Glossodoris atromarginata

Glossodoris atromarginata

Glossodoris atromarginata

Glossodoris atromarginata  known to tropical fish keeping enthusiasts as the Dark Margin Glossodoris is found in Australia, Thailand, Japan, and most of the other tropical and subtropical Pacific and Indian Oceans throughout the world.

Synonymous with Doriprismatica atromarginata, Glossodoris atromarginata is a peaceful species that spends all of its waking hours searching out and feeding on a variety of sponges.

Glossodoris atromarginata is found in rocky coastal reefs, coral reef areas with substantial growths of sponges, hard and soft corals, and areas with sandy, silty bottoms with sea pens, sponges, gorgonians, ascidians, soft corals, hydroids, and seaweed.

The Dark Margin Glossodoris has been seen at depths from 6 to over 30 feet feeding on sponge colonies partly buried under growths.

Glossodoris atromarginata like many sea slugs, are known to secrete trace amounts of poisonous toxins as a defense mechanism when threatened, and should not be housed with aggressive predators that may view them as a meal.

Glossodoris atromarginata

Glossodoris atromarginata

Glossodoris atromarginata range in color from a creamy white, to a pale brown.   A thin black  line borders the very sinuous mantle edge, the black edge to the rhinophore pockets, the black rhinophore clubs and the black edging to the simple gills.   Their beautiful gills wave rhythmically as they crawl along the sandy bottom.

In the ocean near Japan, many individuals have a bright yellow and white colors as well as milky white and light brown solids with black borders.  There are also many solids with strong brown in the southern sea of Japan with the tip of the antennae and the secondary gills colored black, with a white base.

Glossodoris atromarginata is a relatively large sea slug that can reach 4 inches in length.   They have a have quite a small radula and a long oral tube which extends as a long thin tube rather than the big inflated bulb seen in species of Hypselodoris.    The thin oral tube allows them to probe deep into partly buried sponge colonies partly buried under other growths to feed.

Although Glossodoris atromarginata is the most common species of the group, there are a number of almost identically colored species that are very difficult to externally separate from Glossodoris atromarginata.

Because of their specialized feeding habits and relatively short life expectancy in an aquarium environment, Glossodoris atromarginata are recommended only for advanced aquarists.    They are apparently voracious eaters of a variety of sponges  and are best housed in an established reef tank of at least 55 gallon capacity with plenty of mature live rock, a sandy substrate, and plenty of sponges.

Because they need a moderate amount of water movement, at least one powerhead is recommended in the system and like most invertebrates, Glossodoris atromarginata is very sensitive to rapid changes in water conditions and requires stable water quality.

They are especially sensitive to higher levels of nitrates and cannot tolerate any amount of copper in the system.  When purchased they should be slowly drip acclimated with the lights off when introduced into the tank.

In established reef aquariums, regular spawning often occur when Glossodoris atromarginata are maintained together, however, there has not been a great success rate reported by aquarists in raising the larvae.

Glossodoris atromarginata is a specialty feeder that requires live sponges as their primary diet to thrive.   Lacking a steady diet of sponges in their diet, they will usually not eat enough of anything else to thrive and will slowly starve without their primary food source.

Because of this and their short life span, only expert tropical fish keeping enthusiasts should attempt to maintain this species.

Glossodoris atromarginata is occasionally available to tropical fish keeping enthusiasts from specialty shops, Nudibranch forums,  and online from a variety of sources at an approximate purchase size of 1″ to 2″ at reasonable prices.

Glossodoris atromarginata

Glossodoris atromarginata








Minimum Tank Size: 55 gallons
Aquarium Type: Established Reef
Care Level: Moderate
Temperament: Peaceful
Aquarium Hardiness: Relatively hardy
Water Conditions: 72-78°F, dKH 8 to 12, pH 8.1-8.4, sg 1.023-1.025
Max. Size:  4″
Color Form: White, Brown, Black
Diet: Specialty Carnivore
Compatibility: Reef Compatible
Origin:  Subtropical Pacific, Indian Ocean
Family: Chromodorididae
Lifespan: Unkonwn
Aquarist Experience Level: Expert Only

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