Biology Reference
In-Depth Information
this leptin-like immunoreactivity is refl ecting important functions of a
leptin-like protein in metamorphosis of this species. Although defi nitive
identifi cation of lamprey leptin is still pending, recent fi ndings in other
anamniotes provide good rationale to continue the search for lamprey leptin
and the investigation into its possible function in lamprey metabolism and
development, particularly in metamorphosis of species like
P. marinus
.
2.8 Internal Changes During Metamorphosis
Youson (1980) provided a comprehensive summary of the anatomical and
physiological changes that occur during lamprey metamorphosis. This
review illustrated both the magnitude of the changes and the fact that
lamprey metamorphosis has been of fascination to biologists for nearly
two centuries. There is barely an organ or organ system that does not show
some alteration. These changes are either a complete regression or loss of
a larval structure, a transformation of a larval structure to the adult state,
redifferentiation of a larval structure or development of an adult structure
from anlagen that resided in the larva and waited for the metamorphic
stimulus. Needless to say, these anatomical changes were necessitated to
permit, in adult life, a new life style, perhaps in a new environment. The
changes to be described are mostly related to a parasitic and suctorial
feeding, but also to potential for saltwater acclimation, in adults. However,
the anatomical changes during metamorphosis and some physiological
changes that appear in species with a parasitic adult life history also occur
in those with a non-parasitic adult life history. Potter et al. (1982) feel
these common features of development in lamprey metamorphosis are a
refl ection of the origins of non-parasitic species from a parasitic ancestor.
As mentioned above, internal anatomical and physiological changes
during lamprey metamorphosis have had a long history of study and the
reader is referred to Youson (1980) for a historical review to the date of
that publication. The present report, given space restrictions, will focus
on highlighting and updating only a few of the events that surround the
anatomical and physiological changes.
2.8.1 Some selected anatomical and physiological changes
2.8.1.1 Skeletal system
Lampreys have an extensive cartilaginous endoskeleton most of which
is confi ned to the cranial and gill regions. Given the differences in their
mode of life, including feeding and swimming behaviours and habitat,
between larval and adult lampreys, it might be expected that there would
be skeletal differences. As can be seen in Fig. 9 (from Armstrong
et al
.
, 1987)
