Fossils reveal strange reproduction of Earth’s oldest complex organism: the rangemorphs
Scientists from Cambridge, UK have discovered that Ediacaran organisms known as rangeomorphs used a dual approach of reproduction: they first sent ‘advance party’ to settle in a new area, followed by quick colonization in the new neighbourhood, a way used by strawberry plants.
No doubt, Earth was a very different place 575 million years ago. There was little or no life on land, only a few complex organisms lived in seas. That is why the recent discovery in this field is so significant: The scientists from Cambridge have identified the reproduction method used by rangemorphs, believed as one of the earliest complex organisms.
These strange bodies ruled the oceans for around 40 million years, in the Ediacaran period. They used to grow on the deep sea bed and passively absorbed nutrients from the surrounding water. Geometrically, they were perfectly organised, with greatest possible surface area for absorption. They looked like trees or ferns and were up to 2 metres long with no organs. However they mysteriously disappeared in early Cambrian period, about 540 million years ago. Thus it has been difficult to associate rangeomorphs to any modern organisms, or to figure out their mode of living.
Scientists from Cambridge used high-resolution GPS, spatial statistics and modelling to scrutinize the fossils left by Fractofusus, a type of rangemorph found in modern-day Newfoundland, Canada. Their findings suggest that rangemorphs actually reproduced by two methods. The “grandparent” generations distributed randomly by waterborne seeds or spores known as propagules, using either sexual or asexual reproduction. The ‘grandparent’ rangeomorphs were surrounded by distinct patterns of smaller ‘parents’ and ‘children’, proposing the development of subsequent generations via rapid, asexual reproduction through the use of tendrils or stolon sent out by older genarations, just like modern plants.
This switch between two distinct modes of reproduction made rangeomorphs highly successful. The findings also suggest complicated biology within them, making them distinct and remarkable, particularly, at a point of time when most other forms of life were extremely simple.
Emily G. Mitchell et al. Reconstructing the reproductive mode of an Ediacaran macro-organism. Nature, published online August 03, 2015; doi: 10.1038/nature14646
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