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- Chelonia mydasScientific Name
- EndangeredIUCN Threatened Status
Oreo Nudibranch
Jorunna funebris, commonly known as the Oreo Nudibranch, is one of the most recognizable sea slugs found around Koh Tao. Its distinctive white body covered in black spots makes it a favorite subject for underwater macro photographers.
Least Concern
Overview
Jorunna funebris is one of the most frequently encountered nudibranch species around Koh Tao and a popular find among underwater photographers. Commonly known as the Oreo or Dalmatian Nudibranch, it is easily identified by its white body covered in irregular black spots, resembling the cookie or coat pattern of a Dalmatian dog.
Like all nudibranchs, Jorunna funebris is a shell-less marine gastropod. Although small and often overlooked by recreational divers, it is a fascinating example of the incredible biodiversity found on coral reefs. Most individuals measure only a few centimeters in length and are typically found crawling slowly across reef surfaces in search of food.
This species feeds primarily on sponges and is often discovered near its preferred food sources. Its striking coloration serves as a warning to predators that it may contain chemical defenses acquired from its diet.
Jorunna funebris can be found throughout the Indo-Pacific region and is regularly spotted at dive sites around Koh Tao. Divers interested in macro photography frequently search for nudibranchs like this one due to their unique appearance, intricate textures, and photogenic behavior.
While many visitors focus on larger marine life such as turtles and whale sharks, creatures like Jorunna funebris demonstrate that some of the reef’s most fascinating residents can be found only by slowing down and looking closely.
Identification
The defining feature. The body is a clean, bright white, covered in rounded raised bumps — tubercles — each tipped with a small black dot. The pattern is consistent across the entire dorsal surface and is visible even at a distance relative to the animal's small size. No other nudibranch commonly encountered on Koh Tao shares this exact combination.
Logan Brown
Jorunna funebris is small — typically 2–4cm — and moves with the characteristic slow, deliberate glide of most nudibranchs. Found in isolation rather than groups, it tends to stay close to or directly on its cyanobacteria food source. The combination of small size, white colouration, and methodical movement makes it easy to overlook at speed — this is a species for divers who slow down and look closely at the substrate.
Logan Brown
Like many nudibranchs, Jorunna funebris deposits its eggs in a distinctive spiral ribbon attached directly to the substrate, often laid close to or on the cyanobacteria it feeds on. The ribbon is white and delicate, coiled in a neat clockwise or counterclockwise spiral — finding one is a strong indicator that an adult is somewhere nearby. Egg spirals are frequently overlooked by divers scanning for the animal itself, but for macro photographers they make a compelling subject in their own right.
Logan Brown
Conservation Notes
Nudibranchs are fragile animals with no defensive shell and delicate external gill structures. Never touch — even a gentle brush from a fin or glove can cause serious damage. When photographing, avoid getting so close that your exhalation bubbles disturb the animal. Jorunna funebris is not commercially harvested but is sensitive to reef degradation and water quality decline, making it a useful indicator species for overall reef health.
Oreo Nudibranch Facts
Where to find them
Jorunna funebris is a small, slow-moving species that rewards divers who take their time on the reef rather than covering distance. Southwest Pinnacle’s sheltered sections and the rocky substrate at Chumphon Pinnacle are the most consistent locations — look on and around blue cyanobacteria colonies on hard substrate, typically in the 8–20m range. At Sail Rock, check the lower sections of the pinnacle and any sheltered ledges. A torch is useful even on day dives — the contrast between the white body and dark tubercles makes it much easier to spot under a light than in ambient conditions.
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