42
Biology of Sea Turtles, Vol. II
Species are distinguished from one another based upon a combination of
characteristics that include color, the form of the jaws, the scales on top of the
snout (e.g., prefrontals), and the scutes on the carapace. The green turtle, Chelonia
mydas L . , and flatback, Natator depressus G., each have one pair of prefrontal
scales; the other species have two pairs of prefrontals (Pritchard and Mortimer,
1999). Colors change with age. Most develop a cream-colored plastron as adults
(except for an eastern Pacific race of C. mydas known as the black turtle). As
hatchlings, C. myda s are black dorsally and white ventrally. With growth, the
carapace becomes streaked with brown, tan, and black. Flatback hatchlings are
gray and the margin of each carapacial scute starts out dark gray, surrounding a
lighter gray center. The dark color becomes predominant until they are nearly
mature, when the colors shift to lighter gray. The plastron shifts from white or
pale gray to creamy as the animals age. Hatchlings of Caretta caretta L., Eretmochelys imbricata L . , Lepidochelys kempii G., and Lepidochelys olivacea E. are
brown to dark gray in color dorsally; the plastra vary from pale to dark brown.
Juveniles and adults have carapaces that vary from browns ( C. caretta ); to grays
( L. kempii , L. olivacea , and N. depressus ); to the brown, tan, and yellow ( E.
imbricata ); and gray-green to mottled shades of brown and black ( C. mydas )
(Pritchard, 1979; Pritchard and Mortimer, 1999; Wyneken, 2001). The plastra
shift to yellow or light tan ( C. caretta ), to white ( Lepidochelys ) or, in E. imbricata ,
cream-colored scutes, sometimes each with a brown spot. Color provides not only
taxonomic information, but also clues about adaptations for survival in different
environments, probably through different forms of crypsis (Cott, 1966; Owen,
1982). Color may also be used in recognition of conspecifics; however, there are
no studies of marine turtles addressing this hypothesis.
2.2.1 S CALES AND S CUTES
Scutes are keratinous plates found on the shell. Scales are thickened areas of epidermis and keratin that cover the skin and head. Scutes and scales provide taxonomic
information and act as landmarks for describing location on the body. The scutes
and scales provide the color and texture of the animals as well.
Leatherbacks lack scutes. This species has small round or oval scales on the
shell and throat as hatchlings. These are shed as the animal grows so that there is
little or no hint of scales in the adult. The cheloniids have keratinous scutes
covering the skeletal shell. The number and arrangement of these scutes are
species-specific. The scutes are designated by position and number (Figures 2.2
and 2.3). The carapacial scutes along the midline are the vertebrals . The nuchal
is located most anteriorly along the midline. Lateral to the vertebral scutes are
laterals (or costals ), which abut the peripherally arranged marginals (Figure 2.3).
The scutes connecting the carapace and plastron are the inframarginals. The
plastral scutes include the single intergular , closest to the throat, then from anterior
to posterior, the paired gular , humeral , pectoral , abdominal , femoral , and anal
scutes (Figure 2.3). Some individuals have a single unpaired interanal scute
between or just posterior to the anal scutes (Pritchard, 1979; Pritchard and Mortimer, 1999; Wyneken, 2001).
1123_C02.fm Page 42 Friday, November 15, 2002 11:16 AM
Biology of Sea Turtles, Vol. II
Species are distinguished from one another based upon a combination of
characteristics that include color, the form of the jaws, the scales on top of the
snout (e.g., prefrontals), and the scutes on the carapace. The green turtle, Chelonia
mydas L . , and flatback, Natator depressus G., each have one pair of prefrontal
scales; the other species have two pairs of prefrontals (Pritchard and Mortimer,
1999). Colors change with age. Most develop a cream-colored plastron as adults
(except for an eastern Pacific race of C. mydas known as the black turtle). As
hatchlings, C. myda s are black dorsally and white ventrally. With growth, the
carapace becomes streaked with brown, tan, and black. Flatback hatchlings are
gray and the margin of each carapacial scute starts out dark gray, surrounding a
lighter gray center. The dark color becomes predominant until they are nearly
mature, when the colors shift to lighter gray. The plastron shifts from white or
pale gray to creamy as the animals age. Hatchlings of Caretta caretta L., Eretmochelys imbricata L . , Lepidochelys kempii G., and Lepidochelys olivacea E. are
brown to dark gray in color dorsally; the plastra vary from pale to dark brown.
Juveniles and adults have carapaces that vary from browns ( C. caretta ); to grays
( L. kempii , L. olivacea , and N. depressus ); to the brown, tan, and yellow ( E.
imbricata ); and gray-green to mottled shades of brown and black ( C. mydas )
(Pritchard, 1979; Pritchard and Mortimer, 1999; Wyneken, 2001). The plastra
shift to yellow or light tan ( C. caretta ), to white ( Lepidochelys ) or, in E. imbricata ,
cream-colored scutes, sometimes each with a brown spot. Color provides not only
taxonomic information, but also clues about adaptations for survival in different
environments, probably through different forms of crypsis (Cott, 1966; Owen,
1982). Color may also be used in recognition of conspecifics; however, there are
no studies of marine turtles addressing this hypothesis.
2.2.1 S CALES AND S CUTES
Scutes are keratinous plates found on the shell. Scales are thickened areas of epidermis and keratin that cover the skin and head. Scutes and scales provide taxonomic
information and act as landmarks for describing location on the body. The scutes
and scales provide the color and texture of the animals as well.
Leatherbacks lack scutes. This species has small round or oval scales on the
shell and throat as hatchlings. These are shed as the animal grows so that there is
little or no hint of scales in the adult. The cheloniids have keratinous scutes
covering the skeletal shell. The number and arrangement of these scutes are
species-specific. The scutes are designated by position and number (Figures 2.2
and 2.3). The carapacial scutes along the midline are the vertebrals . The nuchal
is located most anteriorly along the midline. Lateral to the vertebral scutes are
laterals (or costals ), which abut the peripherally arranged marginals (Figure 2.3).
The scutes connecting the carapace and plastron are the inframarginals. The
plastral scutes include the single intergular , closest to the throat, then from anterior
to posterior, the paired gular , humeral , pectoral , abdominal , femoral , and anal
scutes (Figure 2.3). Some individuals have a single unpaired interanal scute
between or just posterior to the anal scutes (Pritchard, 1979; Pritchard and Mortimer, 1999; Wyneken, 2001).
1123_C02.fm Page 42 Friday, November 15, 2002 11:16 AM