Marine Invertebrates Ebook
Aquareovirus A genus in the family Reoviridae comprising at least six species (A to F) infecting fresh as well as seawa-ter fish and some marine invertebrates such as clams and oysters. The genome consists of 11 segments of double-stranded RNA (three large, three medium and five small) ranging in length from 0.8 to 3.8kb. On the basis of RNA-RNA hybridization, six genogroups are currently recognized. The type species, Aquareovirus A, includes at least 10 viruses which affect fish and oysters. Aquareoviruses have been isolated from wide geographic areas, and at least five different viruses cause economically important diseases of finfish the golden shiner, grass carp, smelt, angelfish and grouper reoviruses. Most of the viruses replicate well in fish cell lines.
Sources of IHNV other than salmonid fish have not been identified, but potential sources include freshwater and marine invertebrates, sediment and other fish species. Depending on temperature, microflora and electrolyte concentration, IHNV survives in fresh water for from 3 days to several months (Wedemeyer et al., 1978 Toranzo and Hetrick, 1982 Yoshimizu et al, 1986 Kamei et al, 1988b). Infectious haematopoietic necrosis virus survives longer in salt water than in fresh water (Winton et al, 1991), and, although it is unlikely that fish become infected through the ocean water, because of the high dilution factor, this remains a possibility. Ingestion of marine organisms harbouring IHNV is another possible mechanism of infection, but IHNV has not been isolated from marine organisms (Traxler et al, 1997).
Serogroup B consists of a single serotype with fewer than ten strains, which were isolated from fishes and marine invertebrates in Europe (Hill and Way, 1988b). Within this small serotype, some strains are virulent for trout and cause typical IPN disease in brook trout (Ahne et al., 1989b) others are completely avirulent in salmonids and non-salmonids (Hill and Dixon, 1977 Olesen et al., 1988).
Some researchers believe the nucleic acid of IHHNV is single-stranded deoxyribonucleic acid (ssDNA) with parvovirus-like features (Bonami et al., 1990 Bonami and Lightner, 1991). Others suggest IHHNV is picornavirus-like, with single-stranded polyadenylated RNA (Clerx and Lightner, 1985 Lu et al., 1989). The original authors noted viral characteristics similar to those of the cytoplasmic RNA-containing Picornaviridae and the deoxyribo-Parvoviridae (Lightner et al., 1983c). Brock and Lightner (1990) describe the virus as single-stranded RNA (ssRNA), while Lightner et al. (1992b) cite a ssDNA structure. Interestingly, a similar situation is discussed by Brock and Lightner (1990), who note that a small virus reported from the cardiac tissue of a single brown shrimp (P. aztecus) by Foster et al. (1981) could be classified, tentatively, as a parvovirus-like or picornavirus-like virus, based on size and isometric morphology. Johnson (1984), in her review of viral diseases of marine...
Temporary adhesion (Section 3.3) is known for a range of marine invertebrates other than platyhelminths, including gastrotrichs (Tyler and Rieger, 1980), polychaetes (Gelder and Tyler, 1986) and nematodes (Tyler and Melanson, 1979), but there are few examples from marine macroinvertebrates of temporary adhesives that have been characterized chemically. The composition of adhesives in echinoderms (see review by Flammang, 1996 Flammang et al., 1998) and limpets (Mollusca) (see Grenon and Walker, 1978, 1980 Denny, 1983 Smith, 1991, 1992 A.M. Smith et al., 1999) is better characterized than most. They differ from adhesives involved in permanent adhesion such as those reported for marine mussels (Mollusca) which use proteina-ceous byssal threads and plaques (Cook, 1970 Waite and Tanzer, 1981 Waite, 1983, 1985 Waite et al., 1989 Rzepecki et al., 1992 Papov et al., 1995). They also differ from the permanent adhesives of barnacles (Crustacea) (see Walker,
Relatively hard, rigid and non-secretory surfaces such as the carapace of crustaceans probably provide a relatively stable and non-threatening surface for attachment by platyhelminths known to use adhesives such as the temno-cephalans (Sewell and Whittington, 1995). Attachment to cuticular surfaces probably falls between temporary adhesion and tissue adhesion. The biggest likely threat to temnocephalans is moulting when the external cuticle of the crustacean host is shed. Epithelial tissues that line the intestine of vertebrates (e.g. Castro and Harari, 1982 Ishikawa et al., 1994) and which cover the body surfaces, scales, fins and gills of fishes (e.g. Buchmann, 1998a, 1999 Whittington et al., 2000a) are active secretory layers that grow, regenerate and produce mucus containing peptides and carbohydrates that may have immunological activity. The mucus of fish, produced by the goblet or mucous cells in the epithelium, is known to be highly variable chemically between species and there...
One of the best-studied bacterial diseases of marine invertebrates is gaffkemia (or 'red-tail disease') of Homarus americanus and H. gammarus, (see reviews by Stewart, 1980, 1984, 1993, Sindermann, 1990 Brock and Lightner, 1990). Gaffkemia is caused by Aerococcus viridans var. homari (syn. Gaffkya homari and Pedicoccus homari) and causes problems primarily in captive lobsters. The sources of infection include wild lobsters and other decapod crustaceans, which can serve as reservoirs of infection (Stewart et al., 1966 Stewart and Rabin, 1970 Vachon et al., 1981), along with free-living stages of A. viridans var. homari in mud sediments and on lobster-pound surfaces. Experimentally infected crabs (Cancer borealis, C. magister, Carcinus maenas, Libinia emarginata, Chionoecetes opilio, Geryon quinquedens and Panulirus interruptus) and prawns (Pandalus platyceros and Penaeus aztecus) showed
The ubiquity of adhesion in nature was referred to in Section 2. The burgeoning discipline of bioadhesion is testimony to the innate curiosity, interest and importance placed on understanding how adhesion in nature occurs. Other outcomes from bioadhesion studies not only include attempts to replicate in the laboratory or in industry methods of producing such tenacious natural adhe-sives which are known for their toughness (B.L. Smith et al., 1999), but also embrace development of methods to prevent some organisms from adhering (i.e. production of antifoulants). Marine invertebrates are a particularly rich source of natural adhesives and, as Flammang (1996) phrased it so clearly, 'adhesion is a way of life in the sea'. Many marine invertebrates with a benthic or interstitial lifestyle have evolved various organs, organelles and or secretions for adhesion to different substrates. Generally, however, these surfaces are non-living (i.e. abiotic). We have emphasized that some parasitic...
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