A population of three-spined stickleback, Gasterosteus aculeatus L., was sampled every two weeks for 14 months from Airthrey Loch on the campus of the University of Stirling. A total of 857 fish were collected and three species of parasites were studied. The monogenean Gyrodactylus gasterostei was found on the skin and fins and two myxosporean parasites, Sphaerospora elegans and Myxobilatus gasterostei, were present in the kidney. All parasite species were present throughout the year but abundance was correlated with the yearly life cycle of the host fish. Lower prevalence and intensity were observed in summer due to the large number of young fish in the samples. The comparative ultrastructure and development of the two myxosporeans was studied by light and transmission and scanning electron microscopy. Both myxosporeans followed the general pattern of myxosporean development but showed some novel features. Sphaerospora e/egans had two distinct developmental cycles. A proliferative cycle involving extrasporogonic stages occurred in the blood whereas spore production occurred in the kidney. Light microscopy of Giemsa stained blood smears suggested proliferation of extra-sporogonic stages by external budding or plasmotomy. Structural similarities between extra-sporogonic blood stages and sporogonic kidney stages are discussed. Although S. elegans mostly formed disporous plasmodia, monosporous plasmodia were also occasionally observed. Before the appearance of sporogonic cells within the early pseudoplasmodia, certain areas of pseudoplasmodial cytoplasm became electron lucent, eventually acquired cell organeUes and later appeared as sporogonic cells. Developing valvogenic cells contained protuberances at the posterolateral side of spores which disappeared in mature spores. Characteristic lipid bodies were seen in developing capsulogenic cells and developing uninucleated sporoplasmic cells contained abundant glycogen granules. The sporoplasmic cells were devoid of sporoplasmosomes. Plasmodia of M. gasterostei were mono, di or polysporous and showed features of both coelozoic and histozoic myxosporeans, including a unit surface membrane, simple pinocytosis aanand presence of a number of vegetative nuclei and generative cells, the latter which formed pansporoblasts before the initiation of sporogenesis. A membrane bound tubular structure and some electron dense fibrillar bundles are previously undiscovered cytoplasmic organelles of the plasmodia. Developing capsulogenic cells contained characteristic membrane bound vacuoles filled with electron dense (glycogen) material. Myxobilatus gasterostel attached to the epithelial cells by plasmodial surface projections and there were electron dense areas at the point of attachment. Sphaerospora elegans showed occasional hairlike processes projecting from the pseudoplasmodial surface to the microvillous brush border of the epithelial cells. There were no electron dense areas at the point of attachment to the epithelial cells of the kidney tubules. Early undifferentiated pre-sporogonic stages of both parasites were occasionally present intracellularly in the tubular epithelium suggesting this is a route of entry into the tubular lumen. Early stages of S. elegans were also seen in the capillary lumen of the glomerulus. Intracellular and intraluminal stages of S. elegans and M. gasterostel caused pathological changes in different ways. Histopathological changes associated with S. elegans included vacuolation and accumulation of electron dense material in the epithelium whereas M. gasterostei caused large vacuolation with necrosis of the epithelial layer. Both parasites caused destruction of glomerular tufts in heavy infections and an increased number of rodlet cells in the epithelial layer were common in both cases. The two myxosporean species were most abundant during the winter and spring. Extra-sporogonic stages of S. elegans were found only in January and June in the rete-mirabile of the eye, circulating blood and kidney. In infections with S. elegans sex of the host fish was apparently of no significance, whereas significantly lower infestations occurred in male sticklebacks infected with M. gasterostei compared with females. Host size was important in determining the prevalence and intensity of both myxosporean species. Older fish were less heavily infected, possibly due to an acquired immunity or pathogenic effects on the host. A high number of mixed infections indicated that there was no interspeciflc competition between the two parasites. There appeared to be a continuous recruitment of myxosporeans throughout the year. Studies on myxosporean spore shedding suggested that spore production and shedding was continuous throughout the year and was uninfluenced by temperature or season. Gyrodactylus gasterostel was generally more abundant in winter and spring than in summer and autumn, reflecting the greater numbers of small young of the year fish at these times. The age of the host fish was a significant factor influencing the prevalence and intensity of infestation with G. gasterostei. Sex of the host had no apparent influence on infestation. The parasite was highly overdispersed within the host population and its distribution was best fitted by the negative binomial.

