title: Metabolic physiology of the invasive clam, Potamocorbula amurensis: the interactive role of temperature, salinity, and food availability.
abstract: In biological systems energy serves as the ultimate commodity, often determining species distributions, abundances, and interactions including the potential impact of invasive species on native communities. The Asian clam Potamocorbula amurensis invaded the San Francisco Estuary (SFE) in 1986 and is implicated in the decline of native fish species through resource competition. Using a combined laboratory/field study we examined how energy expenditure in this clam is influenced by salinity, temperature and food availability. Measures of metabolism were made at whole organism (metabolic rate) and biochemical (pyruvate kinase (PK) and citrate synthase (CS) enzyme activities) levels. We found in the field, over the course of a year, the ratio of PK to CS was typically 1.0 suggesting that aerobic and fermentative metabolism were roughly equivalent, except for particular periods characterized by low salinity, higher temperatures, and intermediate food availabilities. In a 30-day laboratory acclimation experiment, however, neither metabolic rate nor PK:CS ratio was consistently influenced by the same variables, though the potential for fermentative pathways did predominate. We conclude that in field collected animals, the addition of biochemical measures of energetic state provide little additional information to the previously measured whole organism metabolic rate. In addition, much of the variation in the laboratory remained unexplained and additional variables, including reproductive stage or body condition may influence laboratory-based results. Further study of adult clams must consider the role of organismal condition, especially reproductive state, in comparisons of laboratory experiments and field observations.
authors.affiliation: Romberg Tiburon Center and Department of Biology, San Francisco State University, Tiburon, California, United States of America.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Miller
authors.affiliation: Romberg Tiburon Center and Department of Biology, San Francisco State University, Tiburon, California, United States of America.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: Romberg Tiburon Center and Department of Biology, San Francisco State University, Tiburon, California, United States of America; Department of Integrative Biology, University of California, Berkeley, California, United States of America.
authors.forename: Jonathon H
authors.initials: JH
authors.lastname: Stillman
mesh_terms: D000064:Acclimatization; D000818:Animals; D049872:Bivalvia / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005502:Food; D058865:Introduced Species; D016014:Linear Models; D011770:Pyruvate Kinase / Q000378:metabolism; D054712:Salinity; D013696:Temperature
chemical_list: D002950:Citrate (si)-Synthase; D011770:Pyruvate Kinase