Whether you enjoy them on your plate or not, shrimp are some incredible little animals that play an important part in the marine environment. With nearly 2,000 known species worldwide, living in a variety of marine and freshwater environments, these creatures are surprisingly interesting, particularly some of the larger, more exotic species. While some species are so small that they might escape your notice, others really stand out.
Predators and Prey: Shrimp Facts
Found in habitats all over the world, shrimp are crustaceans, related to lobsters, crabs and crayfish. Of all the known species, only about 20 types are important commercially, with higher numbers being farmed rather than caught in the wild; whether you agree with eating shrimp or not, shrimp farming does help to protect wild populations and prevent trawlers from damaging sensitive marine environments, and farmed shrimp are raised under controlled conditions to prevent overconsumption of pollutants and heavy metals. The shrimp normally consumed by humans tend to be schooling species, rather than the reef species we’ll be looking at here; still, some of these more sophisticated shrimp are considered to be delicacies in various parts of the world.
Most shrimp are smaller than 8 inches long, and unlike their close relatives, they tend to swim by flexing their abdomens, rather than using crawling as a primary means of locomotion. The largest shrimp ever recorded was a Black Tiger Shrimp, which was sixteen inches long. This species is commonly encountered in the Indo-West Pacific, ranging from Africa’s east coast throughout the Arabian Peninsula, and is found in Southeast Asia, northern Australia, and the Sea of Japan, as well. Unfortunately, this animal is on the Greenpeace Red list, as juveniles are often caught and consumed before they have a chance to spawn.
Usually found on muddy or sandy substrate and in reefs, where they like to burrow into rocky crevices or hide among coral formations and inside sponges, shrimp eat both plant and animal material, often cleaning up leftovers other animals leave behind. They are also an important food source for many types of marine life, small and large; many of the filter feeding species are highly resistant to toxins and unfortunately contribute to high toxicity levels in the animals that consume them.
To reproduce, shrimp spawn, with some species releasing up to a million eggs per female at once. Some females will carry fertilized eggs with them on their swimmerets until the eggs hatch; however this is rare. Their life cycles range from as short as a few months, to nearly seven years, depending upon the species. As they grow, they molt, shedding their exoskeletons. Usually colored to blend in with their surroundings, shrimp tend to be white, grey, brown, green, pink, or red, with a variety of different markings such as spots or bands of contrasting color. A few species can change colors to camouflage themselves, while others have a variety of different defense mechanisms that can be quite incredible to witness.
Some shrimp create partnerships with other animals in order to protect themselves from predation. Some species of Pistol shrimp and a few others form symbiotic relationships with various gobies, small fish which share the shrimps den and guard it from predators. Other shrimp, known as cleaner shrimp, set up cleaning stations which they will sometimes share with cleaner fish, such as wrasse. At these stations, they help larger fish and turtles stay free from parasites. On occasion, shrimp will form partnerships with moray eels, helping them to keep their teeth clean. Some divers have had the good fortune to receive a manicure from friendly cleaner shrimp; if you’re considering this, be sure you’re dealing with cleaners! Some other species can cause serious problems if you get too close.
These include snapping shrimp, a family of shrimp called the Alpheidae, which have asymmetrical claws that they snap together with an audible clapping sound. There are around 600 different snapping shrimp species, which are usually found in coral reefs, seagrass flats, and in oyster beds. One species, Betaeus, inhabits cold water, while Potamalpheops is found in freshwater caves. The rest, which when living in large colonies can actually interfere with sonar, tend to live in temperate and tropical marine environments. These shrimp grow to be only 1-2 inches long; however their claws are very strong. They use a hammerlike motion to snap, releasing a powerful wave of bubbles that are capable of stunning fish and breaking glass. These shrimp prey on the small fish they stun, pulling them into their burrows and consuming them there.
Another dangerous species is the Mantis shrimp, which looks much like a praying mantis. Much larger than their snapping cousins, these shrimp can grow to an average of 12 inches long, though the largest recorded specimen was 15 inches long. Beautifully colorful, ranging from shades of brown to brilliant shades of iridescent neon, the shrimp live in shallow tropical and subtropical marine habitats, where they stun or spear their prey prior to dismembering and consuming it. Nicknamed “Prawn Killers” in Australia, and also referred to as “Thumb Splitters” due to their ability to cut human flesh to the point where stitches are necessary, these little creatures spend most of their time tucked away in burrows, where they sometimes create intricate tunnel systems. Capable of breaking through strong aquarium glass, the shrimp are aggressive and tend to be solitary. Depending on the species, you may witness them hunting, chasing, and killing prey during the daytime, though most tend to hunt at dawn and dusk with some emerging at night as well. They are well distributed throughout the Indian and Pacific Oceans between eastern Africa and Hawaii although some do live in temperate waters.
Next time you encounter shrimp while diving, pause to give them a second look. Watch and wait; you might be surprised by the displays and behaviors that you’ll witness. And if you’re like many of us, and enjoy dining on shrimp, consider choosing responsibly farmed shrimp instead of wild-caught; you’ll be doing both the environment and yourself a favor.