This research study is divided into 4 major sections. Section A deals with the world-wide distribution of the haematoprotozoan parasites of marine fishes. These are tentatively divided into 3 major groups: the Haemogregarines, the Trypanosomes and the Trypanoplasms and one group of ill defined and controversal organisms including Haemohormidium sp. and Dactylosoma sp. The results of extensive surveys of the coastal waters of France, Scotland and Wales with added examples from the Mediterranean Sea substantiate the zoogeographical distribution of these parasites. Two species of haematoprotozoan parasites Haemogregarina simondi and Trypanosoma soleae are re-described, earlier accounts dating from the beginning of the century being considered incomplete. A new species of haemogregarine is described from the farmed turbot (Scophthalmus maximus) as Haemogregarina sachai n. sp. and an unidentified species of Haemohormidium found occasionally in turbot and Dover sole (Solea soles) is also described. In addition Haemogregarina sp. were encountered in certain wild marine fish from the Atlantic coast of France e. g. Zeus faber, Sebastes sp., Trisopterus luscus, Pagellus bogaraveo and Raja sp. and from the coastal waters of Malta e. g. Peristedion cataphractum and Oblade melanura. However, they were not found in sufficient numbers to allow a definite description. The value of surveys of wild fish populations is discussed in the light of zoogeographical distribution, the apparent periodicity of these parasites and a seasonal variation of parasitism. Section B attempts to summarize the knowledge of the mode of transmission of marine haematoprotozoan parasites by piscicolid leeches as intermediate hosts and vectors. The developmental stages of a trypanosome, probably Trypanosoma murmanensis from the Atlantic cod Gadus morhua are described in the marine leech Calliobdella nodulifera. Stages of a haemogregaririe were observed in the same leech. The development of the turbot haemogregarine Haemogregarina sachai n. sp. in artificially infected leeches is also described up to the 20th day post infection. Transmission of this haemogregarine to apparently uninfected turbot via this leech was not successful. Various stages of development of Haemogregarina simondi are described in its apparently natural vector, the marine leech Hemibdella soleae, and transmission with infected leeches to apparently healthy hatchery reared soles was achieved. Thus it was shown for the first time that marine leeches can serve also as vectors for haemogregarines. Stages of this haemogregarine are also described in the blood-sucking ectoparasitic copepod Lernaeocera sp. parasitizing the haemogregarine infected soles. These results are discussed in relation to the feeding behaviour and migration patterns of the fish hosts, the periodicity of the parasites and possible other vectors or other ways of acquiring an infection with these haematoprotozoan parasites. In Section C the pathogenicity of the haematoprotozoan parasites of marine fishes is summarized from previous accounts among wild fish populations and compared with the situation in aquaculture. The pathogenicity of the two haemogregarines, Haemogregarina simondi and Haemogregarina sachai n. sp., accidentally introduced into several fish farming establishments connected with the effluent cooling waters of a nuclear power station is described with special reference to the possible source of the infection. The results of therapy trials and control programs are discussed in the light of the periodic reappearance of the parasites, the possibility of carrier fish existing, the immune status of the host and the possible role of an intermediate host or vector in maintaining the infection. Possible means of controlling the pathogenicity of marine haemogregarines and perhaps other haematoprotozoan parasites when they occur in farmed marine fishes are also discussed. In Section D are described for the first time, the ultrastructural characteristics of various stages of the haematoprotozoan parasites of marine fishes in fish hosts and vectors. The electronmicroscopical studies are limited to Haemogregarina sachai n. sp. and Haemogregarina simondi, for which the ultrastructure of schizonts from the spleen and blood, intracellular merozoites and free gametocytes were contrasted. In addition stages of H. simondi were demonstrated in Hemibdella soleae and Lernaeocera sp. The fine structure of the various organelles encountered was compared with that of related organisms from other cold-and warm-blooded vertebrates. In conclusion attention is drawn to the need for more investigations in this field of host-parasite relationship of marine haematoprotozoan parasites and their vectors and their pathogenic-action as seen in a confined and artificial environment such as the marine aquaculture.

