Competition, clade replacement, and a history of cyclostome
and cheilostome bryozoan diversity.
Stenolaemates, including the cyclostomes
, form their skeletons almost entirely of low-Mg calcite; mineralogical complexity is provided by the gymnolaemate cheilostomes (Smith et al., 2006).
Stereotyped axonal bundle formation and neuromeric patterns in embryos of a cyclostome
, Lampetra japonica.
larval nervous systems are therefore functionally convergent with the sensory-motor systems present in some sponge and planula larval types (Woollacott, 1990; Leys and Degnan, 2001; Maldonado et al., 2003; Nordstrom et al., 2003).
Lampreys are jawless vertebrates (agnathans) and the most primitive representatives of the cyclostome
branch from which it is feasible to obtain embryos routinely.
and cheilostome marine bryozoans, two clades with such attributes, have co-occurred in similar environments for 150 million years.
The lamprey, which is a cyclostome
, has spermatozoa that carry a spherical acrosomal vesicle at the anterior end of their heads, subacrosomal material between the acrosome and the nucleus, and a long perforatorium rod through the nucleus (Follenius, 1965; Stanley, 1967; Nicander and Sjoden, 1971; Jaana and Yamamoto, 1981) [ILLUSTRATION FOR FIGURE 6B OMITTED].
Recent research on the skeletal ultrastructure of cyclostome
bryozoans has revealed an unanticipated diversity of calcitic fabrics (e.g., Boardman et al., 1992; Taylor and Jones, 1993; Taylor et al., 1995).
In Fishes of the western North Atlantic, part 1: lancelets, cyclostomes
, sharks (A.
Vertebrata Craniata (First fascile: cyclostomes
The more pronounced pressor responses observed in the trout, toadfish, and eel suggest that teleosts may be more sensitive to the pressor actions of ANGII than are cyclostomes