I did a quick chatgpt search to even articulate what is being transferred in those tunnels. This is what I got:

When a neurite (a developing axon or dendrite) tunnels or connects with another, it can transfer various biological signals and materials, depending on the type of interaction. Some key possibilities include:

1. Electrical Signals

If the neurites form a synapse or a gap junction, they can transfer ions and electrical impulses to facilitate communication between neurons.

2. Chemical Signals

Through synaptic vesicles, neurites can transfer neurotransmitters like glutamate, dopamine, or GABA to modulate activity in the connected neuron.

3. Cytoplasmic Exchange

If the tunneling involves tunneling nanotubes (TNTs), they may transfer cytoplasmic materials such as proteins, mRNA, organelles (e.g., mitochondria), or signaling molecules.

4. Membrane Components

Neurites can exchange lipid membrane components or even receptors, modifying the receiving cell's surface properties.

5. Growth and Development Cues

During development, neurites may exchange growth factors and guidance cues (e.g., Netrins, Slits, Ephrins) to help shape the neural network.

I wonder what it is we are witnessing here!