Scientists discover key to Christmas Island's red crab migration

Aug 27, 2010
Scientists discover key to Christmas Island's red crab migration
Christmas Island red crab. Image by Mrinalini at Bangor University

One of the most spectacular migrations on Earth is that of the Christmas Island red crab (Gecarcoidea natalis).  Acknowledged as one of the wonders of the natural world, every year millions of the crabs simultaneously embark on a five-kilometre breeding migration. Now, scientists have discovered the key to their remarkable athletic feat.

A three-year project conducted by a team led by the late Professor Steve Morris from the University of Bristol’s School of Biological Sciences in collaboration with Professor Simon Webster from Bangor University, has discovered that play a significant role in enabling the crabs to make their journey.

Lucy Turner, a researcher at the University of Bristol, said: “During the wet season on the island, in November or December, and prompted by the arrival of the , millions of the crabs undertake an arduous breeding migration from their home on the high rainforest plateau to the ocean to reproduce. This is a journey of several kilometres - a long way when you are a relatively small land crab (less than 20cm long).

“Scientists have long been puzzled by what mechanisms enable the necessary changes to take place in the crabs’ physiology to allow this journey to take place, and how they make such a dramatic switch from hypoactivity to hyperactivity.”

The results of this project have proven that it is a Crustacean Hyperglycaemic Hormone (CHH) that enables the crabs to make the most efficient use of their stored energy in the muscles (glycogen) and its conversion to glucose to fuel the migration.

This is a Christmas Island red crab. Credit: Mrinalini

Professor Webster, an endocrinologist at Bangor University, added: "Their migration is extremely energetically demanding, since the crabs must walk several kilometres over a few days. During the non-migratory period, the crabs are relatively inactive and stay in their burrows on the floor of the , only emerging for a brief period at dawn, to feed. The reflects a fundamental change in the metabolic status of the animal.

"Surprisingly, we found that hyperglycaemic hormone levels were lower in actively migrating crabs than those that were inactive during the dry season. However, studying the crabs running and walking after giving them glucose resolved the puzzle. During the dry season, forced activity resulted in a tremendous release of hormone, within two minutes, irrespective of whether glucose had been administered. However, in the wet season, the glucose completely prevented the release of the exercise-dependent hormone, showing that they were controlled by a negative feedback loop.

“Glucose levels were clearly regulating hormone release at this time. This made sense since it ensures that during migration, glucose is only released from glycogen stores when levels are low, using the ’ precious reserves of , to ensure that they can complete the migration.”

The research, funded by a Natural Environment Research Council (NERC) grant, is published in the September issue of The Journal of Experimental Biology.

Explore further: Skin coloring of rhesus macaque monkeys linked to breeding success, new study shows

More information: The paper, entitled ‘The adaptive significance of crustacean hyperglycaemic hormone (CHH) in daily and seasonal migratory activities of the Christmas Island red crab Gecarcoidea natalis’, is dedicated to the memory of Professor Morris who died on 11 August 2009 before this work was completed.

add to favorites email to friend print save as pdf

Related Stories

Red crabs lead the way in endurance running

May 06, 2010

(PhysOrg.com) -- Not even professional athletes would consider running a marathon without any training, but this is essentially what Christmas Island red crabs do every year, according to new research from ...

Red knot birds threatened by crab decline

Feb 21, 2006

Virginia Tech and New Jersey scientists say a reduction in the number of red knot shorebirds is linked with a decline in Delaware Bay's horseshoe crabs.

New 150 million-year-old crab species discovered

Oct 17, 2007

Researchers from Kent State University and the University of Bucharest, Romania, have discovered a new primitive crab species Cycloprosopon dobrogea in eastern Romania. Previously unexamined, these ancient crabs from the ...

Regulators allow horseshoe crab harvest

Feb 12, 2008

The New Jersey Marine Fisheries Council has declined to extend a moratorium on horseshoe crab harvesting aimed at protecting migrating shore birds.

Recommended for you

New hope for beloved family pets

13 hours ago

Nearly one out of four dogs will develop cancer in their lifetime and 20 per cent of those will be lymphoma cases.

User comments : 0