Biomechanical constraints on vagile autotrophs

[snorkack]

On Earth, there are no vagile autotrophs.
Microalgae are planctic, but lack ability for complex, active movement.
Bigger plants have propargules that need to move - but only do so passively, not actively.

Many animals are sessile, with vagile larvae - but not autotrophs. Very few, like corals, have symbiosis with algae - don´ t actually carry out photosynthesis with their own cells and genes.

So... what would be biomechanical constraints for an organism whose young actually move actively, with muscles and nerves, and whose adults are sessile autotrophs photosynthesizing with cells and genes that are carried in the young?

What would be the biomechanical constraints for an organism to be actually autotrophic while vagile? A vagile autotroph cannot put down roots... but can actively eat. How much energy can a vagile autotroph catch, and what does a rootless autotroph need to eat?

 

[BillTre]

I don't think there are any biomechanical constraints on autotrophs having either fragile or non-actively moving stages of their lifecycle.
Just to be clear:
Autotrophs are organisms that harvest energy directly from their environment, rather than eating other organisms that either have eaten other organisms or that collect environmental energy themselves. This is usually done through photosynthesis but can also be done be by taking advantage of chemicals in their environment to gain energy for their biological use. There are a diversity of different chemical bases for this, and would include for example organisms that live near different kinds of mineral rich vents at the bottom of the sea.
This is a kind of result of what their place is in their environment. How they gather energy (at the base of the food chain) and how make their way in the world (reproductive cycle).

Biomechanical constraints (to me anyway) are limitations on what a biological organism can due due to how the physics or mechanics of their functioning works.

Ecological, evolutionary, and developmental constraints are more likely to provide good explanations for for the lack of fragile or actively moving life cycle stages of autotrophs.
For example, plants have cell walls that are not easily deformable. They also lack a lot of genes involved in animals moving and lacking those for evolutionary reasons can not be expected to wiggle around and move and they can not develop these functions in particular stages. (Pollen does extend pollen tube prior to fertilization however.)

Among the vent associated animals, there are several examples of symbioses similar to algae and coral. I don't know the details of their development, but some (like coral) are squishy.

I would guess that many autotrophs, which are relying on harvesting low density energy from an environment are not going to expend a lot of their hard gained energy on making and moving things around. They probably are more likely to gain a dependable return on their investment (or energy) by making a lot of propagules (seeds, spores, or whatever) that are distributed well enough by passive means to propagate their species. This would be an r-selection approach ecologically.