The macuja or gru-gru (Acrocomia aculeata (Jacquin) Loddiges ex Martius) is a tall graceful palm native to Central and South America. Depending upon the botanical authority, there are 26 species of Acrocomia or just one or two highly variable species. In 1763, Nickolaus von Jacquin named the gru-gru Cocos aculeatus or coconut palm with sharp points.

Although closely allied to the coconut, botanists realized by the early 1800s that the palm was not a coconut and a new genus was recognized. Since Acrocomia have numerous feathery fronds, Carl Friedrich Philipp von Martius named the palms from the Greek words akros "tip, top, highest" and kome "mane or head of hair". The gru-gru was moved to the new genus in 1845.

The most obvious characteristic of gru-grus are the stout black spines protruding from the trunk. These outgrowths of the palm's epidermis are blade-shaped and become lignified as they age. They are dead and dry at maturity and readily break off in the skin—strong discouragement for even the most-persistent herbivore wishing to climb to the fruit.

Even if an animal succeeds at getting gru-gru fruit, the outside is prickly and unpalatable and the seed inside is protected by a hard, bony endocarp. But there are animals which get around the spines and eat the hard seeds. In his later years, Henry Walter Bates wrote of his time spent exploring the wonders of South America. One of his first observations was the 'macuja' and a remarkable brilliant blue bird. In The Naturalist on the River Amazons, he stated "These nuts, which are so hard as to be difficult to break with a heavy hammer, are crushed to a pulp by the powerful beak of this [hyacinth] Macaw."

Parrots International has a series of photographs of hyacinth macaws including several showing these splendid birds in a gru-gru. To view the photographs, click on the link: http://www.parrotsinternational.org/Species_Pages/hyacinth_photos_2.htm

(Compiled from: "Acrocomia aculeata" W3Tropicos, Jim Solomon, Missouri Botanical Garden, 2005; "Acrocomia", Hortus Third, Staff of the L.H. Bailey Hortorium, New York State College of Agriculture and Life Sciences, Cornell University, Macmillan, 1976; "Spiny Palms", Palm Articles, Palm and Cycad Societies of Australia, 2004 and The Naturalist on the River Amazons, Henry Walter Bates, 1863, published on the internet by Project Gutenberg.)