Etude cytochimique et ultrastructurale de l'�volution ovocytaire de Nereis pelagica L. (Ann�lide Polych�te)

Endocrine and environmental control of reproduction in Polychaeta

In Polychaeta, as in many invertebrates, reproduction is controlled by both environmental and endocrine factors. Although the effects of environmental factors on reproductive behaviour are briefly discussed, this review focuses on the endocrinology of reproduction. As Nereidae are the most intensively studied polychaetes, their epigamic monotelic strategy is discussed first in this review. Although a large number of physiological observations have been made, biochemical data have been greatly lacking until recent years, except, however, for the recent isolation of several pheromones. These substances, such as uric acid and L-cysteine gluthathione disulfide, occur widely and must be present at high concentrations in order to exert their physiological effects. Results obtained from iteroparous species are also considered. The stolonization strategy of Syllidae, the control of vitellogenesis in Nephtyidae, Phyllodocidae, Polynoidae, and Cirratulidae, and the regulation of gamete maturation in Arenicolidae and Pectinariidae are discussed. As with Nereidae, our knowledge of endocrine control is mainly based on experimental data, since only sperm-maturation factor in the genus Arenicola has been identified. Therefore, despite numerous interesting experimental studies in which functional roles for polychaete reproductive hormones have been described, their nature, their primary targets, and their mechanism of action are unfortunately still largely unknown.

The annulate lamellae--from obscurity to spotlight

This review aims to provide a comprehensive and in-depth survey of a cell organelle, the annulate lamellae, that is widely distributed and especially prevalent in both female and male sex cells as well as tumor and cancer cells. The organelle is also present in many somatic cells and plant cells. Emphasis is placed on the contributions that electron microscopy and associated experimental approaches have made in providing information about the distribution, ultrastructure, morphogenesis and relationships of annulate lamellae to other cellular organelles, especially the nuclear envelope and endoplasmic reticulum, as well as cell product. An increasing number of experimental manipulations have recently been shown to alter, either increase or decrease, the amount of annulate lamellae and these studies are explored in depth. Information about the origin and morphogenesis of annulate lamellae in different cells is summarized and extensive coverage is given to several hypotheses about possible annulate lamellae function. A detailed bibliography provides a thorough compilation of research dealing with annulate lamellae. A major goal of this extensive review is to generate increased awareness of, and interest in, this cell organelle for students and investigators of the cell who, by bringing current techniques in cell and molecular biology to bear, might focus and intensify studies on the function of an organelle whose precise role in the cell is presently enigmatic.

Endocrine programmed development and reproduction in Nereis

The pattern of cerebral endocrine activity in Nereis diversicolor is characterized by the maintenance of a high plateau of activity prior to, and during most of, the time occupied by gametogenesis. During the closing stages of the life cycle, the rate of secretion is progressively reduced, resulting in the production of a homogeneous population of gametocytes and subsequently in their final maturation. Secretion has been assayed in terms of the regeneration-promoting, maturation-inhibiting, and gametotrophic activities of the hormone. Assays involved transplantation of living brains, in some cases between animals at different stages of maturity, but evidence is presented that the activity of such brains reliably reflects their rate of secretion in situ. Cerebral control of growth and maturation is probably mediated by a single hormone, an ordered sequence of events occurring as different thresholds for hormone action are reached in turn.

A light- and electron-microscopic investigation of gametogenesis in Typosyllis pulchra. (Berkeley and Berkeley) (Polychaeta: Syllidae). II. Oogenesis

Oogenesis in Typosyllis pulchra begins with a short proliferative gonial phase. Gonial clusters, consisting of six to eight syncytial sibling cells, are surrounded by gonial peritoneum and are eventually liberated into the coelom. At about the same time as the onset of the coelomic phase, one gonial cell in each cluster differentiates, begins to accumulate yolk and increases in size, eventually to become a mature oocyte. Yolk is composed of lipid droplets and membrane-bound protein granules. The protein component appears to be at least partially synthesized by the oocyte. Yolk is composed of lipid droplets and membrane-bound protein granules. The protein component appears to be at least partially synthesized by the oocyte although there are some signs of endocytosis. Nurse cells and peritoneal cells are apparently able to manufacture some protein that may also be utilized by the oocyte. The nurse cells maintain cytoplasmic continuity with the oocyte, and mitochondria and ribosomes are often seen within the intercellular bridges between oocyte and nurse cell. Immediately prior to spawning, oocytes undergo prematuration and cytoplasmic reorganization. Ultrastructural changes which occur during oocyte growth and maturation are described.

[Control of determination and the differentiation of the sexual somatic characters of Nereids (Annelida Polychaeta)]

The modalities of determination and differentiation of sexual dimorphism of Nereids (Annelida Polychaeta) were investigated inNereis pelagica L. andPerinereis cultrifera G. with experiments involving decerebration, castration (by X irradiation), grafts or injection of genital products.The sexual somatic characters of the parapodial cirri (swelling and crenellations) always develop according to the genetic sex, whatever the genital state of the Nereis and the nature of the intervention. Therefore the determination of the sexual somatic characters of the parapodial cirri appear to be determined in a very precocious and stable way (at least 3 months before the genital differentiation).The pygidial papillae, a male sexual character in normal conditions, can be formed by very young females in which heteronereidation is realized prematurely by decerebration, and by females of any age in which heteronereid transformations are realized in a male environment (e.g. by injection of genital products, or grafting onto a male). Therefore the pygidial papillae may be determined precociously in either sex; however their differentiation is normally inhibited in females in the course of genital maturation.