Page 251 - The Virgin Islands

S tingray - Most stingrays have one or more barbed stingers (modified
from dermal denticles) on the tail, which are used exclusively in self-
defense. The stinger may reach a length of approximately 35 cm (14 in), and
its underside has two grooves with venom glands. The stinger is covered
with a thin layer of skin, the integumentary sheath, in which the venom is
concentrated. A few members of the suborder, such as the manta rays and
the porcupine ray, do not have stingers. Stingrays are common in coastal
tropical and subtropical marine waters throughout the world. The conserva-
tion status is more problematic, leading to them being listed as vulnerable
or endangered by IUCN. and also includes species found in warmer temper-
ate oceans. The flattened bodies of stingrays allow them to effectively con-
ceal themselves in their environment. Stingrays do this by agitating the sand
and hiding beneath it. Because their eyes are on top of their bodies and their
mouths on the undersides, stingrays cannot see their prey; instead, they use
smell and electroreceptors (ampullae of Lorenzini) similar to those of sharks.
Stingrays feed primarily on molluscs, crustaceans, and occasionally on small
fish. Some stingrays’ mouths contain two powerful, shell-crushing plates,
while other species only have sucking mouthparts. Stingrays settle on the
bottom while feeding, often leaving only their eyes and tail visible. Coral
reefs are favorite feeding grounds and are usually shared with sharks during
high tide. Stingrays are usually very docile and curious, their usual reaction
being to flee any disturbance, but they will sometimes brush their fins past
any new object they encounter. Nevertheless, certain larger species may be
more aggressive and should be approached with caution, as the stingray’s
defensive reflex (use of its poisoned stinger) may result in serious injury or
death.