Feeding
While polychaete marine worms on or near the sea floor are a major source of nutrition, hagfish can feed upon and often even enter and eviscerate the bodies of dead and dying/injured sea creatures much larger than themselves. They are known to devour their prey from the inside. Hagfish have the ability to absorb dissolved organic matter across the skin and gill, which may be an adaptation to a scavenging lifestyle, allowing hagfish to maximize sporadic opportunities for feeding. From an evolutionary perspective, hagfish represent a transitory state between the generalized nutrient absorption pathways of aquatic invertebrates and the more specialized digestive systems of aquatic vertebrates.
Like leeches, they have a sluggish metabolism and can survive months between feedings; their feeding behavior, however, appears quite vigorous.
In captivity, hagfish are observed to use the overhand-knot behavior "in reverse" (tail-to-head) to assist them in gaining mechanical advantage to pull out hunks of flesh from carrion fish or cetaceans, eventually making an opening to permit entry to the interior of the body cavity of larger carcasses. It is to be expected that a healthy larger sea creature would be able to outfight or outswim this sort of assault.
However, this energetic opportunism on the part of the hagfish can be a great nuisance to fishermen, as they can devour or spoil entire deep-drag netted catches before they can be pulled to the surface. Since hagfish are typically found in large clusters on and near the bottom, a single trawler's catch could contain several dozen or even hundreds of hagfish as bycatch, and all the other struggling, captive sealife make easy prey for them.
The digestive tract of the hagfish is unique among the vertebrates because the food in the gut is enclosed in a permeable membrane, analogous to the peritrophic matrix of insects.
Read more about this topic: Hagfish
Famous quotes containing the word feeding:
“We went on, feeding the hungry, giving drink to the thirsty, clothing the soldier, binding up his wounds, harboring the stranger, visiting the sick, ministering to the prisoner, and burying the dead, until that blessed day at Appomattox Court House relieved the strain.”
—M. E. W. Sherwood (1826–1903)
“It no longer makes sense to speak of “feeding problems” or “sleep problems” or “negative behavior” is if they were distinct categories, but to speak of “problems of development” and to search for the meaning of feeding and sleep disturbances or behavior disorders in the developmental phase which has produced them.”
—Selma H. Fraiberg (20th century)
“Man may have his opinion as to the relative importance of feeding his body and nourishing his soul, but he is allowed by Nature to have no opinion whatever as to the need for feeding the body before the soul can think of anything but the body’s hunger.”
—George Bernard Shaw (1856–1950)