Sawfish are unique marine animals recognized by their distinctive, elongated snout, often called a rostrum or “saw.” This appendage is central to their identity and survival, serving as a complex tool for interacting with their environment in marine and freshwater habitats.
Anatomy and Sensory Functions of the Saw
The sawfish rostrum is an extension of the chondrocranium, made of cartilage and covered by skin. Along its edges, it has rows of whitish, tooth-like projections. These are modified dermal denticles, tough structures embedded in the skin similar to shark and ray scales, which grow throughout the sawfish’s life. The rostrum’s length typically ranges from one-quarter to one-third of the sawfish’s total body length, varying by species, age, and sex.
The saw is equipped with specialized sensory organs called ampullae of Lorenzini. These minute pores are located across the rostrum, particularly on its dorsal and ventral surfaces. Each pore connects to a gel-filled canal, allowing the sawfish to detect weak electrical fields produced by living organisms, such as potential prey. This electroreception is effective in murky or dimly lit waters, enabling the sawfish to locate hidden or buried prey.
Survival Strategies Enabled by the Saw
The sawfish uses its rostrum in multiple ways for survival, including navigating and foraging. For hunting, the saw is employed with precision.
Sawfish make rapid side-to-side swipes with their rostrum through schools of fish, stunning or incapacitating prey. This sweeping action allows them to injure multiple fish at once.
The saw also uncovers hidden food sources. Sawfish use their rostrum to dig into the seabed, dislodging crustaceans, mollusks, and other bottom-dwelling creatures buried in sand or mud. This raking action exposes prey, making it easier to capture and consume.
Beyond acquiring food, the saw acts as a defense mechanism against predators like sharks. If threatened, a sawfish can swipe its rostrum to strike an aggressor. This can inflict serious injuries, deterring larger marine animals.
The rostrum’s sensory capabilities also aid navigation and exploration. The ampullae of Lorenzini assist sawfish in sensing their surroundings, particularly in low-visibility conditions. This electroreception helps them orient and move through habitats, including coastal waters, estuaries, and freshwater rivers. The saw’s utility is important for the sawfish’s survival and adaptation to diverse aquatic environments.