ǃNara Melon

''Acanthosicyos horridus'' is an unusual melon that is endemic to the Namib desert. In English it is known as Nara, butter-nuts, or butterpips; in one of the Khoisan languages it is locally called or ("!" is pronounced with a click, somewhat like the "tsk" when English people are tutting, tsk-tsk).

Description

It is a dioecious, leafless, phreatophyte (meaning its roots penetrate deep down to water near the water table) that is found in sandy deserts but not stony plains, in areas with access to ground water such as ephemeral rivers and paleochannels, where sand accumulating in the shelter of its stems can form hummocks up to 1000–1500 m² in area and 4 meters in height. Its stems may rise more than a meter above the hummocks, while its system of thick taproots can extend up to 50 m downward. The plant is leafless, so modified stems and spines 2–3 centimetres long serve as the photosynthetic "organs" of the plant. The plant can survive many years without water.

Ecology

Its sand-binding characteristics also help nara form microclimates within the desert dunes. These microclimates provide food and shelter for a variety of vertebrates. Presence of the nara plant is associated with significantly increased soil microdiversity likely due to the shade it provides and the attraction of foraging mammals which contribute to organic matter.

''Acanthosicyos horridus'' typically occurs in the absence of other vegetation due to the harshness of the climate, though '' Eragrostis spinosa'' and ''Stipagrostis sabulicola'' grasses may grow between its hummocks. It is regarded as a keystone species because its melons, seeds, shoots, and flowers are food sources for beetles, gemsbok, and ostrich, while small rodents such as ''Rhabdomys pumilio'', ''Desmodillus auricularis'', and ''Thallomys nigricauda'' take shelter amid the spiny tangle of its stems. The katydid ''Acanthoproctus diadematus'' feeds on the plant, moving between different bushes at night.

Black-backed jackals sniff out its ripe melon fruits using their jaws to bite through their tough skins. "The chewing molars of canids make them ideal agents for endozoochorous dispersal of large seeds." Such dispersal is long-distance (7–15.9 km). The jackals urinate on buried fruits and later return to them; it is suggested either to mark ownership or mask their smell from rival jackals. Seeds from their droppings germinate better than those extracted directly from ripe fruit. Further, seeds from their scats may then be collected by scatter-hoarding gerbils which move them into microhabitats further dispersing them and optimising their germination. While other carnivores eat other fruits, this seems to be the first case where they might be a plant's primary dispersers.

Uses

The melon fruits average 1 kg and are pale green and spiny. Within it has a sweet, aromatic, watery, yellow-orange pulp. The large edible seeds, white to cream in color, are known as butter-nuts or butterpips. These have been exported for use in baked goods.Grubben, G.J.H. & Denton, O.A. (2004) Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen.

The fruit serves as a food source for Nama people from February to April and August to September.

See also

* Nabkha
* Hummock

References

External links

PROTAbase on ''Acanthosicyos horridus''
*

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Benincaseae
Endemic flora of Namibia
Desert fruits
Drought-tolerant plants
Taxa named by Joseph Dalton Hooker
Taxa named by George Bentham
Plants described in 1867