Portunidae crabs are described by the smoothing of the fifth set of legs into wide oars, which are utilized for swimming. This capacity, together with their solid, sharp paws, enables numerous species to be quick and aggressive predators.

The family named Portunidae are recognized from whatever is left of the round-fronted crabs by the adaptation of a few of their legs for swimming, to which end these appendages are changed into leveled paddles.

The outcome is regularly to give upon the crabs an intensity of dashing at rapid speed through the water, which would barely be credited by the individuals who have not watched them.


Comparing to this flexibility they have a thin straightened type of body, empowering them to go sideways through the water, and a daintiness gained at the detriment of the defensive cuticle.

These idiosyncrasies give the Portunidae an amazingly unique substantial body from the vigorously manufactured, slow moving Xanthids, or, in other words by a similarly checked distinction of habitat. The Xanthids are normally to be found on the shore or reef exposed to the full power of the breakers.

Furthermore, in this position, the softly manufactured swimming crabs would be ruined to pieces against the stones. Their legitimate haunt is a space of calm waters, for example, the tidal pond of a coral atoll, and as these spots seem to be, in the tropics, usually bottomed with grayish or white coral sand, on which the crabs lie.

In that sand, crabs regularly conceal their bodies, they much of the time mimic it by their pale grayish shading, frequently in a way as striking as that in which leveled fish look like the shingly base they live on.

The family is exceedingly varietal and variable and is presumably experiencing quick development in numerous ways.


NameSwimming crabs
Scientific namePortunidae
SynonymsTrue crabs

Vernacular names

  • English: swimming crab
  • Chinese: 梭子蟹科
  • Japanese: ワタリガニ科
  • Russian: Крабоплавунцовые


The history of Portunidae is given below:


The origin of blue swimming crabs is Indo-West Pacific region.

Distinctive Features of Portunidae

The edges on the carapace are finely jagged. The shade of the crab ranges from dim gray to caramel, with extensive spots scattered on the carapace that is red in the center and dull around the fringe.

Bay Calico Crabs are strolling crabs, implying that their back legs are intended for strolling instead of being straightened and utilized for swimming and burrowing. Bay Calico Crabs are generally foragers as opposed to seekers.

Another fascinating note is that the Gulf Calico Crab, for the most part, has a Tri-hued Anemone, Calliactis tricolor on it’s spinal, which falls off when the crab molts.


The Blue Swimmer Crab is majorly found from Northern Queensland to Eden which is located in New South Wales; South Australian and Western Australia bays; additionally New Zealand and New Caledonia.


The bodies of a majority of Portunidae are protected or enhanced with sharp teeth or thistles, and it is on such characters as the size and number of these and the figure of the lobed front that the sort is usually recognized.

However much of the time enough isn’t known about their lifestyles or behaviors to make it conceivable to state whether, and if so how, these are useful to the creatures.


In the meantime the swimming crabs are in no way means they are altogether restricted to a base of coral sand or even in the tropics. In profound water, where rocks are not related with risk, they are found on each sort of base in about equivalent numbers, and here, in the event that they conceal, it must be under gravels.

They even happen, however not all that all the time, on the reef. In any case, the people found in this position may conceivably have strayed from the tidal pond with the cordial tide.

Most likely, when more is thought about the lives of the species, it will be discovered that some of them keep up their reality on the reef by shielding in squares of coral or under stones, where if anyplace they are constantly found, and that others-positively the majority of people incline toward the tidal pond.

In their conducts these crabs are dynamic and wise, escaping catch with smartness. The tidal pond forms typically hold near the sand and don’t rise in excess of a couple of feet into the water, yet others swim as intensely and firmly as fish

Habitat of Portunidae

Deepness range based on 1 example in 1 taxon.

Ecological ranges
Depth range (m): 27 – 27

Food Habits

Mud crabs are top benthic predators and feed on sessile or moderate moving benthic macroinvertebrates, basically gastropods, shellfish, and mollusks, the arrangement of many food items changes as the mud crab develops.

In little adolescents, foregut substance was dominated by debris while in bigger adolescents and grown-ups, scavengers and fish were the prevailing nourishment items.

swimming crab

This adjustment in the food arrangement was affirmed by stable isotope investigations in Thailand. Little mud crabs are omnivorous, bolstering shrewdly on plants and little crabs, while medium-and extensive sized crabs are rapacious. They feed on benthic spineless creatures or being opportunistic scroungers.

The Blue Swimmer Crab is a famous food in Australia and is focused on and gotten in huge numbers by expert and recreational fishers. Besides this, these crabs enter estuaries as adolescents and develop rapidly, developing following one year.

Behavior of Portunidae

Blue swimmer crabs are occasionally called ‘blueys’ or ‘blue manna’. They are intense swimmers and unquenchable hunters and scroungers. They are focused by business and recreational fishers. Blue swimmer crabs (Portunus armatus; once in the past known as P. pelagicus) are a tropical species and have a place with the Portunidae family.

Portunidae normally walk sideways due to the articulation of their legs which makes a sidelong walk more proficient. In any case, a few crabs walk backward or forwards, including Libinia, raninids, Mictyris platycheles, and emarginata.

A few crabs, remarkably the Matutidae and Portunidae, are additionally capable of swimming. Besides this, the Portunidae particularly so as their last set of strolling legs is leveled into swimming oars.

Crabs have a tendency to be aggressive to each other, and male crabs frequently battle to access females. Furthermore, on rough seashores, where almost all caverns and hole are busy, crabs may likewise battle about concealing gaps.

