1:45 PM - 3:15 PM
[O11-P42] Differences of responses of fishes internal and external stimulation by salinity in coastal brackish waters
Keywords:Ocean brine, Homeostasis, Brackish waters
1. Internal Environment
The whitebait is a fish characterized by its colorless and transparent body.
We have experimented with whitebait collected from a brackish area with 2% salinity.
Utilizing this feature, we observed their nerve structure and compared heart rate and respiratory rate along with the salinity difference.
(1) Method
i) Observation of Nervous System:
The segments of the notochord were counted from above and below the swim bladder organ, counted total of 263 individuals.
ii) Experimental method for salinity and inner body relations:
The Effect of Salinity on Heart Rate and Breathing-- Four individuals of the whitebait fish were divided and placed in 200mL beakers with 150mL of artificial seawater at concentrations of 1%/2%/3%. After acclimatizing each saltwater condition for about an hour, heart rate and respiratory rate were compared.
(2) Results
i) Number of Nervous Systems (Notochord) (N=263):
Above the swim bladder organs, an average of 10.2 notochords was observed, with little error. Below the swim bladder, an average of 20.1 notochords was observed, with a slightly larger error.
ii) Effects of Salinity on Heart Rate and Breathing Rate:
The heart rate at a salinity of 2% (closest to natural sea conditions) was 94.4 beats per minute, while at a high salinity of 3% it was 73.6 beats per minute, and at a low salinity of 1% it was 87.0 beats per minute. The breathing rate was 50.0 breaths per minute at high salinity (3%), 64.1 breaths per minute at 2% salinity (closest to natural sea conditions), and 68.9 breaths per minute at low salinity (1%), indicating that the breathing rate was higher at lower salinity.
(3) Discussion
i) Observation of Nervous System:
The notochord structure shows relatively little individual variation above the swim bladder, while below the swim bladder there is significant variation. This may indicate that the lower body has much grown during development or that there are greater congenital indivisually.
ii) Salinity and inner body relations:
Regarding heart rate, it seems that environments with a higher or lower salt concentration than usual lead to slower blood transportation to avoid drastic change in the internal environment. Additionally, since respiratory rates tend to be slower in higher concentrations overall, it can be inferred that this may function to minimize the intake of water and mitigate environmental changes.
2. External Environment
Pufferfish and mullets are benthic organisms that experience changes in water flow in ocean, but they can also be found in brackish area even though low salinity circumstances. By comparing the differences between offshore and coastal environments, we examined the extent to which variations in activity levels can be attributed by the influence of inorganic environments.
(1) Method
i) Physical Response:
We compared how far pufferfish and mullet could swim against the current at a constant rotational speed in three patterns: seawater (2.8%), brackish water (1.4%), and freshwater.
ii) Visual Response:
We rotated paper shapes modeled pufferfish on the walls of a circular tank at a constant speed and compared the differences with the movement of those shapes.
(2) Results
i) Physical Response:
Mullet which can swim upstream in fresh water, showed strong resistance and swam to upstream to water flow at a concentration of 1.4% in brackish water, while pufferfish exhibited strong resistance saline water which is concentration of 2.8%.
ii) Visual Response: Pufferfish showed the strongest response at 2.8% seawater.
(3) Discussion
Marine puffers have a strong resistance to ocean currents. Brackish water mullets are thought to have a strong resistance to flowing rivers.
The whitebait is a fish characterized by its colorless and transparent body.
We have experimented with whitebait collected from a brackish area with 2% salinity.
Utilizing this feature, we observed their nerve structure and compared heart rate and respiratory rate along with the salinity difference.
(1) Method
i) Observation of Nervous System:
The segments of the notochord were counted from above and below the swim bladder organ, counted total of 263 individuals.
ii) Experimental method for salinity and inner body relations:
The Effect of Salinity on Heart Rate and Breathing-- Four individuals of the whitebait fish were divided and placed in 200mL beakers with 150mL of artificial seawater at concentrations of 1%/2%/3%. After acclimatizing each saltwater condition for about an hour, heart rate and respiratory rate were compared.
(2) Results
i) Number of Nervous Systems (Notochord) (N=263):
Above the swim bladder organs, an average of 10.2 notochords was observed, with little error. Below the swim bladder, an average of 20.1 notochords was observed, with a slightly larger error.
ii) Effects of Salinity on Heart Rate and Breathing Rate:
The heart rate at a salinity of 2% (closest to natural sea conditions) was 94.4 beats per minute, while at a high salinity of 3% it was 73.6 beats per minute, and at a low salinity of 1% it was 87.0 beats per minute. The breathing rate was 50.0 breaths per minute at high salinity (3%), 64.1 breaths per minute at 2% salinity (closest to natural sea conditions), and 68.9 breaths per minute at low salinity (1%), indicating that the breathing rate was higher at lower salinity.
(3) Discussion
i) Observation of Nervous System:
The notochord structure shows relatively little individual variation above the swim bladder, while below the swim bladder there is significant variation. This may indicate that the lower body has much grown during development or that there are greater congenital indivisually.
ii) Salinity and inner body relations:
Regarding heart rate, it seems that environments with a higher or lower salt concentration than usual lead to slower blood transportation to avoid drastic change in the internal environment. Additionally, since respiratory rates tend to be slower in higher concentrations overall, it can be inferred that this may function to minimize the intake of water and mitigate environmental changes.
2. External Environment
Pufferfish and mullets are benthic organisms that experience changes in water flow in ocean, but they can also be found in brackish area even though low salinity circumstances. By comparing the differences between offshore and coastal environments, we examined the extent to which variations in activity levels can be attributed by the influence of inorganic environments.
(1) Method
i) Physical Response:
We compared how far pufferfish and mullet could swim against the current at a constant rotational speed in three patterns: seawater (2.8%), brackish water (1.4%), and freshwater.
ii) Visual Response:
We rotated paper shapes modeled pufferfish on the walls of a circular tank at a constant speed and compared the differences with the movement of those shapes.
(2) Results
i) Physical Response:
Mullet which can swim upstream in fresh water, showed strong resistance and swam to upstream to water flow at a concentration of 1.4% in brackish water, while pufferfish exhibited strong resistance saline water which is concentration of 2.8%.
ii) Visual Response: Pufferfish showed the strongest response at 2.8% seawater.
(3) Discussion
Marine puffers have a strong resistance to ocean currents. Brackish water mullets are thought to have a strong resistance to flowing rivers.