돛새치의 음향 포식
Jul 24, 2023Scientific Reports 13권, 기사 번호: 13820(2023) 이 기사 인용
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돛새치가 바다 표면 근처의 소용돌이에 날치 떼를 모으기 위해 선회할 때, 반대 방향으로 배치된 70° 섹터에 국한된 작은 호형 표면파 패치가 일관되게 분산되는 것처럼 보입니다. 그런데 왜 그럴까요? 물고기의 움직임이 갑자기 멈출 때 우리에 갇힌 무리가 압축되고 꼬리가 추진 소용돌이가 접촉하여 부서지고 원심 소용돌이 회전에서 방출되는 압력을 방출하여 음향 모노폴을 생성하는 것으로 모델링되었습니다. 표면파 패치는 복사 영역의 일부입니다. 돛새치와 날치의 반대 방향으로 배치된 곡선 몸체는 모노폴에 대한 오목한 음향 거울 역할을 하여 그 사이에서 반향하는 종 모양의 망토를 생성하며, 그 사이에서 날치의 귀뼈와 방광을 진동시켜 방향 감각을 잃습니다. 테이블 위에 물 한 컵을 세게 치면 순수한 방사형 모드와 유사한 진동이 발생합니다. 돛새치는 수직면에서 바람에 의해 유도된 수중 토로이드 운동이 무시할 수 있는 깊이에서 학교 주위를 돌며 날치가 위의 순풍 방향을 감지할 수 없어 위로 수영하고 활공하기 위해 올바른 방향으로 나오는 능력이 제한됩니다. . 실험을 통해 날치 꼬리의 강성이 너무 낮아서 빠른 탄도 탈출이 필요하지 않은 것으로 확인되었습니다.
광합성으로 인해 열대 바다의 최상층에는 생명체와 포식자-피식자 상호 작용이 풍부합니다("방법" 섹션에 정의됨). Attenborough1(및 https://drive.google.com/file/d/1gn-uobapyDTq7DYlEkmlRuEBC7ExYxA2/view?usp=drive_link)의 생생한 비디오에서 포착된 돛새치 날치의 포식자-먹이 상호 작용에서 타임 스탬프 m :s 0:45−0:51("방법" 섹션) 동안, 놓치기 쉬운 고도로 조직화된 작은 표면파 패킷이 자유 표면에 나타나 일관성을 유지하면서 방사형으로 분산됩니다. 파동 다발은 어디에서 왔으며 왜 형성됩니까? 더욱이 자유 표면 근처의 바다는 반무한입니다. 그렇다면 돛새치는 어떻게 100여 마리의 날치들을 한 손으로 모아서 그들의 탈출을 막고 활공하기 위해 위로 올라가거나 더 깊은 바다로 내려갈 수 있습니까? (때때로 두 번째 돛새치가 합류하지만 나중에 합류합니다). 돛새치는 우리를 모으는 데는 놀랄 만큼 성공하지만, 적극적인 추적에도 불구하고 날치를 거의 잡지 못하는 이유는 무엇입니까? 후자는 더 놀라운데, 돛새치는 3차 소비자, 즉 정점 포식자이고 날치는 2차 소비자이기 때문입니다. 파도 패치가 어떻게 형성되고 왜 우리가 먼저 그렇게 성공적이었는지 설명하는 이론적 상호 작용 모델이 제공되지만 나중에는 흔하지 않은 위상적 분기 불안정으로 인해 먹이 물고기가 탈출할 수 있습니다.
상호 작용의 중요한 맥락은 돛새치가 처음에 길이 척도로 1m를 설정하는 반면 날치 길이 척도는 순항 속도와 관련된 몸 길이인 0.1m라는 것입니다. 상호작용의 가장 주목할만한 측면은 학교 토폴로지에 있으며, 날치 떼가 서로 평행하게 수영하는 대신 집단으로 가상 세계로 헤엄치는 '점'까지 학교가 압축되고 점근적으로 붕괴되는 순간이 갑자기 나타납니다. 싱크대 흐름에서 유래되었으며, 당황한 듯 입을 벌리고 있습니다. 물리적으로 상호작용 규모는 1m\(\rightarrow\) 0.1m에서 감소합니다. 두려움과 관련된 학교교육은 진화만큼이나 깊기 때문에, 무엇이 그러한 원초적인 본능을 압도할 수 있었겠는가? 위상학적 불안정성과 이에 수반되는 두려움의 유발 요인은 궁극적으로 날치 뇌에 작용하여 견딜 수 없는 고통을 유발하는 음향 자극에 의해 발생하는 것처럼 모델링됩니다. 소용돌이 회전의 운동 에너지는 돛새치에 의해 갑자기 중단되어 반대쪽에 위치한 돛새치와 오목 음향 거울 역할을 하는 날치 떼 사이에서 반향되는 압력 충격을 생성합니다. 오일러 파동과 Lighthill 소음 방정식은 이론을 음향 현상의 자유 표면파 발자국과 비교하는 데 사용됩니다. 충격파의 압력과 시간 규모를 추정하기 위해 와류 파괴 모델이 제공됩니다.
