and Applied Analysis 3 2. Preliminaries It is evident that (0, 0) is a trivial equilibrium of (6). The system (6) has at least four equilibria and at most six equilibria.The existence of nonnegative steady states depends on the locations of the three nullclines: c 11 u + V = z 0 , u + c 22 V = w 1 , u + c 22 V = w 2 . (7) The long-termbehavior of solutions to (6) can be qualitatively different ...

Flatfish such as the Atlantic halibut (Hippoglossus hippoglossus) undergo a dramatic metamorphosis that transforms the pelagic, symmetric larva into a benthic, cranially asymmetric juvenile. In common with amphibian metamorphosis, flatfish metamorphosis is under endocrine control with thyroid hormones being particularly important. In this report we confirm that tri-iodothyronine (T(3)) levels p...

a Centro de Biologia Ambiental, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal b ZoologischesForschungsmuseum Alexander Koenig, Museumsmeile Bonn, Adenauerallee 160, 53113 Bonn, Germany c Departamento de Estatística e Investigación Operativa, Facultade deMatemáticas, Universidade de Santiago de Compostela, Rúa Lope Gómez deMarzoa s/n, 15782 Santiago de Compostela, Spain

Thyroid hormone controls remodeling of the tadpole intestine during the climax of amphibian metamorphosis. In 8 days, the Xenopus laevis tadpole intestine shortens in length by 75%. Simultaneously, the longitudinal muscle fibers contract by about the same extent. The radial muscle fibers also shorten as the diameter narrows. Many radial fibers undergo programmed cell death. We conclude that mus...