New study confirms crustacean sentience

From ANIMAL PEOPLE,  March 2013:

BELFAST––Challenging the global scientific,  regulatory,  and humane communities to recognize crustacean sentience,  Robert Elwood of the School of Biological Sciences at Queen’s University in Belfast,  Northern Ireland,  on January 16,  2013 published his third major study in six years to demonstrate that crustaceans feel and respond to pain. “Billions of crustaceans are caught or reared in aquaculture for the food industry,”  wrote Elwood of his latest research,  published in the Journal of Experimental Biology.  “In contrast to mammals,  crustaceans are given little or no protection,  as the presumption is that they cannot experience pain.  Our research suggests otherwise.  More consideration of the treatment of these animals is needed,”  Elwood emphasized,  “as a potentially very large problem is being ignored.”

Elwood and Queen’s School of Bio- logical Sciences student Barry Magee in Elwood’s most recent investigation of crustacean sentience studied the responses of common shore crabs to mild electrical shocks.  The experiment partially paralleled previous studies in which Elwood showed pain response in prawns and hermit crabs,  but had a more complex goal.

“The experiment was carefully designed,”  said Elwood,  “to distinguish between pain and a reflex phenomenon known as nociception.  The function of pain is to aid future avoidance of the pain source,  whereas nociception enables a reflex response that provides immediate protection but no awareness or changes to long-term behavior.  While nociception is generally accepted to exist in virtually all animals,”  Elwood explained,  “the same is not true of pain.  In particular,  whether crustaceans experience pain remains widely debated.”

Summarized Elwood of his experimental protocol,  “Crabs value dark hideaways beneath rocks where they can shelter from predators.  Exploiting this preference,  our study tested whether the crabs experienced pain by seeing if they could learn to give up a valued dark hiding place in order to avoid a mild electric shock.

“Ninety crabs were each introduced individually to a tank with two dark shelters.  On selecting their shelter of choice,  some of the crabs were exposed to an electric shock.  After some rest time,  each crab was returned to the tank.  Most stuck with what they knew best,  returning to the shelter they had chosen first time around, where those that had been shocked on first choice again experienced a shock.  When introduced to the tank for the third time, however,  the vast majority of shocked crabs now went to the alternative safe shelter.  Those not shocked continued to use their preferred shelter.

“Having experienced two rounds of shocks,”  Elwood continued,  “the crabs learned to avoid the shelter where they received the shock.  They were willing to give up their hideaway to avoid the source of their probable pain.”

The shore crab experiment built upon findings that Elwood and colleague Mirjam Appel reported in March 2009. Elwood and Appel had collected hermit crabs from rock pools in Northern Ireland,  to which the crabs were later returned.  Hermit crabs,  rather than forming shells,  occupy shells discarded by other animals.  Usually these shells are much larger than the hermit crabs’ own bodies.  Once a hermit crab moves into a shell,  the crab typically responds to a threat by retreating farther into the shell.

Elwood and Appel offered the hermit crabs alternative shells to move into,  but shells less attractive to them than the shells they already had.  Elwood and Appel then gave some of the crabs small electric shocks while they were inside their old shells.  The crabs soon changed shells.  Crabs who were not shocked did not change shells.

Published in the journals Animal Behavior and Applied Animal Behavior Science,  the hermit crab study followed by two years a study Elwood published in New Scientist in November 2007,  concerning the behavior of 144 prawns after he daubed one of their antennae with diluted acetic acid.

The prawns immediately groomed and rubbed the daubed antennae,  but not their other antennae.  This,  Elwood wrote,  was “consistent with an interpretation of pain experience.”

“Even a single-cell organism can detect a threatening chemical gradient and retreat from it,”  responded University of Utah pain researcher Richard Chapman.  Elwood designed the hermit crab study to respond to such criticisms of the prawn study,  and then designed the shore crab study to reinforce the findings from the hermit crab study.

In Elwood’s Applied Animal Behavior Science paper about the hermit crab experiment,  he and co-authors Stuart Barr and Lynsey Patterson noted  that crustaceans placed under stress release adrenal-like hormones,  consistent with feeling pain.  Also,  if crabs are given anesthetics or  analgesics,  they show fewer responses to negative stimuli. Feelings of pain and stress in mammals are associated with the neocortex.   Because crustaceans lack a neocortex,   prevailing belief has been that they lack the physiological structure necessary to suffer. Wrote  Elwood,  “Using the same analogy, one could argue crabs do not have vision because they lack the visual centres of humans.”  In actuality,  trilobites,  who are ancestral to modern crustaceans and insects,  were among the first species known to have evolved vision.

Humane attention to crustaceans has been longstanding but sporadic.

Delegates to a 25-nation confer-ence hosted in 1952 by the Dutch-based World Federation for the Protection of Animals approved a resolution seeking the abolition of boiling live crustaceans.  PETA has staged heavily publicized lobster releases almost annually for more than 30 years.  In 2006 two members of Animal Rights Croatia locked themselves into a fish tank to dramatize the fate of lobsters.

The Scottish organization Advoc-ates for Animals in 2005 published a volume entitled Cephalopods & Decapod Crustaceans:  Their Capacity To Experience Pain & Suffering,  summarizing scientific knowledge to that point.  But also in 2005 the Prince Rupert SPCA boiled crabs at a fundraising event.  The parent charity,  the British Columbia SPCA, cancelled a planned sequel in 2006 after Sea Shepherd Conservation Society founder Paul Watson led a campaign against it.

––Merritt Clifton