Filtration and Respiration of the Deep Living Bivalve

7/30/2019 Filtration and Respiration of the Deep Living Bivalve

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cesta excavata(Pteriomorphia: Limidae) Suspension feeders living at 200-800m

below sea level

Highly modified gills

Creation of current

Capture of food

Greater O2 uptake from the water

Amount of H2O pumped

energy expenditure

Oxygen uptakemetabolic rate


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Acesta excavata

Collected in November 2000 and October 2001

At Roberg in Trondheimfjord, Norway between 200 and 530m

depth using triangular dredge

Calipers: shell height, length, thickness

Tank: Flowing water from 130m depth at temp. of 7.7-8.4C

Dry weight: weight of soft tissues after drying for 24hrs at

105C

Methodology


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Control

Clearance Rate1. SpecimensRandom: 100-140cm shell heightKept in containers at a flow rate of1.6L/min at 8CFed once or twice a week with algae

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2. Set up:a) well-oxygenated seawater withoceanic salinityb) a magnetic stirrerc) a small dose of alga

- one bivalve in each 5 aquaria

3. Clearance Rate:Closed system (8C)Collection: duplicate every 5 minsuntil concentration fell below 1000cells/mlConcentration readjusted andcollection repeated

CR = (V/t)ln(C0/Ct)


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1. Respiration rate:After filtration: 16 sameindividuals Constant air temp(8C)

2. Bivalves:Attached with Velcro to walls of 2.81 desiccators One animal was placed in each chamber (samequality of chamber as clearance set-up)

3. Measurement:

Sea water supply was replaced with BOD oxygenmeasuring probeDecline in oxygen tension under constantcondition was measured during the following60mins with reading taken every 5mins

4. After experiment:Water volume in each unit was measured todetermine exact volume for calculation Control for correct bacterial respiration,electrode drift, etc.Respiration rate: last 50mins of measurementwere used, ensuring undisturbed bivalves

Respiration Rate


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Gill Area

1. Bivalves:Sedated for a min. of 12hrsusing 7% MgCl2Removed intact demibranchsMeasure gill area

2. Unintact demibranchSpread in a Petri dish filled with seawaterImage capture of inner, right

demibranch

3. Gill Area:

Calculated in Scion Image Softwarev.1.62cAverage of 3 measurements of eachdemibranch was multiplied by 8 toestimate total gill area


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Table 1. Effect of different explanatory variables on variation in clearancerate ofAcesta excavata from the Trondheimsfjord in Norway

Explanatoryvariable

na

( 1 s.e.)b

( 1 s.e.)F p R2

Shell height(mm)

260.355

(1.585)0.899

(0.938)0.92 0.348 0.04

Dry weight (g) 23 13.356(4.209)

0.483(0.219)

4.89 0.038 0.19

*Clearance rate was significantly correlated with dry weight but not with shell height.

Results and DiscussionClearance Rate


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Explanatoryvariable

na

( 1 s.e.)b

( 1 s.e.)F p R2

Shell height

(mm)

190.0001

(0.0007)

1.743

(1.329)

1.72 0.209 0.09

Dry weight (g) 1613.356

(4.209)0.884

(0.204)18.75 0.001 0.57

Table 2. Effect of different explanatory variables on variation in respiration

rate ofAcesta excavata from the Trondheimsfjord in Norway

*Respiration rate was significantly correlated with dry weight but not with shell height.

Results and DiscussionRespiration Rate


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Table 3. Effect of different explanatory variables on variation in gill area of

Acesta excavata from the Trondheimsfjord in NorwayExplanatory

variablen

a( 1 s.e.)

b( 1 s.e.)

F P R2

Shell height

(mm)

201.468

(3.520)

1.940

(0.505)

14.74 0.001 0.45

Dry weight (g) 197063

(1286)0505

(0.126)16.12 0.001 0.49

*Gill area was significantly correlated with both shell height and dry weight.

Results and DiscussionGill Area


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Clearance rate increasedsignificantly withincreasing gill area.

Clearance rate wassignificantly correlated

with gill area, butclearance rate per mm2 isindependent of animaldry weight.


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Respiration rateincreased significantlywith increasing gill area.


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High clearance rate

Low respiration rate

Large gill area

Lies at extremes of all three variables measured

Values represent adaptations to the sparse food availability in the

deep sea rather than adaptations to depth per se.

cesta excavata


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Not a specialized deep-water phenomenon and several

other tropical bivalves also have developed large gills to

gain sufficient energy.

Respiration rate

Dependent on several factors such as temperature

Low respiration rate value

Due to low and stable temperature at whichA. excavata lives.

cesta excavata

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Filtration and Respiration of the Deep Living Bivalve