Fertilization mode differentially impacts the evolution of vertebrate sperm components

Area of Science:

• Evolutionary biology
• Comparative genomics
• Reproductive biology

Background:

• Environmental changes drive organismal diversification, including cellular morphology.
• Fertilization mode (external vs. internal) is a proposed driver of sperm diversity.
• The impact of fertilization mode on specific sperm components (head, midpiece, flagellum) is not fully understood.

Purpose of the Study:

• To investigate how fertilization mode influences the evolution of sperm component lengths in vertebrates.
• To identify component- and clade-specific evolutionary responses in sperm morphology.

Main Methods:

• Comparative analysis of sperm component lengths across 1103 vertebrate species.
• Phylogenetic comparative methods to assess evolutionary patterns.
• Examination of species with external and internal fertilization.

Main Results:

• Fertilization mode partially explains variation in sperm component lengths across vertebrates.
• The influence of fertilization mode on sperm evolution differs among sperm components and vertebrate clades.
• Rapid midpiece evolution occurs in both external and internal fertilizers, independent of fertilization mode.

Conclusions:

• Fertilization mode shapes vertebrate sperm evolution through complex, component- and clade-specific mechanisms.
• Sperm evolution is not solely dictated by fertilization mode, with other factors driving rapid changes in components like the midpiece.