Procambarus milleri

Miami Cave Crayfish

FWS Focus

Overview

Characteristics
Overview

The Miami cave crayfish (Procambarus milleri) is a subterranean, freshwater crustacean found in the Biscayne Aquifer on the Atlantic Coastal Ridge of southern and central Miami-Dade County, Florida. Miami cave crayfish have been collected from wells and excavations 7.9 to 36 feet (2.41 to 11 meters) deep in the Miami Limestone and Fort Thompson limestone formation within the Biscayne Aquifer. The species was petitioned for federal listing under the Endangered Species Act of 1973, as amended, as a part of the 2010 Petition to List 404 Aquatic, Riparian and Wetland Species from the Southeastern United States by the Center for Biological Diversity. The species has recently adapted to the subterranean environment as indicated by pigment and eye facets in individuals. Miami cave crayfish are opportunistic omnivores, primarily consuming surficial detritus that filter down through the porous limestone.

Scientific Name

Procambarus milleri
Common Name
Miami cave crayfish
FWS Category
Crustaceans
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Physical Characteristics

Characteristics
Color & Pattern

Adult Miami cave crayfish have black eye spots and are most commonly dark orange in color with a distinctive reddish stripe extending medially on the dorsal surface from the first abdominal segment to the sixth. Approximately 83% of 2,451 adults, captive-reared Miami crayfish exhibited this color pattern, while 8.8% displayed a more muted orange coloration. Less common color variations demonstrated by captive-born individuals included hues of pink, blue, red, green, beige and brown, accounting for a combined total of 8.5% of the adults inspected. Egg masses are pigmented, and most of captive-bred juveniles bear red pigmentation upon hatching. However, 10% of the captive juveniles examined in 1994 were albino, a trait lost in the captive population following this generation as a result of disease-related die-offs. The presence of pigmentation in the majority of wild and captive Miami cave crayfish suggests that the species is still in the process of adapting to its subterranean environment. For instance, stygophilic crayfish are adapted to living in both surface and subterranean habitats, versus stygobitic, which are strictly subterranean. 

Size & Shape

In contrast to the sexual dimorphism exhibited by many crayfish species, females and males of the Miami cave crayfish do not demonstrate any significant size differences and adults of both sexes bear relatively large claws. The carapace lengths reported in wild adults range from 0.3 inch (8 millimeters) up to 1.1 inches (27.4 millimeters). Captive-bred adults are larger than are those from wild populations, most likely due to the increased food availability and reduced predatory and competitive pressures in captive settings. The average carapace length of captive adult Miami cave crayfish is 0.05 inch (1.25 millimeters) longer than that of wild adults.

Characteristic category

Habitat

Characteristics
Habitat

Miami cave crayfish have been collected from wells and excavations 7.9 to 36 feet (2.41 to 11 meters) deep, with the majority between roughly 22.9 to 36 feet (7 and 11 meters) deep, in the Miami limestone and Fort Thompson limestone formation within the Biscayne Aquifer along the Atlantic Coastal Ridge in southern and central Miami-Dade County, Florida. Despite significant sampling efforts, no specimens have been recovered from groundwater wells of similar depths within Everglades National Park, even those sampled along the westernmost, isolated segment of the Atlantic Coastal Ridge at Long Pine Key.

Cave or Karst

A natural chamber or series of chambers in the earth or in the side of a hill or cliff. An irregular limestone region with sinkholes, underground streams and caverns.

Characteristic category

Food

Characteristics
Food

Miami cave crayfish eat detritus that filter down through the porous limestone and smaller, sympatric crustaceans. Amphipods and isopods were found in the same trap where Miami cave crayfish were recovered. Potential microcrustacean prey recovered from wells along the coastal ridge in the Homestead area include low densities of Caecidotea isopods, Hyalella amphipods, and a Crangonyx amphipod. Juveniles and adults of Miami cave crayfish ate commercial algal-based trout food chow and Spirulina tropical-fish flake food supplemented by Hyalella spp.

Characteristic category

Behavior

Characteristics
Behavior

Captive Miami cave crayfish display sheltering behaviors in response to threatening interactions. In the wild, they hide in the porous limestone aquifer where they live.

Characteristic category

Life Cycle

Characteristics
Life Span

The age of reproductive maturity and longevity of Miami cave crayfish is unknown. However, in concurrence with life history theory, subterranean species of crayfish generally live longer than their surface counterparts, up to several decades in some cases.

Reproduction

In captivity, Miami cave crayfish exhibit continuous reproduction throughout the year, peaking in the late summer through early winter. When male crayfish molt, they may alternate between reproductively active form I and nonreproductive form II states, a pattern observed in wild Miami cave crayfish.

Life Cycle

Miami cave crayfish begin life as fertilized black eggs that are about 2 millimeters in diameter and adhere to the pleopods underneath a female’s abdomen. After hatching, the young attach to the female by a telson thread, a ropelike structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.

Learn more about structure
binding the eggshell attached to the last segment of the abdomen of the female to the abdomen of the hatchling. Young crayfish undergo a series of molts, or shedding their old exoskeleton, and growing and hardening new exoskeletons while still attached to the female. Juveniles then leave the female to begin life as free-living individuals.

In captivity, Miami cave crayfish exhibit continuous reproduction throughout the year, peaking in the late summer through early winter. Molting is one of the critical life history stages of crayfish. Starting from the time of hatching and continuing until death, crayfish go through a continuous series of molts. This enables crayfish to increase in size throughout life.

In addition to increasing in size, when male crayfish molt, they may alternate between reproductively active form I and non-reproductive form II states, a pattern observed in wild Miami cave crayfish. Molting appears to occur year-round for both sexes and all life stages of Miami cave crayfish as confirmed by wild collections of adult males and studies of a captive population over three years. Captive-reared females molt within two to three weeks of releasing their young, typically mating shortly after completing this molt.

Characteristic category

Similar Species

Characteristics
Similar Species

The Miami cave crayfish is closely related to the surface-dwelling Everglades crayfish (Procamabarus alleni), which lives in brackish water environments with salinity values up to 18 parts per thousand.

Geography

Characteristics
Range

The historical and current range of the Miami cave crayfish is restricted to areas of the Biscayne Aquifer along the Atlantic Coastal Ridge in southern and central Miami-Dade County, Florida east of the Everglades wetland ecosystem.

Timeline

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