The arrow crab is one of the most unique crabs in the ocean. Besides that, one of the top and most useful members for you to help clean up the crew! However, it is also known as spider crab and yellow-lined spider crab. Because of its unusually long spider-like legs. This spider crab is hard to overlook with its unicorn-like horn on its head and extremely long, spindly legs.
Whatever, if you are looking for an unusual crustacean addition to your marine aquarium, you have to choose it. Let us introduce you to this spindly number and the facts about these crabs. So keep reading for everything you need to know to keep these spider crabs in your aquarium.
Scientific classification of arrow crab
- Scientific Name: Stenorhynchus seticornis
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Malacostraca
- Order: Decapoda
- Family: Inachidae
- Genus: Stenorhynchus
- Species: Seticornis
Quick facts about arrow crab
- Minimum Tank Size: 30 gallons
- Minimum Group Size: 1
- Temperament: Semi-Agressive
- Temperature: 72-78 °F
- Salinity: 1.015-1.025
- Difficulty Level: Medium
- Distribution: Caribbean
- pH Level: 8.1-8.4
- Care Level: Easy
- Diet: Carnivore
- Reef Compatible: Yes
- Color Form: Light tan or white with fine dark or brown lines
- Lifespan: Up to 5 years
- Common Name: Arrowhead Crab, Majoid Crab, Yellowline Arrow Crab, Caribean Spider Crab, Spider Crab
Arrow Crab Key Characteristics & Fantastic Facts
Behavior
Usually, night is the best time to see the arrow yellowline crab. Because in the daytime, they are likely to hide under ledges on sponges and sea fans. In the nighttime, they do not feel threatened by divers in the least. However, they can be extremely territorial and are not friendly when it comes to other species of the sea.
Size
The arrow spider crabs can reach up to 2.4 inches (6 cm) in length. Besides, the legs can be more than three times their body length. The male crabs are larger than the female crabs.
Habitat
The arrowhead crab is naturally found in the western Atlantic Ocean. They prefer rocky areas where they can mostly hide in and around Lebrunia anemones during the day. Besides coming out at night to feed on feather dust worms. However, it inhabits shallow coral reef environments from North Carolina and Bermuda to Brazil.
Compatibility
Naturally, arrowhead crabs are easy to care for but have intermediate difficulty. The reason is the compatibility issues that might arise with this species, as they are opportunistic omnivores. Many species might cause problems when they are hungry. They are only tentatively reef-safe species. Besides, they don’t have qualms about munching on coral polyps.
Feeding
There are many benefits you can find in these crabs. But one of the best advantages is their ravenous, omnivorous nature. This can help to feed them an absolute breeze. Arrowhead crabs feed on any bits they can find in the tank, whether they are alive or dead. Typically, you can offer them sinking foods like invertebrate tablets that the other inhabitants might not get quickly in the aquarium.
Breeding
In the home aquarium, these crabs have been observed spawning. Whatever, the tiny planktonic zoea larvae allow them to mature and grow. In the wild and aquariums, the Caribbean spider crabs are nocturnal. They prefer well-protected locations in crevices such as holes or between the tentacles or arms of crinoids and sea anemones.
Reproduction
The male crabs deposit a sperm packet into the female by holding her against his belly during mating time. The female spider crabs can carry their eggs under their abdomens until they hatch. Those newly hatched young can be called zoea and retain this name throughout their larval stage. They molt through their growth stage. Besides, they can enter a new stage of megalops once they are completely molting. In this stage, their body and limbs begin to have a crab look.
How to care for arrow crab
As we have listed above, these crabs are opportunistic feeders. So ensure yours is well fed to prevent it from looking elsewhere for nourishment. Also, you can keep the unique and fascinating creatures in the right setting. However, they require some specific care, like other crabs. They will molt occasionally as they grow and are vulnerable to attack during this period. So never use copper-based treatments in the invertebrate aquarium.
Tank Size
If you like to keep majoid crabs in your aquarium, keep in mind that they can cause trouble in smaller tanks. It is suggested that at least a 30-gallon tank is preferable for them. Because they tend to spend at least a big chunk of the day in hiding. So, it is important to make sure there is plenty of cover available in the aquarium.
Water requirements
If you plan to keep two of the spider arrowhead crabs, a 50-gallon or more tank might do for them. Usually, these crabs do not require any additional supplements to survive in captivity. But you should take care to ensure that the tank water remains at a warm temperature between 72 and 82 °F and around 75 to 79 °F. Besides, keeping calcium concentrations between 400 and 450 ppm is optimal. Also, the pH level should be kept around 8.1 to 8.4, and the alkalinity should be kept at 7 to 12 dKH.
Frequently Asked Questions
Are arrow crabs coral safe?
Usually, arrowhead crabs are safe among the resilient native corals and anemones. Also, they will not bulldoze through the big crabs and the corals. However, it is important to remember that they are omnivores. So if you are not providing enough food, they start picking at your corals.
What should I put in a majoid crab tank?
You can typically provide plenty of shelter options by installing caves, rocks, overhangs and ledges.
Who are the best tankmates of arrowhead crabs?
The best tank mates of arrowhead crabs are damselfish, clownfish, tangles, basslets, cardinalfish, and angelfish.
What does an arrow crab eat?
They can usually eat algae, worms, fruits, and other dead organisms and invertebrates.
Who are the predators of the spider crab?
The predators of these crabs are groupers, triggerfish, puffers, grunts and wrasses.
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