ISSN:
1095-8649
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Ambassidae in the estuaries of south-east Africa are represented by three species which belong to the same trophic level and are similar in external appearance and feeding ecology. Investigations of osmoregulatory capabilities, salinity tolerances and temperature tolerances showed that, under local estuarine conditions, Ambassis productus is a euryhaline species with the ability to maintain a stable internal osmotic concentration in salinities less than 10%o. A. gymnocephalus is essentially stenohaline and is able to maintain internal stability only in salinities greater than 28%o. A. natalensis is moderately euryhaline and is incapable of maintaining a constant blood osmolality in salinities above 30%o and below about 7%o. Feeding ecology studies show that all three species feed mainly on zooplankton, but when physical conditions in estuaries allow overlap in the distribution of two or more species, certain mechanisms increase separation. A. productus feeds mainly on suspended and benthic organisms during the night and early morning, whereas A. natalensis feeds mainly during the day and early evening on insects at the water surface. A. gymnocephalus excludes insects from its diet and preys almost exclusively on zooplankton in the water column.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1095-8649.1989.tb03076.x
