Changes in yolk
total proteins and lipid components and embryonic growth rates during
lobster (Homarus americanus) egg development under a simulated
seasonal temperature cycle
V. Sibert, P. Ouellet, J-C. Brêthes-2004
Marine Biology, 144(6):
1075-1086
Abstract:
From August 2000 to June 2001, seven egg-carrying
female lobster (Homarus americanus) from the Îles de la Madeleine
population (Gulf of St. Lawrence, Canada) were held under a simulated
seasonal temperature cycle to monitor egg development from extrusion to
hatching. For the first time, changes in the yolk components (total lipids
and major lipid classes, total proteins) and embryo growth of single eggs
were monitored separately over the entire development period. Under the
controlled temperature conditions, egg development proceeded in three
phases. (1) Autumn, from extrusion to early December, was marked by a rapid
increase in the Perkins's
eye index and rapid declines in yolk total proteins and triacylglycerols
(TAG). Embryo daily growth rate was estimated between 1 and 2 µg
proteins day–1. (2) Winter, from late December to early April
(temperature stable at ca. 1°C) was characterized by a stationary phase in
the evolution of the eye index and yolk lipid use, and embryo growth slowed
significantly. (3) Spring, from late April to hatching in June was the
period with the most rapid changes in yolk TAG and embryo growth rates >6 µg
proteins day–1 were recorded. Almost 65% of the live biomass
(total proteins) of the hatching larvae was accumulated during the last few
weeks of development. An index of embryo growth efficiency was estimated as
the slope of the relationship between embryo total proteins and yolk TAG
during egg development. A relationship was found between the initial mean
egg dry weight and the embryo growth efficiency index suggesting that under
the same experimental conditions bigger eggs used yolk lipids more
efficiently and sustained faster embryonic growth than smaller eggs. The
relationship may also explain why larger larvae originate from larger eggs.
(Institut des sciences de la mer
de Rimouski (ISMER), Université du Québec à Rimouski (UQAR), 310 allée
des Ursulines, Rimouski, Québec, G5L 3A1, Canada, e-mail: virginie_sibert@uqar.uquebec.ca)