Seeds, eggs communicate with each other to survive
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Scenes of talking plants and animals may not be just a Disney fantasy after all, as Japanese study teams say they are indeed communicating.
All life forms are communicating with others, vacuuming up data from their surroundings and sending messages, good and bad, to their friends and foes.
Dogs bark to battle over territory. Male peacocks gracefully spread their feathers like a fan to woo females. Fish release pheromones crucial to trigger mating. Honeybees dance to tell each other where to find honey.
For them to survive, effective communication is the name of the game.
Sound, light, smell and chemical substances–the communication channels vary depending on the life forms, which have evolved to exchange information in strategic ways.
To survive, plants and eggs signal members of their own species to delay or speed the timing of when they sprout or hatch, according to teams of researchers including Hiromi Mukai at the Forestry and Forest Products Research Institute in Tsukuba, Ibaraki Prefecture.
Mukai and Akira Yamawo, an associate professor of forest ecology at Hirosaki University, discovered the use of communication among seeds of a plant called plantago asiatica, commonly known as plantain, a weed often found on the roadside and elsewhere in Japan.
In the study, Mukai’s team pinpointed the plantain’s key strategy to survive among other plants: grow fast.
Mukai and Yamawo examined differences in the time it took for plantain seeds to sprout using two scenarios: sowing only plantain seeds in a container; and then sowing them together with their known enemy–trifolium reopens, commonly known as clover seeds.
Plantain seeds needed 5.6 days to sprout in solo-species cultivation but only 4.1 days to germinate after being scattered with clover seeds, sprouting 35 hours earlier than in solo cultivation. Ones planted with clover also sprouted relatively at the same time.
Experiments using seed extract showed the same tendency to sprout. Through some kind of hydrosoluble substance, plantain seeds appear to detect clover seeds and exchange signals among their peers to match when to germinate.
Whether such communication gives plantains a competitive edge over other species can be proved if researchers “can confirm the rise in growth of plantain seeds and curb in growth of clover seeds when plantain seeds sprout at around the same time and faster than clover,” Mukai said.
Mukai also unlocked the mystery of a mechanism of synchronized hatching in a joint study with researchers at Kyoto University.
They discovered eggs of stink bugs, notorious insects that feed on rice grains and fruits, perceive signals emitted from their peers as a cue to hatch in unison.
In many egg-laying species, mothers lay several eggs at one location to form a group of siblings. Relationships among siblings are vital, especially right after hatching.
Hatching later than others threatens an offspring’s survival. Therefore, the offspring of many living things have a mechanism to adjust the timing of their hatching to be closer to the one of their siblings so they can hatch together.
But how do they know when their siblings will hatch?
GOOD VIBRATIONS
Vibration is one sign seen in synchronized hatching studies, but the kind of vibration used as a cue to induce hatching has remained unknown.
Brown marbled stink bugs often seen in Japan deposit about 30 eggs at once. When one hatches, eggs nearby follow suit in about 10 to 15 minutes. When the eggs were separated, it took many hours for the entire clutch to hatch, indicating some sort of information is being exchanged between eggs that leads to their synchronized hatching.
When the joint team added micro-vibrations to eggs, commonly generated when eggs are cracked, they hatched, offering evidence that eggs use vibrations to communicate among one another.
The team surmised that eggs need to hatch in unison to avoid being eaten by their siblings.
If eggs hatch one by one, larvae that leave the egg ahead of others could devour those not yet hatched. Differences in body size and the timing of their sloughing off their skin trigger siblings to feast on one another.
When they hatch at once, battles are rare. Communication using vibrations seems to serve as a sort of “cease-fire deal” between siblings.
If we use these natural properties of the stink bug against it, they could help to exterminate the insect, research by the team indicates.
EGGS DELAY, SPEED UP HATCHING
Parents and eggs also sometimes exchange information. Female adomerus rotundus vigorously shake their eggs. Parents appear to urge simultaneous hatching so their children don’t dine on each other.
According to research papers released by a study team including researchers of Deakin University in Australia, babies in eggs of the Zebra finch, a bird often kept as a house pet in Japan, hear their parents’ chirps, which they tend to emit during warm weather. This information seems to help their offspring grow accustomed to the temperature of their environment. This doesn’t necessarily mean that parents sing for their babies, but hearing parents’ vocalizations appears to enable children to prepare for their future.
Eggs also react to outside circumstances in some cases.
When salamander eggs smell their predator, the planarian, they hold off hatching, according to Karen Warkentin, professor of biology at Boston University in the United States.
Planarians eat juvenile salamanders, but not their eggs.
The flexible eggs also sometimes pursue the opposite strategy hatching early, following an apparent game plan of “Run away first.”
Seeds and eggs likely acquired the ability to exchange such information while adapting to environmental changes and participating in the so-called “evolutionary arms race,” a coevolutionary process in which individual organisms are locked in a competitive relationship with different species and their own, such as relationships between males and females or parents and children.
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