Acanthosicyos horridus

Acanthosicyos horridus is an unusual melon that occurs only in Namibia; it is locally called naras or nara. It is a dioecious plant found in sand desert 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 nara plant is leafless, so modified stems and spines 2–3 centimeters long serve as the photosynthetic 'organs' of the plant. The plant can survive many years without water. Nara 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 nutritious melons, seeds, shoots, and flowers are food sources for beetles, gemsbok, and ostrich, while small mammals such as Rhabdomys pumilio, Desmodillus auricularis, and Thallomys nigricauda take shelter amid the spiny tangle of its stems. The melon fruits average 1 kg and are pale green and spiny. Within, a sweet, aromatic, watery, yellow-orange pulp is described as 'tasting like an avocado or a cross between cucumber and pineapple'. The large edible seeds, white to cream in color, are known locally as butterpips. The fruit serves as an essential food source for Topnaar people from February to April and August to September. The katydid Acanthoproctus diadematus feeds on the plant, moving between different bushes at night.