|摘要: ||蓋斑鬥魚 (Macropodus opercularis L.) 是一種小型淡水魚，雄性個體在繁殖期會為了爭奪領域而更具有鬥性，進入鬥爭時，兩魚相互靠近且身體呈現 J 型朝對手的尾部作頭尾方向相反的旋轉行為，前人稱其為「頭尾展示行為」 (Head-Tail Display, HTD)。本研究經由觀察得知多次HTD行為後可決定勝負，然而過去文獻並未探究HTD在鬥爭過程中所扮演的角色，也未解釋胸鰭擺動如何影響兩魚當時的運動。因此，本研究進一步探討HTD時胸鰭擺動行為模式，並推測其同時具有展示及力學較勁的功能，可影響勝負。打鬥行為實驗中，我將兩隻體型相當的雄魚置入靜水缸內，以常速攝影機紀錄完整鬥爭過程，並利用高速攝影以500fps的速度垂直俯拍，以量化胸鰭擺動的頻率及振幅；高速影片分析顯示，HTD開始後胸鰭會進入快速擺動時期，本研究中，我以胸鰭擺動角加速度的最大值及最小值作為HTD的始末時間。結果顯示：（一) 胸鰭擺動的頻率、位置、和振幅在直線游泳與HTD時期有顯著差異。直線游泳時，泳速為1.37±0.37 BLs-1，胸鰭擺動頻率為4.11±1.51 Hz；HTD時，胸鰭擺動頻率增為8.52±1.34 Hz，但泳速反而降低為0.73±0.26 BLs-1。此外，直線游泳時胸鰭擺動的位置為32.56±3.52°處，而HTD時則為84.23±13.45°。（二）HTD時兩魚胸鰭的擺動頻率及振幅相近，但開始的時間不同。先開始HTD行為的攻擊者的內側胸鰭（靠近對手端）會在與身體夾92.06±10.94°處前後擺動，而外側胸鰭則在75.83±8.78°處前後擺動；較晚開始HTD的防守者內側胸鰭以94.45±8.73°前後擺動，外鰭以74.58±11.84°前後擺動。由此可知兩魚內外兩側胸鰭的擺動範圍不同，內側胸鰭在與身體呈90°處前後擺動，可增加碰觸對手的機會，外側胸鰭擺動則產生向前的分力（及力矩）來維持旋轉。（三) 打鬥的優勢者與服從者在HTD時胸鰭擺動的頻率及振幅相近，優勢者內側胸鰭所耗費的功率為0.89±0.55 x 10-4 J/s，略高於服從者的0.70±0.36 x 10-4 J/s；優勢者內側胸鰭擺動的角度為93.60±6.90°，較服從者的119.04±7.40°更接近90°，因此比對手更容易將力學訊息傳達給對方。優勢者內外兩側的擺動位置角度差異大，可提供力矩維持原地旋轉的姿態；服從者內外兩側擺動位置均大於90°，故可以產生向後的推進力以離開HTD成對行為。（四）歸納常速影片中完整的打鬥行為，發現有些打鬥能透過三次以下的HTD來決定勝負，此時個體不會受傷；當打鬥歷經八次以上的HTD行為後，便發生衝撞對手及以嘴互咬等較激烈的行為，且個體可能因而受傷。綜上所述，在HTD時期，雄性鬥魚可透過控制胸鰭擺動方向來調整彼此的相對位置與姿態，並影響能量傳遞效率，因此，HTD兼具展示及力學較勁功能，可避免激烈打鬥所帶來的傷害。|
Male paradise fishes Macropodus opercularis L. fight for territory during breeding season. During fighting a distinctive behavior, so-called “Head-Tail Display” (HTD), can be observed and characterized by the opponents following the other's tail leading to swimming in a rotational fashion, with bodies oriented in parallel and bended in J-shape. After several rounds of HTD, the dominant fish might be determined; but previous studies never investigated the role of HTD during fighting. It is also unclear how flapping of pectoral fins might affect the motion of two fishes during HTD. In this study, I examined the behavioral patterns and kinematics of pectoral fin flapping during HTD, and assessed the physical factors that might determine the results of fighting. To this end, the fighting behaviors were recorded from the top using a regular speed DV (30 fps) and a high-speed video camera (500 fps), from which the flapping frequency and amplitude of pectoral fins were analyzed. The period of HTD could be determined quantitatively as the time between maximum and minimum angular velocity of the pectoral fins. My results show that: (1) Despite lower moving speed (0.73±0.26 BLs-1, N=20) than that of swimming (1.37±0.37 BLs-1, N=17), during HTD the flapping frequency, position, and amplitude of pectoral fins are significantly greater. During swimming, the pectoral fins flapped at 4.11±1.51 Hz, with amplitude of 30.38±3.68° from the position of 32.56±3.52°. But during HTD, the pectoral fins flapped at 8.52±1.34 Hz, with amplitude of 48.91±6.05° from 84.23±13.45°, a position farther away from the body. (2) During HTD, the flapping frequency and amplitude were not significantly different between two fishes. However, whether it started HTD earlier (the attacker, A) or later (the defender, D), the pectoral fin of the inner side (near the opponent) flapped at an angle (A: 92.06±10.94°; D: 94.45±8.73°) significantly greater than that of the outer side (far from opponent; A: 75.83±8.78°; D: 74.58±11.84°). Therefore, the inner fins flapped at an angle close to 90° would have greater opportunity to touch its opponent's body, while the outer fins provided the force (and moment) to maintain rotational motion. (3) The dominances and submissions had similar flapping frequency and amplitude, but the dominances spent more power (0.89±0.55 x 10-4 J/s) flapping the inner fins than the submission do (0.70±0.36 x 10-4 J/s). The dominances flapped their inner fin from a position of 93.60±6.90°, making them easier to transmit mechanical signals to the opponents than the submissions do (119.04±7.40°). Furthermore, the dominances had different flapping angles between two sides allowing it to rotate; while the submissions had similar angles, both greater than 90°, for backward retreat from the HTD pairing. (4) Observations of the whole fighting periods show that in some cases, the dominance could be determined in less than three HTD events and no fish was injured; however, when HTD events were greater than eight times fishes would begin more aggressive behaviors like biting or mouthlocking, increasing the risk of injury. In conclusion, during HTD, the male paradise fishes could control flapping of their pectoral fins to adjust their motion and relative position to each other, and could also affect the transmission efficiency of mechanical signals. Hence HTD provides both functions in display and mechanical rivalry that can reduce injury from aggressive fighting.