Limits...
Functional dorsoventral symmetry in relation to lift-based swimming in the ocean sunfish Mola mola.

Watanabe Y, Sato K - PLoS ONE (2008)

Bottom Line: We conclude that ocean sunfish have functional dorsoventral symmetry with regards to the non-homologous dorsal and anal fins that act as a pair of vertical hydrofoils.Although sunfish lack a swimbladder, we found that they are neutrally buoyant independent of depth because of their subcutaneous gelatinous tissue that has low density and is incompressible.Efficient lift-based swimming in conjunction with neutral buoyancy enables sunfish to travel long distances both horizontally and vertically.

View Article: PubMed Central - PubMed

Affiliation: International Coastal Research Center, Ocean Research Institute, The University of Tokyo, Otsuchi, Iwate, Japan. watanabe.yuuki@nipr.ac.jp

ABSTRACT
The largest (up to 2 tons) and a globally distributed teleost--the ocean sunfish Mola mola--is commonly regarded as a planktonic fish because of its unusual shape including absence of caudal fin. This common view was recently questioned because the horizontal movements of the ocean sunfish tracked by acoustic telemetry were independent of ocean currents. However, direct information regarding their locomotor performance under natural conditions is still lacking. By using multi-sensor tags, we show that sunfish indeed swam continuously with frequent vertical movements at speeds of 0.4-0.7 m s(-1), which is similar to the records of other large fishes such as salmons, marlins, and pelagic sharks. The acceleration data revealed that they stroked their dorsal and anal fins synchronously (dominant frequency, 0.3-0.6 Hz) to generate a lift-based thrust, as penguins do using two symmetrical flippers. Morphological studies of sunfish (mass, 2-959 kg) showed that the dorsal and anal fins had similar external (symmetrical shape and identical area) and internal (identical locomotory muscle mass) features; however, the muscle shape differed markedly. We conclude that ocean sunfish have functional dorsoventral symmetry with regards to the non-homologous dorsal and anal fins that act as a pair of vertical hydrofoils. Although sunfish lack a swimbladder, we found that they are neutrally buoyant independent of depth because of their subcutaneous gelatinous tissue that has low density and is incompressible. Efficient lift-based swimming in conjunction with neutral buoyancy enables sunfish to travel long distances both horizontally and vertically.

Show MeSH

Related in: MedlinePlus

Lateral (red line) and longitudinal (blue line) accelerations recorded from an ocean sunfish (mass, 48 kg).(A) Typical examples. The vertical broken lines delineate the separation of the stroke cycle. (B) Power spectral density (PSD) calculated from the entire data set of this individual. Arrows indicate peaks.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2562982&req=5

pone-0003446-g002: Lateral (red line) and longitudinal (blue line) accelerations recorded from an ocean sunfish (mass, 48 kg).(A) Typical examples. The vertical broken lines delineate the separation of the stroke cycle. (B) Power spectral density (PSD) calculated from the entire data set of this individual. Arrows indicate peaks.

Mentions: Lateral acceleration oscillated regularly, showing that the fish stroked their dorsal and anal fins from side-to-side (Fig. 2A). Longitudinal acceleration also oscillated regularly and peaked twice during one stroke cycle (i.e., the period taken by a fin to move from one extreme lateral position and back to the original position), indicating that each fin stroke (left-to-right or right-to-left) produced thrust. The same results were shown when the power spectral density (PSD) was calculated from the entire data set of each individual. The PSD of lateral acceleration had one peak, while that of longitudinal acceleration had two peaks (Fig. 2B). The peak in lateral acceleration and the lower-frequency peak in longitudinal acceleration are the dominant stroke cycle frequency for each individual (Table 1). The higher-frequency peak in longitudinal acceleration represents the frequency at which thrust is produced (twice the dominant stroke cycle frequency).


Functional dorsoventral symmetry in relation to lift-based swimming in the ocean sunfish Mola mola.

Watanabe Y, Sato K - PLoS ONE (2008)

Lateral (red line) and longitudinal (blue line) accelerations recorded from an ocean sunfish (mass, 48 kg).(A) Typical examples. The vertical broken lines delineate the separation of the stroke cycle. (B) Power spectral density (PSD) calculated from the entire data set of this individual. Arrows indicate peaks.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2562982&req=5

pone-0003446-g002: Lateral (red line) and longitudinal (blue line) accelerations recorded from an ocean sunfish (mass, 48 kg).(A) Typical examples. The vertical broken lines delineate the separation of the stroke cycle. (B) Power spectral density (PSD) calculated from the entire data set of this individual. Arrows indicate peaks.
Mentions: Lateral acceleration oscillated regularly, showing that the fish stroked their dorsal and anal fins from side-to-side (Fig. 2A). Longitudinal acceleration also oscillated regularly and peaked twice during one stroke cycle (i.e., the period taken by a fin to move from one extreme lateral position and back to the original position), indicating that each fin stroke (left-to-right or right-to-left) produced thrust. The same results were shown when the power spectral density (PSD) was calculated from the entire data set of each individual. The PSD of lateral acceleration had one peak, while that of longitudinal acceleration had two peaks (Fig. 2B). The peak in lateral acceleration and the lower-frequency peak in longitudinal acceleration are the dominant stroke cycle frequency for each individual (Table 1). The higher-frequency peak in longitudinal acceleration represents the frequency at which thrust is produced (twice the dominant stroke cycle frequency).

Bottom Line: We conclude that ocean sunfish have functional dorsoventral symmetry with regards to the non-homologous dorsal and anal fins that act as a pair of vertical hydrofoils.Although sunfish lack a swimbladder, we found that they are neutrally buoyant independent of depth because of their subcutaneous gelatinous tissue that has low density and is incompressible.Efficient lift-based swimming in conjunction with neutral buoyancy enables sunfish to travel long distances both horizontally and vertically.

View Article: PubMed Central - PubMed

Affiliation: International Coastal Research Center, Ocean Research Institute, The University of Tokyo, Otsuchi, Iwate, Japan. watanabe.yuuki@nipr.ac.jp

ABSTRACT
The largest (up to 2 tons) and a globally distributed teleost--the ocean sunfish Mola mola--is commonly regarded as a planktonic fish because of its unusual shape including absence of caudal fin. This common view was recently questioned because the horizontal movements of the ocean sunfish tracked by acoustic telemetry were independent of ocean currents. However, direct information regarding their locomotor performance under natural conditions is still lacking. By using multi-sensor tags, we show that sunfish indeed swam continuously with frequent vertical movements at speeds of 0.4-0.7 m s(-1), which is similar to the records of other large fishes such as salmons, marlins, and pelagic sharks. The acceleration data revealed that they stroked their dorsal and anal fins synchronously (dominant frequency, 0.3-0.6 Hz) to generate a lift-based thrust, as penguins do using two symmetrical flippers. Morphological studies of sunfish (mass, 2-959 kg) showed that the dorsal and anal fins had similar external (symmetrical shape and identical area) and internal (identical locomotory muscle mass) features; however, the muscle shape differed markedly. We conclude that ocean sunfish have functional dorsoventral symmetry with regards to the non-homologous dorsal and anal fins that act as a pair of vertical hydrofoils. Although sunfish lack a swimbladder, we found that they are neutrally buoyant independent of depth because of their subcutaneous gelatinous tissue that has low density and is incompressible. Efficient lift-based swimming in conjunction with neutral buoyancy enables sunfish to travel long distances both horizontally and vertically.

Show MeSH
Related in: MedlinePlus