Digestion under Duress: Nutrient Acquisition and Metabolism during Hypoxia in the Pacific Hagfish

Abstract

Hagfish feed by immersing themselves in the body cavities of decaying animals. This ensures a rich nutrient source for absorption via the gills, skin, and gut, but it may also subject hagfish to reduced levels of dissolved oxygen and elevated levels of the products of biological degradation. This study investigated the impacts of hypoxia and ammonia on the assimilation and metabolism of selected nutrients (glycine, l-alanine, and glucose) in Pacific hagfish (Eptatretus stoutii). Throughout exposure to hypoxia, plasma glucose levels increased. This was not accompanied by an increase in gut glucose transport, which suggests mobilization of glucose from body glycogen stores. Hypoxia preexposure enhanced glycine absorption across the gut and the gill, although l-alanine uptake was unchanged in these tissues. A 24-h period of exposure to hypoxia in hagfish concurrently exposed to waterborne radio-labeled glycine led to a large (5.7-fold) increase in brain glycine accumulation. Preexposure to high levels of waterborne ammonia (10 mM) for 24 h had no impact on gut or skin glycine uptake. These results indicate that hagfish are adapted to maintain nutrient assimilation despite environmental stressors and that tissue-specific absorption of key nutrients such as glycine can even be enhanced in order to sustain critical functions during hypoxia.

Adaptations of a deep sea scavenger: High ammonia tolerance and active NH 4 + excretion by the Pacific hagfish ( Eptatretus stoutii )

“…The present study unequivocally supports earlier suggestions that the Pacific hagfish is ammonia-tolerant (Braun and Perry, 2010;Bucking et al, 2011). This tolerance is likely due to an ability to decrease the permeability of the gills to NH 3 , and likely involves the use of an as of yet undefined secondary active transport mechanism to excrete NH 4 + against its electrochemical gradient.…”

Novel Route of Toxicant Exposure in an Ancient Extant Vertebrate: Nickel Uptake by Hagfish Skin and the Modifying Effects of Slime

“…1 Nickel is known to have a strong affinity for glycine, 39 and previous studies have shown a marked effect of nickel chelation on nickel tissue distribution. For example, a lipophilic nickel-binding ligand, sodium diethyldithiocarbamate, caused a 230-fold increase in brain nickel when included in a waterborne nickel exposure to brown trout.…”

High-Frequency Patterns in the Abundance of Benthic Species near a Cold-Seep – An Internet Operated Vehicle Application

“…Their lifestyle is predominantly endobenthic, with animals spending most of their time resting coiled on the seabed (see Fig 2 ) or in self-built burrows [ 58 – 59 ]. Hagfish can opportunistically feed on several trophic levels [ 60 ], combining preying on small invertebrates and scavenging carcasses with the ability to take up dissolved organic matter via their skin [ 61 – 62 ]. While a high percentage of the organic matter within their diet can also originate from chemoautotrophs, many individuals’ isotopic signatures correspond to macroalgal sources ( Eptatretus sp .…”