Reproduction
Like many other species of ray, the
Aetobatus narinari generally breeds in the summer months.
The rays don't become sexually mature until
about 4 to 6 years of age. Once maturation is reached and
copulation has taken place, gestation usually lasts around a
year. The duration of gestation is variant upon the water
conditions however, and can be as short as 8 months if
necessary. The mother ray then gives birth to an average of 1 to
4 pups(Pederson 2011).
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The process of fertilization occurs when a female
is a approached by one or, in some cases multiple, males. The male
attaches himself the female using his tooth plate and grasps onto her
fin. This usually results in wounds left on the females. The male
positions himself under the female and inserts his clasper into the
females cloaca. The process is understood to be relatively quick,
usually lasting from 20-90 seconds (online guide trinadad uwi). Females
have been known to undergo this as many as 4 times before fertilization
is complete and gestation begins (Pederson 2011). The fertilized eggs
gestate inside the mother similar to other large sea creatures like
whales but instead of having a direction connection to their mother via
umbilical cord or placenta, the eggs are instead fed by the yolk of
their own egg. The pups enter into the water column at an average size
of 17-35cm upon delivery, sometimes after being
discharged via aquatic breach by the mother to aid in the pup's hatching
(Bester).
Due to their wide geographic range and consistent
reproduction, the A. narinari is starting to come into question.
The disconnection between these groups of rays has resulted in what
scientists may think is a delineation of the species (Richards et al.
2009). The species has begun to show unique morphology dependent upon
which ocean area they inhabit and seem to display no shared genes.
Consequently, scientists are looking into possibly splitting the
Aetobatus narinari into individual species and subspecies (Richards
et al. 2009).
Here is a
video
showing the mating process of two Spotted Eagle Rays.
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