Breathing versus feeding in the Pacific hagfish

• DOI: 10.1242/jeb.243989
• Publication Date: 2022-03-09T10:36:41Z
• Authors: Junho Eom; Henrik Lauridsen; Chris M. Wood
• Keywords: Hagfish; Nostril; Peristalsis

Hagfish represent the oldest extant connection to ancestral vertebrates, but their physiology is not well understood. Using behavioural (video), physiological (respirometry, flow measurements), classical morphological (dissection, silicone injection) and modern imaging approaches (micro-MRI, DICE micro-CT), we examined interface between feeding unique breathing mechanism (nostril opening, high-frequency velum contraction, low-frequency gill pouch contraction pharyngo-cutaneous duct contraction) in Pacific hagfish, Eptatretus stoutii. A video tour via micro-MRI presented through passages. We have reconciled an earlier disagreement as position of chamber, which powers inhalation nostril, placing it downstream merging point food water passage, such that oronasal septum terminates at anterior end chamber. When occurs by engulfment large chunks dental plates, movement chamber may transiently interfere with breathing. Swallowing accelerated peristaltic body undulation involving ventral musculature, complete within 5 s. After a meal (anchovy, 20% mass), hagfish remain motionless, defaecating bones scales 1.7 days intestinal peritrophic membrane days. O2 consumption rate approximately doubles 1 h feeding, remaining elevated for 12-24 h. This achieved combinations utilization ventilatory flow, latter caused varying increases velar frequency stroke volume. Additional casts light on reasons trend greater more posterior pouches fasted hagfish.