Growth and intermediary metabolism of larval and metamorphosing stages of the landlocked sea lamprey, Petromyzon marinus L

Abstract

SynopsisSeasonal changes in blood, liver and muscle substrate (glucose, glycogen and lipid) concentrations and enzyme (pyruvate kinase (PyK), fructose diphosphatase (FDPase), NADPisocitrate dehydrogenase (ICDH), malic enzyme (ME) and the hexose monophosphate shunt dehydrogenases (HMSD)) activities were assessed in ammocoete and metamorphosing stages of a stream stock of the landlocked sea lamprey, Petromyzon marinus L. In all developmental stages studied, muscle rather than liver tissue served as the main site of carbohydrate and fat storage. Blood glucose and muscle lipid exhibited a positive relationship while liver HMSD and muscle ME activity, a negative relationship, with ammocoete weight. These responses were attributed to a proliferation of red fibers and adipocytes in the ammocoete muscle as the time of metamorphosis approched. Muscle lipid stores of ammocoetes in their last year of larval life increased dramatically during the fall and winter preceding metamorphosis. Changes in tissue enzyme activity of ammocoetes in their last year of larval life indicated that the liver was the site of amino acid incorporation into fat while muscle was the site of lipogenesis from glucose. During the non-trophic period of metamorphosis, stored material was catabolized to provide energy for protein synthesis.

Biology of the southern brook lamprey,Ichthyomyzon gagei

“…The lipid content of large ammocoetes in mid August, immediately prior to the beginning of metamorphosis indicates two categories, one of about 14% wet body weight and a second with values generally below 11'x (Beamish, unpublished data). Similar observations have been made for ammocoetes of Petromyron marinus in tributaries of Lake Ontario (Lowe et al 1973) and Oneida Lake (O'Boyle & Beamish 1977) and for larval Lampetra jluviatilzs by Moore & Potter (1976). There seems little doubt that for most I. gagei the age at metamorphosis is 4f years.…”

“…This is thought to represent the cumulative interactive effects of differing growth rates and variations in physical and biological factors within a watershed (Hardisty & Potter 1971a, Potter 1980. A further complicating factor in identifying the length of larval life is the tendency for at least some ammocoetes to remain at a similar length for one year or more prior to metamorphosis, an interval referred to as 'arrested growth' (Gage 1928, Leach 1940, 1946, Lowe et al 1973, Moore &Potter 1976, O'Boyle & Beamish 1977. During this period lipid reserves are accumulated in greater quantities than are present at any previous time in their development (Lowe et al 1973, O'Boyle & Beamish 1977, Potter 1980.…”

“…A further complicating factor in identifying the length of larval life is the tendency for at least some ammocoetes to remain at a similar length for one year or more prior to metamorphosis, an interval referred to as 'arrested growth' (Gage 1928, Leach 1940, 1946, Lowe et al 1973, Moore &Potter 1976, O'Boyle & Beamish 1977. During this period lipid reserves are accumulated in greater quantities than are present at any previous time in their development (Lowe et al 1973, O'Boyle & Beamish 1977, Potter 1980. These lipid reserves provide the major energy source throughout metamorphosis and, in the case of nonparasitic lampreys, the adult interval when animals are unable to feed due to morphological and structural changes (Weissenberg 1925, 1926, Boenig 1928.…”

Differences in the fatty acid composition of larvae and metamorphosing sea lampreys, Petromyzon marinus

“…The pronounced lipid accumulation in specific organs of pre-metamorphic larvae and the subsequent marked lipid mobilization from the whole body (Lowe et al, 1973) and lipid depot sites (O'Boyle and Beamish, 1977;Kao et al, 1997a) have been observed. Histological and biochemical evidence indicated that sea lampreys, like other poikilotherms (Sheridan, 1994), use a diverse strategy of lipid metabolism before and during their metamorphosis by storing lipids among several depots, including liver, kidney, fat column, subcutaneous tissue and myosepta (Lowe et al, 1973;O'Boyle and Beamish, 1977;Kao et al, 1997a).…”

Spontaneous and induced metamorphosis in the American brook lamprey, <i>Lampetra appendix</i>

“…Metamorphosis is a nontrophic interval in the lamprey life cycle (Potter 1980) and, in P. marinus, the catabolism of lipid is the primary energy source . In nonmetamorphosing sea lamprey larvae, lipids comprise, on average, about 4% of the live body mass, increasing to about 14% of the live body mass during the last year of larval life after the animal has reached a length comparable with that of metamorphosing animals (Lowe et al 1973;O'Boyle and Beamish 1977). Although sea lamprey larvae in an anadromous population in New Brunswick, Canada, must be at least 110 mm (length) and 2.0 g (mass) in size prior to beginning metamorphosis (Potter et al 1978), larvae in landlocked populations from the Great Lakes and Lake Champlain must be at least 120 mm (length) and 3.0 g (mass) in size .…”