Effects of cocoon incubation angle on hatching success of medicinal leeches (Hirudo spp.)

ABSTRACT Protocols for hirudiculture have not been fully established; many issues need to be investigated. The present study aimed to determine the effects of the cocoon incubation angle (CIA) on hatching success in hirudiculture, using leech species of Hirudo verbana. Cocoons were individually incubated in jars at three different angles, horizontally (0°), angled (45°), and vertically (90°) for one month. The rot in cocoons, which was 17.5% in cocoons incubated horizontally, decreased gradually as the CIA increased, was 2.5% in cocoons incubated vertically. The average number of offspring obtained from cocoons increased as the CIA increased. The optimum CIA was determined to be 78.73° and 60.63° for the lowest rot in cocoons and the highest number of offspring, respectively. The present study revealed that although not statistically significant the CIA is a variable affecting the hatching success of medicinal leeches during the incubation period. This result is thought to be because the air ventilation inside the cocoons is more efficient in cocoons positioned at an angle or in a vertical position compared to cocoons incubated in a horizontal position. For profitable hirudiculture, we recommend that cocoons be positioned at an angle close to vertically, more than 60° during incubation.