Creature feature: Opalescent Nudibranch

One of the more beautiful creatures we find in our tidepools is the Opalescent Nudibranch or Hermissenda Crassicornis.  This organism has several adaptations (some of which I mentioned in an earlier post on Mollusks) that make it particularly interesting.  Most impressive is the nudibranch's ability to 'steal' stinging cells from its prey and pass them untriggered to the tips of its cerrata (the orange tipped structures on its back).    

Click to enlarge

As they live less than a year, they must go through their life cycle quickly and seem to do so without respect for the seasons.  Being hermaphrodites, nudibranchs can self-fertilize or mate with any other nudibranch of the same species though they usually choose the latter option (presumably to ensure the diversity of their gene pool).  

Another species, the Barnacle-eating Nudibranch, seen out of water

When tide-pooling, we often find opalescent nudibranchs close to the water line tucked away in rock crevices or sticking to pieces of kelp.  Searching amongst hydroids, one of their main food sources, is another way to increase the chances of an encounter with this nudibranch.  If you do find a sea slug and it is out of water, it is nice to have a small specimen jar or large clam shell that you can fill so as to observe the nudibranch in all its glory.  Be careful though, nudibranchs are delicate animals and cannot withstand rough handling.

Sources:
Monterey bay aquarium
Puget Sound Sealife

The Pebble Mine

The Pebble Mine is a proposed project by a multi-national conglomerate that wants to mine gold and copper from the head of Bristol Bay, Alaska.  If built, the Pebble Mine would be the largest open pit mine in North America and would leave behind a mile-wide hole along with tons of toxic waste.  This is bad enough, but the placement of the mine is even worse.  They want to put this mine at the headwaters of the two richest Sockeye Salmon runs in the world.

The mine will be exhausted in fifty years leaving behind toxic waste that, if not contained properly, could easily destroy not only the salmon runs but many other species (such as Beluga whales) that live in the nearby Cook Inlet.  To compound the ridiculousness of this proposed mine, the mine site is not only in the midst of an extraordinarily rich ecosystem, it is also in an extremely seismically active region (the Pacific Rim of Fire) so any containment of the planned toxic wastes would almost certainly be temporary in nature.

If you enjoy eating good wild salmon or just care about the often unnecessary destruction of our natural world please go to this website, learn more about the Pebble Mine and write a letter condemning the mine.

The brown bears of Hallo bay in Katmai national park

"OK, we're going to just follow this sow and cub for a while and see if they start nursing."

And so the ten of us began following the two brown bears through the tall grass trying to get a better view and hoping to see a cub nursing from it's mother.  It went against nearly everything I'd learned about bears.  But this is what we'd come to do in Hallo bay of Katmai national park: to see bears.  We were extremely close, so close that my camera's paltry 5x zoom was more than enough to grab some good shots.  At one point during our pursuit we lost sight of the cub only to have it raise up behind a stream bank not 15 feet away from us.  You can't appreciate the size of these animals until they get up close.  Our guides estimated the cub at 250-300lbs, substantially larger than anyone in our group.  A female brown bear might get up to 900 lbs and an adult male to 1200lbs or more.  

Because the bears at Katmai have such an abundance of food and had not been hunted or fed or had any poor interactions with people they ignored us completely.  Occasionally a small cub would look up at us but none of the older bears paid us any heed.  To keep safe we were told to always stay within arms reach of someone else and not to make any sudden or loud movements.  We were told that as long as we walked around calmly in a group we would experience no problems with the bears.  

When we'd spent enough time with one group of bears there were always more around that we could walk over to and observe.  The bears are particularly fond of Hallo bay because it provides areas to fish, clam and forage and we witnessed bears getting food by all of these methods.  Despite the good fishing and clamming in the area, a large portion of a bear's diet comes from vegetation.  It was strange watching such a large predator munching away contededly on the grasses in the area.

I was fortunate enough to go on this amazing trip thanks to my parents who came up from Washington D.C. to visit this week.  All it all it was an awe inspiring experience and I would highly recommend it and Kbay air (the company we went with) to anyone looking to do some bear viewing.  I'll just let a few of my pictures do the rest of the talking. 