Larval Anisakis simplex, Pseudoterranova decipiens, Contracaecum osculatum and larvae and adults of Hysterothylacium aduncum were recovered from specimens of cod, haddock, blue whiting and bull rout; however, only A.simplex were retrieved from long rough dab. The epidemiology of infection by these four nematode species was examined both in whole fish, and in individual host tissues and organs. Frequency distributions of nematodes were found to be generally overdispersed in fish. Preliminary investigations revealed no strong evidence to suggest that competi tive interactions occurred between ascaridoid nematodes wi thin fish. Stomach lesions in gadoids were associated with single (partially penetrated) and mul tiple (throughout stomach wall) worm infections of larval A.simplex; such lesions were discrete and raised in appearance. Lesions associated with 1-3 larval P.decipiens in an open cavity within the stomach of angler fish were diffuse and not significantly raised. Histological examination of each form of ulcer revealed general similarities in pathology, with infil tration of inflamatory cells being the initial response to the nematode\s. Changes in the cephalic morphology of A.simplex, P.decip1ens, C.osculatum and H.aduncu were examined at different life cycle stages under scanning electron microscopy. Due to their small size, newly hatched third stage larvae of P .decip1ens were cultured in a bacterial mat prior to fixation for S.E.M., and the external ultrastructure of these larvae is described. The most prominent external feature at this stage is the cephalic boring tooth. Aspects of the internal ultrastructure of A. simplex, P.decipiens, C.osculatum and H.aduncu were examined using transmission electron microscopy. Newly hatched third stage larvae of P.decipiens show little differentiation of internal organs. The ultrastructure of sensory amphids in H.aduncum and A. simplex is cons i stent wi th that of a chemoreceptor, that of the single papilla in P.decipiens a mechanoreceptor. The ultrastructure of the digestive tract, excretory gland and body wall of marine ascaridoids were also examined.

Two 16 mm color films were made to help fill a general need for instructional motion pictures in the area of Parasitology. One film "Haemonchus contortus, a Sheep Stomach Worm," deals with a nematode parasite of sheep, showing all stages of its external development and including a time-lapse sequence of the embryonation of the egg. The other film, "Some Parasites of Freshwater Fishes," shows six parasites; Ichthyophthirius multifiliis, Cotylurus erraticus, Dactylogyrus sp., Lernaea cyprinacea, Trichodina sp., and Diplostomum spathaceum for the first time in motion pictures. The films were photographed through a Wild dissecting scope and a Reichert Universal Camera Microscope, employing the techniques of brightfield, darkfield, phase contrast and Nomarski interference microscopy. The films are available from the Parasitology Laboratory of the Department of Zoology at Brigham Young University.

No description available.

Thesis (M.SC. (Aquaculture)) --University of Limpopo, 2011 / The present MSc dissertation emanates from seasonal surveys conducted by the fish parasitological group of the Department of Biodiversity and Aquaculture Research Unit of the University of Limpopo, Turfloop Campus. The first part of the present study was aimed at investigating the metazoan parasites of three cyprinids occurring in the Nwanedi-Luphephe Dams. The main purpose of it was to determine temporal changes in the intensity of infestation in terms of prevalence, mean intensity and abundance of parasite species parasitizing the cyprinids studied over a two year period. Ecological parameters including species host-specificity, seasonality, and gender preference and host size versus species intensity are discussed for each parasite. Altogether 152 specimens were examined for parasites and a total of 2 432 metazoan parasites of ten species were recorded. At the sampling site, all three hosts co-occurred, however, a substantial proportion of Barbus radiatus was collected from the perennial stream feeding one of the twindams. Fish were sampled by means of gill nets and electrofishing or seine netting in accordance with the habitat conditions. Hosts were killed and organs investigated for metazoan parasites. After collection of parasites, standard methods for processing individual parasites were followed. The results obtained revealed the following groups of parasites; monogeneans (ectoparasites) included Dactylogyrus spinicirrus, D. afrolongicornis afrolongicornis, D. afrolongicornis alberti, Afrodiplozoon polycotyleus, Gyrodactylus sp., and Dogielius sp. (all recorded from the gills); Crustacea, Dolops ranarum was found from the mouth cavity, gills and skin of Labeobarbus marequensis. Of these, only two specialists, both monogeneans, were found on Barbus trimaculatus namely, D. afrolongicornis afrolongicornis and D. afrolongicornis alberti. Based on morphology of the haptoral hard parts, these two species were almost similar to each other than to D. spinicirrus. The appreciable difference between D. afrolongicornis afrolongicornis and D. afrolongicornis alberti was mainly in the shape of the marginal bar. Both D. spinicirrus and A. polycotyleus were widely distributed and recorded on the gills of all hosts during all