Biology Reference
In-Depth Information
metamorphosis, the angle changed by more than 35° (Keith et al., 2008). There
is a phase of very quick modifi cation of the angle in the fi rst days.
In
Sicyopterus stimpsoni
from Hawaii, Schoenfuss et al. (1997) also
reported observation of cranium metamorphosis. When the post-larvae of
this species migrate from the ocean to rivers, they remain in the estuary while
undergoing a total cranium restructuration. Forty-eight hours after entering
fresh waters, both the length of the snout and the height and width of the
head increase considerably. This process requires all the energy produced by
the fi sh's metabolism to the detriment of somatic growth (Schoenfuss et al.,
1997). This stop in individual growth is materialised on the otolith, which
displays a metamorphosis check mark clearly visible on individuals having
spent between 12-14 days in the river (Fig. 3). This check mark is therefore
an indicator of the transition between the sea and the river.
Figure 3.
(a)
S
.
lagocephalus
post-larvae otolith, check mark absent. (b)
S
.
lagocephalus
juvenile
otolith, check mark present. (c)
S
.
lagocephalus
adult otolith. (N: nucleus; CM: check-mark;
MLP: marine larval phase; AL: adult life in freshwater).
