An in vitro assay for gonadotrophic hormone in the polychaete Nephtys hombergii Sav. (Nephtyidae)

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.

Induction of egg spawning in Gibbula umbilicalis (da Costa) by an homogenate of the cerebral ganglia

A putative egg-spawning neurohormone (ESH) has been demonstrated in extracts of the cerebral ganglia from the prosobranch gastropod, Gibbula umbilicalis, using an in vivo bioassay. The active principle is not sex-specific, although spawning in males cannot be induced with injections of ganglion extracts. A partial characterization of the ESH indicates that it is a stable peptide. ESH activity could be detected in the bioassay at a level of 0.625 cerebral ganglion equivalent in a dilution series ranging down from 5.0 ganglion equivalents, with 1.25 ganglion equivalents being the most potent dose. Egg release could be induced for only a short period of the year in vivo, but this period corresponded well with that of natural spawning in the field.