#SEASLUGDAY2016: Nudibranchs eat ALL THE THINGS!

image by Alexander Semenov

Happy SEA SLUG DAY! This educational event began last year (2015) in honor of Dr. Terry Gosliner, nudibranch researcher extraordinaire at the California Academy of Sciences!!   He also happened to coin the name "Bobbit Worm" for the formidable predatory polychaete worm Eunice sp. So, you're welcome worm people! 

This year's Sea Slug Day I thought I would show off the VAST array of feeding diversity in sea slugs, mostly focusing on nudibranchs. (Not all sea slugs ARE nudibranchs).

There are some groups of sea slugs such as Elysia chlorotica, which belongs to the Sacoglossa (i.e., they aren't proper nudibranchs) which can actually PHOTOSYNTHESIZE like plants! 

But when it comes to "proper" nudibranchs, it turns out that they are mostly, if not entirely, carnivorous! That's right, instead of the image of "delightful little dainty, clowns of the sea" that most people seem to have of nudibranchs, perhaps we should instead think of them as hungry little monsters that chow down on all manner of other animals!  Muhahah!

Note: this image probably does not accurately represent the feeding biology of dorid nudibranchs

Food and feeding in nudibranchs appears to be diverse. But like most snails, nudibranchs feed using what's called a radula, which is a belt-like structure which is modified from taxon to taxon to rasp or else assist in food or prey capture.

Some microscope images of nudibranch radula are below (images by Jeff Goddard)

Nudibranch feeding (and prey) are a HUGE topic and I'm almost certainly NOT capturing the full range. But for your SEASLUGDAY pleasure, here's some great imagery and unusual accounts of what nudibranchs eat...which really does include EVERYTHING.

5. Echinoderms (such as brittle stars)
I begin with that most sinister of predatory nudibranch: the echinodermativore! To be sure, the number of sea slugs that are known to feed on echinoderms is a relatively short list-but probably one of the most gorgeous is this Indo-Pacific one: Kalinga ornata!

Here's a GREAT Japanese video of K. ornata below feeding on a brittle star (possibly Ophiocoma scolopendrina?)

4. SHRIMP! I wrote about Melibe on SeaslugDay last year. and I've already shown this video of Melibe viridis capturing this shrimp.. but its VERY impressive. So you get it again...

3. Bryozoans & various Cnidarians (hydroids, anemones, etc.)!  Among the most typical of foods fed upon by nudibranchs are the many, many types of encrusting and/or otherwise sessile animals that live on and around nudibranchs, ranging from small, colonial animals to huge tube-shaped sea anemones! 

Here's a nice pic, for example, of a dorid nudibranchOnchidoris muircata feeding on a bryozoan colony. Bryozoans aka "lace animals" are a phylum of colonial invertebrates that form very delicate skeletons. They are fairly common in many areas as encrusting, colonial forms.. MANY nudibranch species seem to feed on them...

Not sure which species this is..but you can see they've pretty efficiently cleared off the living tissue from the bryozoan skeleton

This species, Crimora coneja was imaged in Oregon feeding on the bryozoan colony here. You can see the stark white regions around the nudibranch where it has fed, versus the lighter, fuzzier areas around the edges.

Here's a GREAT video of Corambe steinbergae, from the west coast of North America showing this species moving across the bryzoan colony and feeding on the zooids. The nudibranch is even sort of camouflaged so that it appears hidden against the bryozoan colony.. 

Here's a lovely aeolid nudibranch of some kind feeding on a hydroid. One of the NEAT things about these is that many of these nudibranchs have whats called kelptocnidae which means that these slugs can actually STEAL the stinging cells from the hydroids and transfer them to their OWN body as defense!! You can read more about this here.

And there is much, much more... tunicates are also potential prey for nudibranchs!

As are sponges! In some cases, the nudibranchs can absorb the chemical defenses of the prey and utilize them for their own defense!

Nudibranch feeding on sponge from BIOPIXEL on Vimeo.

