Structure and function of ciliated peritoneal funnels in the toad kidney (Bufo marinus).

Scanning electron microscopy revealed 600-800 ciliated peritoneal funnels opening onto the ventral surface of each kidney in Bufo marinus. The size and configuration of funnel apertures vary greatly, but individuals course beneath the kidney surface before opening into peritubular blood vessels. Injections of India ink into the peritoneal cavity demonstrate that cilia lining the peritoneal funnels create a current carrying peritoneal fluid into the renal vasculature. Clearance of fluid by the funnels was dependent on pressure in the peritubular vessels, and was increased by arginine vasotocin. Ciliated peritoneal funnels may provide an important route for return of lymphatic fluid from the peritoneal cavity to the vasculature.