ecosystem importance: evolution of predators (Introduction)

by David Turell , Friday, September 29, 2023, 20:30 (210 days ago) @ David Turell

Appeared very early:

https://phys.org/news/2023-09-animal-evolution-predatory-lifestyle.html

"...the researchers were able to show that the young life stages (larvae) of the small sea anemone Aiptasia actively feed on living prey and are not dependent on algae. To capture its prey, the anemone larvae use specialized stinging cells and a simple neuronal network.

"In the early embryonic development of multicellular organisms, gastrulation plays a key role. "In its simplest form, the gastrula develops from a hollow sphere of cells, the blastula, forming a larval stage with gut and mouth; imagine pushing a ball inwards at one side. All animals pass through this gastrula stage, which could also have existed at the beginning of animal evolution," explains Prof. Holstein, a development and evolutionary biologist

"Ira Mägele, a member of his research group, succeeded in proving that already in the late gastrula stage, the larvae of the Aiptasia sea anemone capture prey of suitable size with their stinging cells, ingest them with their mouth and digest them in their primitive gut.

"The Aiptasia sea anemone is a model system for research on endosymbiosis in corals and other cnidarians. "Corals live in nutrient-poor waters and as larvae or young polyps, take up symbiotic algae cells. In Aiptasia, however, this process is important for adults but does not lead to growth and settlement of the larvae, suggesting that nutrition is a critical step in closing the life cycle," states Holstein.

"Laboratory studies of the nutritional conditions showed that the food for the tiny Aiptasia larvae had to be small enough and alive. Nauplius larvae of Tisbe copepods, 50 to 80 micrometers small, are of similar size to Aiptasia larvae, making them an ideal food.

"The larvae increase continually and rapidly in size, followed by settlement on the substrate and metamorphosis into primary polyps. "In this way, we were able to grow mature polyps as well as their descendants for the first time," explains Mägele.

***

"As Prof. Holstein underscores, the data obtained paint a new picture of the predatory lifestyle as a primary characteristic of the cnidarian gastrula. Evolutionary theorist Ernst Haeckel (1834 to 1919) first posed the "gastrula hypothesis."

"'But Haeckel's hypothetical gastrula was a particle-filtering life form, like sponges. In contrast, the predatory gastrula of Aiptasia and other cnidarians possess specialized stinging cells used for capturing prey," says Holstein.

"The predatory lifestyle of gastrula-like forms with extrusive organelles that excrete toxins and are likewise found in single-celled organisms and simple worms, could have been a critical driver of the early evolution of multicellular organisms and the development of complex, organized nervous systems, according to Holstein."

Comment: dhw's worry that God invented a dog-eat-dog predatory lifestyle is shown here, and the Garden of Eden is gone. Trilobites ate what was available:

https://www.msn.com/en-us/news/technology/fossil-of-a-trilobite-discovered-with-its-las...

See the photo.