[Advances in Marine Biology] Advances in Marine Biology Volume 4 Volume 4 || Diseases of Marine Fishes

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<ul><li><p>Adv. mar. Bid.. Vol. 4, 1866, pp. 1-89 </p><p>I. 11. </p><p>111. </p><p>IV. V. </p><p>VI. </p><p>VII. VIII. Ix. x. </p><p>XI. XII. </p><p>XIII. </p><p>DISEASES OF MARINE FISHES </p><p>CARL J. SINDERMANN U.S. Bureau of Commercial Fisheries, Biological Laboratory, </p><p>Oxford, Marylund, U.S.A. </p><p>" One of the most serious gaps in our knowledge of marine ecology is the study of diseases . . . epidemics are common occurrences in marine environments. . . . They may be en important cause of fluctuations, and should therefore have a prominent place in research programs." </p><p>Lionel A. Walford, " Living Resources of the Sea '*, Ronald Press Company, 1958, p. 147. </p><p>Introduction . . .. .. . . . . . . Microbial Diseases . . .. .. . . . . </p><p>A. Viruses .. .. .. .. .. .. B. Bacteria .. .. .. .. .. D. Protozoa .. .. .. .. .. </p><p>Other Parasitic Diseases . . .. .. .. A. Helminths . . . . .. .. .. B. Parasitic Copepods . . .. .. .. </p><p>Genetic and Environmentally Induced Abnormalities Effects of Disease . . .. .. .. .. </p><p>A. Epizootics and Mass Mortalities . . .. B. " Background " Effects . . .. .. C. Economic Effects . . .. .. .. </p><p>Variations in Disease Prevalence . . .. .. A. Geographic Variations .. . . .. B. Temporal Variations . . .. .. .. C. Age Effects . . .. .. .. .. </p><p>Immunity . . .. .. .. .. .. Diseases in Marine Aquaria . . .. .. .. Relationship of Fish Diseases to Human Diseases . . Future Studies of Marine Fish Diseases . . .. Summary .. .. .. .. .. .. References . . .. .. .. .. .. Acknowledgments . . . . .. .. .. </p><p>C. Fungi . . .. .. .. .. .. </p><p>I. INTRODUCTION </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>. . </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>. . </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>. . </p><p>. . </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>.. </p><p>1 4 4 8 </p><p>13 16 24 24 32 35 40 40 44 46 41 41 50 51 52 56 59 60 63 65 89 </p><p>Research commitment to the study of marine fish diseases has been until recently sporadic and inadequate. Although knowledge of fresh- water fish diseases has proliferated, especially in hatcheries, little incentive has existed for comparable investment in Understanding the ills of marine species. The vastness of the oceans, the complexity of natural factors regulating the size of fish populations, and the lack of </p><p>1 </p></li><li><p>2 CARL J. SINDERMANN </p><p>methods to control and manipulate such factors, have tended to discourage continuing and extensive studies of such specific aspects of the marine environment as disease. Growing awareness that the human population is increasing enormously, that over two-thirds of the earths surface is ocean, and that we understand little of the dynamics of production in the sea, has led to increasing scrutiny in recent years of those variables that might a t any particular time become overriding in their influence on population size. Disease is one such variable. </p><p>Diseases of food fishes have logically received greatest attention in past research, and will do so in the present paper. Parasites and diseases, in addition to killing the host, can materially reduce the value of fish as food for humans ; this fact serves as a further incentive to examine diseases of commercial species. Non-utilized fish may receive attention because of some academic interest, but the preponderance of research concerns food species with large biomass. The term disease is used here in its broadest possible sense, to include any departure from normal structure or function of the organism-encompassing those states that result from activities of infectious agents, parasite invasion and genetic or environmentally induced abnormalities. Such a broad definition of disease in marine fishes requires the inclusion of a sur- prising amount of widely scattered literature-probably more than can be comfortably considered in this review, and certainly more than might be expected in view of the apparent neglect of the field. </p><p>Access to the literature on marine fish diseases is a t present indirect. Several general texts on fish parasites and diseases have appeared in the German language (Hofer, 1904 ; Plehn, 1924 ; Schaperclaus, 1954 ; Amlacher, 1961). The latest edition of Schaperclaus excellent text contains information on disease in marine as well as fresh-water fishes. Recently, several shorter texts on diseases of lower vertebrates by Reichenbach-Klinke have been translated into English, expanded, and combined into a more comprehensive work (Reichenbach-Klinke and Elkan, 1965). Kahl, Reichenbach-Klinke, and Schaperclaus have made numerous significant contributions to the German literature. Russian texts, symposium volumes and reviews (Liaiman, 1949, 1957; Dogiel, 1954, 1955; Petrushevskii, 1957; Dogiel et al., 1958; Pavlovskii, 1959, 1962; Polyanski and Bykhovskii, 1959) contain summarizations of marine studies and have appeared