Creature Feature: Juvenile Graeffe's Sea Cucumber

by Dave Burdick

The remarkable little critter pictured below is not what it appears to be…indeed, it “hopes” that potential predators are tricked into thinking it’s actually another creature they wouldn’t want to eat.  What Government of Guam Biologist, Dave Burdick, is holding in the palm of his hand is a juvenile Graeffe’s sea cucumber, Pearsonothuria graeffei.  This individual was found at a Rapid Ecological Assessment site off the coast of Rota, but this species is found throughout the Marianas, and is relatively common across much of the Indo-Pacific.  Juveniles such as this one are rarely seen, but adults are occasionally encountered on reefs across its range. 

A juvenile Graeffe's sea cucumber, Pearsonothuria graeffei, found at a Rapid Ecological Assessment (REA) site off the coast of Rota. Photo by Dave Burdick.

As with most other sea cucumbers, known as balate in Chamorro, this elongated echinoderm uses tube feet to slowly move across the reef in search of food (mostly decaying organic matter), which it picks up using an array of oral tentacles rimming its mouth.  This colorful youngster appears strikingly different from adults of this species – the yellow-spotted, black and white juveniles eventually trade their bright coloration for a more muted, brown and cream-mottled look (see photo below).  

An adult Graeffe's sea cucumber, with its less conspicuous coloration, crawling across a reef on Guam. Photo by Dave Burdick www.guamreeflife.com.

But why would a young sea creature be more colorful than the larger, less vulnerable adults?  Wouldn’t this attract attention to would-be predators?  The strategy employed by this sea cucumber is known as Batesian mimicry, a defense against predators that involves a harmless species mimicking a toxic species that is brightly colored to denote the foul-tasting, or potentially deadly chemical compounds it possesses.  In this case, the juvenile Graeffe’s sea cucumber is likely mimicking the toxic sea slug, Phyllida varicosa (see photo below).

A sea slug, Phyllidia varicosa, in the Batangas, The Philippines. This noxious nudibranch is presumed to be the species that juvenile Graeffe's sea cucumbers mimic to gain protection from predators. Photo by Dave Burdick.

Interestingly, adult Graeffe’s sea cucumbers actually do possess toxins that make them distasteful to potential predators, but the young individuals are not yet equipped with these chemical defenses and have to rely on mimicry to survive long enough to grow into their chemically-defended adult form. 

The development of this marvelous adaptation occurs through natural selection, an elegantly simple mechanism of evolution first described by Charles Darwin in 1859 (and nearly simultaneously by the lesser -known Alfred Wallace), all unbeknownst to these beautiful and fascinating sea cucumbers inhabiting the reefs of the Mariana Islands.  Who knew balate could be so cool?!

Leg II Photo Contest

Congratulations to the winners of the 2011 MARAMP Leg II photo contest! We mixed it up this leg and picked the best photos by category; Fish, Invertebrate, People/Action, and Landscape. Following are the winning photos for each category.

Best Fish Photo
The scorpionfish, Sebastapistes sp., observed at Asuncion.
Photo by Marie Ferguson

Best Invertebrate Photo
The persian carpet worm, Pseudobiceros bedfordi, observed at Asuncion.
Photo by Paula Ayotte

Best People/Action Photo
NOAA diver Edmund Coccagna enjoying another day at the office at Agrihan.
Photo by Kevin Lino

Best Landscape Photo
The NOAA Ship Hi'ialakai off the coast of Sarigan.
Photo by Noah Pomeroy

