21 September 2019 | New Scientist | 29Inglorious mud
Photographer Remi Masson
Agency Nature Picture LibraryEVEN fish can end up fighting
over land. These land-dwelling
great blue spotted mudskippers
are facing off on the mudflats of
Kyushu Island, Japan, their gaping
mouths and raised dorsal fins a
sign of aggression.
Mudskippers are highly
territorial, with some species
building mud walls to keep out
trespassers. Walls also trap a pool
of water in the fish’s territory,
encouraging the growth of
single-celled algae called diatoms,
the main food for this species,
Boleophthalmus pectinirostris.
If a mudskipper infringes on a
neighbour’s territory, a fight may
ensue. The 20-centimetre-long
fish can leap 50 centimetres in the
air during combat, or in mating
displays, by propelling themselves
with their pectoral fins.
As mudskippers have adapted
to spend 90 per cent of their lives
out of water, it is tempting to
see them as a snapshot of our
evolutionary past, when our
ancestors first flapped onto
land. They seem to have easily
overcome many of the challenges
for fish living on land. They move
around using their fins, lay eggs
in water-filled burrows and
breathe through their gills and
skin (although they have to keep
their bodies moist).
This transition isn’t as difficult
as it might seem, however:
amphibious behaviour is reported
in 33 families of fish, and many
may have evolved independently.
The earliest tetrapods, which gave
rise to amphibians, reptiles, birds
and mammals, were more closely
related to lungfish, which gulp air
to help them survive in water with
little dissolved oxygen. ❚Sam WongListen to Helen Scales explore the wonders of life in
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