User:Jtwsaddress42/Projects/Project 3/Sections/Chapter 5/The Intrinsic Characteristics Of The Unicellular Ancestor - Choanoflaggelates, Spermatozoa & Neurons

Their are some interesting, and unexpected similarities in the capabilities and behaviors of Choanoflagellate and spermatozoan germ cells vis a vis neurons of the soma. But perhaps this is to be expected since both have been critical participants in the evolution of animals. Like neurons selectively releasing neurotransmitters at synaptic clefts between neighboring neurons, the spermatozoa cells must selectively localize the release of signalling molecules for entry iinto the egg, to a point of contact with the egg.

Matos et al. list the following correspondences between neurons and spermatozoa.

In addition to sharing:


 * the presence of putative ‘neuronal’ receptors
 * excitable or neuroid cells
 * the presence of calcium ion channels
 * the presence of Ca2+ signalling pathways involved in the regulation of key functions
 * additional common signalling pathways
 * an abundant concentration of polyunsaturated fatty acids (PUFAs)
 * a high metabolic demand

Both are able to activate other cells:
 * Neurons - other neurons or somatic effectors
 * Spermatozoa: oocyte

Both engage exocytosis for critical functionality:
 * Neurons - release of neurotransmitters in the synaptic space via synaptic vesicles.
 * Spermatozoa - release of acrosomal-binding factors at the oocyte surface via acrosomal vesicles.

Such similarities suggest that perhaps neurons don't differentiate and specialize to the same extent or in the same manner as most other somatic cells, perhaps preserving their ancestral plasticity and epigenetic behavioral repertoires, reminiscent of their unicellular ancestors, for other purposes.