0\) and for flying fish \(z > 0\) or \(z < 0\); the sailfish remains in the swimplane thereby increasing the separation. The flying fish cruising returns where \(z > 0\) or \(z < 0\). The interaction then is about reduction of swim velocity and separation−a frictional process. The concave sail fish and flying fish bodies cloak (wrap around) the space of vorticity and acoustics. (c): shaded area is laboratory disk measurements, left line is laminar, right line is turbulent and the curved line is transitional./p>> I_x\) in the sailfish, but \(I_x \approx I_y\) in the flying fish allowing the former to camber easily in the horizontal plane while the latter can apply torsion. One-to-one pursuit shows torsional escape by a corralled flying fish below the swim-plane1. The sailfish then is a planar swimmer while the flying fish is a three-dimensional swimmer. Because the smaller flying fish swim in schools, it is easier to corral them in the horizontal plane. Assume \(\pi d = 2L\), where d is the minimum packing diameter of the school and L is the length of the sailfish. For L = 1 m, \(d =\) 0.64 m. If \(d=20 b\), \(b =\) 3 cm, which is reasonable, that is 10 flying fish are stacked side by side. We get \(10^2\) fish in the school which is approximately as observed1. Alternatively, for a 50 kg sailfish, the equivalent flying fish mass is 0.50 kg which is reasonable. Approximately, the packed flying fish school equates to a sailfish./p>>1\) in the winglets. The wide winglet portfolio means that the sailfish reduces \(C_{di}\) at all speeds. Methods gives the properties of the axial locations of the two primary winglets \(W_1\) and \(W_2\), where the streamlines and circulation gradients change sign in order to improve stability. In Fig. 2d–f, the winglets are deployed then merged back as the camber \(\rightarrow\) 0, and \(U \rightarrow 0\). The sequence is similar to bald eagle landing./p>> | \Gamma _f |\) resulting in \(\Delta r_f (t) \rightarrow 0\) -an irreversible, topological and unstable singularity forms whence at least five fish turn simultaneously inward toward a point ("Methods" section)1. To disturb the equilibrium to induce a topological instability, the sailfish suddenly starts swimming in the counter direction nullifying the induced oscillations in order to still the water. There is evidence that the sailfish motion then is opposite to the school1. The instability is modeled as a one dimensional pitchfork instability given by \(Dz = \theta _b z - z^3\)33. The steady state solutions for \(\theta _b < 0\) and \(\theta _b > 0\) are shown in Fig. 1b where the corralling singularity is located at \(\theta _b, z = 0\). Post-bifurcation, two stable branches are possible. In the lower branch, most of the fish restore the school to swim below the swimplane in the diffuser (Fig. 1). In the upper branch, a few individual fish swim up to the nozzle, breaching the interface in order to glide (Fig. 1)./p>> \rho _a\)) interface of \(\nabla \rho\) under the gravitational acceleration g (Fig. 4). Receiving little resistance, water penetrates the air. As circulations \(+\Gamma , -\Gamma\) deposit sequentially at the inflection points along the interface length, a single mode interface of wave number \(k=2\pi /\lambda\) is formed. The single mode amplitude first grows linearly with time through symmetric crests and troughs. This mode is followed by the growth of multiple modes and nonlinearities when asymmetric crowns and spikes form. The tip of the spike rolls up into a crown. Small scale disturbances appear on the interface, developing into a chaotic regime19,39. In Fig. 4, there are nonuniformities in the spacing and the heights of the spikes meaning that extraneous perturbations contributing to nonlinearities are also growing. Hence, while the stabilizing forces remain the same, the destabilizing inertia forces are higher compared to when the most organized crowns and spikes first form at \(We=\) 20019. The destabilizing force drops during taxiing after emergence, that is when the sailfish threat recedes ("Methods" section)1./p> We > 800\)19 and is similar to in the ocean ("Methods" section). That the emergence is at a shallow angle of 19\(^{\circ }\) and a ballistic 90\(^{\circ }\) exit is not undertaken for a faster escape means the thrust is 0.03 N and not 0.981 N for a 100 g flying fish (60A hardness and not 95A or 75D−Fig. 4A). Moreover, a taxiing (Fig. 4C) is not avoided for quicker gliding. The flying fish is not in a tearing hurry to escape−a surprise. But, then the sailfish does not chase the prey after the topology is fully bifurcated (Fig. 1b). The flying fish motion becomes even more friction limited swimming up breaching the interface at a shallow angle./p> We > 800\) in Fig. 4B vs. \(200< We < 600\) in Fig. 4C) is definitely different (video time stamps in "Methods" section), which indicates the presence