Palms of the Arecaceae family are characterized as monocots, with no secondary growth that gives rise to woody tissue in dicots. The “trunk” of palms that is woody in nature is not the same as woody growth in dicots. This “trunk” is actually a stem made up of fibrous material that gives a woody appearance. These stems of A. aculeata are tall, densely spiny (3-10 cm long), and often swollen (Henderson et al. 1995; Janzen 1983). Leaves are heavily compound and 3-4 m long (Janzen 1983). Dead spiny leaf bases sometimes persist on the stem for long periods of time, seen by the different shades of green and brown leafs on the tree (Henderson et al. 1995). Leaves are grayish green with numerous leaflets arranged irregularly and spreading in four different planes giving the leaf a plumose appearance (Henderson et al. 1995; Janzen 1983). The leaves of A. aculeata are compound, alternate, without stipules and have parallel venation consistent with the monocot classification (Janzen 1983).
Acrocomia aculeata is a perennial, fruit producing palm-tree, from the family Arecaceae and is widely distributed throughout Central and South America (Abreu et al. 2012). A. aculeata is tree-like in growth and appearance (arborescent), but is considered a monocot with no true woody growth. The plant has a single, spiny stem and can reach up to 16 m in height (Abreu et al. 2012). A. aculeata occurs in the dry forests as a naturalized plant, seen in tropical and subtropical savannahs, woodlands, and disturbed areas. Flowers occur in panicles and are monoecious, with a strong odor to attract beetle and Trigona bee pollinators (Henderson et al. 1995; Janzen 1983; Scariot et al. 1981). Examples of beetle pollinators are Andranthobius sp., Curculionidae), Mystrops cf Mexicana (Nitidulidae), and Cyclocephala forsteri (Scarabaeidae) (Scariot et al. 1981). The fruits are smooth, globule, yellowish green, and 2.5-5 cm in diameter (Henderson et al. 1995). The large fruits of A. aculeata are single seeded and were previously dispersed by Pleistocene mammals, but are now dispersed by opportunistic mammals and birds (Janzen & Martin 1982). A. aculeata is used by humans for biofuel and for consumption (Henderson et al. 1995).
A. aculeata is widely distributed throughout the American tropics from Mexico to Argentina, Bolivia, and Paraguay (Henderson et al. 1995). It is seen in lowlands, below about 500 m, but can exceed this elevation range when existing on pastures (Janzen 1983).
Pollination
A strong odor released at the opening of the bracts of A. aculeata helps attract pollinators (Scariot et al. 1991). The pollination syndrome of A. aculeata is beetles, principally Andranthobius sp. (Curculionidae), Mystrops cf Mexicana (Nitidulidae), and Cyclocephala forsteri (Scarabaeidae) (Scariot et al. 1991). Trigona bees are also seen visiting the male flowers and collecting pollen and are predicted to be a pollinator (Janzen 1983). Wind also plays a role in pollination, and the combination of these two pollination strategies, with the plants ability to self pollinate and cross pollinate, makes A. aculeata a successful plant in the colonization of new areas when dispersal is available, though it is often not (Scariot et al. 1991).
Flowering
The inflorescences of the flowers are panicles, with pistillate (female) flowers larger than staminate (male) flowers (Mazzottini-dos-Santos et al. 2014). The inflorescences are borne among the leaves and contain unisexual flowers on the same inflorescence (Henderson et al. 1995). Female flowers occur near the base of the panicle, while the male flowers occur near the tops of the branches and are surrounded by “honeycomb” bracts (Henderson et al. 1995). The flower of A. aculeata discourages herbivory through needle shaped crystals called raphides in the anthers (Mazzottini-dos-Santos et al. 2014). A healthy bract contains about 52,500 male flowers on 95 branchlets, an average of 550 flowers on every branch, and 449 female flowers (Janzen 1983). These flowers are infested with weevils, but the clear purpose of the weevil in A. aculeata is unknown (Janzen 1983).
Fruiting
Fruit fall is between June and March, with a peak in November (Janzen 1983; Scariot et al. 1991). The fruits are smooth, globule, yellowish green and 2.5-5 cm in diameter (Henderson et al. 1995). The fruit has a very body endocarp filled with translucent, white, moderately hard, moist seed contents (Janzen 1983). The exocarp (outermost layer of the fruit) is brittle and easily cracks at maturity, containing one seed (Henderson et al. 1995). Mature trees bear 20-250 fruits and fall the year after flowering (Janzen 1983).
