Specialized Gills Filter Plankton

gray shark with mouth open swimming underwater

Biological Strategy

Basking shark

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Capture, Absorb, or Filter Organisms

Many living systems must secure organisms for food. But just as one living system must capture its prey to survive, its prey must escape to survive. This results in capture and avoidance strategies that include trickery, speed, poisons, constructed traps, and more. For example, a carnivorous plant called the pitcher plant has leaves formed into a tube that collect water. Long, slippery hairs within the tube face downward. When insects enter the tube seeking nectar, they lose their footing and slide inside, unable to climb out and escape being eaten and digested by the plant.

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Fish

Class Agnatha (“without jaws”), Class Chondrichthyes (“cartilage fish”), Superclass Osteichthyes (“bone fish”): Sharks, eels, snapper, hagfish

The fish are a diverse group, comprising multiple classes within Phylum Animalia. The most well-known classes are Chondrichthyes, which has sharks and rays, and superclass Osteichthyes, which has all bony fish like cod and tuna. Unlike other vertebrates, fish only live in water. They use special adaptations like fins, gills, and swim bladders to survive. Most are ectothermic, meaning their body temperature depends on the water temperature around them. Over half of all vertebrates are fish. They’re found from the bottom of the sea to high mountain lakes.

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The gills of basking sharks filter plankton from seawater for nutrition via specialized filters called gill-rakers.

“Torpor or hibernation in fish is rare, but the most remarkable case features the basking shark (Cetorhinus maximus). It swallows great quantities of plankton, straining it from the water via specialized filters called gill-rakers. A common sight drifting just beneath the sea surface during the plankton-rich summer months, these sharks are rarely seen during the winter, when plankton is scarce. This is because they descend to deeper waters where, scientists assumed, they spend the season in a torpid state. However, when scientists examined two basking sharks during winter they lacked gill-rakers and thus couldn’t feed. This unexpected finding suggests that basking sharks hibernate, shedding their gill-rakers and regrowing them in spring.” (Shuker 2001:108)

Last Updated January 17, 2017

References

Book

The Hidden Powers of Animals: Uncovering the Secrets of Nature

Marshall Editions Ltd. | 01/01/1970 | Dr. Karl P. N. Shuker

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