Walk Softly – Jaws!

by Geoffrey Carpentier

People sometimes ask me how I decide what topics to write about, when I tackle my column. The simple answer is, my ideas come to me from various sources and different encounters. Some are linked to nature-related observations I make, some arise from readers’ questions, and some come from odd sources. This column falls into the latter category.

Recently, my wife and I watched all four Jaws movies. Yes, there were four of them! We thoroughly enjoyed reliving the offerings after all these years. It got me thinking about how different creatures use their mouth parts in different ways, to capture, hold, dismember and eat their prey.

I would like to explore this further, in the next series of columns. Each column will only touch the surface, as you can imagine. There are billions of creatures out there who prey on other organisms in one way or another. Let’s start with fish and their close allies as that was, after all, what the Jaws movie was about!

Sharks are perhaps the iconic and most feared of the ocean’s creatures. Over 180 shark-themed movies have been produced. While Jaws may be the most famous, it was not the first. The first one on record was White Death (1936), followed by The Sharkfighters (1956) and then Shark! (1969). Shark movies can have a cult following, as witnessed by the Sharknado fad earlier this century when six movies were released. The underlying thread in all these was the huge, tooth-filled mouth, impressive gape and the power of the jaws as they snapped shut on their prey.

As with many large predatory fish, the jaws can open very wide and rows of teeth grasp, hold, and tear flesh to bits to be swallowed in large chunks. Of course, smaller prey might be swallowed whole, but, for the most part, big fish catch big prey. The one feature sharks and many other fish have, which most other animals don’t, is they can replace broken or lost teeth regularly, over time. The number of teeth a shark has can vary significantly, depending on the species. However, some species may use as many as 50,000 teeth in their lifetime! Many fish have a continuous tooth replacement system, where several rows of teeth exist (i.e. seven rows for the Great White Shark). As teeth are lost or worn down, new teeth from the rows behind move forward to take their place.

Shark’s teeth come in various shapes and forms, based on their purpose. In many sharks, such as the Great White, the upper teeth are large and triangular with serrated edges, allowing the shark to grasp and cut its prey into pieces. The lower teeth are more pointed and less triangular, facilitating a gripping function to hold the prey. The variability in tooth shape and structure is linked to the prey the fish eats. Some species have tiny needle-like teeth, to aid in catching small slippery fish. Basking Sharks have small, essentially, non-functioning teeth, as they feed on plankton exclusively. Bull Sharks have triangular upper AND lower teeth, unlike the Great White, which allows them to hunt a wider range of prey.

Many freshwater fish also exhibit the same ability to replace teeth, throughout their lifetime. This replacement process is known as polyphyodonty. As teeth are lost or the fish grows, the ability to replace them, rapidly and routinely, helps ensure their hunting prowess.

While most fish seem to be toothed hunters, others are more docile, and their jaws and teeth reflect this. For example, the oceanic family of Parrotfish have a small mouth with fused teeth which form a beak-like structure. These teeth are arranged in multiple rows and are continuously replaced as they wear down. This ‘beak’ allows them to scrape algae from coral and rocks. To add to this adaptive tooth structure, they also have a special set of pharyngeal teeth in their throat, for grinding up ingested coral. To finish, a few fish (e.g. lamprey eels) have no teeth at all, while some others have tooth-like structures on their tongues to grind up ingested food.

Next time we’ll look at mammals and their feeding strategies.

Geoff Carpentier is a published author, expedition guide and environmental consultant. Visit Geoff on-line on LinkedIn, Facebook and Instagram.