seasons. Both species were recorded for the first time on B. radiatus. Also, D. spinicirrus was recorded for the first time on the gills of B. trimaculatus. Based on comparison with the original material, the species could be identified to species level. These analyses provided sufficient evidence for restoration of Afrodiplozoon polycotyleus as a valid taxon. The existence of two species, Gyrodactylus sp. and Dogielius sp. were recorded for the first time on B. radiatus in South Africa, and this possibly represents new species. The endoparasites included the following groups: digeneans- Diplostomulum metacercariae from the eyes of Lb. marequensis, Ornithodiplostomum sp. and black spot (grubs) were recorded from B. trimaculatus. The latter was also recorded in the muscle of B. radiatus. Unidentified digenean cysts were recovered from the gills and in the body cavity of both Lb. marequensis and B. trimaculatus; nematodes were represented by Contracaecum larvae in the body cavity of both Lb. marequensis and B. trimaculatus; cestodes were represented by gryporynchid larvae from the intestine of B. radiatus. The general high prevalence and intensities of ectoparasites recorded is an indication that the Nwanedi-Luphephe Dams has a biotic mechanism which might have enabled it to sustain the growth rate of ectoparasite intra-population. There was no correlation between either fish length or condition factor and the number of parasites. The study indicated that the abundance of monogeneans is partly influenced by season and that of endoparasites was principally governed by the presence of intermediate hosts and definitive hosts. The second part of this dissertation dealt with the health status of Lb. marequensis. Fish health was assessed using condition-related indices including condition factor and a modified Health Assessment Index (HAI) and the associated Parasite Index (PI). The HAI was performed to determine and examine any macroscopic abnormalities regarding external features and internal organs. The purpose of combining the two indices was to use the infestation of the metazoan parasites found on and/or in Lb. marequensis to determine whether or not the environment they live in was healthy. Both indices together with the condition factor provided relatively simple and rapid indications of how well fish were coping in their environment. The HAI score varied amongst the four sampling seasons. The highest individual mean value was 63 in winter, followed by a score of 50 in autumn, while the lowest were 42 and 33 in summer and spring respectively. To authenticate the HAI and PI data, certain water quality variables were measured and are discussed in detail in this dissertation. The Nwanedi-Luphephe Dams are generally believed to have good water quality. This was supported in this study; conditions assessed in fish using the aforementioned indices did not differ greatly between seasons, nor did the conditions deviate appreciably from normality. The HAI values were low overall which signifies a healthy fish profile for the system. The present investigation showed the existence of differences in the occurrence of individual parasite to be linked to water temperature changes. Thus, seasonal changes do influence parasite developmental stages to a certain degree. Tested heavy and trace metals were within the permissible limits as provided by the Department of Water Affairs and Tourism (DWAF, 1996).

Non-native parasites pose a significant threat to aquatic bio-diversity and fishery development. Many factors have facilitated the introduction of non-native parasites into England and Wales. Identifying the effects of these parasites and the importance of any changes to wild fish populations represents a considerable challenge. However, in order for the Environment Agency to identify future disease threats, effectively manage resources and implement practical and sustainable control measures, the risks posed by these parasites to fisheries must be better understood. A structured, risk-assessment process for non-native freshwater parasites is proposed. This approach includes procedures for hazard identification, impact assessment, risk management and communication. A quantitative approach to hazard identification provides an initial prediction of impact at the time of introduction to inform decisionmaking and guide preliminary control measures. This is followed by a more comprehensive framework for impact assessment that promotes understanding of changes at host, population and fishery levels. These are placed into context with the economic and ecological value of native resources. An independent 'non-native parasite review group' has been convened to ensure consistency of policy decisions and clear communication of disease risks to interested bodies. It is hoped that this wil assist the management of future invasions and provide a scientifically robust foundation on which to base proportionate control measures. The Category 2 parasites are defined as "species having a significant disease potential when introduced into waters where they do not already exist, or are non-indigenous species with unknown pathogenicity and distribution". Understanding of the dangers posed by these parasites varies considerably. Ergasilus sieboldi, Anguilicola crassus, Bothriocephalus acheilognathi and Lernaea cyprinacea, are