When we are looking at big solitary animals.. we enter the realm of animals such as the slug Tritonia and various sea anemones and sea pens... These are pretty significant predators and ellicit a fairly extreme response from they prey... The slugs in the next two videos are quite big 6 to 12 inches long.

AND as long as we are mentioning cnidarians as prey items, here's the pelagic (i.e. swimming) sea slug Glaucus atlanticus feeding on Porpita porpita (blue button jellies)

Here's a bunch of aeolids devouring a fallen Moon Jelly...

2. OTHER NUDIBRANCHS
Its always interesting how many people are fascinating not just by predation but "cannibalism" which when applied to the animal world seems to mean when one "type" of animal feeds on the same or similar "type" of animal. (i.e. sea stars that feed on sea stars) and not just one species feeding on itself (as it does in humans).

Its not as common but there are several noteworthy nudibranch predators that feed on OTHER nudibranchs...

The formidible Navanax from the North Pacific for example.. They seem to be quite effiicient at swallowing their prey whole! If these were the size of say, a dog or a wolf we would be VERY afraid of them!

 I've always loved the name of this nudibranch. It has a nice ring to it!

and this one, attacking and  COMPLETELY SWALLOWING the sea hare, Aplysia sp. 

In the tropical Indo-Pacific, there is another formidable predator, those slugs in the genus Gymnodoris, which as we'll see feed not only on other sea slugs but have progressed up to vertebrates as food!

Red Bumpy Gymnodoris eats another nudibranch from liquidguru on Vimeo.

1. SLUG EAT FISH! 
This really WAS the most amazing thing to discover. It turns out there's a dorid nudibranch called Gymnodoris nigricolor (name translates into the "black Gymnodoris) which attacks and EATS the FINS of certain FISH!

These slugs basically crawl onto a goby and begin to eat their way down a fin spine, gnawing off the meat on the fin. Some have called this behavior parasitc but I think of it as more predatory. I suppose its really kind of both.

My friends over at BlennyWatcher have a nice little account of this with links, etc. here. I've included a VIDEO of this behavior at the bottom!

New Species of Sea Stars from the North Pacific and BEYOND!

This week I announce a NEW paper in the latest issue of the journal ZOOTAXA describing a new genus and THREE new species of deep-sea starfishes! Vol. 4175 (2): 101-141 

You may recall back in 2009 when I accompanied the Monterey Bay Aquarium Research Institute (MBARI) on a 10 day cruise exploring the North Pacific on the Juan de Fuca and Gorda Mid Ocean Ridges off the Oregon coast. Here was the cruise website.  I blogged about it here.

When we returned from the expedition I was VERY excited because we had collected MANY specimens and several were either new records of rarely seen species or outright NEW species!

I would like to give a big shout out to MBARI because almost EVERY thing they send me turns out to be a NEW species!  Here's a new coral-devouring star I named after MBARI geologist Dave Clague  and here was a poraniid starfish that was observed climbing up a black coral (antipatharian) to devour it

One of my favorite undiscovered starfish was this one, Paulasterias macclaini which I had to describe a whole FAMILY and genus in order to accommodate it!  This species was named for Dr. Craig Macclain, at Deep-Sea News, who had invited me on the cruise.

I wrote about it here.  But he was VERY happy to write up something about it on Deep-Sea News! (here)  

Well, describing that 6 rayed star took quite a bit of effort but there were many, MANY more species to understand!!!

We also collected many of the more 'non-descript' stars that we encountered as well as several others which turned out to be UNDESCRIBED species!! 

And YES its literally taken me almost 6 YEARS to get all of this done. As I've discussed before (here), it can sometimes take quite awhile for a species to be formally described.

 One report made the case it takes an average of 21 YEARS for a specimen to go from collection to publication! (I've summarized it here)

The starfish I reported on in my Zootaxa paper are members of the Goniasteridae, the most diverse family of sea stars, which includes over 260 species in 65 genera!  Most goniasterids live in relatively deep-water (continental shelf and deeper) but historically, there haven't been many of them known from abyssal and lower bathyal (i.e., >1000 meter) depths.

