Individual Variability in Lipid Content of Bivalve Larvae Quantified Histochemically by Absorption Photometry

摘要

Lipid energy reserves in individual larvae of the Teredinid bivalve, Bankia gouldi (Bartsch), were quantified photodensitometrically after staining whole larvae with the lipid-specific stain. Oil Red O. A modification of the two-wavelength densitometric technique of Mendelsohn (1966) was used to document variability in stored lipid in healthy larvae and larvae under imposed nutritional stress. The results were compared with analytically derived total lipid values for the same larval groups. A third wavelength was added to the two-wavelength technique to allow direct background subtraction of tissue and shell absorbance on individual larvae. Lipid content in individual larvae was estimated photodensitometrically to range from a mean of 7 ng in 3-day-old straight hinge larvae, to 175 ng in pediveliger larvae lost which were competent to metamorphose. During starvation, lost lipod at a rate of about 20 ng/day while a loss of 1-2 ng/day/larva was evident in 6-day-old early umbo larvae. Variability in lipid content between individuals of the population was analyzed by frequency histogram and by the product of the third moment to detect abnormal distribution about the mean, i.e. skewness. The variability was high in healthy larvae. It increased substantially during starvation. It is suggested that analysis of lipid energy stores of individuals within zooplankton populations may provide valuable insight into the capacity of natural assemblages to cope with stress, be it chemical, thermal, physical or biological in nature.