Monkey is happy: Monkeys are only happy when they see it, but ants are really happy when they see it

Produced by: Science Popularization China

Author: Qin Yalong (Institute of Botany, Chinese Academy of Sciences, Jiangsu Province, Nanjing Zhongshan Botanical Garden)

Producer: China Science Expo

There is a lot of knowledge in the rich plant groups around us. Today, I will share with you an interesting plant - Sloanea sinensis (Hance) Hemsl., an evergreen tree of the genus Sloanea in the family Elaeocarpaceae.

According to the Flora of China, there are about 120 species of the genus Psoralea in the world, mainly distributed in tropical and subtropical regions of the Eastern and Western Hemispheres. There are 13 species in my country, and Psoralea is the most famous species, native to Guangdong, Fujian, Hainan and other places.

The monkey is happy when it splits open (Photo credit: author)

Monkey's happy name

Each plant has a unique Latin name. The genus name of the monkey joy plant, Sloanea, is to commemorate the British botanist Hans Sloane (1660-1752), and the specific epithet sinensis means "originating in China", which is composed of sin+ensis, and sin- refers to China. The word China comes from the Latin Sina, and -ensis in Latin names refers to a certain place. Together, it shows that the monkey joy plant originated from China .

I still remember the first time I saw the Monkey Joy Tree, I was stunned when I saw the name on the sign. I thought to myself: "How could someone give a plant such a festive name? Monkeys must love this plant!"

There are different opinions about the origin of "Hou Huan Xi". Some say that monkeys like its fruit and are very happy every time they see it, hence the name; some say that its fruit looks very much like chestnuts when it is not yet ripe, and monkeys pick the fruit and find that there are no chestnuts inside, so they are happy for nothing; others say that when the fruit is ripe, it will split open, revealing the purple-red endocarp with black seeds wrapped in orange-yellow arils, which looks like a monkey's face from a distance, hence the name.

Of course, some people say that the fruit of Monkey Joy looks like a monkey's red butt when cracked. Seeing its name will make people think of certain special foods. Those who are interested can look up Cow Joy, Sheep Joy, Pig Joy, etc. I won’t explain too much here.

To this day, there is no record of monkeys eating the fruit of the monkey's joy. Some curious people even tasted its seeds and found them bitter. It seems that monkeys would not be happy after eating them.

Monkey's Happy Phenology

According to the Flora of China, the flowering period of Monkey King is from September to November, and the fruit matures in June or July of the following year.

Ever since the leaves changed color in March, I have been looking forward to the fruit ripening; by May, its fruit was no bigger than a fingernail; by June, the fruit had grown to the size of a quail egg; I slowly waited until July, thinking that it would finally be ripe and burst, but when I looked over, it still looked like a hairy chestnut; I waited until September, and finally, it changed color, the yellow-green thorns slowly turned red, and it looked more and more like the ripe fruit of rambutan.

It was not until mid-October that I finally saw the fruit crack for the first time. The seeds were grown on the purple-red endocarp, which was somewhat similar in shape to the cracked fruits of Sterculia and Sycamore. Soon after, the seeds fell off the endocarp, while the pericarp would hang on the branch in an exploded state until it gradually fell off in the spring of the following year.

Monkeys love June fruits (Photo credit: author)

Monkeys love September fruits (Photo credit: author)

Monkey Joy fruit ripening period (Photo credit: author)

While observing the fruit ripening, I was delighted to discover the Monkey King daisy, which is under ex situ protection in Nanjing Zhongshan Botanical Garden. Its flowers actually bloom at the same time as the ripe fruits. Although the fruiting period is much later than described in the "Flora of China", the flowering period is normal. For several consecutive years, the flowering period has been concentrated from mid-September to mid-October.

Only then did I truly understand why the "Flora of China" described the monkey joy and noted that its morphology and phenological period would vary greatly with changes in habitat conditions.

Monkey's happy form

As a companion of plants, I like to get close to the plants and trees around me. Through continuous observation for several years, I found that the monkey joy will change its appearance briefly around March , and the green leaves will gradually show yellow, orange and red, bringing people the beauty of autumn. During the growth process, if you stop and look, you can always find a few red leaves among the green leaves. They fall without our noticing, completing the replacement of leaves in a low-key manner.

Monkey Joy leaves change color in March (Photo credit: author)

Take a closer look at each small flower of Monkey Joy. The fluffy bracts are the same color as the petals. There are serrated notches on each petal, and in the middle are densely packed stamens, surrounding the fused style that extends prominently from the middle of the flower, and feels prickly to the touch.

Monkey's Happy Flowering Season (Photo credit: author)

After pollination is completed, the petals, bracts and stamens will all fall off, but the hard style will remain, forming a "pressing nail" with the receptacle, as if to defend against enemies, for fear that the development of the fruit will be disturbed.

Monkeys love December flowers (Photo credit: author)

The fruit of the monkey is called a capsule in botany . The surface is covered with a layer of "monkey hairs" that gradually change from green to red as the fruit develops, which is quite beautiful. From a professional perspective, these monkey hairs are called thorns. When the fruit is ripe, it will split into 3-7 pieces, slowly revealing the shiny seeds on the top. After all the seeds fall off, only the capsule with the peel remains, like stars in the night sky.

The monkey happily cracked the fruit (Photo credit: author)

The spread of monkey joy seeds

There are many ways for plant seeds to spread, whether it's the fruit cores discarded by people after eating fruits, the feces excreted by birds after enjoying the delicious food, the seeds that pop out of burst fruit pods, or the seeds stuck on animals, floating in the wind, and drifting with the current. Different plants have their own seed propagation methods, which can be simply summarized as wind propagation, water propagation, animal propagation, self-propagation, etc., and the seed propagation method of monkey joy belongs to ant propagation among animal propagation .

