40
Biology of Sea Turtles, Vol. II
2.1 INTRODUCTION
The anatomy of an animal defines how it can live within and interact with its
environment. The form of an animal gives fundamental clues about its behavior,
ecology, and physiology: how it functions. Its shape and overall design dictate how
the animal can move and feed. The shapes of muscles, bones, and the nervous system,
which controls responses and movements, allow function to match form given the
animal’s ecology.
For the biologist, anatomy provides the raw materials for evolutionary, taxonomic,
and population studies (providing both the morphological data and the tissues that are
sources of biochemical samples). Comparisons between normal anatomy, in contrast
with anatomy that reflects disease or injury, provide information about acute and
chronic changes in health. In addition, it is the remnants of the anatomy, as fossils or
artifacts at archaeological sites (such as shells and skulls described in other chapters),
that provide historical perspective about when and where species occurred, how they
changed through time, and how they were used and valued by ancient peoples.
Extant marine turtles are morphologically distinct from other turtles. They are
characterized by their large adult body size, hypertrophied forelimbs (flippers),
and streamlined shells. In the following sections, external anatomy and gross
morphology of the skeletal, muscular, and nervous systems are discussed because
these components together perhaps are linked conceptually more so than any other
combination of systems. The external morphology is not simply about scutes and
skin, but provides fundamental information about how the animal interacts with
its environment. Body design, color, and ontogenetic changes belie ecological and
behavioral differences as well as provide taxonomic material. A marine turtle gains
much of its overall form from the underlying musculoskeletal system. The homologies of structures, as well as their functions (including both motor patterns and
movements), are dependent on innervations of the muscles. The form of the
skeleton not only shapes what movements are possible, but also defines what and
how organs receive protection. These functional and historical interrelationships
of systems provide the links that bind them together for their description and
discussion here.
2.2 EXTERNAL ANATOMY
The external anatomy includes the scales of the head (and body), the scutes (or lack
of scutes) of the shell, and the form of the limbs and body. All of these characteristics
are frequently used in species identification. Coloration and body design or form
also provide key information about form and function in marine turtles.
Dermochelys coriacea V., a long-distance migrant and deep-diving species,
has a streamlined body that tapers from the shoulders to the caudal tip, and
extremely long clawless fore limbs. The body is black with varying degrees of
white speckling. Five dorsal ridges run the length of the carapace, two ridges form
the margins, and few ridges occur ventrally (Figure 2.1A). The head is oval with
large eyes. A notch occurs in each side of the upper jaw (Pritchard, 1979).
1123_C02.fm Page 40 Friday, November 15, 2002 11:16 AM
Biology of Sea Turtles, Vol. II
2.1 INTRODUCTION
The anatomy of an animal defines how it can live within and interact with its
environment. The form of an animal gives fundamental clues about its behavior,
ecology, and physiology: how it functions. Its shape and overall design dictate how
the animal can move and feed. The shapes of muscles, bones, and the nervous system,
which controls responses and movements, allow function to match form given the
animal’s ecology.
For the biologist, anatomy provides the raw materials for evolutionary, taxonomic,
and population studies (providing both the morphological data and the tissues that are
sources of biochemical samples). Comparisons between normal anatomy, in contrast
with anatomy that reflects disease or injury, provide information about acute and
chronic changes in health. In addition, it is the remnants of the anatomy, as fossils or
artifacts at archaeological sites (such as shells and skulls described in other chapters),
that provide historical perspective about when and where species occurred, how they
changed through time, and how they were used and valued by ancient peoples.
Extant marine turtles are morphologically distinct from other turtles. They are
characterized by their large adult body size, hypertrophied forelimbs (flippers),
and streamlined shells. In the following sections, external anatomy and gross
morphology of the skeletal, muscular, and nervous systems are discussed because
these components together perhaps are linked conceptually more so than any other
combination of systems. The external morphology is not simply about scutes and
skin, but provides fundamental information about how the animal interacts with
its environment. Body design, color, and ontogenetic changes belie ecological and
behavioral differences as well as provide taxonomic material. A marine turtle gains
much of its overall form from the underlying musculoskeletal system. The homologies of structures, as well as their functions (including both motor patterns and
movements), are dependent on innervations of the muscles. The form of the
skeleton not only shapes what movements are possible, but also defines what and
how organs receive protection. These functional and historical interrelationships
of systems provide the links that bind them together for their description and
discussion here.
2.2 EXTERNAL ANATOMY
The external anatomy includes the scales of the head (and body), the scutes (or lack
of scutes) of the shell, and the form of the limbs and body. All of these characteristics
are frequently used in species identification. Coloration and body design or form
also provide key information about form and function in marine turtles.
Dermochelys coriacea V., a long-distance migrant and deep-diving species,
has a streamlined body that tapers from the shoulders to the caudal tip, and
extremely long clawless fore limbs. The body is black with varying degrees of
white speckling. Five dorsal ridges run the length of the carapace, two ridges form
the margins, and few ridges occur ventrally (Figure 2.1A). The head is oval with
large eyes. A notch occurs in each side of the upper jaw (Pritchard, 1979).
1123_C02.fm Page 40 Friday, November 15, 2002 11:16 AM