Crustaceans- Ocipodidae & Macrophthalmidae

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.
  • Suborder Thoracotremata (Gk: thorax= chest; trema= hole; hole-chested)
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    Macrophthalmus hirtipes (Heller, 1862), stalk-eyed mud crab, 

    Hemiplax hirtipes(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: Hemiplax hirtipes, stalk-eyed mudcrab
    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.
    f026930: stalkie posturing
    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
    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;

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