Varuna litterata, an unpopular pet crab, is getting exposure these days at pet stores. But this crab has quite different requirements compared to other crabs and aquarists find difficulties as there is no captive guide about this crab.
The varuna litterata is very easy to care for, but you have to know the proper way to do it. Here I’ll talk about everything you need to know about the river-swimming crab.
quick overview of Varuna litterata
| Name | Varuna litterata, Varuna crab, The river is swimming crab, The herring bow crab, The oceanic paddle crab, The chiti Kankra, and the peregrine crab |
| Care Level | Medium |
| Optimal temperature | 15- 33°C |
| Size | 4 – 7 cm |
| Color | Dark green, reddish brown, gray black, or dark brown |
| Diet | Omnivorous |
| Sleeping nature | Nocturnal |
| Temperament | Semi aggressive |
| Life span | Up to 3 years in captivity |
| Mating | Indirect sperm transfer and courtship ritual |
| Water type | Fresh water, brackish water, and saltwater |
Classification
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Crustacea
- Order: Decapoda
- Family: Grapsidae
Distribution and habitat
Varuna litterata lives in freshwater streams and ponds along with (brackish water and saltwater) near river mouths, mangroves, and the seashore and is frequently found on floating debris, seaweed, or flotsam, drifting along with the currents.
The crab is observed mostly in August, September, and October, being abundant in the Cochin Backwaters throughout the year, and recorded in Indo-Western Pacific tropical waters, including countries such as India, East Africa, Australia, Japan, the Philippines, Hong Kong, Thailand, Indonesia, and Malaysia.
Mainly, they prefer areas with sandy substrates rich in organic carbon content, mainly mangrove litter. A study found 32 different genetic types from 182 samples and the analysis revealed two distinct genetic populations: one in the Andaman Sea and one in the Gulf of Thailand.
Varuna litterata can also be found in a wide range of environments, not just coastal areas, as it can migrate up to 31 kilometers from the coastline into inland areas.
Varuna litterata crab facts
- Dweller of freshwater and saltwater – The unique thing about this crab is; that they can live in both freshwater and saltwater, or brackish water, as they are found in various water bodies in the wild.
- Antibacterial activity – A study was conducted, where researchers tasted ten marine species. Among ten species, Varuna litterata showed the strongest antibacterial effects against common harmful bacteria like E. coli and Staphylococcus aureus.
- Appearance – Varuna litterata has a carapace up to 4 cm wide and features specific markings. The carapace has an H-shaped groove in the center, with the body color ranging from dark green to reddish brown. The size and weight vary depending on male and female:
Carapace Width: Males: 30.5 to 53 mm, Females: 28.9 mm
Carapace Length: Males: 28.9 to 46.5 mm, Females: 29 mm
Weight: Males: 1.06 g to 41.48 g; Females: 2.22 g to 22.53 g
The males have larger claws and both males and females have flattened legs lined with hairs, which helps them swim at short distances.
- Behavior – Female crabs lay eggs up to three times. After a month-long larval stage, the young crabs migrate upstream in groups during the rainy season and autumn. The crabs can be found in shallow freshwater habitats during winter, likely to avoid predators and colder temperatures in deeper waters.
- Graceful swimming – They are known for swimming gracefully; they got their name the river swimming crab but they run on land sideways like other crabs.
How to care for varuna litterata
Care for varuna litterata is comparatively easy, as they don’t have specific water salinity and can adapt to different temperatures. So you don’t have to keep an eye out to track what is going on in the tank.
Tank setup
Tank requirements
Take a 20-gallon tank for 4 crabs or less; as they will need a lot of space to swim. Ensure you close the opening with a lid.
Substrate
A fully sandy substrate won’t be suitable. Mix the typical sand substrate with mud and gravel, ensuring the grains are small. The combo offers them an ideal substrate, like the wild.
You can use commercial substrates like bio stratum can be found on Amazon; to make the substrate better, you can mix it with aqua sugar white sand.
Decoration
Give them enough hiding spots with wood or wooden structures, such as wooden caves or half-log pipes. Hiding places made with rocks is optional, as they don’t have contact with rocks in their natural habitat.
Varuna litterata love open water with aquatic plants, where they prefer swimming. You can place some aquatic plants like gratiola viscidula, eleocharis acicularis, heteranthera zosterifolia, hygrophila araguaia, and rotala rotundifolia to give them a better habitat.
The light should mimic the natural day and light cycle. Typical aquarium LEDs will do the job and ensure they get a minimum of 9 to 10 hours of light.
The right water condition
There is no need to worry about temperature; aim for 15 – 33°C (60 – 90°F) with a pH ranging from 5.3 – 7.5 and a salinity of – 25 ppt (brackish water). Here is how to make brackish water –
Another thing about the water is that it doesn’t like high currents. Slow-moving water would be beneficial as the mangroves don’t have high-flowing water and high-moving water is an obstacle for their swimming. You can use air stones or a powerhead to help with water circulation and oxygenation.
How to feed your varuna litterata
Vanura litterata are omnivorous, meaning you can feed them meat, vegetables, and commercial food. Juveniles feed on detritus and soft foods, keep this in mind. Domestic waste, like discarded parts of tomatoes and cabbage, can be a good option.
- Meat – Dried shrimp, krill, dried fish, mysis, brine shrimp, blood worms and small insects.
- Vegetables and fruits – Broccoli, spinach, kale, apples, watermelon and bananas (Algae).
- Commercial diet – Fish food, turtle food, wet cat food, fish pellets and flakes.
Remove any uneaten food to keep the water quality good and don’t forget about the calcium-rich food like cuttlebone.