Oh, and the views from the plane were spectacular too:

Eagles!

One of the cool things about Homer (and Alaska in general) is the number of Bald Eagles living here.  They are everywhere.  The first time I came to Homer in 2008 there was a woman dubbed "the eagle lady" who fed the eagles near the harbor.  As a result you would see them by the dozen sitting on pilings, along rock walls and on the tops of shops and homes.  She died later that year and there was legitimate concern as to what the eagles would do when deprived of one of their major food sources.  People with small dogs had to be particularly careful as eagles have been known to target them.  In the end they decided to continue feeding the Eagles through the winter and then slowly wean them off the unnatural food source.

Now, a few years removed from "the eagle lady", the eagles are still plentiful but are not as concentrated around the harbor.  Our country has perpetrated a few myths about eagles, portraying them as hunters descending on their prey with a mighty screech. While eagles do hunt for their food, consuming fish, birds or small mammals, they are also scavengers.  The best place in Homer to get photos of Bald Eagles is at the dump.  Eagles, along with the Glaucous winged gulls, are drawn to trash, dead animals and other easy meals.

As for the "mighty screech" that you often hear on TV, whoever first put eagles on film decided that the eagle's actual call was too wimpy to be associated with America's mascot.  Instead they dubbed in the voice of the Red Tailed Hawk which provides that classic screech. Here is a video of a Red Tailed Hawk's call, and here is a Bald Eagle's call.  The eagle's call is quite beautiful but it is not what you would expect from such a large, powerful bird.

Interestingly, the juvenile eagles often appear larger than the adults.  This is due to the juvenile's feathers which are longer and heavier than those on an adult eagle.  The juvenile feathers serve as "training wheels" while young eagles are learning to fly.  The adult's smaller feathers allow them to fly more gracefully and with greater maneuverability than the younger eagles.

Juvenile Eagle between two adults

Despite the cynical attitude I've treated eagles with in this post, I still stop an admire them when they soar past.  They add to the majesty of this place and it is a privilege to be able to see them with such frequency.

Layers of complexity

This photo was taken near Kasitsna bay, where we occasionally run programs.  At first glance the subject of the photo appears to be a striped hermit crab.  The picture itself isn't bad, the colors turned out well and the lighting is nice, but if you look again at the hermit crab you might start to notice some things.

Click for full size

  First of all, the shell that the hermit crab is using is red.  This is because the hermit crab is living inside a wandering sponge.  There are some species of sea sponge that will attach themselves to snail shells and slowly consume the shell until nothing is left but the sponge. Once the snail is dead it is not uncommon for a hermit crab to move in and allow the sponge to continue its wanderings.  

Not many things eat sponges; they are full of sharp spicules that can wreak havoc on a creature's digestive tract.  In an earlier post I covered mollusks and talked a little bit about Nudibranchs, which often eat organisms that nothing else will.  The yellow blob you see sitting on top of the hermit crab is actually a False Lemon Peel Nudibranch that specializes in eating sponges.  

To recap, a wandering sponge began growing on a snail shell which was then inhabited by a hermit crab.  The sponge attracted a nudibranch which is now eating the hermit crab's home.  If you've been following this blog you should be able to name two of the three phylums represented in this photo.  Athropods are represented by the crab, Mollusca by the Nudibranch and Porifera by the sponge.

Even after three seasons of doing this, I'm still consistently amazed by the things that show up on our beaches.

Fab four Phyla part four: Arthropoda

Arhtropoda is the largest and most diverse phlyum on Earth.  The pre-fix Athro refers to joints (as in arthritis) and pod means foot, so the name arthropod refers to animals with jointed feet or legs. The phylum arthropoda encompasses organisms such as insects, spiders and crustaceans.  Besides having jointed legs, athropods also have segmented bodies and a tough chitinous exoskeleton that they occasionally molt.  On our beaches we see mostly crustaceans; i.e. crab, shrimp and barnacles.

