Arnold’s Sea-slug – Gymnodoris arnoldi

, Arnold’s Sea-slug, Gymnodoris arnoldi
Depth: 0 - 60 m

The Arnold’s Sea-slug, scientifically known as Gymnodoris arnoldi, is a captivating species of nudibranch, renowned for its striking appearance and intriguing behaviors. This marine invertebrate is a fascinating subject of study for marine biologists and enthusiasts alike, captivating audiences with its unique adaptations and ecological roles.

Description & Characteristics

Gymnodoris arnoldi is a relatively small nudibranch, typically reaching a maximum size of around 20 millimeters in length. Its body is characterized by a distinctive, elongated shape, with a prominent dorsal hump that lends it a slightly humpbacked appearance. This sea slug exhibits a vibrant, reddish-orange coloration, often adorned with irregular white markings that create a striking contrast. The coloration of Gymnodoris arnoldi serves as a form of camouflage, allowing it to blend seamlessly into its surroundings, especially amidst the colorful corals and sponges of its habitat.

Habitat and Occurrence

Gymnodoris arnoldi is a creature of the shallows, primarily residing in the intertidal and subtidal zones of the tropical Indo-Pacific region. This species thrives in the warm waters of this diverse marine realm, with its distribution spanning a wide geographical range. Gymnodoris arnoldi is commonly found in association with rocky reefs and coral formations, where it can readily access its preferred food sources. The sea slug’s preference for these environments places it within the Neritic zone, the marine region extending from the shoreline to the edge of the continental shelf. This zone is characterized by abundant sunlight penetration, supporting a rich diversity of marine life, including the Gymnodoris arnoldi.

Taxonomy

Gymnodoris arnoldi belongs to a vast and diverse group of marine mollusks known as the Gastropoda, which includes snails, slugs, and nudibranchs. The Arnold’s Sea-slug is further classified within the Order Nudibranchia, a group of sea slugs renowned for their lack of external shells and their striking array of colors and patterns. Gymnodoris arnoldi is a member of the Family Polyceridae, a family of nudibranchs characterized by their relatively small size and typically bright coloration. This family encompasses a wide range of species, each adapted to specific ecological niches within the marine environment.

Feeding

Gymnodoris arnoldi is a carnivore, feeding primarily on bryozoans, colonial invertebrates often referred to as “sea mats.” Bryozoans are filter feeders, consuming microscopic organisms from the surrounding water. The Gymnodoris arnoldi uses its radula, a rasping tongue-like structure, to scrape bryozoans off surfaces and ingest them. While this species is known to prey on bryozoans, its exact dietary preferences and the specific types of bryozoans it consumes remain relatively unexplored. Additional research is required to fully understand the feeding ecology of this intriguing nudibranch.

Associated Species

Image References

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