Reproduction and Development in reptiles | zoology by miller and Harley

Reproduction and Development
Vertebrates could never be truly terrestrial until their repro-
duction and embryonic development became separate from
standing or running water. For vertebrates, internal fertiliza-
tion and the amniotic egg (see figure 20.2) made complete
movement to land possible. The amniotic egg, however, is
not completely independent of water. Pores in the eggshell
permit gas exchange but also allow water to evaporate.
Amniotic eggs require significant energy expenditures by par-
ents. Parental care occurs in some reptiles and may involve
maintaining relatively high humidity around the eggs. These
eggs are often supplied with large quantities of yolk for long
developmental periods, and parental energy and time are
sometimes invested in the posthatching care of dependent
young.
Accompanying the development of amniotic eggs is
the necessity for internal fertilization. Fertilization must occur
in the reproductive tract of the female before protective egg
membranes are laid down around an egg. All male reptiles,
except tuataras, possess an intromittent organ for introducing
sperm into the female reproductive tract. Lizards and snakes
possess paired hemipenes at the base of the tail that are
erected by being turned inside out, like the finger of a glove.
Gonads lie in the abdominal cavity. In males, a pair of
ducts delivers sperm to the cloaca. After copulation, sperm
may be stored in a seminal receptacle in the female repro-
ductive tract. Secretions of the seminal receptacle nourish the
sperm and arrest their activity. Sperm may be stored for up
to four years in some turtles, and up to six years in some
snakes! In temperate latitudes, sperm can be stored over win-
ter. Copulation may take place in the fall, when individuals
congregate in hibernacula, and fertilization and development
may occur in the spring, when temperatures favor successful
development. Fertilization occurs in the upper regions of the
oviduct, which leads from the ovary to the cloaca. Glandular
regions of the oviduct secrete albumen and the eggshell. The
shell is usually tough yet flexible. In some crocodilians, the
eggshell is calcareous and rigid, like the eggshells of birds

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[@biologywithkiran5427]

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[@momalkhan3550]

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[@biologywithkiran5427]

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