When its seeds mature and fall, ants will carry the fallen seeds away, satisfying their appetite while helping to spread the seeds, establishing a mutually beneficial symbiotic relationship between the two.

Animal transmission can be divided into active transmission and passive transmission. For example, passive transmission occurs when seeds stick to the body, while active transmission occurs when animals eat plant fruits and then discard the seeds or excrete them through the digestive system with feces.

Active propagation requires a prerequisite, that is, animals are happy to eat the fruits of plants. These fruits either have fragrant and rich flesh or have fresh and juicy arils. For seeds like Monkey Joy, the arils are very rare, so ants must be more accepting of them.

Research has found that ants do not rely on vision and hearing when looking for food, but on smell. The two antennae on the ant's head, like the nose of an animal, can sense the smell and source of the air.

There are two main types of plant seeds spread by ants: one is that the seeds have oleosomes , and the other is that they are covered with arils . The biggest difference between the two structures is the color. The oleosomes are generally light transparent, but they can emit odors, which can attract ants that cannot see clearly but can smell clearly, such as the seeds of Epimedium and Herba Lysimachiae; while the arils are generally brightly colored, which can attract flying birds to eat, such as the seeds of Taxus chinensis and Nutmeg.

The spread of monkey joy seeds

The seeds of Monkey Joy are wrapped in a circle of orange-yellow aril, which should be particularly conspicuous when they fall to the ground. However, when I looked at the cracked fruits on the tree and searched under the tree, I found nothing. After a careful search, I found a few black seeds with the aril gone.

In order to understand the process, I gently shook off a few seeds from the tree, gathered them together, and then took photos and recorded them under the tree. Before the equipment was set up, an ant found them. After several attempts in front of the seeds, it finally climbed up and ate the aril.

First time eating aril (Video source: author)

Slowly, two, three, four... After an ant came to survey the site, it did not stay to enjoy the delicious food, but hurried away, as if to call friends. Soon, a large number of ants came, some of them feasted on the seeds, and some cut the aril into small pieces, carried them and ran home, presumably to share this delicious food with their families. Perhaps because there were not enough ants, they did not move the seeds away, but just ate the aril of the seeds and left.

Ants eating the aril of the monkey joy plant (Image source: author)

To further verify, I shook off a few more seeds, set up the equipment, and then quietly observed. This time, perhaps the ants had reached a consensus, and compared to the chaos last time, they were well organized this time. Some ants bit the aril into small pieces and carried them away, while most of the ants worked together to carry the whole seed and moved it towards home little by little.

Ants carrying goods (Video source: author)

Along the way, there were raised mounds of earth, low-lying gullies, and layers of fallen leaves. They just kept moving forward, carrying seeds that were many times larger than their bodies. After more than an hour, they had carried each seed to their doorstep one by one.

Ants carrying seeds (Video source: author)

At this time, they encountered a new problem: the seeds were big and the door was small. After in-depth discussion, the ants finally met and formed an alliance. They split into two groups, one group of ants was responsible for removing the door and expanding the hole, and the other group of ants continued to carry the seeds to the hole. In the end, all the seeds were carried back home.

The seed coat of the monkey Huanxi was moved into the ant nest (Photo credit: author)

Next, I waited for them to throw the seeds in the aril out of the nest after a full meal. After get off work, I went to the nest again, but I didn't see any exposed seeds being moved out. Curiosity drove me to slowly open the nest. As soon as I dug down, I found that the ants were moving the seeds out, and the aril was missing.

Ants moving out of the nest (Video source: author)

The ants carry the monkey joy seeds back home, eat the aril and then throw them out of the ant nest. Even though the effect is not as good as sowing, the soil particles and dead branches and leaves moved out of the nest are also very helpful for the germination of monkey joy seeds. Compared with under the tree, the seeds are spread, avoiding competition between offspring, and obtaining a simple seedling bed, thus improving the germination rate of seeds.

Through natural selection, Monkey Joy and ants have established a mutually beneficial relationship. Monkey Joy provides food to ants, and ants help Monkey Joy spread seeds, which also vividly shows us why Monkey Joy is an ant-sown plant.

Comparison of plants of the same genus as Monkey Joy

Scientists have studied the seed dispersal of Sloanea hemsleyana (Ito) Rehd. et Wils., a plant of the same genus as the monkey twig, and found that the smell emitted by its aril is exactly what ants like. Ants will carry the fallen seeds of the Sloanea hemsleyana back to their nests.

Surprisingly, the ants did not eat the aril of the chestnut, but gnawed the seed end that was not wrapped in the aril, and then moved the seeds out. Although this process achieved the spread of seeds, it is estimated that only a few seeds can germinate.

Monkey Joy and Imitation Chestnut are of the same genus, and are very similar in terms of fruit, seeds, and aril, and are also spread by ants. The difference is that ants start to move the aril in small areas from the moment they discover the seeds of Monkey Joy; when there are enough ants, they will move the seeds together; after moving them back to the ant nest and eating them, they will also move the exposed seeds out of the nest, and no exposed ends of the seeds are found.

As for seed dispersal, ants have a significantly greater effect on the spread of monkey chestnut than dovetail chestnut.

Conclusion

Monkey Joy attracted my attention because of its unique name. For most people, it may just be an evergreen tree in the mountains and forests. In the changing seasons, leaves change, flowers bloom and fall, fruits ripen, and life reproduces, adding a touch of green to life and bringing joy to the mood. For me, I would rather plant it in my own garden, with a variety of flowers, plants and trees as companions, from companionship to understanding, to explore the survival wisdom of plants and appreciate the beauty and magic of nature.

(Note: Latin text should be italicized.)