title: Physiological responses to digestion in low salinity in the crabs Carcinus maenas and Cancer irroratus.
abstract: Osmoregulation and digestion are energetically demanding, and crabs that move into low salinity environments to feed must be able to balance the demands of both processes. Achieving this balance may pose greater challenges for weak than for efficient osmoregulators. This study examined the rate of oxygen consumption (MO2) of Carcinus maenas (efficient osmoregulator) and Cancer irroratus (weak osmoregulator) as a function of feeding and hyposaline stress. The MO2 increased 2-fold in both species following feeding. The MO2 increased and remained elevated in fasted crabs during acute hyposaline exposure. When hyposaline stress occurred after feeding, C. maenas responded with an immediate summation of the MO2 associated with feeding and hyposaline stress, whereas C. irroratus reacted with a partial summation of responses in a salinity of 24‰, but were unable to sum responses in 16‰. C. irroratus exhibited longer gut transit times. This may be due to an inability to regulate osmotic water onload as efficiently as C. maenas. Mechanical digestion in crabs can account for a significant portion of SDA, and a short term interruption led to the delay in summation of metabolic demands. Although protein synthesis is reported to account for the majority of SDA, this did not appear to be the case here. Protein synthesis rates were higher in C. irroratus but neither feeding or salinity affected protein synthesis rates of either species which suggests that protein synthesis can continue in low salinity as long as substrates are available.
authors.affiliation: Environmental and Life Sciences, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada K9J 7B8; Department of Ocean Sciences, 0 Marine Lab Road, Memorial University, St. John's, NL, Canada A1C 5S7. Electronic address: chantellepenney@trentu.ca.
authors.forename: Chantelle M
authors.initials: CM
authors.lastname: Penney
authors.affiliation: School of Ocean Sciences, Bangor University, Askew Street, Menai Bridge, Anglesey, LL59 5AB, United Kingdom.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Patton
authors.affiliation: School of Biological Sciences, Bangor University, Deiniol Road, Bangor, Gwynedd, LL57 2RW, United Kingdom.
authors.forename: Nia M
authors.initials: NM
authors.lastname: Whiteley
authors.affiliation: Department of Ocean Sciences, 0 Marine Lab Road, Memorial University, St. John's, NL, Canada A1C 5S7.
authors.forename: William R
authors.initials: WR
authors.lastname: Driedzic
authors.affiliation: Department of Ocean Sciences, 0 Marine Lab Road, Memorial University, St. John's, NL, Canada A1C 5S7.
authors.forename: Iain J
authors.initials: IJ
authors.lastname: McGaw
mesh_terms: D000818:Animals; D003386:Brachyura / Q000502:physiology*; D004063:Digestion / Q000502:physiology*; D005215:Fasting; D005772:Gastrointestinal Transit; D006458:Hemolymph / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D010649:Phenylalanine / Q000378:metabolism; D014176:Protein Biosynthesis; D054712:Salinity; D013270:Stomach / Q000502:physiology; D013997:Time Factors
chemical_list: D010649:Phenylalanine
keywords: Cancer irroratus; Carcinus maenas; Digestion; Osmoregulation; Oxygen consumption; Protein synthesis; Salinity; Specific dynamic action