Art and Science of Nature

Understanding the Beauty of the Natural World

Archive for June, 2010

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My recent trek through Jamaica reminded me of how animals can ably and amazingly adapt to their surroundings. Most noticeably (or maybe not so noticeable) is how an animal’s shape, form, color and pattern can completely camouflage a species into its surroundings.

Rio Grande River and the Blue Mountains of eastern Jamaica. Photo: Alan Gettleman.

As the dominant species on Earth, we {Homo sapiens} have evolved from a lineage of hominids to become anything but stealthy in our world. And, it’s not surprising.

Without any predators to speak of in our daily lives (unless a bill collector or exigent-ex is stalking you) we just envelop ourselves behind the trappings of the human world… “Quick, here they come! Hide in my BMW with the dark tinted windows!”

Animals do not always have the luxury to build a fortress to hide behind. High school science introduces us to a concept called ‘Survival of the Fittest’. Being invisible to predators is one of the best ways for a species to survive. Many examples can be found right in our own backyards. Insects, birds and butterflies are just a few classes of animals that have become seemingly one with their surroundings.

Ever wonder why Praying Mantises look like a stick with wings that mimic lanceolate green leaves? Camouflage (and in the case of mantises, more for being stealthy when preying on other insects)! Is it not just a coincidence that the colors and patterns of many animals subtlety if not completely blend into their host surroundings? And what about the peripatetic Chameleon from Madagascar that changes its appearance to suit its changing background. These animals have given themselves a better-than-average chance to survive as a species when their predators have to work harder to find them.

So what kinds of natural CAMO (my acronym for Camouflaged Animals Meandering Outdoors) did I encounter in Jamaica? Some of the animal camo I observed is almost stupefying!

Alcadia hirsuta, a 20mm Jamaican terrestrial mollusk has developed a series of hair-like structures that effectively camouflage its shell against one of its preferred host leaves. Photo: Richard L. Goldberg ©2010.

Take for instance the suitably named Alcadia hirsuta (C.B.Adams, 1856) with the species name derived from the word “hirsute” meaning covered with hair. This small arboreal species of terrestrial snail has evolved a mane of long wispy hairs spaced at close, even intervals in rows around its shell. The hairs effectively blend the shell into the hairs found on one of its preferred host leaves of a “fern-wood” (a Jamaican English word meaning “unidentified tree”).

A few weeks ago I came across this hairy snail species crawling on the forest floor at about 400 meters above sea level in the John Crow Mountains of eastern Jamaica. The dead “hairy” leaves were the pervasive ground cover of this wet forested hillside. Every time I found this snail crawling on the ground in the underbrush, it was on this type of leaf. Coincidence? I’d go out on a limb and say there’s no coincidence at all!

The shell of Pleuodonte (Dentellaria) picturata is adorned with a creamy-white cuticle of radiating streaks that darken and lighten to match the tree bark during wet and dry periods. Photo: Richard L. Goldberg © 2010.

And then there is the Jamaican snail whose shell is covered with bands of radiating cuticle that blend into the coloring of the tree bark on which it prefers to aestivate. The creamy-white cuticle of Pleurodonte (Dentellaria) picturata (C.B.Adams, 1849) mimics the striations of the dry tree bark. When wet the cuticle darkens to the same dark brown tone of the wet tree, masking the shell in the wet shadowed forest.

The 25mm (1 inch) shell of a Pleurodonte (Dentellaria) picturata as it looks when dry (top) and after becoming wet and darkened (bottom). Photo: Richard L. Goldberg.

This species inhabits the limestone forests of western Jamaica along with a few other closely related snails that have developed the same propensity for adorning its shell with a radiating pattern of cuticle.

Pleurodonte (Dentellaria) catadupae H.B.Baker, 1935 is an extreme example of a Jamaican terrestrial mollusk whose shell is naturally embellished with a zigzag cuticle.

Yet, this unusual adaptation is not unique to terrestrial mollusks of the Western Hemisphere.

Calocochlia cuticle

Cuticle of Calocochlia - Cal. depressa globosa (Moellendorff, 1898) (top) and Cal. festiva (Donovan, 1825) (bottom) are two Philippines Helicostylids whose shells are covered with intricate cuticle patterns providing effective camouflage against the tree bark on which it lives. Photo: Richard L. Goldberg © 2010.

Almost all of the 100 or so species of Helicostylids (heliko-stylids), a group of tree-dwelling mollusks from the Philippines Archipelago have also developed an epidermis or cuticle in a myriad of patterns unique to each species that help camouflage the shell during wet and dry seasons.

Terrestrial mollusks are not alone in using trees as a background for camouflage. In a dry scrub forest of Westmoreland Parish I observed a fist-sized Sphinx moth that was seemingly one with the trunk of a rather large and exposed tree. It took a few glances to realize that there was a moth anchored to the tree. So well does this moth camouflage itself against this tree that from more than a few feet away the moth was virtually undetectable.

A fist-size Sphinx moth is virtually undetectable against a hardwood tree in Westmoreland Parish, Jamaica. Photo: Richard L. Goldberg © 2010.

There are tens-of-thousands of other examples in our world where animals have been able to blend into the background of their environments for protection and stealthiness. Yet, take away stands of trees and destroy habitats and these stealthy animals become sitting ducks. Some animals will continue to survive and adapt as long as the dominant species {us} realize that saving the environment has a greater significance than for just human survival. I will now step down off my soapbox.