Ed. Lund et al., Annual cycle of plasma lipids in captive reared striped bass: effects of environmental conditions and reproductive cycle, FISH PHYS B, 22(3), 2000, pp. 263-275
Protein, lipid and fatty acid concentrations in plasma of eight male and ei
ght female six year old captive striped bass (Morone saxatilis) were monito
red monthly over the course of two reproductive cycles as part of an effort
to investigate the time course of lipid class mobilization and subsequent
deposition in gonads. Total protein levels (44.2 +/- 0.67 mg ml(-1), range
20.6-86.4) showed seasonal fluctuation, but did not vary with sex. Total li
pid concentrations in the plasma of both males (17.7 +/- 0.61 mg ml(-1)) an
d females (14.1 +/- 0.64 mg ml(-1)) showed seasonal fluctuations with the l
owest levels in late Spring during spawning. Plasma lipids in females were
significantly (p < 0.0001) lower than those of the males except during earl
y ovarian secondary growth. Analysis of the lipid class composition reveale
d that the decrease in plasma lipid concentrations in females prior to spaw
ning is primarily due to a decrease of up to 50% in the phospholipid conten
t of the plasma relative to males. Striped bass vitellogenin was found to c
ontain approximately 20% lipid by weight with nearly 80% of the lipid being
phosphatidyl choline (PC). Vitellogenin levels previously measured in thes
e individuals were highest during the winter months and decreased in the 2
months prior to spawning. Although mature striped bass oocytes are rich in
wax esters, no wax esters or fatty alcohols were found in the plasma. Analy
sis of the fatty acyl composition of separated lipid classes suggests that
PC is the primary carrier of the essential (n=3) fatty acids 22:6 (DHA) and
20:5 (EPA) to the gonads. Fatty acid analysis of the lipids associated wit
h vitellogenin revealed that levels of essential fatty acids were low relat
ive to vitellogenin-borne lipids from other teleosts. The lack of detectabl
e wax esters in plasma lipids of female striped bass suggests that these ab
undant lipids in mature eggs are synthesized within the oocytes.