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Endocrinology of the lampreys

1969; Elsevier BV; Volume: 2; Linguagem: Inglês

10.1016/0016-6480(69)90059-8

1095-6840

G. Sterba,

Fish Biology and Ecology Studies

The ammocoetes larvae of the modern Petromyzontiformes are slowly growing filter feeders, and the imagines are rapidly growing macrophagous fish parasites. The larvae demonstrate the prototypal metabolism of the Silurian and Devonian Agnatha; the imagines show the typical metabolism of the Gnathostomata. The metamorphosis repeats the period of evolution in which the Gnathostomata arose from the Agnatha. The graduation and differentiation of the metabolism is also expressed in the endocrine system. These principal conditions are varied throughout the environments in the different phases of the life cycle of Petromyzontiformes. After a long larval period in freshwater the young lampreys migrate toward the sea (catadromous migration). Here they start the parasitic feeding period. After some time they cease irreversibly to feed and gather for the spawning migration. After spawning in freshwater they die. During and after metamorphosis the following endocrine organs are increased characteristically: adenohypophysis; endostyle → thyroid; medulla and cortex cells scattered along the kidneys. Only few changes are visible in the hypothalamoneurophypophyseal system and in the islets of Langerhans. Thymus and parathyroids are absent in Petromyzontiformes. Our knowledge is based predominantly on morphological and classical experimental methods. Biochemical and pharmacological studies are as yet rare. Nothing is known of the marine parasitic-feeding period. The following hormones have been identified in lampreys: vasotocin, thyroxine, triiodothyronine, insulin. Vasotocin affects only sodium metabolism; no antidiuretic action could be demonstrated. The presence of steroids is probable. By investigations of the endocrine system of Petromyzontiformes results may be obtained showing the primary function of the vertebrate hormones.