Costa Rica Rocks!

Researchers collected more than 50 rare white, furry-clawed "yeti" crabs during a recent expedition off Costa Rica.

Abominable snowman crabs, people-sized worms, giant microbes, encountered on deep sea voyage

An interdisciplinary team of scientists that returned March 8 from aresearch cruise off Costa Rica say their 16-day expedition hasyielded a wealth of tantalizing new scientific data, including ahigh probability that some of the species they encountered havenever before been studied.

The CRROCKS! (Costa Rica Rocks) research cruise, led by scientistsat Scripps Institution of Oceanography at UC San Diego, theCalifornia Institute of Technology (Caltech), and Indiana StateUniversity, was one of the first scientific expeditionsconcentrating on the biological aspects of rocks found at thecontinental margin area near Costa Rica.

During 13 dives using the deep submergence vehicle Alvin, theresearchers conducted up-close investigations of seeps, areas wheremethane gas and sulfide rise from the earth’s crust intoocean-bottom sediments and rocks. During the night they studied low-oxygen zones, extracted sediment cores for examination, and mappedseafloor topography. During the day, they studied carbonate rocksmade by microbes from methane, and probed various habitats,including mussel and clam beds, massive mats of bacteria, as well ascorals and dead wood habitats, at water levels spanning 400 to 1,800meters (1,312 to 5,905 feet) deep.

"The Costa Rican margin has not been extensively studied from thisperspective," said Lisa Levin, a Scripps professor of biologicaloceanography and leader of the National Science Foundation-fundedexpedition. "The focus on rocks and the interfacing of methane seepswith the oxygen-minimum zone has yielded animal assemblages notstudied before, with a high probability of many new species thathave novel food sources."

There were thickets of tubeworms, some extending up to two meters(6.5 feet) in length. The tubeworms burrow into and protrude out ofrocks, and live in association with crabs, limpets, and snails.One of the most enticing findings was the so-called "yeti" crabs,animals with thick white coats of bacteria along their front claws.The researchers were mesmerized by images of the rare animals, partof a crab family only first described in 2005, as they waved theirfurry claws hypnotically in the seawater. As with many of thespecies encountered during the expedition, the yeti’s claw bacterialive in a symbiotic relationship with the host crabs.

"The working hypothesis is that the yeti crabs wave their arms toget chemicals to their symbionts, which they then use as a source offood," said Scripps graduate student Andrew Thurber, one of theresearchers on the cruise.

Prior to the expedition only three yeti crab specimens had ever beencollected. The Costa Rican cruise yielded a yeti crab bonanza, withmore than 50 specimens collected.

The scientists also collected starfish, limpets, sea anemones,brittle stars, and scallops, and they encountered deep-sea bacteriathat measured more than one millimeter, a gigantic size formicrobes.

Hundreds of invertebrate specimens were collected, with the majoritydestined to become part of the Scripps Benthic InvertebrateCollection, said Greg Rouse, curator of the collection and one ofthe CRROCKS expedition leaders. Other specimens were taken by CostaRican collaborators on the voyage to become part of the Universidadde Costa Rica collections.

"We already know that more than a dozen new species were found(possibly worms, clams, mussels, and other invertebrates) andupcoming DNA sequencing may reveal even more," said Rouse.

To properly capture and study such a diversity of creatures, Thurberand Levin worked with Ken Duff and David Malmberg of the ScrippsMarine Science Development Center to develop unique specimen housingcontainers. The specially designed aquarium collection bins(nicknamed CRROCKS boxes) allowed the researchers to insulate andisolate the specimens and rocks, partition animal extractions intoseparate compartments, and return them to the ship at naturally coldtemperatures. Transparent compartment walls allowed them to beviewed intact inside the ship’s cold room. The boxes offer a leapforward from previous designs that lumped specimensindistinguishably together and heated them as they traveled throughthe warm ocean surface waters, potentially damaging their tissuesand DNA.

In addition to Levin and Rouse, other researchers leading theexpedition included Victoria Orphan of Caltech and Tony Rathburn ofIndiana State University. Other Scripps participants includedpostdoctoral researchers Paola Lopez and Hank Carson, staff researchassociate Jennifer Gonzalez, and graduate students Christina Tannerand Danwei Huang.

—Mario C. Aguilera

April 2009