Changes in the proximate body composition of the landlocked sea lamprey Petromyzon marinus (L.) during larval life and metamorphosis

Abstract

Estimates were made of the growth rates and proximate body composition of larval and metamorphosing P. marinus (L.) collected at various times of the year from Shelter Valley Creek, Lake Ontario. Analysis of length‐frequency data indicates that the average duration of larval life was 6 years, with metamorphosis occurring predominantly in the length range above 13 cm. Increases in length were almost entirely restricted to the warmest months and did not take place during the final year of larval life. Three categories were thus recognized for the proximate analysis: ammocoetes <13 cm, ammocoetes > 13 cm and metamorphosing individuals. In ammocoetes <13 cm, seasonal differences were observed in the regression coefficients in the logarithmic relationships between wet weight and length and between each of water, lipid and ash and the wet weight. No such difference was found for the regressions between protein and wet weight. For a fixed length (9 cm), the wet weight varied only slightly during the year, although a small peak was seen in May. When considered on the basis of fixed weight (1 g), the relative amount of lipid deposited was greatest in May/July, coincident with a high diatom density. The water content followed an inverse pattern to that of lipid, while the protein and ash contents showed little seasonal variation and exhibited values lower than those normally found in teleosts. Throughout the last year of larval life, the animal stored a greater proportion of lipid, presumably to facilitate the energy demands of metamorphosis during which this food store underwent a marked reduction.

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

“…Much of this lipid deposition occurs during the autumn and winter months (Lowe, Beamish & Potter 1973). As carcass protein content varied significantly neither with season nor with age of the ammocoete (Lowe 1972), it is evident that lipogenesis was not operating at the expense of endogenous protein. There seems little doubt that deposition of lipid in pre-metamorphosing ammocoetes during the autumn and winter months is due primarily to the incorporation of food energy into lipid stores rather than into protein.…”

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>

“…This size is greater than the minimum for premetamorphic sea lamprey larvae from the Great Lakes (≥120 mm (length) and ≥3.0 g (mass); Youson et al 1993), premetamorphic L. fluviatilis and L. planeri (Bird and Potter 1979b), and premetamorphic G. australis . If, as in sea lampreys, lipid is the primary source of energy during the nontrophic phase of metamorphosis (Lowe et al 1973;Kao et al 1997), then the large size of premetamorphic L. appendix larvae may reflect a requirement for larger energy reserves to sustain individuals during the nontrophic periods of metamorphosis and subsequent sexual maturation. However, it is not clear why L. appendix is so much larger (length and mass) than some other nonparasitic species (e.g., L. planeri) before, during, and after metamorphosis.…”

“…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 .…”

“…Because both metamorphosis and the subsequent period of sexual maturation are nontrophic in nonparasitic species, the larvae presumably have greater energy reserves prior to entering metamorphosis than those of parasitic species that feed between metamorphosis and spawning. If, as in sea lampreys, lipid is the primary energy store (Lowe et al 1973;Kao et al 1997), then animal size and condition might also be important requirements for metamorphosis in nonparasitic lampreys.…”