Which statement accurately describes DDE's effect on eggshell formation?

Which statement accurately describes DDE's effect on eggshell formation?

• A. It increases shell thickness
• B. It blocks calcium from reaching eggs during shell formation
• C. It accelerates eggshell formation
• D. It has no effect on eggshells

Answer: (B)

Calcium transport to the site where the eggshell is formed is the key process here. In birds, the eggshell is built in the shell gland as calcium carbonate is deposited around the developing egg, and calcium must be delivered from the bloodstream to the shell formation site. DDE interferes with how calcium is transported and utilized in that tissue, so less calcium reaches the shell during formation. The result is thinner, weaker shells that are more prone to breaking, which matches the observed effect of DDE exposure. This is why the statement describing DDE as blocking calcium from reaching the egg during shell formation best captures the mechanism. It’s not about increasing thickness or speeding up formation, and there is a real effect on shell quality.

Calcium transport to the site where the eggshell is formed is the key process here. In birds, the eggshell is built in the shell gland as calcium carbonate is deposited around the developing egg, and calcium must be delivered from the bloodstream to the shell formation site. DDE interferes with how calcium is transported and utilized in that tissue, so less calcium reaches the shell during formation. The result is thinner, weaker shells that are more prone to breaking, which matches the observed effect of DDE exposure. This is why the statement describing DDE as blocking calcium from reaching the egg during shell formation best captures the mechanism. It’s not about increasing thickness or speeding up formation, and there is a real effect on shell quality.