W. Ray McClain and John Sonnier Few things symbolize Louisiana culture and cuisine like a festive crawfish boil. Every year, wild crawfish are caught in the huge Atchafalaya River Basin. In Louisiana, more than 100 million pounds of live crawfish are raised in ponds that cover about 184,000 acres. Most of this food is eaten in the state, mostly as whole crawfish boiled in spices. People who have never tried this treat before are often told to stay away from crawfish with straight tails and only eat the ones with curled tails. After being fully cooked, most crawfish will have a tightly curled tail (which is actually the abdomen), but sometimes a few will show up with tails that are straight or not curled at all. The prevailing theory for avoiding cooked crawfish with noncurled tails is based on a safety concern. Some people think that cooked crawfish with straight tails were already dead before they were cooked. Since you don’t know how long the animals were dead or how they were stored, it is best not to eat them. When cooked, the muscles in the bellies of many decapod crustaceans, like shrimp, lobster, and crawfish, tend to spasm and curl up. Obviously, if the muscles in the abdomen are broken down enough by degradation or decomposition, then the abdomen would not be able to contract as well. However, looking at how much the abdomen curls may not be a good way to tell if cooked crawfish is safe or of good quality. As an example, we have often seen a few individuals with non-curled abdomens of varying degrees after cooking, even though we knew the crawfish were alive just minutes before cooking (Figure 1). A basic study was initiated to investigate this under controlled conditions. Individual crawfish that were alive, dead, or alive but restrained were boiled, and the amount of curling in the abdomen was measured. On five different dates during the season, live crawfish were quickly and purposely killed. The dead and remaining live crawfish were then put in a cooler that was kept at 38 to 42 degrees F. After being in the cooler for five days, half of the live crawfish were held in place on small wooden stakes by rubber bands, with their bellies flattened. Then, one living crab, one dead crab, and one restrained crab were put in a pot of boiling water for 10 minutes. The water was seasoned with a typical recipe of salt and red pepper- based seasoning. Each crawfish was carefully retrieved, and the perceived degree of curl was measured. We used reference points on the back of the animal at the point where the abdomen meets the carapace and at the backmost part of the abdomen (Figure 2). The cooked crawfish were put on a flat surface upside down so that the dorsal surface of the carapace was on the same plane as the protractor’s base line. The protractor’s starting point was placed at the point where the carapace and abdomen meet, and the angle of curl was found by looking at where the second reference point was located (Figure 3). Crawfish that were stuck on the stake during the cooking process were freed by cutting the rubber bands, being careful not to change the angle of curl (or lack of it). The angle was then measured in the same way. The summarized results are presented in Figure 4. The abdomens of live and dead crawfish that had been stored in a cooler for five days before cooking did not curl at different angles after being boiled (0–10, 20, 30, 40, 50, 60, 70, 80). Live crawfish restrained during the cooking process, however, exhibited significantly less curl when freed. Even though this study didn’t try to test for safety or quality, the results disprove the idea that a “straight tail” in boiled crawfish shows if the animal was alive when it was cooked. To sum up, when cooked, dead crawfish had about the same amount of curl as live crawfish, even after being in a cooler for five days. Additionally, in live crawfish where the abdomen wasn’t allowed to naturally curl during cooking, the abdomen stayed mostly straight. This last observation suggests that at least some of the straight tails seen at a crawfish boil may be due to too many people in the pot, which stops the tails from curling naturally while they’re cooking. To test the effects of crowding, live crawfish were put in a beaker of boiling water and left there for 10 minutes. The results were several individuals displaying less-thantightly curled abdomens. So, this study suggests that the old saying that you should avoid straight-tailed crawfish at a crawfish boil to make sure the food is safe and good may not be true, and it has nothing to do with how alive the animal is when it is cooked. Ray McClain, Professor, and John Sonnier, Research Farm Specialist, Rice Research Station, Crowley, La. (This article was published in the summer 2009 issue of Louisiana Agriculture. ).
As a crayfish owner you may have noticed your crayfish curling its tail under its body. This distinctive posture often leaves crayfish keepers wondering – why is my crayfish tail curled?
Curling the tail under the body is natural behavior for crayfish that can occur for a variety of reasons By understanding the causes behind tail curling, you can ensure your crayfish stays happy and healthy
Anatomy of a Crayfish Tail
The tail of a crayfish is scientifically known as the abdomen or tailfan. This muscular portion of the body is made up of overlapping segments that enable flexibility and movement.
At the end of the tail is the tailfan, consisting of flattened appendages called uropods and telson. Powerful muscles in the tail allow crayfish to swiftly propel themselves backwards to escape predators.
The tail also contains tiny appendages called pleopods or swimmerets. In females the pleopods hold eggs and embryo crayfish. In males some pleopods are modified into copulatory organs.
Now that we understand crayfish tail anatomy, let’s explore reasons your crayfish may curl its flexible abdomen under its body.
Molting and Growth
One of the most common reasons for crayfish tail curling is the natural molting process. Molting allows the crayfish to grow by shedding its rigid exoskeleton.
Prior to molting, the crayfish forms a new soft shell underneath its old one. At this stage, you may notice your crayfish becoming more inactive and reclusive. Tail curling occurs as the crayfish assumes a defensive posture to prepare for its vulnerable molting phase.