A. aculeata is characterized as occurring in dry forests of the tropics. It is seen in tropical and subtropical open savannahs, open woodlands, disturbed areas, and fields in these dry forests at low elevations (Henderson et al. 1995). A. aculeata has significant occurrences in anthropogenically-modified regions of the cerrado biome (Neotropical savannah), especially in grassland environments (Mazzottini-dos-Santos et al. 2014).
A. aculeata occurs only in riparian vegetation along permanent streams. It is predicted to be introduced into many places, such as Costa Rica, by pre-Colombian Indians, because it is only found in sites disturbed by humans, such as pastures, old fields, roadsides, and house sites (Janzen 1983). Due to this habitat type, a common disperser of A. aculeata is cattle, which pass through the gut and are germinated (Janzen 1983).
Humans often burn the habitat that is often occupied by A. aculeata, but the intensity of the fire will not damage the shoot apex and will only scorch the leaves (Janzen 1983). Repeated fires will damage the trunk of the tree, and fires that occur over a couple of years will kill the tree by eroding its water conducting capacity (Janzen 1983). When a single fire occurs near A. aculeata, the tree is damaged minimally and is said to be somewhat fire-resistant (Janzen 1983).
A. aculeata was a prominent species during the Pleistocene era, and is said to be naturally dispersed by Pleistocene mammals (Janzen 1983). Due to the lack of dispersers that exist now, the initiation of growth and the spread of the species to different areas in the dry habitat is almost impossible, and is therefore seen prominently only near pastures with cattle dispersers (Janzen 1983). A. aculeata rapidly invades pastures that are not fire prone due to cattle dispersion (Janzen 1983).
A. aculeata is thought to be one of the plants with seeds dispersed by extinct Pleistocene mammals. This is supported by the large fruits that grow high on the tree, which contain a rich pulp and have large sized seeds that need to be passed through the gut of a large mammal in order to germinate (Janzen & Martin 1982). Due to the lack of original dispersers of A. aculeata, the fruits drop beneath the tree and are dispersed by several opportunistic species, including opossums, water rats, capuchin monkeys, cattle, and thrushes (Scariot 1998). Predators of A. aculeata include the bruchid beetles, Pachymerus sp. and Caryobruchus acrocomiae (Pachimerinae, Pachimerinii) (Scariot 1998).
A. aculeata is considered a promising species for oil-producing palm and is extracted from the endosperm (Henderson et al. 1995). In many countries, the sap is collected, fermented, and sold as palm wine (Henderson et al. 1995).
In the dry forests, A. aculeata is threatened due to deforestation and growth of pastures, while it is cultivated in some areas for the use of biofuel and palm wine (Henderson et al. 1995).
Acrocomia aculeata is a species of palm native to the Neotropics.
Common names include grugru palm, gloo gloo, corojo, macaúba palm, coyol palm, and macaw palm; synonyms include A. lasiospatha, A. sclerocarpa, and A. vinifera.
It grows up to 15–20 m tall, with a trunk up to 50 cm in diameter, characterized by numerous slender, black, viciously sharp 10 cm long spines jutting out from the trunk. The leaves are pinnate, 3–4 m long, with numerous slender, 50–100 cm long leaflets. Petioles of the leaves are also covered with spines. The flowers are small, produced on a large branched inflorescence 1.5 m long. The fruit is a yellowish-green drupe 2.5–5 cm in diameter. The inner fruit shell, also called endocarp, is very tough to break and contains usually one single, dark brown, nut-like seed 1–2 cm in diameter. The inside of the seed, also called endosperm, is a dry white filling that has a vaguely sweet taste like coconut when eaten. The fruit turns yellow when ripe and has a hard outer shell. The pulp is slightly sweet and is extremely slimy and sticky.
The species is found from southern Mexico and the Caribbean south to Paraguay and northern Argentina.
The tree was noted by the English naturalist Henry Walter Bates in his 1863 book The Naturalist on the River Amazons, where he wrote that
[The hyacinth macaw] flies in pairs, and feeds on the hard nuts of several palms, but especially of the Mucuja (Acrocomia lasiospatha). 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 macaw.
— Bates[3]
The plants inhabit a wide variety of climates and situations; in Paraguay, for example, where it is ubiquitous, it is called the coco paraguayo (Paraguayan coconut), as it is much less common in the rest of the world. It has been suggested that grugru nuts, which come in mass numbers from each tree, can be used in the manufacture of biodiesel. The grugru nut, while very hard, can be sliced into thin circles to be sanded and worn as rings. The trunk of the palm can also be 'milked' to yield a fermented alcoholic beverage known as coyol wine.
Acrocomia aculeata is a species of palm native to the Neotropics.
