Observation of the Week, 4/7/2016

This Dendronotus orientalis nudibranch seen by anudibranchmom in Redwood City, California, is our Observation of the Week!

Robin Agarwal (anudibranchmom) is currently travelling and wasn’t able to write us back by publication time, so we have two awesome iNatters chiming in on this find. We’ll post an updated version once we hear back from Robin.

One of iNaturalist’s most prolific users (12,000+ observations!), Robin Agarwal got into nudibranchs due to her daughter’s interest in marine biology, and has quickly branched out into observing many forms of life. But her experience with nudibranchs of the San Francisco Bay Area caused one to catch her eye, as she was unfamiliar with it. She posted photos of it on iNaturalist and Alison Young (@kestrel) the California Academy of Sciences Citizen Science Engagement Coordinator, was able to identify it as Dendronotus orientalis, a species originating in Asia and, as far as we can tell, never before documented in the U.S.! Rebecca Johnson (@rebeccafay), a marine biologist and Citizen Science Lead at the Cal Academy, asked nudibranch expert Terry Gosliner to confirm the ID, and marine invertebrate expert Gary McDonald (@mcduck) also agreed. “This was a truly community effort,” says Rebecca, “and for me, the coolest thing is that the correspondence that would have been normally limited to ‘expert’ emails and hidden is now done in public!”

One of the most active and encouraging members of the iNaturalist community is Susan Hewitt (@invertzoo), a “serious amateur” malacologist, who tells me that nudibranchs are a diverse group of sea slugs, “although the name ‘slug’ hardly does them justice! Many people who are familiar with them feel that nudibranchs are the most beautiful organisms on Earth, their colors and forms rivaling or exceeding even those of butterflies.” Not much is known about this particular species, but Susan points out its most distinguishing feature, which is that the sheaths of its rhinophores (chemoreceptive structures protruding from the body) extend to well past the body length of the animal. And like many other nudibranchs this species eats hydrozoans, tiny predatory (and often colonial) animals related to jellyfish and corals. Some nudibranchs even sequester the stinging cells of hydroids and use them for self-defense!

Dendronotus orientalis

Due to San Francisco Bay’s use as a major shipping port, “more and more species of marine invertebrates were accidentally introduced,” says Susan, “and a large number of them found habitat to their liking, and flourished there.” Rebecca Johnson took a team to collect some of the Dendronotus orientalis that Robin found, for further study, and says “early detection of invasive species is critical for the protection of the San Francisco Bay, [and] thanks to dedicated naturalists like Robin, and the iNat platform, we can learn more about changes in the bay and beyond more rapidly than ever before - and that information can be shared with a bigger community more quickly - so we 'know' when something is really important.”

- by Tony Iwane


- You can check out more of Robin’s awesome photography on Flickr. She also took a video of the nudibranch!

- Susan Hewitt has a great guide to photographing mollusks on her profile page, and she also appears in a video on Wikipedia about “love darts.” Check it out!

- The California Academy of Sciences team took a video crew with them when collecting their specimens, and we’ll post the video on our Facebook and Twitter pages when it’s finished, so follow us there!

Posted by tiwane tiwane, April 07, 2016 11:16 PM

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