Black Clawed Cancer Crab
Its large claws are used to crush barnacles

Most people don't realize that barnacles are so closely related to crabs and shrimp.  Barnacles begin their life as a plankton and as they grow larger they change through various stages until they become a cyprid.  The cyprid's task is to find a good spot to settle on the sea floor and become a barnacle.  They land head first and begin to create a hard, 6 plated calcium shell around themselves.  To feed, they kick out their feet, which are shaped like tiny fans, and collect their food from the water.  We just recently had a barnacle fall out in our area and now everything is coated in the brittle white shells of young barnacles.  You feel bad crushing so many animals underfoot but our beaches are just so packed with life that it is impossible to do otherwise while tidepooling.

Empty molt of a helmet crab

There are several species of crabs on our beaches, though none of them are popular commercially.  Decorator crabs are my personal favorite.  Decorator crabs do not have large claws to protect themselves with, instead they rely on camouflage.  Using their narrow claws, they hang algae and other things from the tiny hooks on the carapace until the blend seamlessly into their environment.  It is nearly impossible to see a decorator crab unless it is moving.  Taking one out of water, they become spider-like, with long narrow legs and a proportionately small body.

A friend holding a decorator crab

Hermit crabs are another popular arthropod found on our beaches.  We have a few different varieties ranging in color from a drab brown to a brilliant orange.  Hermit crabs appropriate the empty shells of other organisms (usually snails) to give themselves additional protection.  Their body curls to fit into the shells and they have legs specifically adapted to hanging onto the shell.  One of their claws is generally over sized and acts as a shield to cover the entrance to their home.  We keep several large hermit crabs in our touch tanks at the field station and you can often watch them squabbling over new shells.

Helmet crabs mating

  At one point there were several species of crabs in Kachemak bay that were commercially important to Homer.  Tanner crabs, Dungeness crabs and King crabs could all be caught in the bay during the late 70's.  No one is exactly sure why the fisheries collapsed; whether it was due to mismanagement, a fuel spill, or just part of a natural cycle, these species no longer exist in Kachemak bay in harvestable numbers.  The Tanner crab and Dungeness crab populations are slowly recovering and hopefully they will continue to do so.

An Orange Hermit crab from our touch tanks

Gull Island

Just a short boat ride from the Homer Spit is Gull Island, a rookery for sea birds.  Gull island is home to more than 15,000 birds during the summer months when they come to nest.  There are eight different species that nest on gull island, including puffins, cormorants and murres.  

There are two species of gulls here.  The larger of the two is the Glaucous winged gull and the smaller is the Black Legged Kittiwake whose wingtips are black in addition to their legs.  Though these birds will scatter before an eagle, using their maneuverability they will often harass the predator from above to distract it from its intended prey.

When stirred up by an eagle or raven trying to hunt or steal eggs they will take off, en masse, swirling around in enormous flocks as the air fills with the sound of their keening.  When they squabble amongst themselves on the rocks, bickering over nest space, it sounds eerily like children screaming.

Islands like this form important habitats for nesting sea birds.  They need safe places to raise their young away from terrestrial predators.  Here they only have to contend with Eagles.  On the mainland they would need to worry about bears, coyotes and other smaller mammals like marmots.

The gulls and cormorants prefer to nest on the rock faces.  They glue bits of grass to the rock with their own feces which gives gull island a rather pungent smell.  Other species nest on different parts of the rock.  Common murres prefer to nest on top of the island, and puffins burrow tunnels into the narrow band of dirt between the grass and the hard rock of the cliff face.

Red face cormorants are in the center with
 murres to the right and  gulls to the left.

Though the gulls put on a spectacular show, most people are interested in the Red Faced Cormorants.  These are a fairly rare bird and are difficult to find in the wild.  Homer is the most accessible place in the world to see these birds whose habitat ranges down the Aleutian change and into parts of Japan.  We get birders from all over the world coming to see the cormorants so they can add something new to their bird lists.

 The two species of gulls are strong fliers and will get food by scavenging and diving to grab small fish off the surface. Other spercies, such as the puffin and the common murre, are excellent divers.  The murre can reach depths of over 600 feet.  Though they are poor and awkward flyers, they maneuver extraordinarily well underwater.  Before they nest, they form giant rafts in the water that can number in the thousands.  As a boat approaches, the murres at the outer edge will begin diving to get away; this begins a domino effect and creates a rippling wave of birds disappearing into the water.

Instead of flying to escape, these murres are diving into the water.