Variability in the gut contents of individual A cartia tonsa from waters off Southern California |
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Authors: | G S Kleppel R E Pieper G Trager |
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Institution: | (1) Fish Harbor Marine Laboratory, University of Southern California, 820 South Seaside Avenue, 90731 Terminal Island, California, USA;(2) Present address: Noya University Oceanographic Center, 8000 North Ocean Drive, 33004 Dania, Florida, USA;(3) Present address: Boston University Marine Program, Marine Biological Laboratory, 02543 Woods Hole, Massachusetts, USA |
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Abstract: | The gut contents of 169 individual Acartia tonsa from Los Angeles Harbor, California, USA, were measured during a 24 h period (16–17 June 1986) by gut pigment (fluorescence) and microscopic analyses. Individual gut-pigment levels varied 10-fold or more within sampling intervals. Some copepods with moderate (0.2 to 0.5 ng) to high (>0.5 ng) gut-pigment levels were present in samples from both day and night collections. While the percentage of copepods containing>0.5 ng pigment was about the same during the day (8%) as at night (10%), the percentage of copepods with 0.2 to 0.5 ng pigment rose from 17% during the day to 55% at night. Significant differences between pigment levels in copepods collected before and after evening twilight were suggestive of a nocturnal feeding habit regardless of intense individual variability in gut-pigment content. Food in the gut was distributed in parcels, indicative of intermittent feeding that potentially contributes to individual variability. Feeding was not synchronized during most of the day and night, but synchrony increased at evening and morning twilights. Although synchrony declined after evening twilight, individual gut-pigment contents were relatively elevated in most of the nighttime samples. Thus, active feeding seems neither to require nor to imply synchrony. |
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