of multistability in the hydrodynamics, tail rigidiy EI and the olivo-cerebellar control of the flying fish tail oscillation18. The inertia force and disorganization are reduced while taxiing on the ocean surface than when emerging because the distance from the sailfish threat has increased. The multistability is not random, but chaotically controlled, depending on the threat perception./p>110\) Hz. The bones between the bladder and ears, the mechanical links, vibrate. The wave interference may cause a sudden bending of the polarized cilia in the fish ear, which are used for direction sensing, disorienting the flying fish36. Theoretically, the resonant frequency of a fish increases with depth. Models of reflection of resonant frequencies from fish show that for a given frequency, the target strength is greater for the side aspect than for the dorsal aspect. Further, the target strength increases with the size of the fish. That is, the ability of the sailfish in reflecting sound is higher than in an individual flying fish, but equals to the school. In shallow waters, the propagation loss due to fish populations is complex. The sailfish-flying fish interaction under consideration occurred in the early morning. It is unknown if the propagation loss increased or decreased when the acoustic predation occurred. However, in some populations there can be a drop during the early morning. The sailfish acoustic predation utilizes body concave mirroring, echo wave interference and precise spatial localization at the prey fish ear drums. The energy expense is lower than man-made noise. The dB level along the black lines in Fig. 3 may only be \(>85\) dB as in humans threshold, but applied suddenly to startle (the bladder does not burst out of the mouth)1. The pile driving guideline of 150 dB re 1 \(\upmu\)Pa (rms) amplitude is irrelevant41. Underwater ambient SPL is as follows. In air, the corn popping mean SPL is 85 dBA18,51. In a controlled 200–300 Hz impulse of amplitude 2 psims for 1 ms in a 9.1 m deep tank the peak SPL is 185.5 dB (re 20 \(\upmu\)Pa) in-water, equivalent to 5.44 psi, causes no human hearing loss at 1006 m away52. The ambient SPL is \(\le\) 70 dB, the quietest sea conditions at dawn. The ocean ambient SPL level near the free surface is \(\approx\)80 dB (Fig. 1)18 . In the UK, the ambient ocean noise is higher, \(\ge\) the survey vessel. It is painful to humans when the intensity is \(\ge\) 85 dB. The noise is unbearable at 120 dB (= disco noise; \(\ge\) trawler noise)15,51,53,54,55. Because the noise is not prolonged, the high dB levels along the bold black lines in Fig. 3a is only what will intensify the SPL in the ears of the flying fish. For the same reason, the energy input in the present example of predation should be lower than more commonly studied man-made noise13,15,36,55. Masking is the hearing threshold above the near free surface oceanic noise which is 70 dB at dawn. Median ocean noise levels ranged in UK measurements from 81.5 to 95.5 dB re 1 \(\upmu\)Pa for 0.33 octave bands from 63 to 500 Hz53, but deeper in the ocean away from the UK shores, the noise level is closer to \(\le\) 70 dB, also \(\approx\) 70 dB re 1 \(\upmu\)Pa due to baleen whales, toothed whales, bottlenose dolphins and killer whales55./p> 0\), the boundary layer has thinning effect; \(\partial \Gamma /\partial x > 0\); the streamlines near winglet-body junction are converging, that is, this is a line sink flow, if \(s, \delta\) are the surface distance and the boundary layer thickness, \(\partial \delta /\partial s < 0\). The rear half of the body and the sail has these opposed properties. The axial pressure gradient is \(\partial p/\partial x > 0\), that is adverse and decelerating; the boundary-layer is laminar, thick and prone to separation; the body axial curvature is concave on the pressure side and destabilizing and convex on the suction side and stabilizing; the axial gradient of the elliptic body cross sectional area A is \(\partial A/\partial x < 0\), the boat tail boundary-layer has thickening effect; \(\partial \Gamma /\partial x < 0\); the streamlines near the winglet-body junction are diverging, that is, this is a line source flow and \(\partial \delta /\partial s > 0\). Inflection in streamline is minimized. The streamlines follow the axial direction closely and not the spanwise direction. Circulation \(\Gamma\) is load whose moment about the center of pressure determines the roll, pitch and yaw control force and moment laws. The circulation is front-loaded (Fig. 2c). The sail is multiply split in the ’boat tail’ where \(\Gamma\) is declining./p> We > 600\), which reproduces the lower We of the flying fish tail strike on ocean surface during taxiing after emergence indicating multistability of We. The unstable We drops as the sailfish threat recedes./p>
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