Omnivory in the calanoid
copepod Temora longicornis: feeding, egg production and egg hatching
rates
H.G. Dam, R.M. Lopes-2003
Journal of Experimental Marine Biology and Ecology,
292(2): 119-137
Abstract:
We measured in laboratory experiments the ingestion,
egg production and egg hatching rates of female Temora longicornis as
a function of diet. The diets consisted of a diatom (Thalassiosira
weissflogii), an autotrophic dinoflagellate (Heterocapsa triquetra),
and a bacterivorous ciliate (Uronema sp.) given as sole foods, or
combinations of these single-food items: diatom+dinoflagellate,
diatom+ciliate, dinoflagellate+ciliate, and diatom+ciliate+dinoflagellate.
For the three single-item diets, the functional response was similar; i.e.,
ingestion rate increased linearly with food concentration (food range: ~25
to ~600 µg C l-1). When all diets were considered, maximum daily
carbon ration (~70% of body weight) was independent of food type. However,
the maximum daily egg production rate (12% of body carbon) was obtained with
the diatom diet. For all diets, both ingestion and egg production rates
increased with food concentration. Ingestion and egg production rates were
affected differently by the interaction of food concentration and food type:
at low food concentrations, ingestion rates were highest on diets containing
the diatom. At high food concentrations, egg production rates were highest
on the two phytoplankter diets and their combination. The presence of the
ciliate in the diet did not enhance ingestion rate or egg production.
Mixed-food diets did not enhance egg production relative to single-food
diets. Hence, dietary diversity did not appear to be particularly
advantageous for reproduction. Carbon-specific egg production efficiency
(EPE; egg production/ingestion) was independent of food concentration and
type, and equaled 9%. Egg hatching success was low (mean<30%) and
independent of food concentration and type, and egg production rates. Our
results are consistent with previous observations that egg production in T.
longicornis is enhanced during diatom blooms. However, the relatively
low EPE and egg hatching success suggest that reproduction and recruitment
in this study were severely constrained by the biochemical composition of
the diet, or the physiological condition of the females towards the end of
their season of growth in Long Island Sound.
(Department of Marine Sciences, University of Connecticut, Groton, CT
06340-6048, USA, e-mail: hans.dam@uconn.edu)