Control of the Reproductive Cycle in Female Eulalia Viridis (Polychaeta: Phyllodocidae)

Abstract

Eulalia viridis (L.) is one of a group of polychaete species which are being used in an experimental analysis of the regulation of gametogenesis and reproduction. The back-ground to these studies and some of the preliminary results have been discussed recently by Olive (1980). Despite the abundant data demonstrating the frequent occurrence of well-defined reproductive cycles in marine invertebrates and observations on the correlations between reproductive events and environmental conditions, the mechanisms by which the reproductive cycles of individual species are controlled are very poorly understood. It has generally been accepted since the publication of the important paper of Orton (1920) that the temperature cycle in temperate and boreal regions plays an important role in determining the reproductive cycle, but the nature of the control mechanism is not, in general, understood and is likely to vary markedly between species. Environ-mental conditions such as relative daylength or biological factors such as the quantity and identity of the phytoplankton organisms (Himmelman, 1978, 1979) could also play important roles in regulating the sequence of cellular events which culminates in successful reproduction. These general problems have been discussed by Giese (1959) and more recently by Barnes (1975), Giese & Pearse (1975) and specifically in relation to Polychaeta by Clark (1979) and Olive (1980).

The influence of photoperiod on oocyte growth and its role in the control of the reproductive cycle of the polychaeteHarmothoe imbricata(L.)

“…A similar system has been postulated in the case of Eulalia viridis [9], concerning the response to elevated temperature. In the case of H. imbricata, at appears that the endogenous Downloaded by [University of Glasgow] at 15:50 18 September 2013 time sense may be reset by the increasing day length regime during the first wave of vitellogenesis, although the roles of the period of exposure to day lengths below the critical value, and the passage from below the critical value to above it in this resetting process, are not as yet understood.…”

“…Each sink was covered and illuminated by a single 15 W tungsten filament bulb, operated by an automatic timing switch. Groups of animals were kept under constant day length regimes of 8,9,10,11,12,13,14 or 15 h of daylight per day. Food, in the form of pieces of the spionid polychaetes Scolelepis squamatus or Malacoceros fuliginosus was supplied once per week, and the water in the beakers was changed the day after each feed.…”

Gonadotrophic hormone inEulalia viridis(Polychaeta, Annelida): Stimulation of vitellogenesis

“…Although low temperature inhibits oocyte growth, females exposed to elevated temperatures before January fail to develop a population of full-sized oocytes. In NE England this endogenous regulation is removed progressively in the period January-March so that by that time oocyte growth is controlled by external temperature (Olive, 1981a). The precise mechanism of control is not known, but an endocrine involvement in the regulation of the potential for oocyte growth is not unlikely.…”

The effects of climate change on the reproduction of coastal invertebrates

“…In E. viridis , temperature alone moderates gametogenesis although there is an endogenous component to the cycle that ultimately dictates the development of the oocytes (Olive 1980). Oogenesis and vitellogenesis are initiated in the spring with breeding occurring in the summer (Olive 1975, Franke & Pfannensteil 1984).…”