During molting, the crayfish extracts itself from the old shell, usually starting by splitting it between the carapace and abdomen. The soft new shell rapidly expands with water uptake and hardens over the next few days.
Younger crayfish may molt every 2-3 weeks in summer, while adults molt 2-3 times a year. Molting allows rapid growth with some crayfish increasing 40% in weight after a single molt!
Stress Behavior
Crayfish can curl their tails when feeling stressed or threatened. Potential stressors include:
- Tankmates like fish
- Overcrowding
- Sudden water changes
- Excess noise or vibrations
- Handling by humans
- Poor water quality
By curling the tail under the body against the legs, the crayfish assumes a defensive posture. The folded tail protects vulnerable underside areas.
Stressed crayfish may also show other body language cues like raised claws, rapid backwalking, or hiding away in shelters. Try to identify and remove the stressor to keep your crayfish happy and healthy.
Preparing to Mate
Dominant male crayfish may curl their tails as a display of strength to attract females and intimidate competing males. If you have a mixed male and female crayfish tank, watch for males exhibiting this reproductive behavior.
Females also curl their tails to signaling molting and mating readiness through release of pheromones from pores at the base of the tailfan. So in a mixed population, curled tails can signal both males and females preparing to mate.
Defensive Posture
When feeling threatened by predators or competitors, crayfish instinctively curl their muscular tails under for protection. They may also raise their front claws in an intimidating manner.
In the wild, predators like raccoons, fish, frogs, turtles, and waterbirds all feed on crayfish. The defensive posturing allows crayfish to appear larger and more intimidating to would-be attackers.
If you notice these behaviors frequently in a tankmate setting, consider providing more hiding spaces or separating aggressive crayfish.
Normal Resting Position
Some crayfish species like Australian Redclaw purposefully curl their tails even when resting. So tail curling is not always a cause for concern!
In these cases, it’s simply the crayfish’s natural posture and part of their distinctive body language. Cherax quadricarinatus crayfish, for example, tend to habitually curl their tails whether active or at rest.
Signs of Health Problems
While tail curling is normal crayfish behavior, it can also sometimes indicate an underlying health issue. Look for these other signs suggesting illness or parasites:
- Clamped tails for extended periods
- Lethargy and loss of appetite
- White spots or patches on shell
- Cloudy eyes
- Wounds or lesions on shell
- Frequent rubbing against objects
Common crayfish illnesses include fungal infections, bacterial diseases, viruses, and parasites like gill worms. Seek veterinary advice if you suspect your crayfish is sick. Quick diagnosis and treatment can help restore your crayfish back to health.
Preventing Tail Curling
Fortunately, there are some easy ways to prevent excessive tail curling and keep your crayfish relaxed:
- Provide a roomy tank with plenty of hiding spots
- Use gentle filtration and avoid strong currents
- Maintain excellent water quality
- Feed a varied, nutrient-rich diet with calcium
- Avoid overcrowding and competition for resources
- Handle crayfish gently to avoid stress
- Keep tank decor natural with rocks, logs, plants
With some simple adjustments to their habitat and care, you can help prevent your crayfish from feeling the need to curl its tail defensively or from stress.
Treating an Injured or Clamped Tail
If your crayfish’s tail was injured or is clamped for unknown reasons, there are a few options:
- Add aquarium salt to help heal wounds and fight infection
- Do frequent partial water changes in the tank
- Provide clean, high-quality food to support healing
- Make sure tankmates aren’t nibbling or harming the crayfish
- Provide ample hiding places so the crayfish feels secure
Unfortunately, manually straightening a clamped tail can further injure the crayfish. Let the crayfish relax its tail on its own as it heals. Seek exotic veterinary assistance if clamping persists.
Now You Know!
Monitor for any other signs of stress, illness, or injury. But in most cases, a curled crayfish tail is completely normal and nothing to worry about! With proper care, your fascinating crayfish will continue thriving while showing off its cute tail curling quirks.
3 signs your crayfish will die soon
FAQ
What does it mean when a crawfish curls its tail?
Why do lobsters curl their tails in tanks?
Do crayfish tails bend?
Is it normal for crayfish to lay on their side?
Do crawfish have curled tails?
Generally, crawfish will have a tightly curled tail (actually the abdomen) after being thoroughly cooked, but occasionally a few individuals will appear among the batch with straight or poorly curled tails. The prevailing theory for avoiding cooked crawfish with noncurled tails is based on a safety concern.
Why does crawfish’s abdomen curl when cooked?
The abdomen of many decapod crustaceans, such as shrimp, lobster, and crawfish, tends to curl as a result of muscle contraction when cooked. Obviously, if muscle tissues in the abdomen are sufficiently deteriorated by degradation or decomposition, then the ability of the abdomen to contract would clearly be affected.
Why is my crayfish laying on its back?
It’s not common to see your crayfish lying on its back. The crayfish owners look for the reasons responsible for their crayfish laying on its back. Generally, stress is the common reason for lying on the back of crayfish.
Why do crayfish molt?
Crayfishes generally face problem with molting when something is wrong with the water. Lack of iodine can also cause this problem. Crayfishes are generally very hardy creatures. They can handle a wide range of water parameters. Consistent water parameters are more important than trying to hit the correct number.