The Marvellous Mantis Shrimp: A Colourful, Complex Predator in Reef Aquariums
Mantis shrimp, also known as stomatopods, are some of the most fascinating and complex creatures in the marine world. Known for their vibrant colours, intricate behaviours, and incredible predatory capabilities, mantis shrimp have captured the imagination of scientists and aquarium enthusiasts alike. However, they can be both a blessing and a curse in reef aquariums. This comprehensive guide explores the biology, behaviour, and care of mantis shrimp, providing valuable insights for anyone considering adding these remarkable creatures to their marine tank.
Understanding Mantis Shrimp
Mantis shrimp belong to the order Stomatopoda, a group of marine crustaceans that have been around for over 400 million years. Despite their common name, they are not true shrimp but are more closely related to crabs and lobsters. There are over 450 species of mantis shrimp, ranging in size from less than an inch to over a foot long.
Anatomy and Physiology
Mantis shrimp are renowned for their unique anatomical features, which contribute to their impressive predatory abilities:
• Raptorial Appendages: Mantis shrimp are divided into two main types based on their predatory appendages—‘smashers’ and ‘spearers.’ Smashers have club-like appendages used to bludgeon prey and break open hard shells, while spearers possess sharp, spiny appendages designed to impale soft-bodied prey.
• Eyes: Mantis shrimp have some of the most complex eyes in the animal kingdom. Each eye is capable of independent movement and contains up to 16 types of photoreceptors, allowing them to see a wide range of colors, including ultraviolet light. Their trinocular vision provides exceptional depth perception.
• Carapace and Abdomen: Their bodies are protected by a tough exoskeleton, and they can rapidly curl into a defensive posture when threatened.
Habitat and Distribution
Mantis shrimp are found in tropical and subtropical waters around the world, typically inhabiting burrows in sandy or muddy substrates, crevices in coral reefs, and under rocks. They are highly territorial and can be aggressive toward intruders.
Behaviour and Ecology
Mantis shrimp exhibit a range of fascinating behaviours that reflect their complex ecology and evolutionary adaptations.
Predatory Tactics
The predatory strategies of mantis shrimp are as varied as their forms:
• Smashers: These mantis shrimp, such as the Peacock Mantis Shrimp (Odontodactylus scyllarus), use their powerful clubs to strike with incredible speed and force, delivering blows that can reach speeds of up to 50 miles per hour. This impact generates cavitation bubbles that produce additional shock waves, capable of stunning or killing prey.
• Spearers: Species like the Zebra Mantis Shrimp (Lysiosquillina maculata) lie in wait for unsuspecting prey to pass by their burrows. They then launch their sharp, spiny appendages to impale and quickly retract their catch.
Social and Reproductive Behaviour
Mantis shrimp are known for their complex social interactions and mating behaviours:
• Territoriality: They are highly territorial and use their raptorial appendages and visual displays to ward off competitors and potential threats.
• Communication: Mantis shrimp use a combination of body postures, color changes, and rapid movements to communicate with each other, especially during mating rituals.
• Mating and Brooding: Many mantis shrimp are monogamous, forming long-term pair bonds. Females typically care for their eggs, guarding them in burrows until they hatch.
Mantis Shrimp in Reef Aquariums
The decision to keep a mantis shrimp in a reef aquarium is not to be taken lightly. While their vibrant colours and fascinating behaviours make them attractive additions, their aggressive nature and predatory instincts can pose challenges.
Benefits of Keeping Mantis Shrimp
• Intriguing Behaviour: Mantis shrimp are highly interactive and display a wide range of behaviours, making them a captivating focal point in any tank.
• Pest Control: They can help control populations of unwanted pests such as bristle worms, small crustaceans, and other invertebrates.
Challenges and Considerations
• Aggression: Mantis shrimp are highly aggressive and can attack and kill tank mates, including fish, other crustaceans, and even corals.
• Tank Requirements: They require a specialised environment with plenty of hiding places, such as live rock and PVC pipes, to mimic their natural burrows.
• Feeding: Mantis shrimp are carnivorous and need a diet of live or frozen foods, such as shrimp, crabs, and fish.
Setting Up a Mantis Shrimp Tank
Creating a suitable environment for a mantis shrimp involves careful planning and consideration of their specific needs.
Tank Size and Setup
• Tank Size: The size of the tank should match the size of the mantis shrimp. Smaller species can be kept in tanks as small as 10 gallons, while larger species may require tanks of 30 gallons or more.
• Substrate and Decor: A sandy or muddy substrate is ideal, with plenty of live rock and PVC pipes to provide hiding places. Ensure that the decor is securely anchored to prevent the mantis shrimp from rearranging the tank.
Water Parameters
Maintaining stable water conditions is crucial for the health of your mantis shrimp:
• Temperature: Keep the water temperature between 75-80°F (24-27°C).
• Salinity: Maintain a salinity level of 1.023-1.025 specific gravity.
• pH and Hardness: Aim for a pH of 8.1-8.4 and a hardness of 8-12 dKH.
Feeding
A varied diet is essential to keep mantis shrimp healthy and active:
• Diet: Offer a mix of live or frozen foods, such as shrimp, crabs, fish, and mollusks. Some mantis shrimp also enjoy occasional feedings of squid or octopus.
• Feeding Schedule: Feed your mantis shrimp 2-3 times a week, adjusting the frequency based on their size and activity level.
Case Studies: Keeping Mantis Shrimp
Case Study 1: A Peacock Mantis Shrimp
An aquarist decided to keep a Peacock Mantis Shrimp (Odontodactylus scyllarus) in a 30-gallon reef tank. The tank was set up with a deep sandy substrate and plenty of live rock for hiding places. The mantis shrimp thrived, displaying vibrant colours and fascinating behaviours. However, the aquarist had to move other tank inhabitants to a separate aquarium to prevent predation. Regular feedings of live crabs and shrimp kept the mantis shrimp healthy and active.
Case Study 2: A Zebra Mantis Shrimp
Another aquarist chose to keep a Zebra Mantis Shrimp (Lysiosquillina maculata) in a species-specific tank. The setup included a deep sand bed and PVC pipes to replicate its natural burrow. This mantis shrimp displayed impressive predatory skills, quickly capturing live prey introduced to the tank. The aquarist enjoyed observing its ambush tactics and complex social behaviours, noting the importance of providing a secure and enriched environment.
Conclusion
Mantis shrimp are among the most captivating and complex creatures in the marine world. Their vibrant colours, intricate behaviours, and formidable predatory capabilities make them fascinating subjects for both scientific study and aquarium keeping.
However, their aggressive nature and specific care requirements pose significant challenges for reef aquarists. By understanding their biology, behaviour, and ecological needs, aquarists can create a suitable environment for mantis shrimp, enjoying their remarkable presence while minimising potential risks to other tank inhabitants. Whether viewed as a marvel of nature or a formidable predator, mantis shrimp undoubtedly add a unique and intriguing dimension to the marine aquarium hobby.
