Geoscience Reference
In-Depth Information
they hatch. Others lay their eggs in water-filled holes in trees or bromeliads. Several
genera brood their eggs on the female's back.
Glass frogs occur in tropical forests from Mexico to Bolivia. Their abdominal
skin is scarcely pigmented, making their intestines visible. They tend to be small
and spend their lives in the forest trees.
Another family of frogs with a Neotropical distribution is that of the poison dart
frogs. One group is dull-colored, nontoxic, and lives alongside rivers and steams.
The second group consists of the poison frogs. These usually small to tiny colorful
frogs tend to be diurnal. They come in bright blue, red, yellow, black, green and
black, and other color combinations (see Plate IX). Best known are the poison dart
frogs, whose skin excretes an alkaloid poison that affects the nervous system of
those who touch it. This acts as a defense mechanism against would-be predators.
Indigenous tribes of the Choco in Colombia rub the poison on the tips of their
blowgun darts when preparing to hunt. The toxicity of poison dart frogs varies
from species to species. Their bright colors serve as warning to any would be preda-
tors. These frogs will often lay their eggs in humid places high in the canopy, where
they are typically guarded by the male or female. When the tadpoles are formed,
they crawl onto their guardian's back and are carried to water.
The microhylid frogs occur throughout the tropical forests of the world. They
include both arboreal and burrowing frogs. Three other South America families of
frogs—Ruthven's frog, gold frogs and tree toads, and paradox frogs—each with
very few members, all occur in the rainforest. The paradox frog is named because
its tadpoles grow to remarkable sizes, up to 10 in (250 mm) in length, yet after met-
amorphosis, the largest adult frog is only 2.5 in (70 mm).
Salamanders are not as numerous as frogs in the Neotropics, but the lungless
salamander family is quite diverse. These small, slender amphibians live in the
deep shade of the forest. They are either fossorial or arboreal.
Caecilians are legless, tailless amphibians that are numerous in South America
and found in the tropical rainforests throughout the world. Caecilians resemble
earthworms and move through underground tunnels.
Fish
Fish play important roles in flooded forests of the Amazon and its tributaries.
About 200 different kinds of fish consume the seeds and fruits of forest trees and
are active dispersing agents. Seasonal flooding of the rivers lets fish swim among
the trees and forage on dropped fruits. Some tropical fish also eat woody plant
material, leaves, and detritus as well as invertebrates, small vertebrates, and
zooplankton.
Insects and Other Invertebrates
The Neotropical rainforest is home to innumerable insects and other invertebrates
that exploit whatever opportunities they can. Invertebrates evolved more than 350
mya and are quite adept at adaptation and survival. They have endured countless
