Nesting environment may drive variation in eggshell structure and egg characteristics in the Testudinata

Area of Science:

• Zoology
• Evolutionary Biology
• Herpetology

Background:

• Testudines (turtles) display significant variation in eggshell calcification.
• This calcification influences embryonic water physiology, calcium metabolism, and gas exchange.
• The evolutionary drivers behind different turtle eggshell types remain largely unexplored.

Purpose of the Study:

• To investigate the underlying reasons for variations in turtle eggshell calcification.
• To explore the relationship between eggshell type, reproductive parameters, and environmental factors.

Main Methods:

• Phylogenetically controlled analyses were conducted on approximately 200 turtle species.
• Data included egg size, shell mass, clutch size, and body size.
• Species were categorized based on laying either rigid- or pliable-shelled eggs.

Main Results:

• Eggshell type influenced relative egg breadth, egg mass, and relative shell mass.
• Clutch size, egg size, and total clutch shell mass were not significantly affected by shell type.
• Calcium availability appears linked to body size, potentially mediating clutch and egg size.
• Nesting environment pH may be a key factor, with low pH potentially leading to thicker shells for protection against erosion.

Conclusions:

• Turtleshell calcification differences may reflect adaptations to nesting environment acidity rather than solely reproductive strategies.
• Nest pH could influence eggshell integrity and erosion, driving variations in calcification.
• Calcium availability and nest pH may interact to constrain clutch size.
• Further research is needed to confirm the correlation between turtle eggshell calcification and nest pH.