Controlling Growth And Reproduction In The American Lobster

Abstract

ABSTRACT Somatic and reproductive growth are antagonistic in the lobster, and it is difficult to manipulate one without affecting the other. High temperature may accelerate ovary maturation but cause ovary reabsorption due to molt cycle acceleration. Sustained high temperature promotes rapid molting but may also interfere with ovary development. In the natural environment lobsters have seasonal cycles of molting and are refractory to warm water during winter months. This annual cycle is regulated by the eyestalk neurosecretory complex and can be eliminated by eyestalk ablation. The relationship between temperature and molt frequency is linear between 5 and 20 C. At lower temperatures this relationship can be modified by photoperiod, but at 20 C or higher the effect of photoperiod disappears. Eyestalk ablation may have a place in the culture process but ecdysterone shows little potential because of excessive cost and unpredictable results with intact animals. Vitellogenesis occurs in two distinct phases separated by a coldwater period, and is inhibited during premolt. Each age class of female has a characteristic pattern of molting and reproductive events, and molt and oviposition do not always occur in alternate years. When molt is due to occur shortly after oviposition, the eggs will not be extruded and the ovary will be reabsorbed. Embryonic development shows the same temperature relationship as molting and the two may be very similar, indicating that larval hatching can be spread throughout the year by simple temperature manipulation.