COURTSHIP BEHAVIOR IN THE DWARF SEAHORSE, HIPPOCAMPUS-ZOSTERAE

The seahorse genus Hippocampus (Syngnathidae) exhibits extreme morphol ogical specialization for paternal care, with males incubating eggs wi thin a highly vascularized brood pouch. Dwarf seahorses, H. zosterae, form monogamous pairs that court early each morning until copulation t akes place. Daily behavioral observations of seahorse pairs (n = 15) w ere made from the day of introduction through the day of copulation. F our distinct phases of seahorse courtship are marked by prominent beha vioral changes, as well as by differences in the intensity of courtshi p. The first courtship phase occurs for one or two mornings preceding the day of copulation and is characterized by reciprocal quivering, co nsisting of rapid side-to-side body vibrations displayed alternately b y males and females. The remaining courtship phases are restricted to the day of copulation, with the second courtship phase distinguished b y females pointing, during which the head is raised upward. In the thi rd courtship phase, males begin to point in response to female pointin g. During the final phase of courtship, seahorse pairs repeatedly rise together in the water column, eventually leading to females transferr ing their eggs directly into the male brood pouch during a brief midwa ter copulation. Courtship activity level (representing the percentage of time spent in courtship) increased from relatively low levels durin g the first courtship phase to highly active courtship on the day of c opulation. Males more actively initiated courtship on the days precedi ng copulation, indicating that these seahorses are not courtship-role reversed, as has previously been assumed.