cyclostome


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cyclostome

(sī`kləstōm'), jawless fish, member of the vertebrate superclass Cyclostomata (see ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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). This group includes the hagfishhagfish,
primitive, jawless marine fish of the family Myxinidae, of worldwide distribution in cold and temperate waters. Its rudimentary skeleton, of cartilage rather than bone, has a braincase, but no jaw. The circular sucking mouth has rows of horny teeth.
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 and the lampreylamprey,
name for several primitive marine and freshwater jawless fishes of the order Petromyzontiformes. As in the other jawless fish, the hagfish, the adult lamprey retains the notochord, the supporting structure that in higher vertebrates is found only in the embryo.
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.
References in periodicals archive ?
Recruitment of cheilostome and cyclostome bryozoans was measured from 1991 to 1994 at Powell Rock, Signy Island, Antarctica.
Recruitment of cheilostome and cyclostome bryozoans was measured from 1997 to 2001 at Lough Hyne Marine Nature Reserve, County Cork, West Ireland.
Other investigations of cyclostome skeletons have failed to reveal unequivocal semi-nacre.
Fishes of the Western North Atlantic, Lancelets, cyclostomes, and sharks.
Males have also been observed eating benthic-dwelling elasmobranchs (Condit and Le Boeuf 1984) and are known to prey on cyclostomes, a behavior that is rare in females (Antonelis et al.
Timing of genome duplications relative to the origin of the vertebrates: did cyclostomes diverge before or after?
A possible explanation is that the main Palaeozoic encrusters (trepostomes, cryptostomes, echinoderms, corals) had scour-susceptible soft tissue covering their skeletons, whereas the dominant Mesozoic encrusters (serpulids, bivalves, most cyclostomes) had true exoskeletons into which soft parts of the living animals could withdraw completely (Palmer 1982).
Because all vertebrate hemoglobins are intracellular heterotetramers of the type [[Alpha].sub.2][[Beta].sub.2] (except for those of the cyclostomes) (1), and because sickling is controlled by the molecular makeup of the Hb molecules (1, 2), variations in sickling among the species appear to be due to variations in the globins.
In future studies, we should use these probes to isolate endostyle-specific genes from cephalochordates, cyclostomes, and hemichordates.