Effects of temperature and
food ration on gonad growth and oogenesis of the green sea urchin, Strongylocentrotus
droebachiensis
C. L. Garrido, B. J. Barber-2001
Marine Biology, 138(3): 447-456
Abstract:
To assess the effects of both temperature and food
ration on gonad growth and oogenesis of the green sea urchin, Strongylocentrotus
droebachiensis (O.F. Müller), individuals collected December 1996
(winter experiment) and June 1997 (summer experiment) were maintained for 3
months in one of four experimental treatments: (1) 3 °C and fed ad libitum
(high ration), (2) 3 °C and fed one-seventh of the maximum ration
(low ration), and (3) 12 °C and fed the high ration; (4) 12 °C and fed the
low ration. All individuals were fed an artificial diet and exposed to only
1 h of light every day. At the end of both experiments, mean gonad indices
of sea urchins fed the high ration had increased significantly (11-24% and
6-19% in the winter and summer experiments, respectively), while the gonad
indices of individuals fed the low ration did not change. At the high ration
(both experiments), the increase in gonad index of sea urchins occurred
primarily as the result of a significant increase in the mass of nutritive
phagocytes, as revealed by histological analyses. Primary oocytes were
significantly larger in individuals held at 3 °C than at 12 °C throughout
the winter experiment, regardless of food ration; during the summer
experiment, primary oocytes were significantly larger in individuals
receiving the high ration, regardless of the temperature at which they were
held. These results suggest that: (1) food availability is the most
important factor regulating energy storage and the relative size of gonads
throughout the year, (2) temperature affects the rate of growth and
maturation of primary oocytes during the later stages of oogenesis, and (3)
once gametogenesis has been initiated, mature ova will be produced, even
under conditions of low food availability. Conditions of high food
availability in summer and low temperature in winter would thus favor
reproductive output in sea urchin populations.
(School of Marine Sciences, University of Maine,
Orono, ME 04469, USA, E-mail: bjbarber@maine.edu)