May 31, 2016 by Robyn Mills
A tiny marine crustacean with a
great big claw has shown that not only does size matter, but left or
right-handedness (or in this case, left or right-clawedness) is important too.
The 5-6mm marine amphipod Dulichiella appendiculata, related to
the land-based beach-hopper or sand flea we see hopping around on beaches, has
one large claw on one side (either right or left), and a small claw on the
opposite side.
A University of Adelaide study of
the amphipod, published in the Journal of
Crustacean Biology, has discovered that males with the large claw on the
right-hand side are more gregarious and attract more females than their
left-clawed competitors.
"Having a large claw on one
side is a really cool aspect to this species," says Dr Pablo Munguia,
ecologist and evolutionary biologist at the University of Adelaide's School of
Biological Sciences.
"While it's common for males
to have large structures of various kinds to attract females – think elk horns
or peacock tails – there are very few species in nature with such asymmetry.
The only other species are also crustaceans, such as male fiddler crabs, which
also have one large claw.
"But in this case, it's not
just the size that matters. With Dulichiella
appendiculata the right-clawed males not only have a larger claw than the
left-clawed males but they are more gregarious, hanging out with other males as
well as attracting more females.
"The left-clawed males are
more solitary. Interestingly we think this is why the left-clawed males have
survived in the population – in fact there is about 50:50 ratio of each. The
left-clawed males tend to disperse more rapidly and occupy more habitats, so
there is probably a greater chance of them coming across a female while on
their own and uncontested."
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