Page 24 - Shark

Live young

The majority of sharks give birth to live young instead of laying
eggs. Most are ovoviviparous, producing large yolky eggs that are kept
inside the mother’s uterus. The developing pup, or embryo, is fed by
the yolk sac attached to its belly. When this is used up, the pup
is fully developed and ready to be born. In some shark species, the
first pups that develop eat eggs and also embryos in their mother’s
uterus. In sand tiger (pp. 24–25) and mako sharks, only one of the
young cannibals survives in each side of the paired uteri, having eaten
Mother and baby all its unborn brothers and sisters. A more complex pregnancy occurs
Human babies need
to be looked after for in a few viviparous sharks, such as lemon (pp. 54–55), blue, and bull, as
many years, but
shark pups are not well as hammerhead (pp. 42–43) sharks, in which nourishment from the
so lucky. They mother’s blood passes through the placenta to the embryo via the umbilical
must fend for
themselves as soon cord. This is also how human babies develop, as well as other placental
as they are born. mammals, such as dogs and elephants.

1

how a leMon
shark is born
(1) The tip of the
pup’s tail is just
visible poking out
of its mother’s
opening, or cloaca
(pp. 10–11).
Pregnant lemon
sharks come into
shallow coastal
lagoons that are
sheltered from the
waves to give birth.
Scientists studying
sharks at Bimini
in the Bahamas
sometimes catch
female sharks for
their investigations.
(2) Here, the female
has begun to give
birth. (3) The
scientist is acting
like a midwife
and is helping the
passage of the pup
out of the mother’s
birth canal.
2 3

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