SPECTROFLUOROMETRIC QUANTIFICATION OF NEUTRAL AND POLAR LIPIDS SUGGESTS A FOOD-RELATED RECRUITMENT BOTTLENECK FOR JUVENILES OF A DEPOSIT-FEEDING POLYCHAETE POPULATION
Bt. Hentschel, SPECTROFLUOROMETRIC QUANTIFICATION OF NEUTRAL AND POLAR LIPIDS SUGGESTS A FOOD-RELATED RECRUITMENT BOTTLENECK FOR JUVENILES OF A DEPOSIT-FEEDING POLYCHAETE POPULATION, Limnology and oceanography, 43(3), 1998, pp. 543-549
A growing body of evidence suggests that juveniles of species that dep
osit feed as adults are more susceptible to food limitation than are c
onspecific adults. To quantify ontogenetic variations in the nutrition
al condition of the deposit-feeding polychaete Pseudopolydora kempi ja
ponica, I modified existing spectrofluorometric assays of neutral and
polar lipids. The hydrophobic fluorochrome Nile red fluoresces yellow-
orange when bound to neutral lipids and red-orange when bound to polar
lipids. The ratio of neutral lipids (energy storage) to polar lipids.
(cell membranes) provides an index of nutritional condition that is sc
aled to body size. For individual P. kempi japonica ranging in length
from 2 to 12 mm, I quantified the florescence from each lipid class an
d analyzed size-dependent variations in the neutral/polar lipid ratio.
P. kempi japonica showed a size-dependent increase in the neutral/pol
ar lipid ratio up to a body length of similar to 6-8 mm; Little size-d
ependent change in the ratio occurred beyond this size. Ontogenetic ch
anges in both particle-size selection and the assimilated diet of P. k
empi japonica display size-dependent patterns that are similar to the
lipid data. Together, the three lines of evidence suggest that P. kemp
i japonica juveniles experience a food-related recruitment bottleneck
until they grow to similar to 6-8 mm. Once juveniles grow beyond this
size, they appear to forage like adults and achieve adult levels of ne
utral lipid. Because deposit-feeding benthos ingest a low-quality and
nutritionally dilute diet that will be difficult for small juveniles t
o digest, ontogenetic niche shifts and food-related recruitment bottle
necks during the juvenile stage may be common in the population ecolog
y of species that deposit feed as adults.