Changes in respiration and excretion rates of boreal zooplankton after capture (Saanich Inlet, British Columbia, Canada)

Brief description

The herbivorous copepods, Calanus plumchrus and Paracalanus parvus, the herbivorous euphausiid, Euphausia pacifica, the carnivorous amphipod, Parathemisto pacifica and the carnivorous ctenophore, Pleurobrachia pileus used in this experiment were collected from Saanich Inlet, British Columbia, Canada, between May and August 1975.All animals, except for Paracalanus parvus, which were used immediately, were left overnight in unfiltered sea water collected from the same site as the zooplankton. Zooplankton were then maintained in 300 to 500 ml beakers containing well aerated filtered seawater in a constant temperature room at 10°C ± 1°C. Two different feeding regimes were used for the experiment, with one group of each species fed excess food and the other starved by placing the zooplankton in filtered sea water only. Calanus plumchrus, Paracalanus parvus and Euphausia pacifica were fed a diet of cultured Chaetoceros spp., originally collected from the same site as the zooplankton. Parathemisto pacifica were fed chopped fresh Euphausia pacifica and Pleurobrachia pileus were fed freshly collected Calanus plumchrus.Prior to starting the experiment, a subsample was taken from each species, except for the ctenophore, Pleurobrachia pileus, to establish the mean dry body weight of the experimental animals. At the end of the experiment, the mean dry body weight of the survivors was also determined. Dry body weight was measured by placing specimens in a desiccator over silica-gel at approximately 20°C for 1 week. For Pleurobrachia pileus, the equatorial diameter, measured by placing each specimen with a small amount of sea water in a shallow dish under the dissecting microscope was used as a measure of body size.Respiration rate was measured with an oxygen electrode (YSI oxygen monitor system). Zooplankton were incubated in a 6.3 ml cell with filtered water for 20 to 30 minutes. Rates of ammonia and inorganic phosphate excretion were measured after removing the zooplankters from the cell, rinsing with filtered sea water and incubating in 30 to 40 ml of filtered sea water in a small beaker fitted with a glass lid for 2 to 4 hours. Ammonia and inorganic phosphate were determined by the phenol-hypochlorite and molybdate methods, respectively. Zooplankters, except for Paracalanus parvus, which was too small to handle repeatedly without damage, were then returned to beakers, with or without food, for subsequent measurements. Depending on the species, zooplankters were maintained between 3 and 49 days, with between 3 and 10 respiration and excretion measurements taken over the maintenance period.On day 34 of the experiment, the body surface of starved Calanus plumchrus specimens were observed to be covered with epiphytic pennate diatoms, which were later identified as Navicula spp. Licmophora sp and Synedra sp.. By day 49 both starved and fed Calanus plumchrus were covered with these diatoms. Respiration rates and ammonia and phosphate excretion rates were measured in herbivorous and carnivorous species of zooplankton, maintained under different feeding regimes, to determine whether the previously observed progressive decreases in respiration and excretion rates of some zooplankton species kept in the laboratory after capture, was due food shortage. This experiment is a component of the project "The effect of laboratory conditions on the extrapolation of experimental measurements to the ecology of marine zooplankton".

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The method used to measure respiration rate is described in: Ikeda T (1976) The effect of laboratory conditions on the extrapolation of experimental measurements to the ecology of marine zooplankton. I. Effect of feeding condition on the respiration rate. Bull. Plankton Soc. Japan 23, 1-10.Ammonia and inorganic phosphate were determined by methods described in:Strickland JDH and Parsons TR (1972) A practical handbook of seawater analysis. Bull. Fish. Res. Bd Can. 167, 1-310.The results for days 34 and 49 for Calanus plumchrus were compromised due to the presence of epiphytic pennate diatoms on the body surface of starved specimens at day 34 and on both fed and starved individuals by day 49. The implications of the presence of epiphytic pennate diatoms is discussed in:Ikeda T (1977) A pelagic marine copepod associated with diatoms. Bulletin of the Plankton Society of Japan 24: 115-118.The starved replicates were not successful for Parathemisto pacifica because cannibalism occurred in all but 1 replicate as soon as the experiment began. Young larvae appeared in one of the fed replicates of Parathemisto pacifica on day 4. A large number of larvae was produced in all replicates of fed Pleurobrachia pileus from day 5.

Notes

Credit
Ikeda, Tsutomu, Dr (Principal Investigator)