Nudibranchs of the Northwest By Karin Fletcher

Copper rockfish swimming away Ling cod swimming away…but what’s in the background? One of the joys of scuba diving is taking pictures of fish  One of the disappointments of scuba diving is taking pictures of fish tails 

Red sponge nudibranch But there are some things that sit still – Nudibranchs! Yellow margin dorid

What are nudibranchs?

Aeolid anatomy Dorid anatomy Subclass of gastropod molluscs (chitons, bivalves, univalves, octopus, squid) Sea slugs are adapted to a marine environment gills or cerata (instead of lungs) a reduced or non-existent shell , except in larval stage

White –and-orange-tipped nudibranch heartbeat open circulatory system copper-based blood (hemocyanin) Hover over image to reveal play button for video

About 3,000 species worldwide About 86 in the Salish Sea Dorid Aeolid Other Dendronotina Arminina

Dorid body type – non-branching digestive system Gills in the back No cerata but can have toxin-filled glands around the mantle margin to deter predators Can have needle-like spines in their mantle called spicules to deter predators Often have dorsal bumps called papilla or tubercules

Close-up of tubercules and spicules

A number of toxic chemicals have been isolated from nudibranchs but most are too toxic to be used on humans. More than 300 chemicals have been described from only a fraction of the total nudibranch species Cooper’s dorids change metabolites they eat into more toxic chemicals Montery dorids have toxic chemicals in them that are not present in the food they eat Marine Opisthobranch Molluscs: Chemistry and Ecology in Sacoglossans and Dorids Neville Coleman’s World of Water

Aeolid body type – branching digestive system Each blood-filled ceras has a duct of the digestive gland Can store stinging cells called nematocysts from the corals, hydroids, bryozoans or anemones they eat in the tips of their cerata for their own defense http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2783962/

Diamondback nudibranch Orange doto Dendronotina Orange-peel nudibranch Hooded nudibranch

Neurologists study nudibranchs at the University of Washington’s Friday Harbor Laboratories on San Juan Island One study involved comparing how a neuron in the Pink tritonia and the same one in the Hooded nudibranch is used for different forms of movement http://digitalarchive.gsu.edu/cgi/viewcontent.cgi?article=1014&context=biology_diss&sei-redir=1#search=%22friday%20harbor%20neurology%20nudibranch%22 Pink tritonia Hooded nudibranch

Striped nudibranch Arminina Golden dirona White-and-orange-tipped nudibranch Frosty-tipped nudibranch

Other marine gastropods related to nudibranchs Headshield slugs Spotted aglajid Sea hares Taylor’s sea hare Sap-sucking sea slugs Enteromorpha-eating sapsucker Side-gill marine slugs California berthella

How big (or small) are they?

Grains of rice Rustic aeolid nudibranch Some nudibranchs are small

Pink Tritonia Pink Tritonia and fin Other nudibranchs are huge

How do nudibranchs get around?

Primarily crawl using cilia on the underside of their foot which beat and move it along the mucus secreted by its foot Able to crawl on the surface tension of water Some can swim – giant nudibranch, hooded nudibranch White-and-orange-tipped nudibranch Giant nudibranch swimming

How do nudibranchs eat?

Nudibranchs, like all molluscs except bivalves, have a tongue-like chitonous toothed ribbon called a radula which they use to grasp, scrape or shred the sponges, corals, anemones, hydroids, bryozoans, tunicates, barnacles, sea pens, algae, and sometimes other nudibranchs that they eat. These are the “teeth” or denticles of a coral-eating nudibranch. http://www.seaslugforum.net/find/corafeed

Another type of mollusc – a chiton- with a path that its radula made

A much wider eating path

Nudibranch life cycle

San Diego or Leopard dorid with egg ribbon Red sponge nudibranch pair with egg ribbon Have both male and female reproductive organs, generally not self-fertilizing Can store sperm and lay eggs at a later time Lifespan – some less than a month, others up to one year

http://myfwc.com/research/saltwater/fishstats/commercial-fisheries/nudibranchs-of-florida/

White-lined dirona larva after hatching Notice the shell Photos by Cameron Hirtle http://invert-embryo.blogspot.com/2010/06/veliger-stage-of-marine-gastropods.html Hirano, Y.J., 1999 (June 21) Flabellina amabilis Larval metamorphosis. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/flabama2 Charming aeolid larval metamorphosis - Settling on food - Casting off shell - Breakfast!

What do nudibranchs eat?