in English translations. Among the important contributors to the Russian literature have been Dogiel, Petrushevskii, Polyanski and Shulman. Other nations have also made significant summarizing contributions to the general literature on fish diseases. Bergman (1923) published an early monograph in Swedish; kujita (1943) published a text on diseases of fish and shellfish in </p></li><li><p>DISEASES OF MARINE FISHES 3 </p><p>Japanese; Davis (1953) published an English language text on culture and diseases of fresh-water game fishes; and Ghittino (1963a) recently published a handbook in Italian. A symposium on fish diseases held at Turin, Italy, in 1962 has been published by the Office International des Epizooties (Altara, 1963). English-language reviews and symposia on selected aspects of fish-disease research, usually including references to marine diseases, have appeared (Kudo, 1920, 1924, 1933; Sproston, 1946; Nigrelli, 1952a; Oppenheimer and Kesteven, 1953; Snieszko, 1954; Manter, 1955; Hoffman and Sindermann, 1962, Oppenheimer 1962; Sindermann, 1963; Post, 1965; Putz et al., 1965; Snieszko et al., 1965). Texts which include considerations of marine fish diseases and parasites include: Breed et al. (1957)-bacteria; Johnson and Sparrow (1961)- fungi; Kudo (1954)-protozoa; Yamaguti (1958-63)-helminths; Dawes (1946, 1947) and Skrjabin (1947-62)-trematodes; Wardle and McLeod (1952)-cestodes; and Yorke and Maplestone (1926)-nematodes. Johnstone, Kabata, Linton, Nigrelli, Snieszko and Templeman are among those who have made important contributions to the English and American literature. </p><p>The general plan of this paper is to consider examples of the signi- ficant diseases of marine fishes, concentrating sensibly on those that have received somewhere near adequate scientific attention, and attempting to include those caused by a wide variety of pathogens and parasites. In the necessary process of selection a t least two things happen : (1) many examples and much literature must be neglected or not treated in sufficient depth, and (2) a natural tendency arises to choose examples close a t hand or drawn from the authors research. Thus, illustrative material has been taken to a large extent from studies in the North Atlantic, although comparable material could be obtained from other geographic areas. Omitted is much of the great but scattered fund of published information from parasite surveys, including a large part of the ecological parasitology of the USSR, which has been effectively summarized by Dogie1 et al. (1958). Many descriptions of occasional parasites of fishes have not been considered, even though effects of such parasites may be properly included in the broad definition of disease used in this paper. The literature cited thus includes only a small part of the often extensive published information on any particular parasite group. The references, extensive as they may seem, represent a too-small sampling of the world literature. This is particularly true of the older literature, which for groups such as the Myxosporidea and Microsporidea is voluminous and elaborate. Refer- ences to some of the early literature have been compiled by McGregor (1963); access to other early work can be gained through bibliographies </p></li><li><p>4 CARL J. SINDERMANN </p><p>included in more recent papers. For such parasite groups as the haemo- gregarines, the monogenetic trematodes, the cestodes, the nematodes, or the parasitic copepods, the consideration in this paper therefore represents only a tiny, but hopefully a representative, fraction of the whole. </p><p>Diseases of estuarine and anadromous species are included, as well as those of species that are strictly marine, except that treatment of anadromous fishes is limited to situations where the pathogen or parasite is of marine origin. Diseases of fishes from saline inland seas have been considered, since many of the hosts and their parasites are of marine origin. Many of the diseases discussed are characteristic of inshore or estuarine waters, where abnormal conditions are more readily noted and examined than in the open sea. Fish carcasses washed up on beaches or floating in shoals near shore are much more likely to elicit action, scientific or otherwise, than would similar events a hundred miles from shore. Also, scientific studies of marine animals in the past have often varied inversely with distance from the shore. As a result, much of the world literature on fish diseases concerns inshore events. </p><p>11. MICROBIAL DISEASES Included in the category of microbial diseases , and aggregated </p><p>here largely for convenience, are those of viral, bacterial, fungal and protozoal etiology. They include the infectious diseases of fishes, caused by parasites capable of destruction of host tissue and multiplica- tion within the fish. Resultant pathology and the course of disease may depend on such factors as infective dose, virulence and resistance of the individual host animal as well as host nutrition and other environmentally influenced variables (Snieszko, 1957a, 1964). The disease condition may range