Insects Left Their Crustaceans Ancestors in the Ocean to Settle on Land Millions of Years Ago [Study]

Insects are some of the oldest living organisms on Earth dating back hundreds of million years ago and the only invertebrates with wings.

Coinciding with mammals and other animals, insects play an important role in the world's ecosystems, wherein some are pollination agents and predators to even other insects.

Moreover, some insect groups like mosquitoes are carriers of deadly pathogenic diseases.

However, our perception of some insects, such as being pests all the time, is only limited due to anecdotal observations of our time and available scientific data.

Some of this knowledge also include their origins and evolution, which remained a mystery only until modern times.

Today, most insect groups have a large population due to their capability to quickly reproduce, with some both on water and land.

In a new study led by researchers in the United States and Japan, a hypothesis came to light suggesting why currently few insects live in the ocean, as well as why most of them left the hydrosphere towards the lithosphere in the first place.

The answer is simple and is not as complicated as one might think, according to the research team.

Insects on Land

(Photo : Image by Tony Cordaro from Pixabay )

The new study was published in the journal Royal Entomological Society on April 17, wherein Tsunaki Asano from the Tokyo Metropolitan University and his team theorized that eco-evolutionary implications are a possible contributory factor of cuticle hardening system when it comes to insect evolution and terrestrialization.

The said system allowed ancient insects to adapt to terrestrial or land environments along the evolutionary line.

The hypothesis specifies that a unique enzyme helped the insects to harden their casings, called as multi-copper oxidase-2 or MCO2.

This evolutionary trait made insects to be rare in marine environments, as cited by the website Science Alert.

The study explains while insects diverged from their crustacean ancestors, both still have exoskeletons with protective cuticles.

However, the special mechanism developed by insects to harden their outer layer uses oxygen and MCO2.

This contrasts with crustaceans that mainly use calcium from seawater to strengthen their cuticles into shells, the report noted.

Also Read: Nyctinastic Plants: Insect Bite Marks Shows the Evolution of Plants' 'Sleeping Movements'

Unanswered Question of Science

Prior to the new study, scientists in the past have also pondered on the question of why insects have failed to thrive and colonize the oceans.

This is in the contrasting reality that insects live and dominate every landscape of the world except the sea, which comprises of 70% of the Earth's surface.

In 2018, South Africa's experts, including Professor Emeritus Charles Griffiths and Professor Mike Picker, said there are several different theories about why there are only a few insects in the ocean.

Such mystery is one of the unanswered questions of science, according to Griffiths, a marine biologist with the University of Cape Town, the Deutsche Welle media company reported.

In terms of the ones left in the ocean, the only true marine insects living in the waters far from any mainland coasts is the sea skater or Halobates, but even they are not living in the water, according to the report.

Marine Insects

To clarify, the experts said almost all marine insects live in the "intertidal zone."

It is an area where the ocean meets the land or lithosphere between high and low tides, according to the National Oceanic and Atmospheric Administration (NOAA).

Insects only spend a portion of their lives in the said underwater area, primarily when they are still in their egg, larval, and pupae stages, according to the Deutsche Welle report.

On land, this phenomenon is evident as some insects use bodies of water or even open still water when reproducing.