well recognised non-native fish pathogens that pose a considerable threat to fisheries. Conversely, the effects of other introduced parasites remain poorly understood. In many cases, a paucity of published literature at the time of introduction has limited a reliable assessment of impact. Four non-native parasites were considered a priority for further study. These were Paraergasilus longidigitus (Copepoda: Poecilostomatoida), Ergasilus briani (Copepoda: Caryophylldae) Poecilostomatoida ), Atractolytocestus huronensis (Cestoda: and Philometroides sanguinea (Nematoda: Philometridae). Pathological, epidemiological and experimental investigations were undertaken to assess the effects of these parasites at host and population levels. P. longidigitus can cause pronounced pathological changes to the olfactory epithelium of infected fish. Although this damage provides the potential for disruption to spawning through reduced sensitivity to reproductive chemical cues, experimental observations combined with seasonality studies suggest that the parasite is unlikely to disrupt reproduction within infected cyprinid fisheries. Similarly, studies conducted on the caryophylidean cestode A. huronensis provide little evidence to suggest that the parasites poses a threat to car fisheries. Damage within the intesinal tract was characterised by relatively mild mechanical and inflammatory changes. Infections of up 213 parasites had no adverse affect upon the conditon of common carp. Based on these findings and the application of the aformentioned risk model, P. longidigitus and A. huronensis are considered to be of low disease risk to fisheries. The pathology of E. briani and P. sanguinea are described for the first time. Literature suggests that both parasites are pathogenic to juvenile fIsh. E. briani causes a number of pathological changes within the gils of juvenile cyprinids, although these remain localised due to the very strict site specificity of the parasite. Migrations of the nematode P. sanguinea causes damage to the fins and caudal musculature of juvenile crucian car. For both parasites, the extent and severity of pathological changes are inversely proprtional to host size. Further studies at the population level are needed before an assessment of impact to fisheries can be made. The difficulties associated with studying the effects of introduced parasites to juvenile fish populations in the wild are recognised. Recommendations for further study are given.

This study is concerned with two strigeid genera which utilise fish as their second intermediate host and piscivorous birds as a definitive host, i.e. Apatemon (Apatemon) Sudarikov, 1959 and Ichthyocotylurus Odening, 1969. Although the lifecycle has been ascertained for most Ichthyocotylurus spp., confusion and disagreement still exist as to the constituent species, while all of the life-stages have been described for only a single member of the subgenus Apatemon (Apatemon). In order to clarify species membership to these taxa and indeed the taxonomic position of the subgenus Apatemon (Apatemon) further information was required on the life-cycles and life-stages of these strigeids. Although, metacercariae from this family have been recorded from a variety of British fishes, confirmed records, i.e. those supported with life-cycle data, are limited to a single species. It was this lack of confidence in identifying metacercariae recovered from fishes and the lack of known good criteria for distinguishing the adults that prompted the present study. Collections of metacercariae from a variety of hosts and locations were made, from which all subsequent life-cycle stages were obtained. The project aims were to establish the identity of the forms occurring in British fishes, by applying discriminatory techniques to the experimentally reared life-stages. In addition to traditional methods, techniques with little previous application to these genera were used and included, scanning electron microscopy (SEM), chaetotaxy, principal components analysis (PCA), and karyology. Furthermore, behavioural aspects such as the release patterns of cercariae from their molluscan hosts were studied to investigate whether they would prove to be of diagnostic value. Metacercariae obtained from the sampling survey were tentatively identified, using all currently employed methods for their determination, i.e. morphology, nature of cyst, host and site specificities, as Ichthyocotylurus erraticus (Rudolphi, 1809), I. variegatus (Creplin, 1825), Apatemon gracilis (Rudolphi, 1819) and A. annuligerum (Nordmann, 1832). Material collected from Finland was considered to contain both Ichthyocotylurus spp. recovered in the U.K., as well as I. platycephalus (Creplin, 1825) and I. pileatus (Rudolphi, 1802). The Ichthyocotylurus spp. were found to be more host specific than A. gracilis, although A. annuligerum was considered oioxenic to perch Perea fluiatilis L. Records of I. erraticus from gwyniad Coregonus lavaretus (L.) and grayling Thymallus thymallus (L.), and A. gracilis from arctic charr Salvelinus alpinus (L.) constitute first listings from Britain. The large number of sensilla present on the body surface of these metacercariae, observed by SEM and chaetotaxy, precluded their diagnostic use. PCA was, however, found to be of value for distinguishing between species and determining