# NUDIBRACH Nudibranchs are pronounced "noody-brank" (rhyming with "tank") rather than "branch" (like a tree branch) because of their Greek and Latin roots Nudibranch aka sea slugs; a group of shell-less marine mollusks; name means "naked gill" 3000 known species of nudibranchs Carnivorous exposed gils and club shaped rhinophore two main types based body structure and gill placement, dorid & aolid Rhinophore detect chemical signals in water ocellio (eyes) light and dark hermaphrodites bottom-dwelling carnivores Dr. Terry Gosliner is widely regarded as the world's leading expert on nudibranchs. As the Senior Curator of Invertebrate Zoology at the California Academy of Sciences; aka Slug Lab Butterflies of the Sea - Nudibranchs, commonly called sea slugs, are widely believed to be some of the most colorful creatures on earth ## Nudibranchia and Sacoglossa Nudibranchia and Sacoglossa are both diverse orders of shell-less marine gastropods commonly referred to as "sea slugs" They differ by diet and feeding habits * Nudibranch are carnivorous; kleptonidy (steal stinging cells * Sacoglossa are herbivorous; kleptoplasty (steal chloroplasts) ## Aposematism Aposematism is a biological defense strategy where animals use conspicuous signals-like bright warning colors, distinct patterns, or loud sounds-to advertise that they are toxic, venomous, or otherwise dangerous. aposematic signals-warning colors that advertise the presence of toxins or unpleasant chemicals. Apo-sema-tism Aposematism is natures “no trespassing” sign Aposematic coloration or olfactory aposematism or auditory aposematism Acoustic aposematism Cost free retreat Tiger moths and bats - tiger moths use a special organ called tymbals to emit a high frequency ultrasound click to warn a bat Batesian mimicry - when a harmless non toxic species develops aposematic signals of a toxic species to gain protection Fish have good eye sight and recognize color The 200m mark in the ocean signifies the exact boundary where the sunlit zone ends and the "twilight" (mesopelagic) zone begin nudibranchs switch to black and white contrasting patterns Nudibranchs are primarily eaten by reef fish (like wrasses and damselfish), crabs, sea turtles, sea spiders, and other predatory sea slugs. Costasiella kuroshima (also known as a leaf slug, sea sheep, or leaf sheep) - found in Japan Sea sheep (not a nudibranch) but a species of sacoglossan sea slug they perform photosynthesis via kleptoplasty. no animal is capable of true, independent photosynthesis because animals lack chloroplasts and chlorophyll but some animals harness the sun's energy through symbiosis (harbouring algae inside their cells) or kleptoplasty (stealing and utilizing chloroplasts from consumed algae). Aeolid nudibranchs eat cnidarians (like anemones) and store the undigested stinging cells (nematocysts) in their own backs to use as a defense against attackers. nudibranchs are chemical factories; have medical potential; e.g., one nudibranch has chemicals that inhibit HIV replication. ## Humboldt tips Humboldt's rocky intertidal zones and bays are home to a vibrant array of sea slugs, particularly brightly colored nudibranchs and the massive California sea hare. Baker Beach: Located just north of Trinidad, this spot is highly recommended by local naturalists for finding sea slugs in sea grass and rock crevices. Trinidad State Beach & College Cove: Excellent rocky tide pooling spots where you can often spot opalescent nudibranchs. Aim to arrive 1-2 hours before the lowest tide of the day. Early morning spring low tides provide the best visibility. ### Local Nudibranch * Opalescent Nudibranch (Hermissenda crassicornis): One of the most common and easily recognizable sea slugs in the Pacific Northwest. They feature neon-blue or white electric lines and feathery breathing structures on their backs. Opalescent nudibranchs are one of the prettiest and most colorful species of nudibranchs. Aggressive fighters. * California Sea Hare (Aplysia californica): A large, rust-brown sea slug that can grow up to 15+ inches long. When disturbed, they can release a cloud of purple ink. * Frosted Nudibranch (Dirona albolineata): Translucent with distinctive frosted, white-tipped edges, they are often found navigating rocky tide pools. * Hopkins' Rose Nudibranch (Okenia rosacea): Bright pink, inch-long sea slugs that occasionally boom in population along the Humboldt coast during periods of warm ocean currents. [Toxic Beauty Rideable Nudibranch — Stephanie Metz](https://www.stephaniemetz.com/work/toxic-beauty) [I LOVE NUDIS](https://ilovenudis.com/) nudibranch eats toxic sea sponges Nudibranchs often eat toxic sea sponges and store the sponge's toxic chemicals in their own bodies for defense A significant number of nudibranchs obtain their chemical arsenal directly from their prey. By feeding on sponges, corals, anemones, or other invertebrates that possess toxins, they accumulate these compounds in their tissues. This is a clever way to exploit the defenses of their prey for their protection.