HONORABLE MENTION - FISH

Photo by Kaylyn McCoy

Photo by Chris Sullivan

Photo by Noah Pomeroy

Photo by Marie Ferguson

Photo by Jake Asher

Photo by Kevin Lino

Photo by Jill Zamzow

HONORABLE MENTION - INVERTEBRATE

Photo by Paula Ayotte

Photo by Marie Ferguson

Photo by Kaylyn McCoy

Photo by Kaylyn McCoy

HONORABLE MENTION - PEOPLE/ACTION

Photo by Kaylyn McCoy

Photo by Jake Asher

HONORABLE MENTION - LANDSCAPE

Photo by Jake Asher

Photo by Jake Asher

Photo by Noah Pomeroy

CNMI Residents Tour the Hi'ialakai

by Dave Burdick.
NOAA photos by Annette DesRochers

With the Hi'ialakai in port after a 17-day expedition to the Mariana islands north of Saipan, the Ship and her crew welcomed nearly 200 government officials, students, teachers, and other residents interested in the Hi'ialakai and her mission to the breathtaking string of volcanic islands that comprise the Commonwealth of the Northern Mariana Islands.  Guests were given a tour of the Hi'ialakai by the Ship's crew and were briefed by scientists from the NOAA Pacific Islands Fisheries Science Center Coral Reef Ecosystem Division on the coral reef assessment and monitoring activities carried out from the ship.  The warm, inviting sun over Saipan accompanied a parade of feet, both big and small, across the deck of the Hi'alakai.  The invigorating day was filled with questions posed by inquisitive guests, intriguing anecdotes from the expedition to the northern islands, and even some laughs as the Ship's visitors listened intently as the crew of the Hi'ialakai and NOAA scientists eagerly shared their experiences of life on the ship and on the reef.  Below are a few photos of the day's events...

Chief Scientist for the 2011 Marianas expedition, Jacob Asher, briefs a delegation of local CNMI officials on the goals of NOAA CRED's Reef Assessment and Monitoring Program and an overview of the methods they use to achieve them.

A group of young visitors are given a tour of the Hi'ialakai's impressive bridge by Operations Officer, Lieutenant Tony Perry.

NOAA CRED Benthic Biologist, Edmund Coccagna, points out the location of towed-diver surveys around Saipan to a group of guests, while holding the impressive tow board and mounted camera in-hand.

Junior Officer, Ensign Brian Elliot, introduces a group of students to the dive chamber aboard the Hi'ialakai, which can be pressurized to treat injured divers in the event of a dive emergency

The Ship's guests are both informed and entertained by an animated demonstration of an ecological acoustic recorder (aka EAR), by NOAA CRED Oceanographer, Frank Mancini.

A group of local CNMI students examine the Coral Reef Ecosystems of the Mariana Islands, a report released in 2010 that presents the findings of the first three years of data collected by the NOAA CRED team.

A delegation of CNMI officials join the Ship's captain, Commander John Caskey, and NOAA CRED scientists for a group photo in front of the Hi'ialakai

Creature Feature: The Mosaic Boxer Crab Lybia tesselata

by Kerry Grimshaw and Annette DesRochers

One of the participants on this cruise is Steve McKagan, a fisheries biologist and NOAA partner from the Pacific Islands Regional Office (PIRO) located in Saipan. While Steve's role on this mission is with the Fish REA team, he has also taken an interest in the ARMS project. He is working with local agencies in Saipan to start up a Biosecurity (i.e., marine invasive species) project and is considering using ARMS methods and materials to establish a baseline for the harbors of Saipan, Tinian, and Rota. As such, he spent a day at Maug with the ARMS team to learn how ARMS are deployed in the field and how they are processed, which was a win-win situation for both sides as he captured some excellent photographs while observing the activities.

Taking advantage of the opportunity, following are some of Steve's photos capturing a bit of the ARMS recovery process followed by Kerry's writeup on one of the creatures that he found most intriguing. As an honorary ARMS team member—Data Managers serve dual roles on RAMP missions by helping to process the ARMS once they have been recovered—I too am enamored with these critters.

ARMS team member Russell Reardon recovering an ARMS unit at Maug. NOAA photo by Steve McKagan.

Transiting a recovered ARMS unit on the small boat back to the ship to be processed. NOAA photo by Steve McKagan.

Russell Reardon, hard at work in the ARMS "office". NOAA photo by Steve McKagan.

ARMS team members Kerry Grimshaw and Russell Reardon begin processing an ARMS unit. NOAA photo by Steve McKagan.

