top of page

193. Dark Margin Glossodoris (Glossodoris atromarginata aka Doriprismatica atromarginata)


This elongated nudibranch is sometimes referred to as “cheesecake nudibranch” due to the resemblance of colour with the cream-white body (the cheese) and the darker brown to almost black lined very sinuous mantle edge (the crust), and the dark to black rhinophores and branchi or gills.

The Dark Margin Glossodoris (Glossodoris atromarginata aka Doriprismatica atromarginata) is a day active nudibranch native to the tropical waters of the Indo-Pacific region. It can reach a total length of 6cm/2.4inch or so. There are several of almost identically coloured species that are difficult to distinguish from the Dark Margin Glossodoris. Apparently there are also different morphotypes (any of a group of different types of individuals of the same species in a population) within this species depending on their location; the species from the south-western Indian Ocean (Madagascar and the Mascareignes archipelago), like the one in this underwater videoclip, bare small specks with a golden hue, and the dark mantle edge is much less sinuous than species from other parts of the Indo-Pacific region.

The Dark Margin Glossodoris is a carnivorous sponge predator, to put it simple; this nudibranch mainly feed on sponges. Its preferred prey are the sponges of the genus Hyatella (a type of encrusting sponges). It is therefor most likely to be found on or in the vicinity of its favourite food source. However, the specimen filmed in this underwater videoclip was found in the middle of a very large sand plateau at a depth of about 22m/72ft and far away from any type of reef or place where sponges grow.

This nudibranch has two little cephalic tentacles above and in front of its mouth. These tentacles are used by the slug to feel, taste, and smell. In this short underwater videoclip these lobes are clearly visible.


This crawling Dark Margin Glossodoris was filmed moving towards the camera for different reasons. When filming an animal underwater, whether it's moving towards or away from the underwater videographer and his camera, there are certain factors to consider that can affect the overall quality and impact of the footage. While both scenarios have their own advantages and challenges, filming an animal moving towards the camera often provides a more engaging and visually appealing result for several reasons:

Visual Perspective:

When an animal moves towards the camera, it creates a sense of depth and perspective in the footage. The viewers can perceive the animal's movement in relation to the camera, which adds a dynamic element to the scene. This perspective can create a more immersive experience for the audience.

Action and Energy:

Filming a fish swimming towards or in this case a nudibranch approaching the camera captures a sense of action and energy. The movement towards the camera can create a sense of anticipation and excitement, making the underwater footage more engaging and visually interesting. It allows the audience to feel like they are taking part in that dive and observing a part of the animal's journey.

Subject Focus:

When an animal moves towards the camera, it becomes the primary focus of the underwater shot. The subject occupies a larger portion of the frame, and there are fewer distractions in the background. This helps direct the viewer's attention to the animal and enhances the overall composition of the footage.

Filming location:

This short underwater videoclip has been filmed in Mauritius 🇲🇺

More on this topic:

For an other Glossodoris insight please go to vlog posts 48 or click here

Join us on a journey of discovery and entertainment as we explore fascinating marine wildlife topics and explore the many exciting underwater adventures on our YouTube channel and our Facebook page!

Bring the beauty of the ocean to life with our online Marine Wildlife Videography course!


bottom of page