Revista Chilena de Historia Natural 81 (1): 69-81, 2008
RESEARCH ARTICLE
Stranded algal wracks on a sandy beach of south central Chile: feeding and habitat
preferences of juveniles and adults of Orchestoidea tuberculata (Nicolet), (Amphipoda, Talitridae)
The amphipod Orchestoidea tuberculata, is the numerically dominant
scavenger in the upper intertidal levels of sandy beaches from south central Chile. The main food source for juveniles and adults of this
amphipod are the macroalgae stranded on the beach. Experiments of food preferences were carried out to analyze the eventual
partition on the most common macroalgae on that beaches (Durvillaea antarctica, Macrocystis pyrifera
y Lessonia nigrescens) by .juveniles and adults of this amphipod. While juveniles preferred to consume L.
nigrescens, adults showed a significant preference for D. antarctica. Similar to the laboratory results, that of field
studies shows that juveniles of O. tubercula ta did not show significant preferences between D. antarctica
and M. pyrifera, while adults preferred to consume D. antarctica instead of M.
pyrifera. That suggest that D. antarctica is an important source of food (and habitat), for adult amphipods.
Due to the fact that L. nigrescens could not be included in the field experiments, the possibility that juveniles also prefer
this macroalgae in those conditions remains as an open question. Although the reasons underlying the differences in the food
preferences of juveniles and adults are unknown, two possibilities can be proposed: ontogenetic changes in the morphology of mouth
structures used for feeding and/or ontogenetic changes in nutritional requirements. However, the fact that juveniles preferred to
consume the macroalgae with the lowest nutritional content (L. nigrescens) among the three species offered as food,
suggest another explanation to the observed differences. This refers to the fact, that by preferring different food ítems, juveniles can
avoid the cannibalism of adults, biological interaction previously demonstrated for O.
tuberculata.
Key words:
exposed sandy
beaches, stranded macroalgae, food preferences, amphipods, south central Chile
