| Between life and death |
By: Prof. Fabio German Cupul Magaña - Official Member of the Mexican
Society for the Divulgation of Science and Technology SOMEDICYT
March 2006 |
Year after year, the highways that lead to the Punta de Mita area to the north of the Bay and towards Boca de Tomatlan to the south are interrupted by rivers that transport life. Those rivers transport hundreds and even thousands of crabs, all coming down from the wooded mountains that border the coastline, in search of the warm waters of the Pacific Ocean.
Throughout their frantic pilgrimage to the sea, many of those nomads die on the asphalt of the road, flattened under the wheels of passing vehicles. Nonetheless, this adversity does not slow down or intimidate this tenacious organism as it seeks the fulfillment of the biggest goal of its life: the perpetuation of its species.
In Spanish, the land crab is called and known in the region as "moyo". It is a species totally adapted to life in a terrestrial environment, feeding on plants or the remnants of some animal or other, and living in the burrows it digs in the ground.
And it is in the terrestrial environment that it achieves the procreation of its descendants. The male fertilizes the female and she develops a great mass of eggs that she carries and protects under her abdomen. She remains within the burrow for approximately two weeks in order to give the eggs time to mature.
Once this maturation period is finished, the female abandons her subterranean refuge and heads for the coast, in search of the sea that is impatiently waiting for the precious cargo of life.
 The arrival at the beach coincides with the time of the highest tides, thus enabling the females to deposit their eggs within the aquatic environment without having to cross large distances or be washed away by big waves.
The number of eggs a female can leave in the sea varies between 10,000 and 100,000. Despite those numbers, only one will survive to reach adulthood and emulate the heroic deed of its parents.
Unfortunately and although water is the basic element to achieve the reproductive cycle, many crabs often perish by drowning or being smashed against the rocks by the waves because they are not adapted to life in a marine environment.
After one month, larvae will form from the eggs that have been deposited in the sea. These will feed on minute marine plants and develop until they transform themselves into minuscule crabs (5 mm. or less than ¼ inch). They are now ready to leave the ocean waters and begin their colonization of the wooded mountainsides where they will feed and grow until they become adult specimens that will reinitiate the lifecycle.
In some parts of the coast of the Mexican state of Jalisco, this event of colonization from the ocean to the wooded mountains is something truly impressive as we can observe hordes of hundreds of thousands of little crabs advance towards the continent, overcoming all types of obstacles along the way, obstacles that make the difference between dying and living long enough to procreate and perpetuate the species within the natural world.
Prof. Fabio German Cupul Magaña
E-mail: fcupul@pv.udg.mx
The publication of this article is possible thanks to the authorization of Prof. Fabio German Cupul Magaña, author of the books "Tales of natural history in Vallarta - University of Guadalajara" (Relatos de la historia natural vallartense - Universidad de Guadalajara) and "Natural environment: Selection of essays of scientific disclosure - Coastal University Center of the University of Guadalajara". (Ambiente natural: Selección de ensayos de divulgación científica - Centro Universitario de La Costa Universidad de Guadalajara).
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