114 Sharks: The Animal Answer Guide
from the male’s teeth, with the result that the fins of many Nurse Shark
females bear obvious tears and scars. Because of females’ resistance, fewer
than 10% of mating attempts actually end in successful clasper insertion. A
female Nurse Shark may mate with several males during June, which is the
primary mating season in south Florida.
The one aspect of reproduction that all chondrichthyans have in com-
mon is internal fertilization of the female’s eggs. Internal fertilization and live
birth have apparently been characteristics of sharks since their earliest evolu-
tion. Fossil sharks have structures that look much like the claspers of mod-
ern sharks, and some fossils have shark embryos inside apparent mothers.
Violent mating behavior may seem a strange way to reproduce, but it too
has been around for much of shark evolution, and adaptations to it show
up in several aspects of elasmobranch anatomy. In Blue Sharks, a female’s
skin is thicker than the male’s teeth are long, whereas males have thinner
skin. The teeth of some male scyliorhinid catsharks (Halaelurus, Apristurus)
are longer and have fewer side cusps than those of females, presumably to
aid in holding onto females. Outside of the mating season, male Atlantic
Stingrays have blunt, rounded teeth similar to those of females, an appro-
priate design for crushing clams. As mating time approaches, mature males
develop teeth with long, sharp edges that are better for gripping females.
A male may court and mate successfully, but that doesn’t necessarily
mean he will fertilize eggs, or at least not immediately. Females can store
sperm, probably in the shell gland, for periods of a few weeks to more than
a year, depending on species. Sperm storage thus delays the time when
eggs are actually fertilized. For example, female Blue Sharks mate before
they are sexually mature. They store sperm, not releasing it until 10 to 20
months later. Other sharks known to store sperm include Whitespotted
Bamboo Sharks (Chiloscyllium plagiosum) and Tiger Sharks, both for three
to six months; Nervous Sharks (Carcharhinus cautus, one month); Topes
(five months); Whiskery Sharks (Furgaleus macki, six months); and Chain
Catsharks (Scyliorhinus retifer, one year). Lamniforms are not thought to
store sperm.
Courtship and mating have been observed in a few skate and ray spe-
cies. Males follow females and maintain contact by biting, as with the Eagle
Rays mentioned earlier. In some skates, sexually mature males have ad-
ditional structures that either help them hold onto a female or perhaps
stimulate her to mate. These structures are thorny, hooklike spines around
the top of their heads or on the upper surface of their pectoral fins.
Skates and chimaeras are egg-layers with internal fertilization. Male
chimaeras have a special stalked, hooklike structure on their heads that
ends in a spiky bulb. Instead of biting down on a female with his parrot-like
beak, a male uses this cephalic (head) clasper to hold the female’s pectoral
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