Meeting Abstract
Cetaceans rely on sound production for successful foraging and communication. Most mammals produce sound via the larynx, but odontocetes produce sound via the nasal complex. In addition, odontocetes produce sound on breath-hold dives and must manage oxygen stores at depth in response to locomotor and vocal muscle demands. Elucidating the physiological properties of sound production muscles can provide key information as to how cetaceans evolved to produce sound underwater. We examined aerobic [myoglobin (Mb) concentration] and anaerobic [acid buffering (AB) capacity] capacities of cetacean vocal muscles in two odontocetes: Tursiops truncatus (n=4) and Phocoena phocoena (n=2). Vocal muscles included the nasal musculature (NM) around the phonic lips and the palatopharyngeal sphincter (PPS), which is involved in pressurizing air within the nasal complex. When available, matched locomotor muscles were compared. The vocal muscles of T. truncatus had lower [Mb] (NM=1.33±0.1g Mb·100g tissue-1; PPS=1.72±0.29g Mb·100g tissue-1) and AB capacities (NM=29.07±1.50 slykes; PPS=34.27±3.78 slykes) than published locomotor values. Similarly, the vocal muscles of P. phocoena had lower [Mb] (NM=1.90±0.09g Mb·100g tissue-1; PPS=1.70±0.15g Mb·100g tissue-1) and AB capacities (NM=21.45±0.19 slykes; PPS=29.67±3.89 slykes) than matched locomotor muscles. Overall, the vocal muscles of both species exhibited similar aerobic and anaerobic capacities, but these values were less than half of species-specific locomotor muscle values. Our results suggest a relatively low energetic cost of sound production compared to locomotion in these species.
