A comparison of absorption and assimilation efficiencies between four species of shallow- and deep-living fishes |
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Authors: | Jeffrey C Drazen Kim R Reisenbichler Bruce H Robison |
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Institution: | (1) Department of Oceanography, University of Hawaii, 1000 Pope Rd, Honolulu, HI 96822, USA;(2) Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA |
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Abstract: | We captured two species of deep-sea zoarcids, Melanostigma pammelas and Lycodapus mandibularis, from Monterey Bay California and maintained them in the laboratory. One shallow-water zoarcid, Eucryphycus californicus, and an ecologically and morphologically similar stichaeid fish Xiphister atropurpureus were collected from intertidal and subtidal habitats in Monterey Bay. We investigated the absorption and assimilation efficiencies
of these fishes to determine whether deep-sea species have evolved mechanisms to increase their efficiency of food use. Fishes
were placed in experimental chambers and fed a known quantity of food. Ammonia excretion was measured and feces were collected
daily. Both food and feces were analyzed for water, protein, lipid and ash to determine specific absorption efficiencies.
Absorption ranged from 87.7 to 92.4% and assimilation efficiencies from 84.0 to 86.5%. Meal sizes from 0.5 to 4.0% of body
weight did not affect the results. No significant differences were found between deep-sea and shallow-water species fed single
meals or fed ad libitum for 10 days. This suggests that the selective pressure to maximize absorption and assimilation is
universal and is not affected by the productivity of the habitat occupied. However, the relative size of the intestine in
the deep-sea species was significantly smaller suggesting that they had a lower metabolic cost to maintain their digestive
apparatus. It could not be concluded whether this was the result of pressure to conserve energy or rather the tendency of
the shallow-living species to ingest more refractory material (i.e. sediment, algae). |
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