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Ph.D. / Female adult specimens of Lamproglena clariae attach to gill filaments of freshwater fish of the family Clariidae, penetrate the gill tissue and consume blood. Previously, studies have been done on the taxonomy of this parasite, but little research has been published on biological aspects. Hence, it was the aim of this study to determine and record L. clariae’s aspects of biology such as ecology, life cycle and pathology. The study was conducted through both field and laboratory observations with specimens collected from the Vaal Dam and Vaal River Barrage. A positive correlation was observed between the host's physical dimensions and the size of the parasite, parasites from both sites preferred the fourth gill and the median part of the gill arch for attachment. There was no significant host gender preference by parasites. Three free living nauplius stages, four copepodite, a cyclopoid and adult stages were recorded as life stages of this parasite. Observations suggested that development of larval stages of L. clariae is influenced by both photoperiod and temperatures. Furthermore low infestation success of the experimental fish was observed. This parasite caused localised infestation as varying degrees of swelling of gill filaments were observed only in the vicinity of its attachment site. Histological examination revealed epithelial hyperplasia, resulting in fusion of gill lamellae and necrosis of the host tissue in the vicinity of the parasite. No correlation exists between the infestation intensity and fish haematocrit values. Although L. clariae causes localized infestation, high intensity of infestation may be detrimental to the fish. Hyperplasia of epithelial tissue resulting in fusion of lamellae would result in restriction of oxygen passage and thus hinder the process of respiration of the host. / Prof. A. Avenant-Oldewage

Copepods comprise an ecologically important role in freshwater and marine ecosystems, which is why they are often considered an important ecotoxicological model organism. The International Organization for Standardization’s (ISO) 14669 protocol is the only guideline for the determination of acute toxicity in three European marine copepod species: Acartia tonsa. The goal of this project was to assess the feasibility of establishing and maintaining cultures of Acartia tonsa, as well as to refine current culturing and egg separation methods. Initial culture methodology proved difficult for consistent production of eggs and collection of nauplii. The development of an airlift system for the separation of eggs from nauplii and adults, based on size, successfully increased the availability of eggs, nauplii and adults. The sensitivity and relative conditions of the copepod species was assessed by running a series of 48h acute toxicity tests with the reference toxicants 3,5-dichlorophenol, 4,4’-methylenebis(2,6-di-tert-butylphenol. The acute 48 hour median lethal dose concentration (LC50), the no observed effect concentration (NOEC), and the lowest observed effect concentration (LOEC) was analyzed for the three reference compounds for of A. tonsa.

