The posterior part of the kidneys of most male snakes is sexually dimorphic. A portion of the distal tubules, called the "sexual segment", shows a seasonal enlargement and cellular changes. A phospholipid secretion is produced here and is incorporated into the seminal fluid. | The posterior part of the kidneys of most male snakes is sexually dimorphic. A portion of the distal tubules, called the "sexual segment", shows a seasonal enlargement and cellular changes. A phospholipid secretion is produced here and is incorporated into the seminal fluid. |