Mollusk squid

Molluscan shellfish play an important role in human nutrition and the world economy (Wild and Lehrer, 2005). Table 4.2 provides data on the worldwide production/catch of various molluscan shellfish species for 2005. The most widely available species are oyster, squid, clam, mussel, and scallop. Aquaculture has become an important contributor to the production of molluscan shellfish with the exception of the cephalopods. However, the popularity and frequency of consumption of various molluscan shellfish varies widely across various countries and cultures. Accurate information on comparative consumption patterns for molluscan shellfish in various countries does not exist. Molluscan shellfish are consumed as freshly cooked or even raw seafood items particularly in coastal communities. But mollusks also are consumed as processed foods in a variety of forms. 

Cephalopods are the smartest and most complex of the mollusks. This group includes squid, octopus, cuttlefish, and chambered nautilus. The ammonites were an extremely diverse and successful group of cephalopods that roamed the world s oceans for millions of years until their extinction at the end of the Cretaceous period, about 65 million years ago. 

Mesozoans are parasites of a wide range of marine invertebrates, including flatworms, roundworms, mollusks, and echinoderms. Two main groupings have been recognized the order Qrthonectida, which are free-living within their hosts, and the Dicyemida, which have specialized cells on the body wall that serve to attach them to the walls of the kidneys in species such as octopus and squid. 

The largest number of species of mollusks are in the class Gastropoda, which includes snails with a coiled shell, and others lacking a shell. The next largest group are the bivalves (class Bivalvia), the chitons (class Am-phineura), and octopus and squid, (class Cephalopoda). The other classes of mollusks are the class Scaphopoda (consisting of a few species of small mollusks with a tapered, tubular shell) and the class Monoplacophora, a... 

Nervous tissue of a variety of invertebrates has been screened for OPA anhydrase activity. Other mollusks have been reported to contain OPA anhydrases, notably Octopus, Anisodoris (sea-lemon), Aplysia (sea-hare), and Sepia (cuttlefish) (Hoskin and Long 1972). Sepia and Octopus hydrolyze DFP faster than tabun, a squid-type OPA anhydrase characteristic employed at that time, and now by the DFP/soman ratio. Conversely, Aplysia, Spisula, andHomarus (lobster) hydrolyze tabun faster than DFP (Hoskin and Brande 1973), a typically Mazur characteristic. Soman to DFP ratios and Mn2+ stimulation for several species are shown... 

The hemocyanins are the oxygen-transport proteins of the three largest classes of mollusks (e.g., snails and squids), and of arthropods (e.g., spiders and scorpions). Mollusk and arthropod hemocyanin resemble each other in function... 

The mollusk Watasenia scintillans is a small bioluminescent deep-sea squid. The squid has three black-pigmented light organs (< 1 mm diameter) on the tip of the fourth pair of ventral arms and the light emission from the arm light organs is extremely bright when stimulated. 

Humans eat fish of more than 1000 fish species approximately 350 of these species are regarded as commercially valuable. The term fish products applies to all marine and freshwater animals, including finfish (i.e., scale fish or bony fish, and sharks and rays) and shellfish (i.e., the crustaceans [e.g., prawns, shrimps, lobsters, Antarctic krill], and mollusks [e.g., squid, oysters, abalone]). The only exceptions are aquatic mammals and frogs (EC Directive 91/493/EEC). Overall, the number of species from aquatic environments consumed by humans is consequently much higher. The marine and freshwater fish consumed by humans are mainly wild-caught. On the other hand, cultured fish contribute about 12% to the world fish catch, but these are mainly freshwater fish. Edible parts of fish include fillets (mainly the muscle tissue called the fish meat, with or without skin), carcasses (e.g., canned), and by-products of some fish species, mainly gonads (roe) and livers (of lean fish). 

