two photos below were found on 3 January 2009 on Halimeda plants on the sandy lagoon bottom at a depth of about 35m.
Created 14 December 2005
Updated 17 November 2021