Hydroids Related to anemones; tentacles have stinging cells Individuals are connected to each other; food is shared throughout colony Embedded sea fir hydroid Pink-mouthed hydroid Hedgehog hydroid

Hydroid close-up

Bryozoans – “moss animals” More complex than hydroids and worms Tentacles have horseshoe-shaped cilia around mouth Encrusting bryozoans develop spicules in response to predation Spiral bryozoan Fluted bryozoan Kelp-encrusting bryozoan

Sponges, anemones and sea pens Sponges contain toxins for defense Anemones and sea pens contain stinging cells to immobilize their prey Red sponge Tube-dwelling anemone Orange sea pen

Red gilled nudibranch on California sea cucumber Cuthona sp. on California sea cucumber Nudibranchs are often found on sea cucumbers – perhaps they graze on particles that stick to the cucumber’s skin

Before eating After a meal of orange social tunicates Nudibranchs are what they eat

Nudibranch defense and coloration

Bright color denotes a toxic or unpleasant taste (aposematic) Cryptic colors blend in with the environment

Pink-mouthed hydroid and anemone Fernald’s aeolid on pink-mouthed hydroid

Fernald’s aeolid close-up

Hedgehog hydroid Pink cuthona in hedgehog hydroid

Pink cuthona in the open

Giant nudibranch Tube-dwelling anemone

Giant nudibranch

Red sponge Red sponge nudibranch

Red sponge nudibranch is easier to see when it’s not on a red sponge

What eats nudibranchs?

Decorator crab with nudibranch egg ribbon – caviar for crabs? Sea spiders Mosshead warbonnet has been seen bending a nudibranch in half to eat it* * http://slugsite.us/bow/nudiwkps/nudiwk24.html

Maybe this Blackeye Goby had indigestion later, but he sure didn’t hesitate to dine on this clown dorid* *Thanks to Gene Coronetz for this info and to Talon for the photo

Looks like something tried to take a bite out of this nudibranch Its cereta will grow back in just a few days

Finding nudibranchs and identifying them

Food Egg ribbons Best places to look for nudbranchs: on the foods they eat (hydroids, bryozoans, anemones, etc) near their egg ribbons

White dendronotus Bushy-backed dendronotus

Nudibranch identification can be challenging! Six different aeolid nudibranchs all with reddish cereta

Price’s aeolid – ridges on rhinophores and wide foot

Red gilled nudibranch – rhinophores are chalky, no ridges; long tail with white center line

Red flabellina –longer mouth than the red-gilled nudibranch; shorter tail

Three lined nudibranch – ridges on rhinophores like Price’s aeolid, but it has a line down center

San Juan aeolid –no white encrustation on rhinophores or oral tentacles

Pink cuthona –no white encrustation on rhinphores; cereta start in front of rhinophores

Opalescent nudibranch and White-and-orange-tipped nudibranch Easy to spot differences side-by-side

Which is which? White-and-orange-tipped nudibranch Opalescent nudibranch

White-lined dirona Golden dirona Easy to tell these two dirona apart…

White-lined dirona, gold variation Golden dirona …Not as easy with this color variation

Yellow Margin Dorid Hudson’s Dorid Look closely to tell these two dorids apart

Can you spot the differences? Noble sea lemon Monterey Dorid

Researchers at the California Academy of Sciences are studying the DNA of the Onchidoris family because coloration alone isn’t enough for positive ID

You could even discover new ones!

http://www.wildlifeextra.com/go/news/sea-slug.html#cr

Photograph courtesy Terry Gosliner, dean of science and research collections, California Academy of Sciences June 28, 2011 - New Nudibranch The Philippines expedition discovered at least 50 new species of nudibranch, including this one in the Armina genus. The area surrounding Luzon is renowned for its nudibranch diversity, with more than 800 species known. This makes the discovery of 50 new species even more remarkable, Burke said— especially because expedition leader Gosliner, a nudibranch expert, has been diving around Luzon since 1992. http://news.nationalgeographic.com/news/2011/06/pictures/110628-philippines-new-species-deep-sea-ocean-rare-animals-sharks-nudibranchs/#/philippines-new-species-rare-animals-armina-nudibranch_37078_600x450.jpg

Thank you! Questions?

References Marine Life of the Pacific Northwest – Andy Lamb and Bernard P. Hanby Biology of Opisthobranch Molluscs – T. E. Thompson Eastern Pacific Nudibranchs – David W. Behrens and Alicia Hermosillo Nudibranch Behavior – David W. Behrens Sea Slug Forum (http://www.seaslugforum.net/) Nudi Pixel (http://www.nudipixel.net/) The Slug Site (http://slugsite.tierranet.com/) Nudibranch food (http://www.theveliger.org/nudibranch_food.html) Bibliographia Nudibranchia (http://escholarship.org/uc/item/8115h0wz) Encyclopedia of Life – online (http://www.eol.org/) Nudibranchs of Florida (http://myfwc.com/research/saltwater/fishstats/commercial-fisheries/nudibranchs-of-florida/) Dive-OZ (http://www.diveoz.com.au/nudibranchs/nudibranch.asp?info=anatomy) A Snail’s Odyssey – a journey through the research done on west-coast marine invertebrates (http://www.asnailsodyssey.com/index.php)