The study investigated biological and ecological parameters controlling and influencing the production and distribution of the free-swimming larval stages of Lepeophtheirus salmonis (Kroyer, 1838), and to a lesser extent Caligus elongatus Nordmann 1832, in the natural environment The reproductive output of L. salmonis was influenced by seasonal effects. The number of eggs produced per brood showed an inverse relationship with increasing temperature. The number of eggs per brood was also influenced by adult female body size (cephalothorax length), which in itself exhibited an inverse relationship with increasing temperature. Photoperiod had no significant effect upon the number of eggs produced or on adult female size. Mean egg size of L. salmonis varied significantly over the year; larger eggs were produced during the summer months and smaller eggs over the winter. However, factors controlling the size of the eggs were not elucidated. The proportion of viable eggs per L. salmonis ovisac remained constant throughout the year. Large variations in egg number per egg string were found in both L. salmonis and C elongatus populations sampled at one point in time. These were attributed in part to phenotypic variation in adult female size and also the number of broods individual females had produced. Egg viability was not correlated with brood size, but mean egg size was related to the number of eggs per brood. Experimental studies indicated that hatching and development of L. salmonis was highly variable. The percentage of eggs hatched and the time period over which hatching occurred varied markedly, even when held under constant and optimal environmental conditions. Temperature did not affect hatching success or viability of the nauplius I stage, although at higher temperatures the period over which hatching occurred was reduced. Low and medium salinities caused a significant decrease in both hatching success and nauplius viability. Photoperiod had no effect on initiation of hatching. Hatching occurred in a manner similar to that observed in free-living copepods. The nauplii were enclosed by two egg membranes, the outer one bursting within the ovisac, the inner one after the ovisac membrane has split. Swelling of the egg and its subsequent hatching was attributed to osmotic effects, with water being taken up from the external environment. Development was also highly dependent upon both temperature and salinity. At 5'C, nauplius 11 stages failed to enter the moult to the copepodid stage. At 7.5'C, although moulting was initiated, in a large proportion of cases it was not successfully completed. At I O'C, development to the copepodid stage was successful. Nauplii only developed successfully to the copepodid stage at salinities of 25%o or greater. Copepodids raised under optimal conditions then exposed to a range of salinities had a greater salinity tolerance than nauplii. Biochemical analysis of the eggs of L. salmonis revealed that lipids constituted a large proportion of their dry weight. Naupliar stages contained a discrete area containing lipid which decreased in size over time, suggesting that the free-swimming larval stages utilised this as an energy reserve. Rate of depletion was faster in nauplii held at higher temperatures. Longevity, activity and infectivity of the infective stage decreased with age. However, both spontaneous and stimulus dependent activity ceased many hours before death and both activity and longevity were affected by temperature. Infectivity of I day old L. salmonis copepodids was higher than 7 day old larvae, and was considered to be related to the size of the energy reserves. The settlement and distribution pattern of copepodids did not change with age of copepodid, the majority being recorded from the fins. All three L. salmonis free-swimming larval stages demonstrated a "hop and sink" swimming pattern. The velocity and duration of both passive sinking and active swimming was recorded for both nauplii and copepodids. Although greater periods of time were spent passively sinking, the speeds obtained during both upward spontaneous and stimulated swimming meant that a net upward movement of larvae in the water column occurred. At higher temperatures spontaneous swimming activity increased, whilst low salinities caused a cessation of such ability. L. salmonis larvae were positively phototactic and negatively geotactic. As well as their positive responses to light intensity, the nauplius 11 and copepodid stages reacted positively to blue-green spectral wavelengths. Moulting times were relatively short, although the larvae were not able to swim during such periods. No relationship was found between the level of lipid reserves and the overall buoyancy of the larvae. Naupliar stages of both L. salmonis and C. elongalus were obtained from the water column as a result of a plankton sampling programme at a commercial Atlantic salmon farm. No copepodid stages of either species were found. There was no difference in the vertical distribution of the two L. salmonis naupliar stages. Live larvae tended to aggregate between 0 and 5m in depth, with no diurnal vertical migration. Dead nauplii, and those with low lipid reserves, were found deeper in the water column. Naupliar stages, and in particular the first larval stage, were concentrated in number within cages indicating that the cages have a retentive characteristic. A novel control method in the form of a commercially available light lure was tested. Though increasing the numbers of free-living copepods captured, it had no effect on the numbers of L. salmonis naupliar or copepodid stages obtained in plankton samples. The present study has therefore provided valuable data concerning the biology and ecology of the free-swimming larval stages of sea lice, in what was a comparatively poorly understood area.

M.Sc. / There are 39 known species of Lamproglena to date. A review of all species including the species name, the author, as well as an accompanying sketch and information regarding the distribution, pathology and host preference is given. Lamproglena clariae is a copepod gill parasite found on Clarias gariepinus. It has been observed that they cause extensive gill tissue proliferation, which may interfere with respiration. It is uncertain on which tissue type Lamproglena feeds, as red blood is never apparent in the gut of Lamproglena monodi, whereas in the cases of both L. clariae and L. barbicola they undoubtedly feed on blood, proven by the frequently blood-filled gut. Even thought the mouthparts are not fully understood as yet, it is deduced that feeding involves only the maxillae and maxillipedes. Many poecilostomes lacks mandibles. Also, in the lernaeids the mandible is appendage is the smallest and from the 39 known Lamproglena species, the mandibles are described in only eight species. This study examines the digestive tract and the structure of the mouthparts using both light and scanning electron microscopy and tracts the nerves to establish if L. clariae does possess mandibles. Specimens were collected from Clarias gariepinus in the Vaal Dam after the fish were euthanised and the gills removed. The samples were fixed in an aceto formaldehyde alcohol solution and preserved in 70% ethanol prior to dehydration and embedding in resin. Serial section were made at 5 pm and stained with a trichrome stain. A schematic as well as graphic reconstruction of the digestive system is presented. The digestive system consist of three predominant parts, the fore, mid and hindguts. The foregut has a cuticularised epithelium. The oesophagus has a muscle layer iv which stretched and contracts in order to aid feeding and it extends into the midgut via a funnel-like structure. There are four designated zones within the midgut. The hindgut is a simple, cuticle lined tube. Cell structures are discussed. The bilobed protocerebrum in L. clariae is present. The deutocerebrum innervates the antennules. The tritocerebrum consist of two lobed parts and innervates the antennules. The ventral nerve cord is situated posterior to the cephalon. It protrudes dorsally, from where the posterior commissures innervates. The anterior commissures innervates closer to the tritocerebrum. The nerves leading to the mandibles are innervated from the anterior commissure. The more posteriorly located commissure innervates the nerve to the seta located between the antennae and the maxillae. Both the nerves to the maxillae and the endopodite to the maxillae are innervated from this commissure. Mandibles were left out of previous species descriptions of L. clariae. Other Lamproglena species descriptions, showing the mandibles, revealed slender looking mandibles located in close proximity to the mouth opening. This is contrary to the stout mandibles of L. clariae. Future research topics are highlighted and discussed