Endocrine and environmental control of reproduction in Polychaeta

Abstract

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 spermmaturation 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.Résumé : Chez les polychètes, comme chez de nombreux invertébrés, la reproduction est sous le contrôle de facteurs de l'environnement et de facteurs endocriniens. L'objet essentiel de cette synthèse est le contrôle endocrinien de la reproduction; des données plus fragmentaires ont trait aux effets des facteurs environnementaux. Puisque les Nereidae sont les polychètes les mieux connus, l'étude de leur stratégie monotélique épigame est envisagée dans un premier point. Toutefois, malgré de nombreuses observations physiologiques, peu de données biochimiques sont disponibles, si l'on excepte l'isolement récent de plusieurs phéromones. Celles-ci, comme l'acide urique et le disulfure de L-cystéine glutathion, sont des substances ubiquistes qui, de ce fait, doivent être présentes en concentrations élevées afin de pouvoir exercer une action physiologique. Les résultats obtenus chez les espèces itéropares font l'objet d'un second point. La stratégie de stolonisation des Syllidae, le contrôle de la vitellogenèse des Nephtyidae, des Phyllodocidae, des Polynoidae et des Cirratulidae, ainsi que le contrôle de la maturation des gamètes des Arenicolidae et des Pectinariidae sont examinés. Comme dans le cas des Nereidae, notre compréhension du contrôle endocrinien repose essentiellement sur des données expérimentales. Seul est identifié le facteur de maturation des spermatozoïdes d'Arenicola. Ainsi, malgré les nombreuses études expérimentales réalisées chez les polychètes et les multiples actions hormonales décrites dans les processus de reproduction, la nature des hormones, leurs cibl...

The endocrine control of reproduction in Nereidae: a new multi-hormonal model with implications for their functional role in a changing environment

“…The animal's ability to regenerate lost segments is greatly reduced (Golding 1967), and this is coupled with a decrease in the growth rate of the animal. At the same time, the gametes begin to develop (Clark & Ruston 1963;Clark & Scully 1964;Andries 2001). The stage of oocyte development appears to be correlated with the regenerative ability of the animal.…”

“…Furthermore, Golding (1983) reported little or no change in cerebral endocrine activity throughout gametogenesis in N. diversicolor. Oocytes only became homogeneous during the final five months when the juvenile hormone titre was found to decline (Golding 1983;Andries 2001). In addition, oestradiol-17b has recently been isolated from the coelomic fluid of N. virens where it has been shown to promote the secretion of vitellogenin by the eleocytes of mature females (Garcia-Alonso et al 2006).…”

Evaluation of different procedures for fertilization and larvae production inHediste diversicolor(O.F. Müller, 1776) (Nereididae, Polychaeta)

“…In many polychaetes species, body growth and gametogenesis are controlled by a hormone produced by the cerebral neuroendocrine system, which is also essential for segment regeneration processes (Andries, ; Golding, ; Lawrence & Soame, ). In nature, the transition from short to long photoperiod is an important factor for the start of the gametogenesis.…”

Annual Variation of the Reproductive Activity of Three Exogoninae Species (Polychaeta: Syllidae) from the Western Mediterranean

“…Much literature has been published on the many different reproductive strategies in polychaetes (Wilson, 1991; Giangrande, 1997). The mechanisms involved in reproductive processes are now a main topic in Polychaeta research, and the life cycles and the control and triggering of gamete development and spawning have been studied in several species (Andries, 2001). Most such work, however, has been performed under laboratory conditions and refers to species that can be easily cultured.…”