Biology Reference
In-Depth Information
NC
T
O
N
VMLB
B
1a
T
O
NC
N
1b
B
P
Figure 9.
Diagrammatic representations of the elements of the skeleton of the larval (upper
fi gure) and adult lamprey. In the larva the cartilaginous structures are shaded black. The
neurocranium consists of the nasal capsule (N), trabeculae (T), and otic capsule (O). The
branchial cartilages (B) compose the branchial arches (basket). A special connective tissue,
mucocartilage, appears stippled. A region of mucocartilage, the ventromedial longitudinal bar
(VMLB), develops into the piston cartilage (see adult below). The same neurocranial cartilages
are present in the adult but there are more cartilages supporting the suctorial disc. The piston
cartilage (seen in black) develops from the larval (VMLB), the branchial cartilages are more
elaborate, and there is a new pericardial cartilage (P). NC, notochord. (From Armstrong et
al., 1987).
genes for lamprin during metamorphosis (Robson, 1998), for certain areas
occupied by mucocartilage in larva become replaced by lamprin-containing
cartilage (Armstrong et al
.
, 1987). Thus, mucocartilage is not a true cartilage
but a form of loose, embryonic connective tissue that, once metamorphosis
is initiated, demonstrates its embryonic nature, by dedifferentiating into
a mesenchyme-like tissue that redifferentiates into chondroblasts that lay
