虎斑烏賊改變偽裝花紋的能量支出

Abstract

長期以來，頭足類動物展現的高度發達且獨具特色的變換體色行為被認為需要極高的能量代價。然而，個體層級的實際代謝成本至今尚未被明確量化。為釐清此行為的能量使用，本研究將虎斑烏賊（Sepia pharaonis）分別飼養於三種實驗環境中：白色背景（穩定環境，無偽裝需求）、固定邊長的黑白棋盤方格背景（穩定環境，有偽裝需求），以及週期性變換邊長大小的棋盤方格背景（動態環境，有偽裝需求）。本研究透過三項指標進行評估個體的能量代謝：其一，於養殖實驗結束時測量鰓與外套膜中乳酸去氫酶（LDH）與檸檬酸合成酶（CS）的酵素活性；其二，每五日量測一次個體耗氧量；其三，飼養期間骨板的 δ¹³C 值。 結果顯示酵素活性與耗氧量在三組處理間並無顯著差異。然而，有偽裝需求的處理組δ¹³C 值顯著降低，顯示其單位體重代謝率的增加。本研究指出，與偽裝行為相關的能量消耗具有時間動態性，相較於瞬時測量的耗氧量或酵素活性指標， δ¹³C 值所代表的時間整合訊號更能捕捉到能量消耗的動態變化因而具有較佳的解釋力。由 δ¹³C 值重建推估的耗氧量進一步顯示在有偽裝需求的環境下，個體的能量消耗相較於在無偽裝需求的環境約增加兩倍。此結果不僅提供支持體色變換為一具高代謝成本之行為的證據，也為頭足類的代謝生態學提供了嶄新的理解視角。

Cephalopods exhibit extraordinary camouflage behaviors which are unique compared to other marine organisms. This behavior has long been considered energetically expensive, yet it has rarely been quantified at the individual level. To quantify the energetic cost, we study the cuttlefish Sepia pharaonis by rearing individuals in three distinct environments: a white background (stable environment without camouflage requirement), a fixed square size of black-and-white checkerboard (stable environment with camouflage requirement) and a checkerboard with constantly changing square sizes (dynamic environment with camouflage requirement). Energy use was assessed via (1) enzyme activities (LDH and CS) measured in gill and mantle tissues at the end of the experiment, (2) oxygen consumption measured every five days, and (3) δ13C values recorded in the cuttlebone over the one-month rearing period. Enzyme activities and oxygen consumption showed no significant differences among treatments. However, δ13C values were significantly more negative in a camouflage-requiring environment, indicating elevated mass-specific metabolic rates. Our results show the energy expenditure of camouflage is dynamic and better captured by time-averaged δ13C signals rather than snapshot measurements of oxygen consumption or enzyme activity. Reconstructed oxygen consumption from δ13C values further suggests a two-fold increase in energy use under camouflage-requiring conditions, providing new insights into cephalopod metabolic ecology.