Enter the sea dragon
Bizarre and beautiful, leafy sea dragons inhabit an unusual world
under the ocean … a world where males bear the young!
by Paula Weston
They look like floating leaves and seaweed, use an air bladder to move up and down
in the water, and the males give birth to the young.
So what are these amazing creatures?
They are known as sea dragons, spectacularly camouflaged marine creatures
with some truly incredible design features. They are found only in coastal southern
Australian waters and can be either ‘leafy’ (looking like aquatic ‘leaves’)
or ‘weedy’ (resembling blades of brown seaweed).
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The colour of sea horses and sea dragons is determined by the crustaceans they have
been eating!
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Due to their many similarities, sea dragons are classified, along with pipefish,
in the same family as sea horses, i.e. Syngnathidae. (Greek: ‘together-jawed’.)
This relates to their ‘tube-snouted’ mouths.1
Adult sea dragons grow to about 45 cm (18 inches). They have no teeth or stomach,
and feed on small shrimps. Making the most of their camouflage, sea dragons float
seemingly harmlessly in the water, sucking unsuspecting passing prey into their
mouths.
Sea dragons and sea horses also possess an internal air bladder, used for vertical
motion. With little effort, they can rise or settle to another depth simply by changing
the air volume within the bladder.2
But probably the most incredible feature shared by sea dragons and sea horses is
the role played by the male in hatching the young. The female deposits as many as
250 eggs within a specialised area of soft skin beneath the male’s tail, known
as a brooding pouch (or ‘patch’). These eggs are then fertilized by
the male, and protected in a cup-like indentation for up to eight weeks before hatching.3
When the eggs are ready to hatch, the male contorts his body and expels the young
through a single opening in the pouch.4 The fully-developed young hatch
over a period of several days, dispersing over a wide area.
Encyclopædia Britannica notes that fossil sea horses (with
which it appears to include sea dragons) are unknown, and there is only ‘limited
paleontological [fossil] data’ available to trace the (alleged) evolutionary
history of the order to which they belong (Gasterosteiformes).5
Design is a far better explanation than random mutations and selection to explain
the specialized features of the sea dragon such as its sensational camouflage, its
air bladder, and the reproductive technique displayed in the sea dragon. The latter
especially perplexes evolution-minded scientists, given the reproductive role reversal.
Of course, there is no mystery if we accept that the sea dragon did not evolve over
millions of years, but is instead yet another example of the ingenious design of
the Creator.
References and notes
- In The Dragon’s Lair, <www.nexus.edu.au/schools/Kingscot/Pelican/seadragons/sd_menu.htm>.
- The New Encyclopædia Britannica, 15th Edition, 19:254,
1992.
- Underwater World Perth, <www.coralworld.com/perth/gallery/seadragons/>.
- Ref. 2, 10:579.
- Ref. 2, 19:255.
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