Crabs are a diverse group of crustaceans that live in oceans all over the world. Their lifespan can vary greatly depending on the species. Some crabs live for just a year, while others can live for decades.
Lifespans of Common Crab Species
Here are the typical lifespans for some of the most common crab species:
- Fiddler crabs: 2-3 years
- Hermit crabs: 5-10 years
- King crabs: 6-10 years
- Snow crabs: up to 15 years
- Dungeness crabs: up to 10 years
- Spider crabs: up to 20 years
- Horseshoe crabs: 19-20 years
As you can see, lifespans range dramatically between crab types. Smaller crab species like fiddler crabs and hermit crabs tend to live just a few years. Larger crab species can reach ages of 10-20 years. The longest living crab species is the giant Japanese spider crab, which can live up to 100 years!
What Impacts Crab Lifespans?
There are several key factors that influence how long crabs live:
- Species – Some crab species are genetically predisposed to live longer than others. Larger crabs tend to live longer than smaller crabs.
- Habitat – Crabs that live in optimal habitats with plentiful food and few predators will live longer than crabs in suboptimal conditions.
- Molting – Crabs must periodically shed their exoskeletons to grow. Crabs that successfully molt often will live longer.
- Injuries/disease – Crabs that become injured or diseased will likely perish sooner.
- Predators – Crabs with more predators have higher mortality rates.
Crabs that have access to plentiful resources and few threats in their environment are most likely to reach their maximum lifespans for their species.
Stages of a Crab’s Life
Crabs go through several distinct life stages as they grow, molt, and reach maturity. The stages of a crab’s life include:
- Egg – Crabs begin life as eggs carried by the female. Eggs hatch into larvae.
- Larva – Crab larvae float in the ocean feeding on plankton. Larval stages last weeks to months depending on species.
- Juvenile – After the larval stage, crabs settle to the sea floor as juveniles. Juveniles hide from predators while growing.
- Adolescent – Rapid growth occurs as crabs reach adolescence. Crabs periodically molt their exoskeletons as they grow.
- Mature Adult – Once sexually mature, crabs reach their adult size and can mate. Maximum size depends on species.
- Old Age – In old age, crab growth slows. Molting may become difficult. Eventually crabs weaken and perish from natural causes.
The length of each life stage depends on the species. Fast growing crabs may reach maturity in 1-2 years, while slow growing crabs may take 5+ years to fully mature and start reproducing.
Molting and Growth
One key factor impacting crab lifespans is the process of molting. In order to grow larger, crabs must periodically shed their rigid exoskeletons in a process called molting or ecdysis. Here’s how it works:
- A new soft shell starts forming under the hard shell.
- The crab extracts itself from the old shell, which splits apart.
- For a few days, the crab has a new soft shell as minerals harden the new shell.
- Once fully hardened, the new shell allows room for more growth.
Crabs that fail to successfully molt will perish. Young juvenile crabs may molt several times a year as they grow rapidly. Older crabs molt less frequently – sometimes annually or even less often. The molting process becomes more difficult for aging crabs, eventually leading to mortality when they can no longer molt.
Reproduction and Offspring
Mature female crabs produce large numbers of eggs. The number of eggs can range from thousands to millions! The eggs are fertilized by male crabs and carried by the female until they hatch into free-floating larvae. Neither parent provides any care for the offspring after hatching.
Most juvenile crabs perish soon after settling to the seafloor due to predators and lack of resources. Therefore, even though females produce huge numbers of offspring, only a tiny fraction survive to adulthood. However, those that do survive can live many years as adults.
Differences Between Males and Females
Male and female crabs can be distinguished by certain physical characteristics:
- Males often have narrower abdomens or tails.
- Females have broader abdomens to carry eggs.
- Males may have larger claws for defense and shows of dominance.
- Some species, males have different coloration.
The differences result from the reproductive roles of each gender. Females put more resources into generating eggs, while males invest more in fighting and mate attraction.
In terms of lifespan, there is little difference between male and female crabs of the same species. Both genders go through the same stages of life and face similar mortality risks in the wild.
Extreme Long-Lived Examples
While most crabs live just a few years, some individual crabs attain remarkably old ages. These elderly crabs give insight into the extreme upper limits of crab lifespans:
- In 1977, scientists estimated the age of a giant spider crab caught off the coast of Scotland. Based on size and growth rings, they estimated the crab was around 100 years old!
- Ocean researchers have applied growth rates to estimate the largest king crabs at 15-25 years old.
- Fossil evidence shows extinct crabs related to horseshoe crabs may have lived up to 60 years.
- A captive hermit crab was reported to have lived for 32 years in an aquarium, surpassing the typical 5-10 year lifespans in the wild.
While not typical, these examples show that some crabs do have the potential under ideal conditions to live many decades and even approach a century. Captivity and lack of predators allows captive crabs to far exceed normal longevity.
Longevity in Different Crab Families
Looking at some of the major crab taxonomic families provides more insight into differences in average lifespans between crab types:
Portunidae – Swimming Crabs
Examples: Blue crabs, mud crabs
Lifespan: 2-3 years
Cancridae – Rock & Spider Crabs
Examples: Dungeness crab, king crabs
Lifespan: 5-15+ years
Majidae – Spider Crabs
Examples: Japanese spider crabs
Lifespan: Up to 100 years
Varunidae – Swimming Crabs
Examples: Mangrove tree crabs, crab eggs
Lifespan: 1-2 years
The longer living crab families (spider crabs, rock crabs) tend to have larger body sizes and slower growth compared to shorter lived crabs like portunids and varunids. Slower growth allows for longer lifespans.
Effects of Temperature on Lifespan
Water temperature plays an important role in crab growth rates, molting frequency, and overall lifespan. Colder temperatures generally extend crab lifespans:
- Crabs in cold high-latitude regions live longer than crabs from warmer low latitudes.
- Food intake and growth are slower in cold water, leading to greater longevity.
- Warmer temperatures speed up metabolism, resulting in faster aging and shorter lives.
- However, extremely cold temperatures can prevent molting and growth entirely.
Ideally, crabs should inhabit regions with water temperatures cool enough to limit fast growth, but warm enough to enable regular molting throughout their lifespan.
Lifespans in Captivity vs. Wild
|Wild||Up to 20 years, depending on species|
|Captive as Pets||Up to 30+ years in rare cases|
|Commercial Fisheries||Many crabs harvested at 1-3 years old|
Crabs generally live longer lifespans in captivity compared to the wild. Ideal tank conditions provide plentiful food, no predators, and few diseases. Some pet crabs have lived up to 30 years.
However, crabs raised in commercial fisheries are often harvested for meat at young ages before reaching maturity. So lifespans in fisheries are shortened to just 1-3 years typically.
In summary, lifespans for crabs can range dramatically from 1 year up to 100 years for rare Japanese spider crabs. Most crabs live 2-10 years on average depending on genus and habitat. Larger crab species with slower growth live longer than small, fast growing crabs. Factors like temperature, food availability, predators, and ability to molt all impact ultimate longevity.
While many crabs meet an untimely end from predators or fishing, those able to survive can potentially live for decades. By studying crabs in the wild and in captivity, marine biologists continue to learn more about crab life cycles and maximum lifespans.