Sturgeons, often referred to as “living dinosaurs,” are ancient fish species with a lineage extending back millions of years. Unlike many fish that possess prominent teeth for capturing prey, adult sturgeons generally do not have the hard, bony teeth found in other species. This absence of teeth is a key adaptation for their unique feeding strategy and bottom-dwelling lifestyle.
The Sturgeon’s Unique Mouth
Sturgeons feature a highly specialized mouth structure. Their mouths are positioned ventrally (on the underside of their head) and are highly protractible, capable of extending outwards. This mouth design, often described as tube-like or siphon-like, forms an inverted U-shape or semicircle when closed.
Their firm, pointed snout plays a significant role in foraging. Four sensitive, whisker-like barbels are located just in front of their mouth. These sensory tools drag along the substrate to detect food items in murky waters where visibility is low. A hardened tissue layer above their upper lip protects them from injury during feeding.
How Sturgeons Feed
The sturgeon’s unique mouth is well-adapted for its primary feeding method: suction feeding. When a sturgeon locates food on the riverbed or ocean floor, its protractible mouth extends rapidly to create a vacuum. This action allows the fish to suck up food items, along with sediment, directly from the substrate.
Sturgeons are primarily benthic feeders, foraging for food on the bottom of aquatic environments. Their diet typically consists of small invertebrates, such as worms, insect larvae, mollusks, and crustaceans. Some larger species can also swallow small fish, including whole salmon, and detritus. Since they do not possess teeth to chew, food is swallowed whole and processed by a muscular, gizzard-like stomach that crushes items for digestion.
Sturgeon Teeth Through Life Stages
While adult sturgeons are characteristically toothless, the presence of teeth varies across their life stages. Some sturgeon species do possess small, temporary teeth during their larval or very early juvenile phases. These tiny, pointed teeth assist young fish in their initial feeding on microscopic prey.
Larval sturgeons, for example, often rely on zooplankton and small macroinvertebrates like copepods, mayflies, midges, and blackflies. These temporary dental structures are typically lost as the fish grow, usually when they reach about 30 millimeters (1.2 inches) in length. This developmental loss of teeth coincides with a dietary shift and the full development of their adult suction-feeding mouth, allowing them to transition to a bottom-feeding lifestyle.