Factors Influencing the Prospect of Asexual Reproduction in Holothuria Arenicola (Semper, 1868)

Asexual reproduction by transverse fission was studied in populations of Holothuria arenicola through investigation of different factors affecting the fission and survival rates. Size, fission position, and temperature impacts were experimentally assessed. It was observed that higher fission rate was recorded in small specimens as compared to large ones. The fission position at 30% yielded higher fission rate (90%) as compared to that obtained in 45% fission (70%). Temperature showed a considerable effect on either fission or survival rate with a direct proportional relationship between temperature and both rates. At 20°C, fission started in the 2nd day to be at rate of 20% which was gradually increased until reaching 100% by the 8th day; sharp decline of survival rate was occurred reaching 35% by the 9th day. At 25°C, fission reached 70% by the 8th day; the survival rate became constant at 50% from the 17th day onward. At 30°C, the highest fission rate was attained in the 4th day but the survival rate was zero in the 5th day. It was noted that the woundhealing period took longer time at 30°C than at 20°C and 25°C. Additionally, changes of anterior parts (A) and posterior parts (P) internal organs were followed weekly over two months after fission induction to detect both of the dissolved structure and regenerated one.