morphological variation within a species. I. erraticus, I. variegatus and A. gracilis adults were successfully reared in experimental hosts using metacercariae from a variety of fish hosts, sites within a single fish host and geographical sites. The adults obtained enabled clarification of the identities assigned to the metacercariae. Those metacercariae believed to represent I. pileatus and A. annuligerum failed to establish in experimental hosts. Herring gulls and lesser black-backed gulls proved to be extremely good experimental hosts for both Ichthyocotylurus spp., with the vast majority of infections establishing and providing high yields of eggs and adults. These infections yielded information on the establishment, development, fecundity, site specificity, longevity and morphological variability of the adults. Aspects of the morphology and biology of I. variegatus adults recorded were found to support its validity as a species discrete from I. platycephalus which was in some doubt. The experimental hosts used for A. gracilis infections, domestic and mallard ducklings, were found to be less satisfactory. Challenges were performed with A. gracilis metacercariae from three sources, rainbow trout, salmon parr and stone loach. The latter source was the only one to result in egg producing adults, with specimens exhibiting normal morphology and demonstrating an increased longevity over adults raised from salmonid metacercariae. These findings suggest that the metacercarial host may affect the successful completion of the life-cycle. Eggs of known origin were collected for all three cultured strigeid species, enabling further life-cycle studies, these were incubated and miracidia successfully raised. Developmental periods were found to be temperature dependent and differed for the three species at 20°C: A. gracilis < I. erraticus < I. variegatus. Light microscopy revealed the morphology of all three species to be identical, as were the epidermal plate formulae and chaetotaxy, indicated by silver-staining. The nomenclature for the distribution of miracidial sensilla derived by Dimitrov et al. (1989) was amended to enable a full description of these species. Osmotic shock resulted in an improved deciliation of the miracidia compared to sonication and subsequent SEM observation confirmed the arrangement of body surface structures, while revealing sensilla forms. Behavioural aspects of I. variegatus miracidia were examined, with a maximum longevity (< 11 hours) recorded at the lowest temperature studied (l0 degrees C), and host finding demonstrated to occur by an increased turning response in the presence of substances emitted from the susceptible snail host, following an initial unresponsive dispersal phase. Ichthyocotylurus cercariae were found in naturally infected Valvata piscinalis which constitutes the first record in Britain of cercariae of this genus. Cercariae of I. erraticus and I. variegatus were successfully raised experimentally from miracidia of known identity and origin within naive, experimentally raised V. piscinalis hosts, while A. gracilis cercariae were obtained from laboratory reared Lymnaea peregra. Cercarial developmental periods within the molluscan host were found to be temperature dependent and markedly different for the strigeid genera investigated, as were their behaviour and morphology. The Ichthyocotylurus spp. exhibit a distinct diurnal emergence rhythm from their molluscan host, being shed during the hours of daylight, while A. gracilis cercariae demonstrate a reciprocal pattern, emerging during the hours of darkness. Behavioural contrasts were also observed in longevities, emergence strategies (route of exit) and swimming behaviour. The two Ichthyocotylurus spp. were extremely similar, the only cercarial features found to be of diagnostic use were: the presence or absence of eye-spots; their differing developmental periods from miracidium to cercaria; the number and distribution of sensilla when compared by PCA; and their differing longevities at 20 degrees C. Characters considered to be of value in differentiating between strigeid cercariae at the species level, including the armature, chaetotaxy pattern and resting posture, did not differ between these two species. SEM observations enabled descriptions of the variety and structure of sensilla present on different life-stages, while transmission electron microscopy revealed the internal structure of cercarial sensory structures. Experimentally raised cercariae were found to be infective and the life-cycle was completed for the three strigeid species. Host specificities were observed for I. erraticus and A. gracilis, being particularly stringent for the latter species, while site specificities recorded were as observed in natural infections. Metacercarial maturation periods (for encystment) were highly temperature dependent, being comparable for the two Ichthyocotylurus spp. and more rapid than for A. gracilis specimens.

M.Sc. (Zoology) / Please refer to full text to view abstract

The objective of the present study is then limited to investigate the parasitic fauna of marine fishes from Ensenada, Baja California, and to compile in a single manuscript all data (Host-Parasite list, Parasite-Host list, and distribution of parasites) on digenea previously reported from the Mexican Pacific and the Gulf of California.