
Robillard'S Dendronotid
dendronotus robilliardi
Robillard's Dendronotid is a stunning marine gastropod that inhabits cold-temperate marine waters. Like other members of the Dendronotidae family, this nudibranch is characterized by its magnificent, branching dorsal appendages, which resemble miniature underwater forests. These appendages, called cerata, not only assist in respiration but also mimic the hydroids upon which the animal feeds, offering superb crypsis. Observant divers and tidepoolers are often spellbound by the delicate, translucent bodies of these sea slugs as they slowly navigate rocky substrates. Their presence is a great indicator of a healthy, diverse benthic ecosystem rich in colonial cnidarians. Spot a Robillard'S Dendronotid? Identify it instantly with the Snappit nature app.
Habitat: Typically found in cold-temperate intertidal and subtidal rocky reefs, often clinging to bryozoan mats and colonial hydroids.
Appearance
This species is a small nudibranch, typically reaching lengths between 1 to 5 centimeters. Its body is translucent white, sometimes flushed with pale orange, pink, or yellow undertones. It is adorned with branching cerata along its back, which have tipped variations of opaque white or golden yellow. Bright orange or reddish-brown speckles are often dotted across its body, and its highly branched rhinophores (sensory tentacles) protrude elegantly from the head, creating a complex, frilly silhouette that blends seamlessly into marine turf.

Category
InvertebrateRarity
Common
Danger
1/5 · Very low
Snaps
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Interesting facts
Its highly branched rhinophores function as chemical receptors, allowing the nudibranch to 'smell' food and mates in the water column.
Like many nudibranchs, it is a simultaneous hermaphrodite, possessing both male and female reproductive organs to maximize mating opportunities.
The elegant branching structures on its back act as gills, maximizing surface area for oxygen absorption directly from the seawater.
Special abilities
Arborescent Crypsis
Its highly branched body appendages perfectly mimic the hydroid colonies it lives on, making it virtually invisible to visual predators.
Chemical Deterrence
It sequesters toxic or distasteful compounds from its cnidarian prey, rendering its own body unpalatable to potential predators.
Regenerative Cerata
If attacked, it can autotomize (shed) its branching cerata to distract a predator and later fully regenerate them without permanent damage.
Measurements & details
- Length
- 1-5 cm
- Weight
- 0.001-0.005 kg
- Lifespan
- 1 years
- Clutch Size
- 500-5000
- Incubation
- 7-21 days
Diet & Feeding
Feeds almost exclusively on colonial hydroids, using its specialized radula to scrape and consume the individual polyps.
Primary Foods
- Colonial Hydroids
- Garland Hydroids
- Obelia species
Foraging Method
- Grazing
Ecological connections
Garland Hydroid
Sertularella turgida
Preys directly on colonial hydroid colonies, stripping polyps from the branching stalks.

Sunflower Sea Star
Pycnopodia helianthoides
Is occasionally preyed upon by specialized sea stars in rocky subtidal zones.
Traits
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Also known as
No aliases listed yet.
Collections
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Safety
Danger
1/5 · Very low
No special safety notes yet.
Frequently Asked Questions
How to identify Robillard'S Dendronotid?
The easiest way to identify Robillard'S Dendronotid is to use the Snappit nature identifier app.
How long is Robillard'S Dendronotid?
1-5 cm
How much does Robillard'S Dendronotid weigh?
0.001-0.005 kg
How long does Robillard'S Dendronotid live?
1 years
What does Robillard'S Dendronotid eat?
Feeds almost exclusively on colonial hydroids, using its specialized radula to scrape and consume the individual polyps.
Where is Robillard'S Dendronotid usually found?
Typically found in cold-temperate intertidal and subtidal rocky reefs, often clinging to bryozoan mats and colonial hydroids.
How does Robillard'S Dendronotid hunt?
Grazing
How many eggs does Robillard'S Dendronotid lay?
500-5000
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