As the ARMS are processed, crabs are separated out to be photo documented and for taxonomic identification. NOAA photo by Steve McKagan.

As Kerry explains, one of the characters we have seen often in the ARMS on this cruise has been the Mosaic Boxer Crab, Lybia tesselata.  While many of the crabs that are collected are unique and dare I say beautiful, this little guy highlighted below tends to stand out from the others.

Mosaic Boxer Crab, Lybia tesselata.  NOAA photo by Kerry Grimshaw.

These small crabs, commonly known as pom-pom crabs for the small anemones they hold in their pincers, have a mutualistic symbiotic relationship with anemones.  The boxer crab’s pincers are small and are so well adapted to holding their anemones that they are rendered nearly useless for defense, yet they are able to take advantage of the anemones to serve this purpose. The stinging anemones act as a deterrent to predators by giving an extra punch to the crab's defense tactics; it advertises its weapons by waving its pincers with the anemones in the direction of any potential predator as if it’s shadowboxing.

The Boxer Crab versus the fish. Source: YouTube.  

Possessing such a pair of specialized pincers can be beneficial and has proven useful as there are a number of different species of Lybia that carry anemones; however, there are disadvantages too. Having such small pincers with only a few grippers unfortunately means the crab's pincers aren’t strong enough to tear up food as other crabs do. To overcome this boxer crabs have adapted to using their second pair of legs for this purpose by tearing food into small pieces and then moving it towards its mouth.  Another way that boxer crabs have been observed to feed is by using the anemones as “mops” which are swiped along the substrate to collect food particles on the tentacles of the anemone which can then be removed by the crab’s mouthparts.

The Mosaic Boxer Crab in action. Source: YouTube.

The boxer crabs can put their anemones down, but doing this would make them very vulnerable to predation. However they must do such a risky thing when molting their exoskeleton.  The crabs will place each anemone in turn in a safe place and then as quickly as possible free itself of its old exoskeleton. Then it quickly grasps its anemones in its pincers before quickly retreating to a safe place where it can allow its new body to harden.

There's even a YouTube video showing a Boxer Crab molting. This one takes a little more patience, it's not quite 5 minutes long, though it's not really worthwhile to watch until about 3:30.

And yet another video showing the Boxer Crab that just molted recovering its pom poms!

The Makings of a Marine National Monument

by Jake Asher and Annette DesRochers

Farallon de Pajaros (FDP), also known as Uracas, was our northernmost stop of this cruise.  Once known by the pseudonym, “Lighthouse of the Western Pacific”, FDP’s last known eruption was back in 1967. Even after 44 years, the landscape above the shoreline remains largely barren.

The Hi’ialakai positioned in front of FDP to recover dive teams. 
NOAA photo by Edmund Coccagna.

In stark contrast, the Islands of Maug crater—there are three small islands all together with a submerged caldera in the center—are lush with vegetation compared to FDP. As a former Geographic Information Systems Specialist, Maug happens to be one of my favorite places in the Pacific to map because of its unique horseshoe-shaped topography with a subsurface pinnacle rising from the depths in the middle.

 Maug bathymetry (seafloor) map.
Source: Pacific Islands Benthic Habitat Mapping Center.

One of the small boats, HI-1, returning to the Ship with the islands of Maug in the background. NOAA photo by Annette DesRochers.

FDP, Maug, and Asuncion (highlighted earlier this week), make up the “Islands Unit” of the Marianas Trench Marine National Monument. The other two Units of the Monument are the Marianas Trench itself and the Volcanic Unit which includes the numerous submerged volcanoes and hydrothermal vents along the Mariana Arc (click here to see a map). Supply Reef, also one of the places surveyed during this mission, is one of the undersea volcanoes that are protected by the Monument designation under the Volcanic Unit.

Abundant marine life can be found throughout the Marianas Trench Marine National Monument. NOAA photo by Edmund Coccagna.

