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The CPO, also known as the Orange Mexican Dwarf Crayfish, is a small freshwater crayfish native to Lake Pátzcuaro, Mexico. Its compact size, bright orange coloration, and generally peaceful behavior make it a popular aquarium invertebrate. Cambarellus patzcuarensis explores the bottom, climbs plants, and is especially active around dusk. It remains opportunistic, however, and may catch very small shrimp or fry. This species is fairly common in the aquarium trade, particularly in the selectively bred orange form.

General description of the species

Cambarellus patzcuarensis is a dwarf crayfish from the family Cambaridae, adapted to bottom-dwelling life in calm or slow-moving water. Its compact size suits well-planned community aquariums, provided aggressive or very large tank mates are avoided. It spends time searching through the substrate, climbing décor, and looking for shelter. Although it is generally peaceful toward adult fish, it remains a small opportunistic predator. Hiding places are essential, especially during molting, when its shell is particularly vulnerable.

Geographic origin and habitat

Country of reference: Mexico. The species is endemic to the Lake Pátzcuaro basin in Michoacán, west-central Mexico. It inhabits shallow shoreline areas where the bottom may consist of mud, sand, and plant debris. The natural environment includes shores with shelter among stones, roots, and aquatic vegetation. The water is generally soft to moderately mineralized and temperate rather than strongly tropical. In aquariums, stable, well-oxygenated water free of copper supports success, because copper is highly toxic to crustaceans.

Precise location and local name

The natural range is centered on Lake Pátzcuaro and its shoreline habitats in Michoacán, Mexico. The most widespread aquarium name is CPO, a trade abbreviation derived from Cambarellus patzcuarensis “Orange.” The English name Orange Mexican Dwarf Crayfish directly describes its color and origin. The orange form sold in the aquarium trade is selectively bred; wild individuals are usually more subdued, with brownish or grayish tones. In its native range, it is a small crayfish associated with shoreline habitats and bottom shelters.

Appearance and physical characteristics

The body is stocky and protected by a hard shell, with two relatively small claws and an articulated tail. The commercial variety displays a bright orange to reddish-orange coloration, which may vary with age, sex, and rearing conditions. Long antennae help it explore its surroundings, while the walking legs allow it to move, climb, and handle food. Adult size remains small, reaching about 4 cm at most, excluding the antennae. Males are generally slimmer, with narrower claws and a thinner abdomen; females have a broader abdomen suited to carrying eggs.

General diet

Cambarellus patzcuarensis is an omnivore that consumes plant matter, organic debris, biofilm, and small organisms. In aquariums, offer invertebrate pellets, sinking foods, blanched vegetables, and occasional protein such as suitable frozen foods. Catappa or oak leaves can also provide grazing surfaces and an additional food resource. A varied diet supports growth and shell formation, but leftovers should be removed promptly. Favor sinking foods that are easy to reach, given in small portions, with enough calcium to support molting.

Essential data

• Name of the original river: Lake Pátzcuaro; no original river is associated with this species.
• Local name used: CPO; Orange Mexican Dwarf Crayfish in English-language aquarium keeping.
• Origin of the scientific name: The name combines the genus Cambarellus with the epithet patzcuarensis, referring to Lake Pátzcuaro.
• Etymology of the full name: Cambarellus means “small Cambarus,” referring to a crayfish genus; patzcuarensis means “from Pátzcuaro.”
• Common/vernacular names: CPO; Orange Mexican Dwarf Crayfish; Mexican orange dwarf crayfish.
• Family: Cambaridae.
• Subfamily: Cambarinae.
• Name pronunciation: kam-bah-REL-lus pat-skwa-ra-EN-sis.
• Discovery: Alejandro Villalobos Figueroa, 1943.
• Maximum adult size: About 4 cm.
• Water temperature and pH: Approximately 18 to 24 °C; pH around 7.0 to 8.0.
• Appearance of the waterway and surrounding vegetation: Calm or slow shoreline areas with mud, sand, plant debris, stones, and aquatic vegetation.
• Typical tank mates: Small peaceful fish such as Poecilia reticulata, sturdy snails, and other similarly sized invertebrates; fry and very small shrimp may be caught.
• Temperament and behavior: Generally peaceful, exploratory, opportunistic, and more active in the evening; limited territoriality when shelters are plentiful.
• Water depth: Shallow shoreline areas of the lake.
• Sexual dimorphism: Males are often slimmer, with narrower claws; females are broader and have a more developed abdomen.
• Bottom structure and flow: Muddy or sandy-muddy bottom mixed with debris, with calm water or low flow.

In your aquarium

To succeed with Cambarellus patzcuarensis, provide a covered, fully cycled aquarium with plenty of hiding places and a smooth substrate. Stable water, moderate temperatures, and adequate calcium availability are essential. Avoid treatments containing copper and monitor feeding to limit pollution. During molting, leave the crayfish undisturbed and provide tight refuges. With a reasonable stocking level and calm tank mates, this dwarf crayfish offers fascinating behavior and a highly decorative orange coloration, while requiring careful attention to compatibility with shrimp and fry.