Fiddler crabs also dig tunnels in mud or sand, which they use for stowing away, mating, and resting, and to safeguard against intruders.

Crabs are omnivores and they feed fundamentally on green growth and taking some other food like mollusks, different shellfish, worms, microscopic organisms, debris and fungi contingent upon their accessibility and the crab species.

For some crabs, a blended eating routine of animal and plant matter outcomes in the quickest development and most prominent wellness. Nonetheless, a few species are more experts in their eating regimens. Some eat microscopic fish, some eat shellfish like mollusks, and some even catch fish.

Furthermore, crabs are known to cooperate to give protection and food to their family, and amid mating season to locate an agreeable spot for the female to discharge her eggs.

Mating of Portunidae

In the two females and males, a difference between morphological, physiological, and functional developments can be made.

Furthermore, physiological development in males is described when spermatophores create in the vas deferens after the pubertal shed, however, the outer appearance of the crab may be the one of a pre-adult/adolescent crab once the male grows extensive paws, morphological maturity is reached.

Practical maturity portrays the capacity to effectively mate, or, in other words ‘mating-scars’ on the sternum and on the first set of strolling legs of the male. Despite the fact that some juvenile males have mated. Besides this, functional development was undeniably pervasive in morphologically developed males.

The ovaries and testicles of mud crabs lie underneath the carapace as they paired. The distinctive developmental phases of the gonads. In both genders, the development stages can be distinguished by various size and hue of the gonads.

Mating happens when the maturating or mature female is on the verge of shedding. The male uses its strolling legs to tenderly grab the female by its carapace and keeps holding her until the point that she sheds and is delicate shelled.

At that point he turns her around, both open their ventral fold, and the male impregnates the female by putting the spermatophore into the female’s spermathecae by inserting his gonopodia into the female’s genital openings showing that females can store the sperm, or, in other words, it is common feature in bigger decapod shellfish or crabs.

Life cycle of  Portunidae

Mating season happens from the month of May through October. Jimmies, or males, meet with females, known as sooks, in the salty center waters of the Chesapeake Bay. Besides this, the male companion conveys the female into a secured region while she gets ready for her last shed or the shedding of her hard outer shell.

Furthermore, the crabs mate after she sheds, and the female catches the sperm for later preparation of the eggs. A while later, the male keeps on conveying the female until the point when her external shell hardens once more.

This conduct is particularly fundamental for the fruitful proliferation of the species since the female crab mates just once in her life.

Spawning Process of Portunidae

While the guys search out another mate, the females move to brackish waters of the lower Chesapeake Bay and tunnel in the mud. Moreover, a female will prepare the eggs and can brood them on numerous occasions over a time of two to a year.

A splendid orange mass creates by female’s apron and the fold on her tummy – containing somewhere in the range of 750,000 to 2 million eggs. Furthermore, this sponge will obscure in shading as the hatchlings devour the orange yolk. The hatch-lings are discharged from the mother inside about fourteen days and moves toward the Atlantic sea.

Zoea and Megalops

The small hatchlings measure under 1/1000 of an inch amid the zoea stage. Besides this, they look more like shrimp than crabs, with see-through tops including a single substantial tail and eye. The zoea feed on tiny fish and shed up to eight times more than 31 to 49 days as they keep on developing.

female crab

Moreover, zoea at that point transform into the megalops, a phase that keeps going six to twenty days and is the last larval shed. Still minor, the megalops has a whitish shade yet begins to look like a crab. There is the presence of legs and front paws, however, the creatures still sport lobster-like tails.


The adolescent stage denotes the crab’s arrival to the upper Chesapeake Bay and its streams; male crabs will travel more distant north than females. Youthful crabs at long last look like grown-up blue crabs however they are little, estimating scarcely 1/100 of an inch wide.

They will shed a few more occasions’ before achieving development at 12 to year and a half of age. Besides this, adolescents crab can eat little fish, dead living beings and amphibian plants. When developed, the crabs will change up their eating routine, including worms, mollusks, shellfish, mussels, snails and considerably littler blue crabs.

Communication & Reception Portunidae

Crabs are typically very active creatures with complex standards of conduct. They can communicate with each other by waving or drumming their pincers.


In an ongoing report, it was discovered that the evaluated size at which half of males and females achieved maturity was 4.6 cm and 4.4 cm CL, individually.

Lifespan of Portunidae

Portunidae can live for more than 3 years.


Health benefits

Crab meat, specifically the dark colored meat from the crab, for example, that present in crab pâté and dressed crab, is a decent source of key minerals and vitamins, for example, selenium, vitamin B12, iodine and zinc can likewise contain variable levels of cadmium.

Besides this, in the body, vitamin B12 is required for a strong blood and sensory system while selenium works as a cancer prevention agent, and like zinc, is required for the appropriate function of the immune system.

Furthermore, cadmium is a characteristic component which is available in the atmosphere around us and also in tobacco smoke, anyway in non-smokers, nourishment is the primary source.

Similar Species

Fun Facts of Portunidae

There are many fun facts about Portunidae:

Funfact swimming crab

Although, these fun facts are quite interesting yet there are some dangers as well.


  1. www.animaldiversity.org
  2. www.marinespecies.org
  3. www.britannica.com
  4. www.eol.org
  5. www.en.wikipedia.org
Aymen Nizam

Aymen Nizam

I am IT (Graduate) from Bahria University Islamabad currently writing blogs on animals and plants, I am a content writer by profession and passionate about writing all information about living things. TapeDaily has provided me a chance to share my expertise with you.

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