The mussel pump: properties and modeling

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130

The nature of the bivalve filter-pump was further elucidated in the n~ussel Mytilus edulis by investigating effects of temperature on pump and system characteristics. Pumping rates increased with temperature, linearly correlated with the temperature-determined decrease in viscosity of the water. The variation in pumping rate with temperature thus corresponded to the varying viscous resistance to water flow in the canal system of the mussel-pump. The increase in beat frequency of the lateral cilia with temperature therefore had no clear effect on the pumping rate. Also, spawning stimulation of beat frequency was without effect on pumping rates. In the back pressure-flow characteristic of fully open, active mussels, pump pressure at zero flow (AH;) was independent of temperature. Predictions based on the pump modelled as a leaky, viscous, constant-force pump were in good agreement with measured and estimated pump parameters, further supporting the concept of suspension-feeding bivalves as filter-pumps that process the ambient water autonomously -that is, in the absence of physiological mechanisms for regulating water pumping.

Section: Pump Modelmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 95%

Effects of temperature on the mussel pump

Jørgensen¹,

Larsen²,

Riisgård³

1990

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130

“…Surprisingly, the CR was inhibited by exposing the mussels in a stepwise manner to different additions of serotonin for 40 min. Previous studies also found that different treatments with serotonin elicited contrasting pumping responses in bivalves (Gosselin 1961, Jørgensen et al 1988, Jones & Richards 1993. The CR was inhibited by dopamine in a concentration-dependent manner.…”

Section: Metal Uptake Influenced By Food Concentration and Clearance mentioning

confidence: 89%

Cd and Se aqueous uptake and exposure of green mussels Perna viridis: influences of seston quantity

Wang¹

2002

Trace metals are available to marine bivalves through uptake from both the aqueous and dietary phases. In this study, I sought to determine if there is any interaction between these 2 exposure pathways. The uptake of Cd and Se by green mussels Perna viridis from the aqueous phase was measured at different phytoplankton concentrations (green alga Chlorella autotrophica). Controlled experiments were performed to ensure that, in the presence of algal particles, the majority of metal accumulation by the green mussels was due to uptake from the aqueous phase. The influx rate of metals was independent of the food concentration and the clearance rate of the mussels, indicating that metal uptake from the aqueous phase was not directly related to the food concentration. These results verify the assumption that metal uptake from different exposure pathways is additive and that there is no direct interaction between different routes of exposure. Metal uptake by green mussels was further tested after exposing the mussels to neurotransmitters (serotonin which stimulates ciliary pumping and dopamine which inhibits ciliary pumping). Complete inhibition of ciliary pumping was reached after addition of 100 µM of dopamine. Despite changes in the pumping activity due to exposure to neurotransmitters, there was no evidence showing the reduction or enhancement of metal uptake. A bioenergetic-based kinetic model was then employed to model the influence of seston quantity on the exposure pathways of metals in the mussels. Our calculations indicated that the seston quantity substantially influences the relative importance of aqueous versus dietary exposure, primarily due to the dependence of a green mussel's ingestion activity on seston quantity. At a higher seston concentration, the exposure pathways are not influenced by the change in seston concentration due to the maintenance of a maximum ingestion rate and pseudofeces production.KEY WORDS: Metals · Mussels · Exposure pathway · Uptake · Cadmium · SeleniumResale or republication not permitted without written consent of the publisher

“…Maximal stimulation of the lateral cilia was obtained at about 10 -5 M 5-HT. At this concentration, the laterofrontal cirri were also overstimulated and thus removed from the interfilament canal (Jørgensen 1975, Jørgensen et al 1988, Nielsen et al 1993. Therefore, 10 -5 M 5-HT was adopted as a standard treatment in subsequent video-microscope experiments with gill-preparations in which the beat frequency of lateral cilia was studied as a function of seawater (20 psu) temperature in the observation vessel (regulated step-wise up and down using a Lauda RE 04 heater/cooler system).…”

Section: Methodsmentioning

confidence: 99%

Viscosity of seawater controls beat frequency of water-pumping cilia and filtration rate of mussels Mytilus edulis

Riisgård¹,

Larsen²

2007

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The small-scale movements of cilia make the temperature-dependent viscosity of water a key physical/mechanical factor. In mussels and other suspension-feeding bivalves, bands of waterpumping lateral cilia produce the feeding current through the interfilamentary canals of the enlarged gill (which mainly serves as a water-pumping and food-particle collecting organ). Because the viscosity of seawater is inversely related to temperature, the linear increase of filtration rate with temperature in mussels cannot be explained solely by increased biological activity. To resolve the question of whether change in filtration rate with temperature in mussels Mytilus edulis is under mainly biological/physiological or physical/mechanical control, we conducted laboratory experiments on mussel-gill preparations stimulated with serotonin, and on intact mussels. In gill-preparations, the beat frequency of the water-pumping lateral cilia was measured both as a function of temperature and as a function of kinematic viscosity in dextran-and PVP-manipulated seawater at constant temperature. Data on kinematic viscosity of seawater and viscosity-manipulated seawater were converted to 'temperature equivalents' of seawater by measurement of the viscosities, and this showed that the effect of temperature on lateral cilia activity in gill-preparations is purely mechanical, controlled by the viscosity of the ambient seawater. Further, the ciliary beat frequency was found to depend on kinematic viscosity to the power -3/2 (f ≈ ν -3/2 ), a relation we used to develop a musselpump model for the filtration rate of intact mussels vs. viscosity. The model is in agreement with filtration rates measured in intact mussels, suggesting that viscosity of seawater is the controlling factor for the beat frequency of lateral pump-cilia and filtration rate in mussels. According to the model, the mussel pump yields a constant power within the temperature-tolerance interval.