Abstract
M.Sc. (Zoology)
Temperature plays a very important role in the metabolic
environment of coldblooded animals such as fish.
The primary objective of this study was to evaluate the quality
of digestive processes and the importance of temperature in the
digestive system of Labeo capensis. An important consideration
in the choice of the experimental animal was the economic
potential and widespread occurrence of Labeo capensis in the riversystems
of the Transvaal.
The experimental animals were kept at three different acclimation
temperatures ( 14, 19 and 25 + 1°C) for a period of six weeks.
An assessment of the influence of acclimation temperature on
enzyme activity vas made using test kits supplied by BOERINGER-MANNHEIM.
No information exists on the morphohistology of Labeo capensis
and therefore investigation on the anatomy of the digestive
system was carried out in this survey.
The ventro-anterior mouth is ideally situated for bottom-feeding.
Pharyngeal teeth and a pharyngeal pad (or palatal organ) is
situated dorsally at the entrance to the oesophagus.
A short oesophagus, which possesses both a supra- and infraoesophageal
valve, exists. No stomach is present and the
intestinal bulge affixes the intestine to the oesophagus.
The exceptionally Iona intestinum proper lies coiled in the
abdominal cavity. No rectum can be identified.
The micro-anatomy of the intestinal proper and bulge differs
minimally. The intestinal bulge possesses longer, slimmer villi
in comparrison of the flat thickened villi of the intestine
proper. The bulge lacks a longitudinal muscle layer.
L. capensis cellulase and dicarrboxylase activty may be
contributed to the intestinal microflora and/or foodstuffs
present in the digestive system.
Amylase possesses the highest and the proteases (trypsin and
chymotrypsin) the lowest activity.
The effect of acclimation temperature is most evident on amylase,
and to a lesser extent on the phosphatases. Trypsin and
chymotrypsin activity is less affected by acclimation temperature,
although a distinctive loss of activity is recorded for both these
enzymes. The loss of acid phosphatase activity is partially
contributed to the rise in intestinal pH.
The effect of reaction temperature was measured and recorded as
AT-values.