Difference Between Neoteny and Progenesis

Key Difference – Neoteny vs Progenesis
 

During evolution, organisms develop and change at a specific rate of a time that is known as the Heterochrony. If a mutation disturbs the heterochronic development of an organism, it leads to Paedomorphism. Paedomorphism is referred to as a juvenile developmental condition, where the reproductive organism is more juvenile than its ancestors. Paedomorphism can take place due to two main reasons; Neoteny and Progenesis. Neoteny is the condition where the germ cell development of an organism takes place in the required rate but, the somatic cell development is retarded. Progenesis is the condition where the somatic cell development of an organism takes place in the required rate but the germ cell development is accelerated, thus giving accelerated sexual maturation. The key difference between Neoteny and Progenesis is the type Paedomorphism they show. Neoteny shows a retarded somatic cell growth and a normal germ cell growth whereas, Progenesis shows accelerated germ cell growth and normal somatic cell growth.

CONTENTS

1. Overview and Key Difference
2. What is Neoteny
3. What is Progenesis
4. Similarities Between Neoteny and Progenesis
5. Side by Side Comparison – Neoteny vs Progenesis in Tabular Form
6. Summary

What is Neoteny?

Neoteny is commonly seen in young individuals, where they show retarded somatic cell growth and a normal germ cell growth. The normal germ cell growth corresponds to the parental germ cell growth.  A germ cell is referred to as a gamete and it undergoes meiosis. The two main germ line cells are the ovum cell and the sperm cell. The somatic cells correspond to all the non-germ line cells and they undergo mitosis during their cell division phase.

In Neoteny the individuals have a normal sexual development phase whereas their growth and development of other cells and cellular activities are retarded. Neotenic changes may include the flat face, short arms and legs and large head. In the initial stages of development, the neotenic changes are not observed, but with the maturation of the organism or the individual, they can be more prominently observed.

Neoteny is a resultant of a mutation that is epigenetic. Thus, the mutation is resulting from an extrinsic factor such as the environment. These acquired mutations may influence the body’s metabolism and the production of biochemicals including enzymes, growth factors, and hormones, etc. In Neoteny, the sexual developmental features remain unaltered in most instances. The emotional responses to stimuli are also normal in most neotenous organisms.

What is Progenesis?

Progenesis refers to the condition where an organism shows normal somatic cell growth that resembles its parent generation but has an accelerated germ cell development. Therefore, the sexual maturation of organism is undergoing in an accelerated manner during the progenesis. Progenesis is much faster and rapid process. Therefore, during Progenesis, the juvenile organisms show advanced sexual characteristics such as secondary sexual characteristics, etc.

What are the Similarities Between Neoteny and Progenesis?

• Both Neoteny and Progenesis lead to Paedomorphism and show juvenile characteristics.
• Both Neoteny and Progenesis take place due to heterochronic mutations.
• Both Neoteny and Progenesis are related to the development processes.

What is the Difference Between Neoteny and Progenesis?

Summary – Neoteny vs Progenesis

Heterochrony is an abnormality in the timing of the development events of an organism. Paedomorphism resulting from heterochronic mutations can be mainly categorized as Neoteny and Progenesis. Neoteny shows a normal sexual development as parents but shows retarded somatic cell development. Progenesis shows normal somatic cell development but shows an increased germ line cell development. The acceleration of the sexual maturation is seen during the progenesis. Progenesis is much faster and rapid. Thus both conditions are giving rise to juvenile organisms disturbing the growth rate of the organism. This is the difference between neoteny and progenesis.

Reference:

1.“Timing is Everything: Morphogenesis, Heterochrony and Evolution.” Heterochrony. Available here
2.Denoël, M, and P Joly. “Neoteny and progenesis as two heterochronic processes involved in paedomorphosis in Triturusalpestris (Amphibia: Caudata).” Proceedings of the Royal Society B: Biological Sciences, U.S. National Library of Medicine, 22 July 2000. Available here  

Image Courtesy:

1.’Human development neoteny body and head proportions pedomorphy maturation aging growth’By Ephert – Own work, (CC BY-SA 4.0) via Commons Wikimedia