What the vampire squid really eats

What the vampire squid really eats Squids and octopods, also known as cephalopods, use an intriguing variety of feeding strategies to pursue and capture food. What they all have in common though, is the fact that they hunt for living prey. This paradigm has recently shifted with a discovery by scientists at the Monterey Bay Aquarium Research Institute (MBARI), who studied the feeding habits and behavior of the elusive vampire squid. The vampire squid is an ancient animal that shares characteristics with both squids and octopods. Vampire squid have eight arms, two long filaments and a cloak-like web, but they lack the feeding tentacles used by many squid for capturing prey. When disturbed they wrap their arms around their body exposing rows of spiny looking projections, and drastically changing their appearance. Their scientific name, Vampyroteuthis infernalis, was given to them more than a century ago. In all that time no one knew exactly what or how the vampire squid eats, until surprising details on their feeding were revealed in a paper by MBARI researchers. Using remotely operated vehicles, over the past 25 years, MBARI has observed nearly 200 individual vampire squid in their natural ocean habitat. Vampire squid were frequently observed drifting motionlessly, with their fins gently undulating, and one of their two filaments extended. The function of these long, retractile filaments has puzzled marine biologists for years. During feeding experiments in the lab back on shore, food particles were found to adhere to the filament and vampire squid were observed repeatedly drawing a food-covered filament between their arms, removing particles, and depositing them near their mouths. Stiff, microscopic hairs on the filament likely function to secure particles, while a layer of sensory cells may signal the presence of food to the brain. After drawing the filament between their arms, the food is wrapped in mucus secreted from glands in the suckers, then finger-like projections called cirri move the resulting mass towards the mouth. In their natural environment, marine snow, or sinking organic particles, were found on the squids’ filaments, arms, or in their mouth. Ingestion of marine snow aggregates was further confirmed by examination of the stomach contents of animals from museum collections. The ingestion of non-living food is unknown for any other cephalopod. Vampire squid are typically observed at depths with very low levels of oxygen, also known as oxygen minimum zones. Most other animals become stressed or die in the extreme oxygen conditions found in these regions. However, vampire squid have developed several adaptations that enable them to live successfully where there is little oxygen. The dark appearance of vampire squids reduces their visibility to predators and therefore the need for rapid escape. They also have several types of bioluminescent display, which may deter predators or attract prey. Vampire squid are neutrally buoyant and they have very low metabolic rates. All these adaptations reduce the need for investment in muscle tissue for locomotion, and save energy. The vampire squid’s remarkable ability to feed as a passive detritivore sets them apart from other cephalopods and gives them yet another energy-conserving advantage for a life in the oxygen minimum zone. This hostile environment supports few animals, but aggregates of marine snow sinking from the water above are plentiful. Using its many unique adaptations, the vampire squid thrives in the center of the oxygen minimum zone, where its food source is abundant, and predators are few.