Opalescent Nudibranch

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While on a tidal pool adventure at Pillar Point, California, I came across this brightly colored marine invertebrate. Though it is small, only growing to about 2 inches, it is one of the prettiest and most colorful of the sea slugs.

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The Opalescent Nudibranch feeds mainly on hydra-like marine organisms such as sea anemones. It sometimes attacks other sea slugs and will eat smaller specimens of its own species. It can be found around tidepools, as well as on rocks, pier pilings and mudflats. It can also be found from low-tide line water to water up to 100 feet deep.

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Not only is it beautiful, but this creature is also a model organism and used in studies into classical conditioning, memory consolidation and associative learning, the structure of neural circuits and neural physiology. In addition, it is widely used in studies of ecology, pharmacology and toxicology.

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Red Rock Crab

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As its name implies, this crustacean is often found in and around rocky places and features reddish-purple coloration.

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It can grow to more than 10 inches across, but 4 to 6 inches is more common. Its large claws are tipped in black and they have a wide, fan-shaped body.

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This cool creature crushes barnacles with its large pincers and eats them. It also eats smaller crabs, sea cucumbers, and many other intertidal invertebrates, as well as dead fish.

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While searching tidepools, I saw this “shell” move. It didn’t take long to realize that it was not a shell at all, but rather a juvenile Red Rock Crab, which can be white with a pattern of dark lines.

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I enjoy finding these hard-shelled creatures, whose other common names include Red Crab, Cancer Crab and Red Cancer Crab.

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Monkeyface Prickleback

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While exploring tide pools in north-central California, I came across this wonderful little fish. It tends to stay near the coast, rather than roaming the open ocean, and is often found in rocky areas.

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Young Monkeyface Pricklebacks, like this one, feed on zooplankton and crustaceans, while adults are primarily herbivorous, mainly consuming red and green algae.

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These long, slender fish, grow to about 18 inches in length and possess the unfishlike ability to breathe and survive out of water while hidden under seaweed or rocks. This was one of many fun finds during my tidal pool adventure.

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Sea Lemon

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While investigating tide pools near San Francisco, I found several cool creatures, this was one of them. It is a medium-sized, shell-less colorful Sea Slug – a marine gastropod mollusk. Its common name comes from this animal’s visual similarity to a lemon, featuring roughened skin, an oval shape (when seen from above), and its yellow coloration.

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Its bright colors are an advertisement to its distastefulness; its fruity, penetrating odor and acidic taste repels most predators, though Sea Slugs eat other Sea Slugs, this type feeds mainly on sponges. Like a land slug, it uses its filelike tongue to scrape sponges, its favorite being the Breadcrumb Sponge.

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The Sea Lemon has a ring of upright feathery gills, which are quickly retracted when a disturbance is sensed, similar to how a land slug retracts its eyes. It is hermaphroditic, possessing both male and female organs. This fascinating invertebrate is relatively short-lived, having a lifespan of about a year.

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