Only recently have we been seeing better collections of these animals from these depths. As I've reported below, some were collected from below 4000 meters!

Sibogaster nieseni! 
The first few specimens of this species were collected by the Monterey Bay Aquarium Research Institute from Taney Seamount (off the coast of San Francisco) from abyssal depths (over 3000 meters!).

It is named for one of my former advisors from San Francisco State University: Professor Tom Niesen (now emeritus)! Author of the Marine Biology Coloring book and noted intertidal naturalist/ecologist along the California coast! 

He gave me my first shot at grad school and happily, his advice and instincts correctly guided me through my early years as a Masters degree student!

photo by J. Sharei

It seemed VERY appropriate to name this species, from off central California, after someone who has done so much to educate others about the significance of the invertebrates of the coast!! 

Interestingly, as I was in the process of writing it up, I suddenly became aware of multiple specimens of similar individuals from OTHER oceans in museums where I was NOT expecting to see them!

This one for example, turned out to be almost identical to the Pacific one I was working on but was from the tropical ATLANTIC! and even one from the deeps of Indonesia... 

Also, unusual is how, such a moderately big animal (about 4 to 5 inches in diameter) could have gone undescribed for so long?  But given how deep it was found (2100 to 4175 meters !) its been well "hidden"! 

This species is likely the deepest member of the Goniasteridae known.

and like several other abyssal species, such as the deep-sea sea cucumber Psychropotes, occurs widely, sometimes in multiple oceans

Ceramaster pointsurae! 

This was a tiny little species that I think we collected as part of something else.. perhaps sampling sediment or some other part of the physical environment.

BUT it turns out that it is likely a new and distinct species with some resemblance to the shallow-water species of Ceramaster (aka the cookie stars) in shallow waters..

This species was found during my 2009 trip on the President Jackson Seamont at about 1975 meters! 

This species is named for the Moss Landing Marine Laboratories retired vessel, the Point Sur which was finally retired in 2014. 

I spent many a day sorting deep-sea invertebrates on the deck of the Point Sur and I was saddened to hear about its retirement.

Bathyceramaster careyi! New genus and NEW species! 

Figuring this one out required a bit of detective work, as it turns out...

Several years ago when I was working as a technician for the California Academy of Sciences, I had the pleasure of studying a newly deposited collection of deep-sea starfishes from Oregon State University.

It turned out, that one of the species in the collection was a rarely known species called "Mediaster elegans" collected by oceanographer Drew Carey. To the best of the knowledge of the workers at the time, it was thought that this was a new occurrence, since the original specimens were only known from South America (collected in 1905). 

But as it turns out, after comparing Carey's specimens with the newly collected material by MBARI AND the original type series (i.e., the specimens on which the species was based) it turned out there were actually TWO species present, "Mediaster elegans" (original name) AND this one!  And the one seen by Carey in 1972 was actually undescribed! So, what I'd argue was actually "Mediaster elegans" turns has not actually been seen until now...

and not only that, it had to be placed into a new GENUS in order to be correctly described! 

Boom! NEW genus described! New SPECIES described!

This species was ultimately found to occur throughout the North Pacific between 1700 and 3363 meter depths! 

With this one, named for Dr. Andrew Carey, formerly of Oregon State University! 

The gut contents described by Carey's paper in 1972 suggests that this species feeds on deep-sea sponges.

The paper outlines several goniasterids from the North Pacific at depths below 1000 meters, including several which have not been seen since their description. 

Now that the new genus Bathyceramaster has been described, I can also follow up with a note I made on one of the recent Okeanos dives to Wake Island! 

This white goniasterid we saw at about 2000 m MIGHT be Bathyceramaster, but I'd need to more closely examine the surface to be sure. But if the closeups of the surface texture were correct.. I think maybe??

New discoveries that lead to new questions!! 

What are they eating down there? How do they get so big? Why do some of these species always seem to be alone when you see them? 

My thanks to the Monterey Bay Aquarium Research Institute, the California Academy of Sciences'  Department of Invertebrate Zoology and the Museum national d'Historie naturelle in Paris!