The Physiology of the Brood Pouch of the Male Sea Horse Hippocampus erectus

In the spotted seahorse, Hippocampus erectus Perry, the male carries the eggs and young in an abdominal brood pouch, which provides a controlled environment for development. During the incubation period, the sodium ion concentration of the fluid within the pouch increases while the serum sodium remains relatively constant. The calcium concentration of the pouch fluid decreases as incubation progresses. Also, radioactive calcium is taken up by the embryos in the pouch. Young removed from the pouch show a greater mortality when placed into full strength sea water than do those introduced into 0.4 sea water. The pouch provides optimum ionic and osmotic conditions for development and serves as an osmotic adaptation chamber for the young. The anatomical relationships between embryos and paternal tissue, and the histology of the pouch epithelium are described. Histochemical analysis of glycogen, lipid, and phospholipid are given for animals in the various stages of brooding and non-brooding.