Atya scabra

The African Filter Shrimp, also known as the Cameroon Fan Shrimp, is a fascinating and peaceful giant for the freshwater aquarium. Its most noticeable feature is the set of fan-like appendages on its front legs, which it uses to filter tiny food particles out of the water current. Growing to an impressive size, often larger than many common aquarium fish, their coloration can shift between shades of grey, blue, and brown depending on their environment and mood.

These shrimp are gentle giants and won't harm even the smallest fish or other shrimp. They are most comfortable in an established aquarium that has a strong current, which they need to feed properly. You'll often see them perched on driftwood or rocks, facing the flow with their fans extended. Because they are excellent climbers and can find their way out of small gaps, a a tight-fitting lid on the tank is essential. To feed them, simply crush high-quality fish flakes or use specialized powdered shrimp food and release it into the water stream ahead of the shrimp. They are a wonderful addition for anyone looking to add unique and active invertebrate life to a community tank.

Atya scabra, commonly sold as the African Filter Shrimp or Rough-clawed Shrimp, is a robust crustacean prized for its unique feeding behavior. Unlike scavenging shrimp, this species is a specialized rheophilic suspension feeder, meaning it thrives in fast-moving water where it can capture suspended organic matter. Its foremost pairs of pereiopods are modified into intricate chelate fans, which are unfurled to form a biological sieve. A key indicator of their well-being is observing this feeding posture; if the shrimp is frequently seen scraping substrates with its fans, it's a sign that the water current is too weak or that there is insufficient food in the water column.

To properly house them, one must emulate their natural habitat of fast-flowing coastal streams. This requires mature aquarium with stable water chemistry and a powerful water flow, often supplemented with a powerhead or a strategically aimed filter outlet. They are highly dependent on this flow for both feeding and respiration. Their diet in captivity should consist of finely ground, high-quality foods like spirulina powder, crushed flakes, and commercially available foods for filter-feeding invertebrates, which can be target-fed using a pipette upstream from the shrimp's location.

While they can be kept singly, keeping them in small groups can encourage more natural and visible behavior. They are largely peaceful but their substantial size can intimidate smaller, more timid species. They are reclusive after molting, as their new exoskeleton needs time to harden. Providing an environment rich in calcium and other minerals, as implied by the recommended water hardness, is crucial for successful ecdysis (molting). The 'Rough-clawed' name refers to the enlarged and spiny first walking legs on males, used for gripping surfaces in strong currents. Breeding in an aquarium is exceptionally challenging as Atya scabra has an amphidromous life cycle. The female carries eggs that hatch into larvae which must drift into a brackish or full marine environment to develop before migrating back to freshwater, a process nearly impossible to replicate without a dedicated, multi-stage system.

Atya scabra (Leach, 1815) is a decapod crustacean of the family Atyidae, notable for its wide but disjunct distribution across coastal drainages of the tropical West Atlantic (Americas) and East Atlantic (Africa). This extensive range is facilitated by an amphidromous reproductive strategy, where planktonic larvae undergo a lengthy marine development phase before recruiting back to freshwater habitats as juveniles. This complex life cycle makes captive breeding exceptionally difficult, requiring precise manipulation of salinity, diet, and flow across multiple larval (zoeal) stages.

Morphologically, A. scabra is distinguished by its robust, fusiform body adapted for a rheophilic existence. The primary diagnostic feature is the set of modified chelae on the first and second pereiopods, which bear dense rows of setae that form efficient filtering fans. These are used to sieve fine particulate organic matter (FPOM), detritus, and microorganisms from the water column. In males, the first pair of pereiopods is notably enlarged and spinous, used for anchorage in high-velocity currents and likely for intraspecific interactions. This species is an important functional component of its native ecosystems, serving as a primary consumer that channels FPOM into the broader food web.

Physiologically, its reliance on strong water flow is twofold: it is essential for the delivery of suspended food and for maintaining high levels of dissolved oxygen across its gills, even though its basal metabolic oxygen consumption is relatively low. As a tank inhabitant, its medium waste production and non-trivial bioload factor (2.6) necessitate robust filtration. Its notable climbing ability, classified as a 'tank escape artist' trait, requires aquarists to maintain secure enclosures to prevent extra-limital excursions. Although its IUCN status is Least Concern (LC) due to its wide distribution, local populations can be vulnerable to habitat degradation, particularly the disruption of hydrological connectivity between freshwater and marine environments, which is essential for the completion of its life cycle.