Ontogeny of Marine Turtle Gonads
219
7.6.6 REGRESSION
Following a reproductive episode, each male and female turtle must return to its
foraging area to recuperate. Each must recover the nutrient and energy reserves
depleted during the breeding migration as well as fulfill its requirements for physiological maintenance before it can begin to accumulate the reserves required to
initiate another reproductive episode. For the female, this may require a year (L.
olivacea: Plotkin et al., 1994), a few years, or a decade or more (Limpus et al., 1992;
Limpus and Limpus, in press). The ovary of a turtle that has just returned from a
breeding episode may contain a few mature follicles, possibly some corpora hemorrhagia and numerous corpora albicantia from previous clutches in the season still
supported on fluid-filled vesicles, and atretic follicles. Small (<4 mm) corpora
albicantia from previous breeding seasons may be present. These characteristics
become less obvious as the interval from the oviposition of the last clutch increases.
The corpora albicantia continue to heal, decreasing to about 2 mm diameter over 2
years; the atretic follicles are fully resorbed during about a year. The small regressed
corpora albicantia remain as permanent scars in the surface of the ovary. The oviduct
of a regressive female remains flaccid, and the convolutions may not be as closely
aligned as in a quiescent turtle. At times, the oviduct may appear thicker and/or
contain visible blood vessels, more like an oviduct in a reproducing turtle.
In the male, seminiferous tubules of the testis are pale white to salmon. Histologically, remaining spermatozoa are resorbed and seminiferous tubules become
involuted and lined with only spermatogonia (Wibbels et al., 1990). The epididymis
loses the turgid appearance, and the color changes to pale white.
7.7 SUMMARY
Although the general pattern of ontogeny of the gonads of marine turtles can be
described, there is much to be learned. Further descriptions of the changes in the
structure and ultrastructure of individual parts of the genital system should be made
among several species. The application of high-resolution laparoscopy, magnetic
resonance imaging, and high-resolution ultrasound (among other techniques) to the
study of the progression of development would maximize the information obtained
from the fewest embryos. The illustrations of Agassiz (1857), Mitsukuri (1888; 1894;
1896–98), and others could be incorporated into modern computer graphic studies
of ontogeny of marine turtles.
ACKNOWLEDGMENTS
This review is based on the pioneering work of literally dozens of researchers whose
efforts before 1980 are often ignored in computer-based literature searches. Their
descriptive prose and detailed drawings provide a wealth of information that should
not be overlooked. It is more than good science to review the older literature; it is
also good conservation because it helps to avoid unnecessary duplication and allows
better formulation of research questions.
1123 book.book Page 219 Monday, November 11, 2002 11:11 AM
219
7.6.6 REGRESSION
Following a reproductive episode, each male and female turtle must return to its
foraging area to recuperate. Each must recover the nutrient and energy reserves
depleted during the breeding migration as well as fulfill its requirements for physiological maintenance before it can begin to accumulate the reserves required to
initiate another reproductive episode. For the female, this may require a year (L.
olivacea: Plotkin et al., 1994), a few years, or a decade or more (Limpus et al., 1992;
Limpus and Limpus, in press). The ovary of a turtle that has just returned from a
breeding episode may contain a few mature follicles, possibly some corpora hemorrhagia and numerous corpora albicantia from previous clutches in the season still
supported on fluid-filled vesicles, and atretic follicles. Small (<4 mm) corpora
albicantia from previous breeding seasons may be present. These characteristics
become less obvious as the interval from the oviposition of the last clutch increases.
The corpora albicantia continue to heal, decreasing to about 2 mm diameter over 2
years; the atretic follicles are fully resorbed during about a year. The small regressed
corpora albicantia remain as permanent scars in the surface of the ovary. The oviduct
of a regressive female remains flaccid, and the convolutions may not be as closely
aligned as in a quiescent turtle. At times, the oviduct may appear thicker and/or
contain visible blood vessels, more like an oviduct in a reproducing turtle.
In the male, seminiferous tubules of the testis are pale white to salmon. Histologically, remaining spermatozoa are resorbed and seminiferous tubules become
involuted and lined with only spermatogonia (Wibbels et al., 1990). The epididymis
loses the turgid appearance, and the color changes to pale white.
7.7 SUMMARY
Although the general pattern of ontogeny of the gonads of marine turtles can be
described, there is much to be learned. Further descriptions of the changes in the
structure and ultrastructure of individual parts of the genital system should be made
among several species. The application of high-resolution laparoscopy, magnetic
resonance imaging, and high-resolution ultrasound (among other techniques) to the
study of the progression of development would maximize the information obtained
from the fewest embryos. The illustrations of Agassiz (1857), Mitsukuri (1888; 1894;
1896–98), and others could be incorporated into modern computer graphic studies
of ontogeny of marine turtles.
ACKNOWLEDGMENTS
This review is based on the pioneering work of literally dozens of researchers whose
efforts before 1980 are often ignored in computer-based literature searches. Their
descriptive prose and detailed drawings provide a wealth of information that should
not be overlooked. It is more than good science to review the older literature; it is
also good conservation because it helps to avoid unnecessary duplication and allows
better formulation of research questions.
1123 book.book Page 219 Monday, November 11, 2002 11:11 AM