Acanthosicyos horridus Welw. Ex Hook.f.

Cucurbitaceae

 
Author:Janine E. Victor
Synonyms

Common names

!nara (Topnaar); nara melon (English); butterpips

 

Taxonomy

Cucurbitaceae

 

Origin and geographic distribution

The nara melon grows in the coastal region of the Namib Desert in Namibia, as far north as Mossamedes in southern Angola and as far south as Port Nolloth in the Northern Cape province of South Africa. It grows where underground water is available, colonizing shifting sand dunes. The name nara melon is derived from the name of one of the areas where it is commonly found, the Nara hills, which is in turn derived from the indigenous Topnaars’ language, Nama, in which it is known as !nara (the ! denoting a palatial click of the tongue). At Sandfontein east of Walvis Bay, advancing dunes have forced the Kuisib River beneath the ground. This creates ideal conditions for the Naras to grow.

Fossil evidence indicates that the nara existed some 40 million years ago. The nara was probably utilized in the stone-age, and was probably the sole reason why the desert tribes survived in their habitat to modern day.

 

Description

Perennial leafless shrub 0.5–1.0m tall, densely tangled and spreading up to 1500m2 in area. The shrub is heavily armed with 2-3cm long straight, sharp, paired spines growing on longitudinally grooved stems up to 1m long. Stomata occur in the grooves of the stems. Spines, stems and flowers are all photosynthetic and green. The flowers are 3cm in diameter and are solitary. Male flowers are produced all year, on separate plants to the females that produce flowers form August to April. Female flowers have an inferior warty ovary that develops into a melon, green at first and orange-yellow when ripe, 15cm in diameter and covered with small spiky protuberances. Many (about 250) cream-coloured delicious seeds are embedded in an orange-yellow protein-rich pulp. The thick woody taproot can grow to 40m.

 

Phytochemistry

The fresh fruit contains cucurbitacins that burn the mouth.

 

Use

The nuts of the fruit are the staple diet of indigenous people of Namibia, most notably the Topnaar people, who still live for a considerable part of the year almost exclusively on the naras and hence are known by the tribal name of narani (Fox & Norwood-Young 1982). Historically the fruit has been the staple food of indigenous people for several months of the year, and can form almost the exclusive food for the inhabitants of the Namib (Schapera 1937). Seeds are dried and stored for use in winter months.

More recently, the fruit has had economic importance in South Africa, being used in the confectionary industry. Part of the harvest of the Topnaar people is sold to traders in Walvis Bay who export them to Cape Town.

The seeds are highly nutritious, containing 57% oil and 31% protein (Van Damme & Van Den Eynden 2000). In South Africa the seeds are eaten like nuts and taste similar to almonds; or used in confectionary. The sweet fruity flesh of the fresh fruit can be eaten raw, but it can burn the mouth. It is traditionally dried to form flat cakes that can be chewed or added to porridge. This preparation can be stored and eaten over many months.

The peels of the nara fruit are fed to donkeys and goats, and the seeds to chickens.

The nara also has medicinal properties. A decoction of the bitter roots is believed to cure many ailments. Fresh fruit is said to relieve stomach pains, and oil from the seeds moisturizes the skin and protects it from sunburn (Van Damme & Van Den Eynden 2000).

 

Toxicity

Unknown

 

Ecology

Ecologically, nara is a keystone species, being the most important sand stabilising plant in the Namib desert.

In the Skeleton Coast Park it forms a very important food source for the dune-dwelling lizard, Angolosaurus skoogi. The plant also shelters a wide variety of insects and reptiles including snakes.

 

Growth requirements and habitat adaptations

The nara melon is adapted to uninhabitable conditions of the dune fields where no other plant is able to withstand the high temperatures, violent sandstorms and rainless climate. A prerequisite for growth is a source of underground water, which is why it is commonly found on dry riverbeds that still have subterranean water, and plinths of dunes. Upon germination, the seedling roots grow rapidly until contact is made with moist layers of soil below. Shoots then grow, penetrating any sand deposited above, conquering the developing sand dune with a thorny crown of dense, scrambling branches. These clumps trap and bind the sand, stabilizing the dunes and forming hillocks several meters high and wide (Wilkins-Ellert 1999). The nara ability to survive the extreme conditions of the desert is owed to its taproots that are able to grow up to 40 m long in search of the water table. In addition, the leaves are modified into thorns to minimize water loss, and the arrangement of the spines coupled with the channeled stems may be an adaptation to enable water from fogs to condense and be utilized by the plants. Hairs on twigs help absorption of condensed fog. Stomata occur within the grooves of the stems, and under extremely dry conditions the sides of the grooves become pressed together and the ridges fit into each other, providing further protection against water loss. Although not exclusively dependent on fog for survival, the nara is only found as far inland as mist or fog reaches.

The sand of the Namib is unusual, being composed of gypsum quartz fragments with negligible clay and other normal soil constituents, and also has 0.5% salt content (Versfeld & Britten 1915).

Plants can live to over a hundred years old. They are most likely insect pollinated.

 

Conservation

Although it occurs over a fairly widespread area and is not at this stage threatened with extinction on a global scale, the nara is locally threatened around the towns of Walvis Bay and Swakopmund, and the South African populations are regionally Vulnerable (Victor 2002). The natural populations of nara have been declining continuously for a number of decades, and the Topnaar people are very concerned that their fruit harvests are diminishing significantly. This decline is mainly the result of decreased groundwater levels brought about by extraction of water in the towns of Walvis Bay and Swakopmund (Breuninger 1997). Decreased access to water affects the production of fruits, and limits the ability of males to produce flowers, limiting reproductive capabilities (Eppley & Wenk 2001).

 

Diseases and pests

Flowers are eaten by nara crickets (Acanthrous species) and meloid beetles. The soft and juicy growing tips are eaten by ostrich, springbok, nara cricket, meloid beetle and lizards (Berry 1991).

  Links
 

References

Berry, C. 1991. Nara: unique melon of the desert. Veld & Flora 77.1: 22-23.

Breuninger, B. (1997). Minutes from the Nara workshop: Topnaar community and the Desert Research Foundation of Namibia, 19 November 1997, Lauberville.

Eppley, S.M. & Wenk, E.H. 2001. Reproductive biomass allocation in the dioecious perennial Acanthosicyos horrida. South African Journal of Botany 67: 10–14.

Fox, F.W. & Norwood-Young, M.E. 1982. Food from the veld. Delta Books, Johannesburg.

Schapera, I. 1937. The Bantu-speaking tribes of South Africa. Maskew Miller, Cape Town.

Van Damme, P. & Van Den Eynden, V. 2000. Succulent and xerophytic plants used by the Topnaar of Namibia. Haseltonia 7: 53–62.

Versfeld, W. & F.G. Britten 1915. Notes on the chemistry of the !naras (Acanthosicyos horrida Hook.) South African Journal of Science 12: 232–238.

Victor, J.E. 2002. South Africa. In: J.S. Golding (ed.) Southern African Plant Red Data Lists. Southern African Botanical Diversity Network Report 14: 8–11.

Wilkins-Ellert, M. 1999. In praise of nara. Cucurbit Network News 6,1: 2-3.