M.Sc. / At present 35 species of Argulus are recognized in Africa. From a summary of the literature available for Argulus species in Africa it is clear that species descriptions are often the only information available for the majority of species. Information on the anatomy and histology of African Argulus species is even more scant. However, previous literature reveals that the anatomy and histology of the digestive system is similar in most branchiurans. The first study includes a description of a poorly known Argulus species described using SEM. Sixteen male and one female specimen of Argulus personatus Cunnington, 1913, were collected from Bathybates ferox Boulenger, 1898, from Lake Tanganyika in northern Zambia. Results from light and scanning electron microscopy (SEM) examinations documented a thickening of cuticle located on the dorsal surface between the last thoracic segment and abdomen, which was rectangular in shape; the pre-oral spine and the proboscis ornamented with simple scales; a set of 3 large simple setae on the distal end of the basal plate; the dorsal distal end of second podomere of the maxillae ornamented with scales resembling those of a fish; the second and third podomeres of maxillae ornamented with two types of pectinate scales (with fine bristle-like ends and scales with large pointed ends); the ventral distal end of third and fourth maxillary podomeres bearing large teardropshaped scales; a pair of tubular structures present adjacent to the anterior projection; a peg on the fourth pairs of legs of males bearing shallow grooves running irregularly across surface; and an accessory cushion bearing minuteprojections. These characters found in A. personatus were addressed in a redescription. The digestive system of Argulus japonicus metanauplii is described following reconstruction from serial sections. The similarities between the larval and adult digestive system are described. Both digestive systems consist of an oesophagus, oesophageal funnel, anterior midgut, midgut enteral diverticula, posterior midgut and a hindgut. Histologically, the foregut of both the adult and larva consist of cuboidal epithelium and both the adult and larval hindguts are composed of columnar epithelium. Despite the similarities between the adults and larvae some differences exist. Differences include that the epithelium lining of the midgut of newly hatched larvae contain yolk. The midgut diverticula are less ramified than in the adult. The posterior midgut is lined with large swollen cuboidal epithelium with large vacuoles and a ciliated border whereas the adult posterior midgut is lined by large papilliform cells. Argulus japonicus larvae only survive a day after hatching without nutrition from a host and once the first stage larvae start to feed on host tissue they feed mainly on epithelial cells and mucus. There was no blood observed in the lumen of the digestive system. It is concluded from the study that much work remains concerning the taxonomy of African species. Many of the species remains inadequately described and new identification keys must be created. New environmentally safe treatments should be a focus of future development. Also, many physiological aspects of the argulid digestive system remain unknown and provide another focus of future research. / Prof. A. Avenant- Oldewage
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:12443 |
| Date | 16 October 2008 |
| Creators | Tam, Quinton |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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