Ontogenetic constraints on foraminiferal test construction

Area of Science:

• Evolutionary biology
• Developmental biology
• Paleontology

Background:

• Developmental processes significantly constrain adult morphology and evolutionary diversification.
• Spiral shell coiling patterns in organisms offer insights into developmental constraints and evolutionary trade-offs.

Purpose of the Study:

• To investigate the disparity of coiling patterns in planktic foraminifera using quantitative morphometrics.
• To understand the role of developmental constraints in shaping foraminiferal evolution and morphological conservatism.

Main Methods:

• Synchrotron radiation X-ray tomographic microscopy (SRXTM) was used to reconstruct shell morphology.
• Raupian parameters were measured to quantify coiling patterns and disparity across eight representative species.

Main Results:

• Foraminifera display a limited range of coiling patterns, indicating morphological conservatism.
• Early ontogeny shows highly similar coiling patterns across species, suggesting strong, common developmental constraints.
• Morphological disparity and evolutionary innovation are primarily observed in the adult stages.

Conclusions:

• Developmental constraints, particularly in early ontogeny, limit the potential for novel forms in foraminifera.
• Changes in accretion and translation during ontogeny accommodate new chamber shapes and influence adult morphology.
• The conservative nature of foraminiferal development may explain the repeated evolution of similar morphotypes throughout their history.