Biology Reference
In-Depth Information
5. CONCLUSIONS
Teleosts undergo a spectacular diversity of postembryonic metamor-
phic transitions, but most of these transitions have been described only su-
perficially. Even in the most familiar teleosts, the proximate endocrine and
genetic mechanisms for different elements of metamorphosis have yet to be
described. Nonetheless, this period of profound remodeling encompasses
many inherently interesting developmental phenomena involving funda-
mental processes of morphogenesis and differentiation. Moreover, this pe-
riod of coordinated tissue modification offers the opportunity to examine
differential tissue responses to global endocrine signals. Genetic modifica-
tions to these postembryonic processes have contributed to the spectacular
diversity in adult morphology seen within teleost lineages, and elucidating
their attendant molecular mechanisms will lend considerable additional in-
sight into this diversification (
Harris, 2012
). Although the weight of evi-
dence supports roles for TH signaling in promoting metamorphosis in
teleosts, roles for other factors remain likely but uncertain, and the precise
mechanisms by which TH effects particular morphogenetic or physiological
outcomes remain largely unknown. Given the diversity of teleost metamor-
phoses and the particular tractability of some species (such as zebrafish) for
analyses of developmental, genetic, and endocrine mechanisms, it seems
certain that further studies of teleosts will provide important insights into
the evolution of metamorphosis and, more generally, the diversification
of physiology, behavior, and form.
GLOSSARY
Adult Reproductively mature form of an organism, possessing all adult organs and mature
gonads. Adults are not always in breeding condition as many species are seasonal
spawners.
Amphidromous Fish that migrate back and forth between fresh and salt water habitats, not
necessarily for the purposes of breeding.
Anadromous Fish that spawn in fresh water, then migrate to marine habitats.
Benthic Associated with the lower layers of the water column, just above the substrate.
Catadromous Fish that spawn in marine environments, then migrate to fresh water
habitats.
Demersal Associated with the very bottom of the water column, close to or in physical con-
tact with the substrate.
Diadromous Fish that migrate between salt water and fresh water environments (catadro-
mous and anadromous).
