Newport's Eelgrass and Its Residents: Mollusks

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Photo courtesy of Pacific Northwest National Laboratory National. Photo Source and License

Scallops, Oysters and Mussels are all mollusks but there are a few more not-as-well known mollusks that live in the eelgrass beds of Newport Bay. Introducing the California Jackknife, Navanax, Bubble Snail, and the Sea Hares.

 

California Jack Knife Clam

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"Razorclm" by RazorClam23 - Own work. Licensed under Public Domain via Commons.  

The California Jack Knife Clam, Tagelus californianus, is a four inch brown clam with a vertical shell. It burrows up to 20 inches deep into the mud, usually staying there for its entire life. The vertical shape of its shell allows it to glide upwards to the top of its burrow for feeding and slide down to hide from predators. Similar to oysters, the jack knife clam feeds on organic particles in the water.

Navanax

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Photo curtesy of Eva Funderbugh. Photo Source and License.

Navanx inermis is a predatory sea slug that feeds on various other sea slugs on the seafloor. Reaching more than 22 cm in length, it uses chemoreceptors to track down slime trails of prey and mates. It is a hermaphrodite, meaning it has both female and male reproductive systems. To mate, Navanax would often form chains of three or more members with individuals in the middle acting as both male and female. 

Here is a video showcasing Navanax mating!

And one of Navanax swallowing a bubble snail whole!

Gould's Bubble Snail

Gould's bubble snail, Bulla gouldiana is named after the biologist Augustus Addison Gould. Reaching over 55 mm in length, it is one of the larger mollusks found in eelgrass meadows. The shell has a distinctive pattern with varying degrees of blue pigmentation. The bubble snail lives in protected waters on the sandy bottom feeding on green algae. Spending the day mostly buried in the sand, the snail is most active at night. 

Eelgrass Sea Hare

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 Photo curtesy of Ken-ichi Ueda. Photo Source  & License

Phyllsplysia taylori, commonly known as eelgrass sea hare or Taylor's sea hare, is a primitive species of sea slug. It is well camouflaged and only found on eelgrass. The shape of the sea slug makes it almost invisible on the leaves of eelgrass. Not only are the colors similar to that of eelgrass, but it can also orient its body lengthwise along the leaves. It feeds on other small organisms on eelgrass blades usually leaving behind feeding scars on the leaves. It can grow up to eight cm in length but usually stays around half that size.

California Sea Hare

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Sea hare, Aplysia californica. License  

The California Sea Hare, Aplysia californica, is a species of sea slug found in sheltered coastal waters, usually where vegetation is thick. Adults prefer shallow tidal zones while juveniles prefer deeper waters up to 60ft. Sea hares usually reach up to eight inches in length and 2.5 lbs but are known to grow twice the usual length and weight. They have two pairs of antennas on their heads, one near the mouth for smelling and the other behind the eyes for locomotion. California Sea Hares mostly feed on red algae, which gives their body a reddish hue. 

California Sea Hares are hermaphrodites, meaning that they possess both male and female reproductive systems. Like the Navanax, they can create chains of multiple members (up to 20!) while mating. Each Sea Hare can lay up to 80 million eggs, most of which are unfortunately eaten by predators. The Sea Hare itself has very few predators due to its ability to produce toxins from consuming algae. When disturbed, they can also produce two different kinds of ink that acts like an irritant against predators. Sea Hares have a short lifespan, usually dying after laying eggs but their life cycle can be extended by delaying when they spawn eggs. Living in cooler waters usually delay the time it takes to spawn eggs while warmer waters accelerate the process.  

A video showcasing the California Sea Hare releasing ink as defense against a spiny lobster!:


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