from chronic to acute, with varying degrees of host response. </p><p>A. 8 truses Virus diseases of marine fishes, although not unknown, are not </p><p>reported abundantly in the scientific literature. Much of this lack of knowledge probably stems from the absence, until recently, of adequate techniques for study. With the successful establishment of fish cells in culture (Wolf and Dunbar, 1957 ; Clem et al., 1961 ; Wolf and Quimby, 1962), a most important tool has become available, and understanding of the role of viruses in marine fish populations should increase greatly in the next decade. Viruses are best known in marine fishes as suspected or known etiological agents of several neoplastic, hyperplastic and </p></li><li><p>DISEASES OF MARINE FISHES 5 </p><p>hypertrophic diseases. Lymphocystis disease and certain papillomas have long been felt to be of viral origin, based on epizootiological and transmission studies, and on the presence of inclusions in affected cells. </p><p>Lymphocystis is probably the best known virus disease of marine and fresh-water fishes. First described from the European flounder, Pleuronectes jlesus (L.),* by Lowe (1874), and soon after from other species (McIntosh, 1884, 1885 ; Sandeman, 1892 ; Woodcock, 1904), the disease has since been reported from the orange filefish, Alutera schepfi (Walb.), by Weissenberg (1938) and Nigrelli and Smith (1939); the killifish, Fundulus heteroclitus L., by Weissenberg (1939a) ; the red mullet, Mullus surmuletus (L.), by Alexandrowicz (1951) ; and from other marine and fresh-water species (Smith and Nigrelli, 1937; Weis- senberg et al., 1937; Weissenberg, 1945). Recently several cases of presumed lymphocystis in striped bass, Roccus saxatilis (Walb.), have been observed (Anonymous, 1951 ; Sindermann, unpublished). The disease was originally thought to be caused by parasitic protozoa or eggs of another animal laid under the skin of fish (Sandeman, 1892; Woodcock, 1904). Weissenberg (1914, 1920) and Joseph (1918) were the first to recognize lymphocystis cells as hypertrophied fibroblasts. Transmission studies (Ragin, 1927, 1928; Weissenberg, 1939b, 196lb; Wolf, 1962) have demonstrated the infectious nature of the disease and have suggested some degree of host specificity. Definitive evidence that a virus is responsible for lymphocystis was obtained by electron micro- scopy (Walker, 1962; Walker and Wolf, 1962) and by transmission of the disease with ultracentrifugates and bacteria-free filtrates (Weissen- berg, 1951a; Wolf, 1962). Manifestations of lymphocystisinclude whitish nodules on body and fins caused by hypertrophy of fibroblasts and osteoblasts (Fig. la). The connective tissue cells grow to enormous size (5 mm in some cases) and become surrounded by a thick hyaline capsule. In severe cases most of the body surface may be involved. Weissenberg (1921a) reported that in some areas up to one-third of a population of fish could be affected. A great body of literature has accumulated on lymphocystis, and much of the early work was well summarized by Nigrelli and Smith (1939). A history of research on the disease has just been published (Weissenberg, 1965). </p><p>A recent and apparently sharply defined outbreak of lymphocystis </p><p>* Throughout the paper an attempt has been made to give common and scientific names of fishes when they are first mentioned, and only the common name thereafter. In some cams this is not possible, aa for example when the =me common name ia applied to several different species in different geographical are-, or when a species m y have a different common name in different areas. Scientific names of fishes from North American watera follow the recommendations of the American Faeries Society (1960). </p></li><li><p>FIG. 1. (0) Lymphocystis disease of the dorsal fin ; ( 6 ) papilloma of flounder ; (c) cauliflower disease of eel. </p></li><li><p>DISEASES OF MARINE FISHES 7 </p><p>in American plaice, Hippoglossoides platessoides (Fabr.), of the Grand Bank was reported by Templeman (1965b). Infected fish were first seen in 1960, and in 1964 the infection level in American plaice on the eastern slope of the Grand Bank was approximately lo/. Badly infected fish, called " scabby " or " seedy " by fishermen, were thrown overboard, and estimates of such discards ran as high as 300-400 pounds per set in areas of heavy infections. Trawlers usually moved to other locations where fewer fish were diseased. Templeman suggested several possible explanations for the outbreak, including the possibility that the disease is enzootic in the population and may increase in intensity periodically. Nordenberg (1962) found infections as high as 12% in flounders, Pleuronectes Jlesus, from the Oresund, with some indication of higher prevalence in the warmer months of the year. </p><p>Neoplastic or hyperplastic diseases, some thought to be of virus origin, include dermal and epidermal papillomas of many flatfish species (Fig. lb). Such diseased conditions have been reported from : halibut, Hippoglossus hippoglossus L., by Johnstone (1912a) ; plaice, Pleuronectes platessa (L.), by...</p></li></ul>