| dc.description.abstract | The uptake of Rhodamine-labelled bacteria by cod larvae was
demonstrated using a fluorescent microscopy technique, which
allowed a quick estimate of bacterial uptake and gut clearance.
Live or heat-killed bacteria, isolated from cod-eggs, were
rapidly ingested by larvae at yolk-sac and older stages. A
substantial uptake could be seen after 15 min exposure, and
eventually the bacteria became densely packed in the digestive
tract.
Some morphological details in the developing gut of the cod
larvae could be observed after ingestion of the fluorescent-labelled
bacteria. In yolk-sac larvae, bacteria were bound in
discrete areas in the midgut, indicating clustering of receptors
or internal folding or segmentation of the gut. In older
larvae, which had ingested bacteria or other cells, the hindgut
was never emptied, not even after starvation. The results
indicate that particles of undigested material are retarded in
the hindgut, and that probably absorption by endocytosis takes
place in this area.
The results reported in this paper point to a possible role
for bacteria in the early life of cod larvae. Aspects discussed
include the mechanism of uptake of bacteria, entrapment
in the gut, digestion or elimination of bacteria by extracellular
or intracellular processes, and the role of an
indigenous microflora with respect to feeding strategies and
health hazards of cod larvae. | en |
