Dk. Branstrator, PREDICTING DIET COMPOSITION FROM BODY LENGTH IN THE ZOOPLANKTON PREDATOR LEPTODORA-KINDTI, Limnology and oceanography, 43(3), 1998, pp. 530-535
Leptodora kindti and many other species of zooplankton predator range
widely throughout temperate-zone lakes, yet these species are rarely i
ncluded in size-based studies of food webs. This oversight derives mai
nly from a lack of predictive functions that quantify their effects on
prey communities. With laboratory experiments I measured the handling
time and phosphorus ingestion of L. kindti fed three cladoceran speci
es radiolabeled with P-33 as a tracer of dry weight (DW). In general,
laboratory results show that predator body length exerts strong influe
nce on maximum prey length, on prey handling time (and indirectly pred
ation rate), and on prey profitability (expressed as mu g DW ingested
time(-1)) in systematic ways that may be useful in predicting predator
y effects of L. kindti on natural prey communities. The prey-capturing
structure of L. kindti, called the trap basket, constrains the maximu
m length of prey that is consumable, and handling times on prey increa
se exponentially as prey length approaches the maximum dimensions of t
he trap basket. The empirical relationship is given by the following e
quation: Handling time = 1/[0.067(Trap basket length/Prey length - 1)(
0.436)]. I use handling time and body length data to evaluate the pred
ictive nature of two previously published regression models that relat
e L. kindti trap basket length to body length. This note offers a leng
th-based approach to analysis of diet composition in L. kindti that wi
ll hopefully encourage increased consideration of this species in futu
re studies of food webs.