North American Recent Soft-Shelled Turtles (Family Trionychidae)Webb, Robert G. (Robert Gravem)
Science
North American Recent Soft-Shelled Turtles (Family Trionychidae)
Webb, Robert G. (Robert Gravem)
Soft-shelled turtles
Many of the females collected in June or July contained corpora lutea
four to eight millimeters in diameter in addition to enlarged ovarian
follicles. Presumably the corpora lutea indicate clutches deposited
earlier in the current season, and the enlarged follicles represent
clutches to be deposited in the current season. One female of
_muticus_ (OU 27593) obtained on July 10, contains oviducal eggs,
ovarian follicles 15-17 millimeters in diameter, and corpora lutea of
different sizes that exceed the number of oviducal eggs; possibly this
female was capable of laying three clutches each season. Corpora
lutea, representing ovulation points of eggs in the oviducts, are
approximately eight millimeters in diameter. In order to establish
definitely the reproductive potentials of any species of turtle, it is
desirable to know the approximate size of ovarian follicles that are
retained by sexually inactive females, and the rate of regression of
the corpora lutea. The data suggest that, in southern populations at
least, two and possibly three clutches of eggs are deposited in the
annual breeding season. Mitsukuri (_in_ Cagle, 1950:38) found that _T.
sinensis_ deposited four groups of eggs each season.
It is suggested that the seasonal reproductive potential of northern
populations (averaging about 20 eggs per clutch, and probably one
clutch per season) is less than that for southern populations
(averaging about 10 eggs per clutch, but three clutches per season).
But owing to variation, there may be no great discrepancy between the
actual potentials of northern and southern populations.
_Eggs_
The eggs of _Trionyx_ are white and spherical having a brittle shell.
Some eggs are occasionally abnormal in shape and size; overcrowding of
eggs in the oviducts may result in small, irregular-shaped eggs, or
large double-yolked eggs. Presumably enlargement of the eggs occurs in
the oviducts and within a short period after deposition prior to
complete hardening of the brittle shell; therefore some eggs in the
oviducts are smaller than those in nests.
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