Crabs, etc. The effect of heavy metals on unclean food of the crab type is being identified on an increasing basis. The effects of free cupric ion activity in seawater on metallothionein and growth in crab larvae have been demonstrated by Sander, Jenkins Sinda and Costlow (see ASFA Pt. 1, Vol. 14 No. 6, item 14194 - 1Q14). Their data reveals predicable relations between cupric ion activity in seawater and processes at the cellular and organismic levels. Zinc and tin pollution also affect the eco-system, polluting the intertidal environment entering the system at the invertebrate and suspension feeder level. Again, this is a prohibited food source under the food laws. It has also been demonstrated that the synoptic state of fish may be a kind of self-guard action to prevent the accumulation of toxic compounds into their bodies. It is probable that this has a direct bearing on the clean and unclean varieties (Ogawa, Tonogai, Ho, Twaida, Osaka 1983 – from ASFA Pt. 1, Vol. 14 No. 6, item 14232 - 1Q14). It is also worth noting that some species of shellfish accumulate cadmium from uncontaminated sources at greater rates than from contaminated sources. For instance, Frazier and George, 1983, examined two species of oysters, O. gigal (L) and O. edulis (L). They demonstrated that O. edulis accumulated cadmium from an uncontaminated environment. Thus, these food prohibitions are not polluted environment specific, but apply generally. One of the unfortunate safeguards of some clean fish to heavy metal poisoning (in this case, trivalent chromium) is demonstrated by its effect on the early life stages of the steelhead trout. Stevens and Chapman, 1984, demonstrated that contamination produced complete mortality in early life stage exposure from newly fertilised eggs to 30 d post swim up at 495 ug/l and significantly reduced survival at lesser levels. Hatching survival was significantly reduced at 271 ug/l. No acclimation resulted from previous chromium exposure. In other words, these clean fish, if contaminated, do not live or reach maturity and do not develop any immunity over time. The food laws thus remain constant. This law is the same yesterday, today and tomorrow. It was also demonstrated by Cai, Chera, Wu and Xu, in 1983, that the critical organisms for the accumulation of cobalt (Co) are phytoplankton and clam, and that of caesium (Cs), are phytoplankton and shrimp. In fish, the accumulation organs of Co and Cs are stomach, intestine and liver, thus eliminated by cleaning, whereas the whole of the other organisms are involved, except for shrimp where the accumulative organs of Co are head and chest and Cs distributes in the whole body of the shrimp (or prawn). This demonstrates that different forms of metals distribute themselves in various ways throughout the invertebrates and molluscs. It further demonstrates that the higher forms and clean species have more efficient systems of eliminating toxins. However, at too high a level, metals are uncontrolled. With cadmium, hematocrit value and red blood system is affected. At low levels the haemoglobin concentration, hematocrit value and red blood cell count is affected. Above that, liver damage and anaemia result (Kayama and Ozaki, 1984). It has also been demonstrated that increased levels of copper reduce respiratory and feeding rates of fish and maturity and fecundity as well as reducing the food chain from primary productivity, plankton and chromial production (Mukhopadhyay, 1983). Increased pollution will therefore limit also clean fish production. Ambient marine ecosystems are also prone to intake of concentrations of petroleum hydrocarbons. Observations on the blue mussel show increases after oil spillage clean-ups from a background 40 ug/g to 652 ug/g at 3 miles and 533 ug/g at 4.5 miles from shore. It becomes increasingly more dangerous to disregard the food laws and the susceptibility to pollutants among (particularly American) harbours of mussels and clams is well documented. All harbour environs worldwide are affected. Whilst increases in pollutants will necessarily mean an increase in the level found in fish, it could be argued that some clean fish, such as flatfish (i.e. flounder) are necessarily more at risk. It is true that zinc accumulation in external organs is important. It is argued that the Benthic way of life may not be responsible for a preferential bioaccumulation of trace metals in flatfish. The hypothesis of an uptake via food and sediment cannot be rejected, however (Amiard et al., 1983). It has also been established that many viruses of human origin are widely distributed in estuaric and coastal areas and have been isolated from seawater, marine sediments and shellfish samples. Evidence indicates that bacterial indicators are not true measures of the presence of viruses in polluted samples (Ellendar and Cook, 1981, and Flondorfer, 1984). Unclean foods are thus prohibited for their capacity to transmit entero-viruses also. Some also contain paralytic shellfish poisons on a widespread basis. One of the causes of paralytic shellfish poisoning in the green mussel, Perna oriental, in samples in the Philippines in 1983 was the dinoflagellate, Pyrodimium bahamense var compresse - a cause of a series of red tides in the early and middle 1970s. Toxicity levels were high and that indicates another aspect of both shellfish and red tides (see Gacutan et al., 1985). Poisoning appears at levels of about 60 ug toxin per 100 g meat; and is a serious problem in the northern coastal areas of the United States (Sullivan and Iwaska, 1983). There are now more than 12 known toxins involved in red tides and paralytic shellfish poisoning. The Gonyaulax toxin is widespread in the USA. Investigations also reveal weakly toxic organisms in areas never previously reported (Shuniza, 1983). Human pathogenic bacteria have been found to be high in crabs and oysters. With the exclusion of Staphylococcus aurcus, all of the pathogens were present in highest numbers in the live crabs and oysters suggesting that processing is effective in controlling the numbers of pathogens present in these types (Elliot and Colwell, 1982, pub. 1983). However, not all bacteria were controlled by processing. Tests have also revealed that even for clean fish, curing is an imperfect way of processing with defects in imperfect cleaning, inadequate salting, and unhygienic conditions of processing (Joseph et al., 1983). Fungus can be removed and fungal re-infestation can be prevented in dry fish products infested with fungus and red halophilic bacteria by washing, drying and then smearing with a mixture of 3% sodium propionate in dry refined salt in a ratio of 1 part dry mixture to 10 parts dry fish. The shelf life is five months (Nair et al., 1983). The bacteria Vibrio Flurialis has been isolated from shellfish in the Adriatic Sea. Eleven strains of this disease have been isolated in shellfish on the shores and for sale in retail shops. Vibrio Flurialis is a Ralophilic, causing human diarrhoea vibrio in fishery products of the Mediterranean, (Gionella et al, 1984). In the Galician, mussels appear not only to be infected with Gynadinium catenatum in addition to Protogonyaulax tamarensis causing paralytic shellfish poisoning, but also infections of a diarrhetic kind (Spain, 1983). The contamination of the estuaric environment in the USA by sewage has led to numerous outbreaks of Hepatitis A, Norwald illness and non-specific gastro-enteritis among shellfish consumers (Durham, NH USA, pub. June 1985, ISSN 0160-8347). A re-infective environment is thus set up amongst shellfish consumers and virus enteric illness (including Shigelloides) places these people at high risk. The diseases are thus self-inflicted wounds. Some of the infections of soft tissue wounds by estuaric vibrioneceae have also led to some fatalities. Consumption of shellfish and other unclean species appears to be sheer folly or, at best, a form of Russian Roulette. Man’s systematic destruction of his environment will ultimately destroy the delicate environment from which he subsists and the distinction between clean and unclean may become academic in the marine environment, as none may exist at all.
Posted on: Sun, 14 Dec 2014 12:43:00 +0000
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