Lipid content of finfish can vary over a wide range (0.3 to 45%, w/w). In contrast, shellfish, which are mostly crustaceans (prawns, crabs, lobster, crayfish), and mollusks (bivalves, squids) usually only contain 1 to 2% lipids. In Poland, where many high-lipid finfish are consumed, fish can be divided into four basic groups lean (below 2% lipid), medium fat (2 to 7% lipid), fat (7 to 15% lipid), and high fat (more than 15% lipid) (Table 12.1). This classification differs from the commonly used classification of Lambertsen (1978), who divided fish into the following four classes (Ackman, 1994) ... 

Fish sterol content is relatively stable and ranges between 40 and 60 mg per 100 g edible fish muscle (Ackman, 1994 Krzynowek et al., 1990) 250 to 650 mg per 100 g roe (Sikorski et al., 1990) and 480 to 1150 mg per 100 g oil in livers of cod, herring, menhaden, and salmon (Kinsella, 1987 Kennish et al., 1992). In finfish, 95% of the total sterol is cholesterol. Shellfish usually contain two to three times more total sterol than finfish (Table 12.3). In a study of Australian seafood, the highest sterol contents (120 to 160 mg/100 g) were recorded in shellfish such as prawns, squid, octopus, and scallops (Nichols et al., 1998). In mollusks, such as the oyster Crassostrea gigas and abalone Haliotis spp., cholesterol is usually the main sterol, but a complex suite of other sterols are present (e.g., Dunstan et al., 1993 Dunstan et al., 1996). 

Bivalves (e.g., clams, oysters, scallops, mussels), gastropods (e.g., abalone, snails), and cephalopods (e.g., squid, octopus, cuttlefish) are highly appreciated seafood in many countries. In contrast to fish, mollusks could not be differentiated satisfactorily by protein-based methods. Unlike fish fillet, meat of mussel consists of a number of tissues with different protein profiles. Therefore, PCR is especially useful for identification of mollusks, as all tissues contain the DNA of the same sequence. In the case of... 

Pyloric ceca, pancreatic tissues, intestines, hepatopancreas (stomachless bone fish, sardine, capelin, cod, cunner, salmon, chovy, palometa, Atlantic white croaJcer, carp, hybrid tilapia, herring, spiny dogfish, rainbow trout, crustaceans, mollusks, short-finned squid)... 

NATURAL RESOURCES Chitin is a biopolymer found in crustaceans shells (crab, shrimp, prawn, lobster) in some mollusks (krill, oyster, clam shells, squid skeleton). It is also found in fungi (mushrooms, yeast) and in various insects (cockroaches, silkworms, spiders, beetles). 

There are numerous sources of chitin (Fig. 1) and chitosan is obtained by deacetylatmg chitin with a hot alkali solution. Chitin has been found in a wide array of natural sources, namely crustaceans, fungi, yeasts, insects, annelids, nematodes, mollusks, coelenterate, marine diatoms, squid pens, etc. [16-19]. However, chitosan is primarily manufactured from the exoskeleton of crustaceans (crab, shrimp, prawn, lobster, krill, and crayfish) because of its abundant availability as a by-product of food processing [20, 21]. 

The spear-type glass microelectrode (Hinke-type) (2) (Figure la) has been used to determine the intracellular pH of the crab muscle fibers (3,4), cytoplasm of the giant squid axon (5), rat sartorius muscle fibers (6), rat atrial muscle fibers (7), vacuole of the algae Nitella flexilis (8), rat kidney tubular fluid (9,10), nerve cells of mollusk ganglia (11), and skeletal muscle fibers of the rat (4,12,13,14). 

With more than 100 000 species, the phylum MoUusca is the second largest after the Arthropoda and, like the latter, the MoUusca includes as many marine species as terrestrial species. There are at least 50000 species of marine mollusks, and many of these are very familiar to the general public - everybody knows what a cuttlefish, a squid or an octopus is. MoUusk sheUs have been of considerable economic importance since antiquity. ... 

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