Declared in early 2009, the Monument seeks to protect the biologically diverse and abundant marine life found in the waters of these islands, seamounts, and hydrothermal vents.  These unique habitats are home to one of the most diverse collections of corals found in the Western Pacific, and also support some of the largest biomass of reef fishes found in the region.

Large schools of bigeye jack (Caranx sexfasciatus) present at both FDP and Maug, providing divers with an eyeful. NOAA photo by Jake Asher.

Maug, in addition to having a diverse and abundant benthic environment, is of particular scientific interest due to its underwater vents.  Hydrothermal vents within the caldera seep hot (60^oC), acidic water into the environment around it and provide a unique platform for researchers to study the effects of highly acidic water in a coral reef environment. This is of particular interest as the pH of the world's ocean water appears to be lowering due to the uptake of anthropogenic CO₂. This ‘acidification’ of the water is reducing the availability of bicarbonate in the oceans, which is the main building block for calcifying animals, such as corals, to grow and survive.

REA fish diver Marie Ferguson takes advantage of the warmth emitted by the hydrothermal vents at Maug. NOAA photo by Jill Zamzow.

In close proximity to the vents are some of the most impressive Porites rus stands that divers on this cruise have ever seen.   NOAA photo by Jeff Anderson.

Both the REA benthic and fish teams surveyed the areas near the vents, and the oceanography team used an auto-sampler to take water samples at a high frequency.  The hourly samples will be analyzed for dissolved inorganic carbon and total alkalinity and from these the aragonite saturation levels in the water can be determined.  The saturation level of aragonite determines the amount of the ion that is available for corals to use as building blocks for their structure.  Theoretically, the more acidic the water, the less aragonite ion is available in the water for corals to use for growth.  Salinity, temperature and current flow was also measured using additional instruments in the area.  These data will help us understand more about a natural coral reef environment under highly acidic conditions.

A remote access sampler (RAS) was deployed near a vent site inside the caldera at Maug for two days in order to collect hourly water samples over a 48 hour period. NOAA photo by Jake Asher.

Maug just might be considered the “crown jewel” of the Monument.  Listening to divers recount the highlights from their surveys at Maug certainly substantiates that notion. With astounding coral cover reaching up to 75% in some places, the benthos teems with life, keeping scientists on both the benthic REA and towed-diver teams occupied.

A diver photo-documenting the unique habitat and organisms found in the Monument. NOAA photo by Edmund Coccagna.

While the benthic environment at FDP is largely depauparate in places, likely the result of ‘recent’ geologic activity, it too has its gems. That being said, some of the most spectacular views during our short time at FDP happened to be topside.

Sunrise over Farallon de Pajaros. NOAA photo by Jake Asher.

Moonrise over Farallon de Pajaros. NOAA photo by Jake Asher.

A day of rest

by Jake Asher

Supply Reef, an active submarine volcano, was mostly a rest day for all teams, except for one.  The oceanography team set out at Supply Reef to recover a salinity and temperature recorder, along with an old wave and tide recorder anchor.  While shark sightings have been uncommon at all our other stops aside from the occasional whitetip reef shark (Triaenodon obesus) and small grey reef shark (Carcharhinus amblyrhynchos), Supply had a few greys that were larger than what we had seen to date.

A grey reef shark, Carcharhinus amblyrhynchos, at home amongst a school of Caesio teres. NOAA photo by Oliver Vetter.

Including some that were more “friendly” than others!

A grey reef shark, Carcharhinus amblyrhynchos, getting up close and personal!  NOAA photo by Oliver Vetter.

Needless to say, divers recovered their equipment, snapped photos, paid respects to the locals, and completed their operations safely.

A barred filefish (Cantherhines dumerilii). NOAA photo by Oliver Vetter.

Meanwhile, the rest of the scientific staff enjoyed a much needed day off after 10 straight days in a row of dive operations. Not to worry though, the oceanography team, while they were busy prepping for ops at Supply, still enjoyed a day off from dive operations on the previous day. The favorite activity aboard the ship on days off?  Trying to make up for all those lost zzz's.