Abstract
Amphipods are the most ubiquitous animals, after nematodes, on earth. Although
there are several terrestrial amphipod species, most are aquatic. They are
familiar animals in the water table exposed in cave environments and boreholes.
The food source on which the amphipods depend was not directly observable in
the cave environments frequented by the amphipods. In order to establish the
role cave-dwelling amphipods play in ecology, the primary purpose of this study
was thus to determine what cave-dwelling amphipods feed on.
Amphipod, water and sediment samples were collected from five different caves,
in the northern part of South Africa, namely Koelenhof Cave, Sterkfontein Cave,
Ficus Cave, Peppercorn’s Cave, and Irene Cave. Following collection and
transportation, resulting in zero amphipod mortalities, all of the samples were
transferred to rectangular fish tanks stored in an environmental room, set up in
such a way as to mimic the conditions in the caves as closely as possible. Long
term adaptability and survival proved to be a successful undertaking, resulting in
the death of only two amphipods per tank.
Scanning electron microscopy was used to observe the mouthparts of the
amphipods in order to begin establishing their feeding behaviour.
Standard microtechniques were carried out to establish the general histological
orientation and histology of the gastrointestinal tract. A Histochemical
Fluorescent staining method was employed, and a reddish-orange fluorescence
was observed, thereby indicating the presence of mucous in the GIT.
Several feeding experiments were carried out, and it was established that on
average amphipods can survive without a food source for a maximum of sixty
ABSTRACT
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days. Through a series of different feeding experiments, it was determined that
amphipods ingest bat faeces, leaf litter, sediment and yeast, with leaf litter
producing the highest rate of survival. It was also observed that amphipods,
regardless of body size, are predators, scavengers, and cannibals, which may
provide an explanation as to why amphipods display evasive behaviour.
Microbiology plays a vital role in determining what amphipods feed on, and
therefore water, soil, and digestive contents of amphipods were studied using a
wide array of microbiological analyses: Heterotrophic Plate Counts; Total
Coliforms; Faecal Coliforms; Faecal Streptococci; Confirmatory test for
Escherichia coli; Detection of Clostridium, Pseudomonas, and Salmonella.
According to the South African Bureau of Standards, the quality of the water
contained within all four of the caves in this study may not be used for human
consumption prior to undergoing various purification processes.
Once the role that cave-dwelling amphipods play in ecology has been firmly
established it may then be possible to make use of amphipods as biological
indicators, because since they inhabit cave streams and groundwater and are
sensitive to pollutants, declines in their populations could indicate a decline in the
water quality in their streams and surrounding groundwater supply.
Dr. J.F. Durand