cyclostome

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Related to cyclostomes: agnathans, Ostracoderms

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 ?
Peak recruitment of the two clades was, as at Signy Island, out of phase but in a regular manner: cyclostomes peaked just before cheilostomes in each study year.
In contrast to the monthly recruitment patterns, clades differed with respect to scale: cheilostomes typically occupying more space than cyclostomes (despite the similarity in recruitment).
A clear succession was apparent at 12 m; the cyclostomes were the initial major space occupiers but were replaced sequentially by cheilostomes, polychaetes, and sponges.
Cyclostomes were poor spatial competitors at Lough Hyne, being overgrown by most other encrusting faunal groups.
The highest measured performance of cyclostomes against cheilostomes was in Alaska (data from Barnes and Dick, 2000), but further analysis suggests that the assessment depends on the method of measurement.
Cyclostomes occupy less space and have lower species richness in the temperate and polar study localities, but the intensity of their recruitment is similar to that of cheilostomes (Figs.
New investigations of cyclostome bryozoans have shown that calcitic semi-nacre is widespread, particularly in the fixed-walled suborders Tubuliporina and Articulata.
Other investigations of cyclostome skeletons have failed to reveal unequivocal semi-nacre.
Comparison with other cyclostome bryozoan ultrastructures
The semi-nacreous structure is very similar to that described in Hornera (Taylor and Jones, 1993), a free-walled cyclostome belonging to the suborder Cancellata.
The subdivision of the cyclostome bryozoan tablets into alternating soluble and less-soluble sectors has important bearing on the relationship between cyclostome calcitic semi-nacre and molluscan aragonitic nacres.
The form and complexity of the organization of the calcitic semi-nacre of cyclostome bryozoans resembles that of the aragonitic nacreous tablets in molluscs.