The family of Macrophthalmidae has only one
representative in New Zealand, the native stalke-eyed mud crab, or stalkie
as it is called endearingly. The stalk-eyed mud crab lives on the sand
flats, preferably amongst the eelgrass, and grows large in clean reaches
of an estuary.
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(L:
hirtus=hairy/
rude/ shaggy; pes= feet; hairy feet) the stalk-eyed mud crab has
an elongated carapace (back), up to 40mm wide, and brightly coloured in
large specimens. It derives its name from its decidedly long stalked eyes,
with which it can observe its surroundings, while hidden under the sand.
The stalkie makes extensive burrows underneath the eelgrass, and also digs
itself into the sand, wherever it happens to be. It roams around more freely
than the tunnelling mudcrab.
Like the tunnelling mud crab, it also feeds from the nutritious mud. Unlike
the mud crab, which has symmetrical spade-like flat nippers, the stalkie
has its nippers pointing down. Whereas the mud crab prefers higher tide
levels, the stalkie prefers the zone lower down. It can occasionally be
found in sheltered waters deeper than the intertidal. It cannot survive
more than 8 hours above water. The crab is mainly active at night, with
small individuals active during high tide and large ones during low tide.
It can be found in concentrations of 10-20/m2. It has many predators, including
cod, eel, eagle ray, snapper and sea birds, including herons and kingfishers.
The stalkie has a deep green carapace with scattered, dense brown spots.
Its legs are yellow-green and nippers red dorsally. It is a beautifully
coloured crab. It is reported that few grow larger than 20mm CW, but one
can find much larger and older crabs in the clear reaches of an estuary.
This crab does not tolerate brackish or fresh water.
Life history: Females mature at 10-13mm CW and can produce 2-3
batches of eggs during one season, which extends from May - February. Eggs
are small (0.25mm) and a large female can carry up to 20,000 eggs under
her abdomen. Mating happens without observable foreplay and lasts for up
to 18 minutes, with the male lying on his back and the female on top.
Distribution: Endemic to New Zealand, distributed over both the
North and South Islands, Stewart Island and Campbell Island.
f026921: A large colourful stalk-eyed mud crab in its natural
environment, the eelgrass beds. Here is where the larger ones are found.
Notice its beautiful colouring, and stalked light-blue eyes.
f026931: a large stalk-eyed mud crab posturing in the setting
sun. When approached with care, these animals do not seem afraid, even
though they have many enemies.
f026923: stalkie in eelgrass habitat
Closeup of the photo on left, showing details of the stalkie's
colouring.
Related species: M latifrons in Tasmania; M japonicus
in Japan;
(L:
hirtus=hairy/
rude/ shaggy; pes= feet; hairy feet) the stalk-eyed mud crab has
an elongated carapace (back), up to 40mm wide, and brightly coloured in
large specimens. It derives its name from its decidedly long stalked eyes,
with which it can observe its surroundings, while hidden under the sand.
The stalkie makes extensive burrows underneath the eelgrass, and also digs
itself into the sand, wherever it happens to be. It roams around more freely
than the tunnelling mudcrab.
