Revista Chilena de Historia Natural 77 (4): 607-616, 2004
RESEARCH ARTICLE
Mandible characteristics and allometric relations in copepods: a reliable method to estimate
prey size and composition from mandible occurrence in predator guts
The size and shape of the cutting edge of the mandibles from the five most abundant
copepod species found in Mejillones Bay are described with the aim to create a helpful tool for the identification of copepod prey and
their size from predator gut contents. Good allometric relationships were found between the carapace length and the mandible width
for the species Paracalanus parvus, Centropages brachiatus and Acartia tonsa. By contrast, the
cyclopoids Oithona sp. and Corycaeus sp. did not present a good relationship between these two
parameters, presumably due to the presence of more than a species in the study area. Applying the edge index (Itoh 1970) the
copepods were classified as herbivores (e.g., P. parvus), omnivores (e.g., C. brachiatus and A.
tonsa), and carnivores (e.g., Oithona sp.). In general, there was a tight relationship between the
morphometric characters of the mandible blade and the trophic ecology of each species. The good relationship between the mandible
width and the carapace length of the calanoid species will permit the estimation of the size of an ingested copepod by a predator, within
a certain degree of accuracy, by measuring the width of the mandibles found in gut contents. This relationship and the supplementary
characterization of the mandible blade will help improve the knowledge of the feeding ecology of the mesozooplankton in northern
Chile.
Key words:
copepod mandibles,
feeding habits in copepods, gut content analysis, Humboldt Current System
