On the Sexual Biology of Pandalus Borealis (crustacea Decapoda) Iii. the Initiation of the Female Phase by D. B. Carlisle

In the second paper of this series (Carlisle, 1959b) I have described the results of various experimental manipulations upon the termination of the male phase in the protandric hermaphrodite Pandalus borealis Kmyer. In this paper I shall be concerned with the effects of such interference upon the initiation of the female phase of the life history. In a number of papers Panouse (1943-8) provided evidence, based upon extirpation experiments, that the sinus gland of the eyestalks of the common European prawn Palaemon (= Leander) serratus secretes a hormone which inhibits the development of the ovary and in particular vitellogenesis. His results were confirmed by Takewaki & Yamamoto (1950a, b), who worked upon the Japanese prawn Paratya. Since the above work was completed much evidence has accumulated that the sinus gland is not in itself an endocrine organ, but a neurohaemal organ (Carlisle & Knowles, 1953); that is to say it is the terminal organ of a neurosecretory system, whose main function is to release into the blood hormones produced elsewhere, within neurosecretory cells. It is generally (but not universally) accepted that the hormones stored in the sinus gland, and released into the blood there, are produced mainly within the neurosecretory cells of the ganglionic X organs (see discussion in Carlisle & Knowles, 1959). In agreement with this view I have found that, both in Palaemon (Carlisle, unpublished) and in the Mediterranean prawn Lysmata seticaudata (Carlisle, 1953a, b), it is possible to extract an ovary-inhibiting substance from the sinus gland and from the ganglionic X organ which lies in the medulla terminalis of the brain (see Carlisle, I953c). This substance, after intravenous injection, produces involution of the developing ovary in the intact animal, or effectively counteracts the result of eyestalk ablation, so far as ovarian growth is concerned. Extirpation of the sinus glands alone leads to an increase in ovarian weight significantly less than does total eyestalk ablation-as indeed Panouse also found. Ablation of the ganglionic X organ of the medulla terminalis leads to a delayed onset of increase in ovarian size, but once this increase has begun it proceeds as rapidly as after total eyestalk ablation (Carlisle, unpublished). We may