Blue crabs come from the family Portunidae a group of animals having jointed legs, segmented body, and a hard outer shell. (Capossela, 1990) It is a crustacean as are lobsters and shrimps. This crab stays in water although it could survive shortly out of it.
The growth of blue crabs is slowed in areas of high salinity. In the waters of average salinity, male crabs may grow to seven-nine inches. Females seldom make it past six. They can live an average of 2-2 1/2 years, although some make it to four years of age. The crab has to shed his hard shell in order to grow. It sometimes has to do this 25-30 times in his life, for about two days each. At this time the crab is called a softshell. (Capossela, 1990) Small crabs shed every 3-5 days.
The blue crab occurs along the Atlantic Coast from Cape Cod south to Florida and around the Golf of Mexico to the Mississippi, and next to the lobster is our most valuable food crustacean being highly valued for its edible qualities. It is also known as the hard-shell or soft-shell crab, suitable for the market not only when the shell is hard but also immediately after molting before the new shell has hardened (Headstorm, 1985).
Between late spring and late summer, the abdomen of a mature female crab will bulge with an egg mass of about 700,000 to two million eggs. The mass gradually turns from bright orange to yellow or brownish and then to blackish as they consume the individual egg yolks. The female at this time is called a sponge crab, and must be returned in some states. (Bower, 1994) When the eggs hatch, theyre very small and become part of a planktonic mass. At this stage they are called zoea larvae, and they look more like shrimp than crabs. During the first months of existence, they pass into a post larval stage, or megalops (where only a few million reach maturity.) After that, they begin to take on the shape of sdult crabs. Some crabs are swept in a group out in to the ocean, but those that make ir back into the estuary make their way to fresher water.
Blue crabs dig into the mud in winter where they lay semidormant from early December to late March. The further south it is the shorter the dormancy period becomebecomes until a sluggish period happens in warm gulf waters. The crabs dont molt during the winter dormancy. When summer comes the crab will molt severaltimes.
A lot of mating is known to occur in late summer. Males usually mate several times, but females only once. The avereage male, usually about 15 months old and 5inches in length, will seek out a female of about the same age, but is smaller and about to shed because fertilization can only take place during this time. At this stage the female crab is called a peeler. The male or Jimmy picks his chosen crab, and holds her gently to him with his legs. This is called cradle carring. He protects her for a few days before and aftercopulation (the act of uniting).
At this point the crabs are called doublers. They usually find well-protected places in shallow water, often in or close by vegetation, for their mating. After the pair has mated and parted, it is Adair 3 probably around early October. Shortly after being fertilized, female crabs will begin to migrate toward the ocean. Before winter comes, many of them will end up in depths of water averaging at around 20-30 feet where salinities are around 25p.p.t. Mature males and probably immature males also, are known to go into deeper water when winter comes.
Blue crabs eat both plant and animal matter, living and dead. Alot of people think that the crab is a scavenger, when in fact the crab will scrape up most any type of dead meat or fish that it cames upon.
Hermit Crab
Hermit Crabs do not have a cover shell that protects their posterior part of their body like most crabs. They have to seek protection for their soft, defenseless abdomens by inserting them into some hollow object which is usually the shell of a gasteropod mollusk. They appear well fitted to adjust to surroundings. Their body becomes spiral to conform to the shell.
The abdomen of a hermit crab is usually not symmetrical but elongate, and soft. Then antennae and eyestallks are long, and the first pair of thoracic legs are muich larger than the others. (Headstrom, 1985) The right leg is usually much larger than the left, and the usual functions of capturing and crushing prey, it serves as a lid to close the opening of the shell when the crab retires in it. The second and the third pair of legs end in simple hooks and are used for walking and dragging itself along when it moves over the ground. The fourth and fifth pair are modified to hold the animal in the shell. For females, some legs are for carrying eggs.
Hermit crabs have to go house-hunting now and then, so they can find larger shells to accommodate their increase in size as they grow. Sometimes it finds a shell that appears suitable on first inspection, but more often it has to try several before it finds one it choses to live in. House-hunting is a very careful and meticulous job. (sullevant, 1992) If the crab sees that it is clean, he goes into it to see if his abdomen fits into the shell. The crab inspects the shells with their antennae and legs. Sometimes the shells of hermit crabs becomes the home of hydroids sea anenomes that live with the hermits.
A common hermit crab, found from Maine to Florida, is Pagurus pollicaris. It is a rather large hermit, with pale red coloring. It shows up at low-water marks on rocky and shelly bottoms of bays and sounds. Another large species are Pagurus bernnardus. It is bright red in color and is rough and very hairy. It lives in the shells of gaint whelk and moon shells. A quick moving hermit crab is Pagurus longicarpus. It has long chilapeds and its eyes are detailed at the end of the eyestalks. (Colliers Encyclopedia, 1992). This species can easily be recognized by its light, metallic coloring.
Fiddler Crabs
The family of fiddler crabs is Ocypodiae. It has a pinching claw, which is usually on the right. This identifies them without any further description. They carry large claw horizontally in front of the body and it has been seen to fiddle the smaller claw like a bow which simulates the playing of a fiddle. That trait brings about their name.
The carapace of these crabs is square, and the eyestalks are usually very long, each horizontally in an elogated groove along the front of the carapace. Fiddler crabs are light brown, which harmonize well with the dark sand of salt marshes and the mud flats in which they live. In these places, they congregate in large numbers and make burrows which serve as their home. The burrows are an inch to two inches in diameter and usually a foot or two deep. They are found on salt marshes, far up in estuaries, and along the mouths of rivers often where the water is fresh.
One species of fiddler crabs is Uca minax. They build an observation house over the mouth of its burrow where he sits and surveys its surroundings but quickly moves inside when danger threatens him. Uca minax are found from southern New England to Florida and may be found on salt marshes farther away from sea than most species. It is the largest of fiddler crabs and many be distingueshed from other by a red patch at the joints of the legs. It lives off small algae in its vegetarian diet. It can stay without food for many days. (Headstrom, 1985).
