Page 40 - AlertDiver_Spring2013

LIFE AQUATIC
38 | SPRING 2013
Jellyfish also have a two-act life cycle. Drifting jellyfish
larvae settle on the seafloor whereupon they morph into
flowerlike polyp structures that bud asexually — like mother
ships releasing tiny flying saucers from a stack, one after
another. These are the baby jellies that drift and develop into
the familiar bell form.
One of the most significant transformations takes place
in tunicates (sea squirts). As adults these typically look
like colorful clusters of tiny tubes attached to the bottom.
However, sea-squirt larvae resemble tadpoles — complete
with tails and notochords. Once a suitable attachment site
is found, the tadpolelike larva attaches to the seafloor by its
head, the tail degenerates, and it proceeds to change into the
adult sea-squirt form.
A crab undergoes the transition from cute, Pac-Man
zoea to crawling and clawed adult in numerous stages. In
crustaceans, molting plays an important role early in and
throughout their lives. With a hard exoskeleton or carapace,
crustaceans must molt their shells to make way for bigger
bodies. In addition, these animals must be appropriately
outfitted for a life afloat in the early days of their existence,
hence their adornment with spines and feathery cilia.
In the ocean’s planktonic young, change is often dramatic,
illustrating the complexity and diversity of life in the sea.
The variations on the theme are many, but the overall goal is
the same: to survive. AD
Ellen Prager, Ph.D., is the author of Sex, Drugs and Sea Slime:
The Oceans’ Oddest Creatures and Why They Matter.
About the Author
Larval flounder (with an eye still on each side of its head)
ONLINE INCIDENT REPORT
Report an incident at:
DAN.org/IncidentReport
Phone: +1-919-684-2948
DAN has established an online dive safety
reporting system, designed to enable divers
to anonymously report nonfatal accidents
and the details surrounding the event.
The data gathered will help identify trends and
establish baselines to further research efforts
and enhance the safety of our sport.
Your Dive Safety Association
Cedric Guigand