Muscle Activity Patterns and Feeding Kinematics in Atlantic Hagfish (Myxine glutinosa)
Erick J. Maravilla
Adam P. Summers
We investigated motor patterns of the three largest muscles in the hagfish feeding apparatus: the
deep protractor muscle (DPM), clavatus muscle (CM), and tubulatus muscle (TM). The anatomy
of the DPM and CM suggests they respectively protract and retract the dental plate. Bipolar
electrodes were implanted in anesthetized Myxine glutinosa. After recovery, we simultaneously
videotaped behaviors and muscle activity patterns from the feeding specimen. Ingestion required
three gape cycles (dental plate protraction-retraction events), and intraoral transport required four
gape cycles. Percutaneous implantation of electrodes did not inhibit normal feeding behaviors.
Time to maximum gape was significantly longer during transport events than capture events.
Gape cycle and dental plate retraction times were similar in both capture and transport. The DPM
was active during protraction, while the CM and TM were active during retraction. In both
capture and transport phases, the DPM had longer bursts (414 ms) than the CM (308 ms) and TM
(255 ms). For each muscle, burst duration was similar in both capture and transport phases. All
muscles were active during every gape cycle in the capture phase. In the transport phase, the
DPM was active in all gape cycles, while the CM and TM were active during the first two gape
cycles. We propose TM activity during retraction provides a fixed point for the CM to retract the
dental plate. Decreased TM and CM burst frequencies during transport phases raise the
possibility that elastic recoil of the CM tendon is sufficient to passively retract maximally
protracted dental plates.