ArthropodsArthropods

The Armored Achievers:The Armored Achievers:

Numerically the largest Phyla Numerically the largest Phyla and literally means jointed and literally means jointed foot.foot.

Sub Phylum - CrustaceaSub Phylum - Crustacea – – Crab, shrimp, barnacle, and lobsterCrab, shrimp, barnacle, and lobster

Segmented body and displays Segmented body and displays bilateral symmetry.bilateral symmetry.

Jointed appendages have a variety Jointed appendages have a variety of specialized functionsof specialized functions

The body is covered by an The body is covered by an exoskeleton made of chitonexoskeleton made of chiton– Advantage: good protection, Advantage: good protection,

muscles attach to it for strengthmuscles attach to it for strength– Disadvantage: heavy, does not Disadvantage: heavy, does not

grow: must molt becomes grow: must molt becomes vulnerable to preyvulnerable to prey

Body has 2 segments – cephalothorax covered by the Body has 2 segments – cephalothorax covered by the carapace and the abdomencarapace and the abdomen

Meroplanktonic larvae do not compete with adults for Meroplanktonic larvae do not compete with adults for food: metamorphosis provides a gradual change to adultfood: metamorphosis provides a gradual change to adult

Open circulatory system contains a blue pigment called Open circulatory system contains a blue pigment called hemocyanin to transport oxygen from gills to the bodyhemocyanin to transport oxygen from gills to the body– Blood carries copper instead of ironBlood carries copper instead of iron– Excellent medium for long-term lab tests because it will Excellent medium for long-term lab tests because it will

not support bacterial growthnot support bacterial growth Ventral nerve chord with a well-developed brain and Ventral nerve chord with a well-developed brain and

compound eyes. compound eyes. – Neurosecretory cells control molting, color changes, food storage Neurosecretory cells control molting, color changes, food storage

and hormonesand hormones..

The Small CrustaceansThe Small Crustaceans

CopepodsCopepods BarnaclesBarnacles Beach HoppersBeach Hoppers IsopodsIsopods KrillKrill

BarnaclesBarnacles

Decapods – ten leggedDecapods – ten legged

Five pairs of walking legs – first Five pairs of walking legs – first pair usually heavier and has a pair usually heavier and has a clawclaw

Shrimp, lobster and crabsShrimp, lobster and crabs

Horseshoe crabHorseshoe crab

Only living member of Only living member of MerostomataMerostomata

Living fossilLiving fossil Not a true crabNot a true crab

MoltingMolting

Like many animals with hard shells, a horseshoe Like many animals with hard shells, a horseshoe crab must molt or shed its shell as it grows. crab must molt or shed its shell as it grows. Before molting, a new shell begins to form. When Before molting, a new shell begins to form. When this new shell is ready, the horseshoe crab this new shell is ready, the horseshoe crab absorbs water through its gills, making itself absorbs water through its gills, making itself bigger. bigger.

The old, hard shell cannot expand and splits in The old, hard shell cannot expand and splits in the front where the top and bottom join. The the front where the top and bottom join. The horseshoe crab crawls out the front, leaving the horseshoe crab crawls out the front, leaving the old shell behind. It takes about 24 hours for the old shell behind. It takes about 24 hours for the new soft shell to harden. With each molt, the new soft shell to harden. With each molt, the horseshoe crab increases in size by an estimated horseshoe crab increases in size by an estimated 25-30%.25-30%.

Sea SpiderSea Spider

Feeds on soft invertebratesFeeds on soft invertebrates Common in cold watersCommon in cold waters

Hermit CrabsHermit Crabs

Not a true crabNot a true crab ScavengerScavenger Hide abdomen in Hide abdomen in

empty gastropod empty gastropod shellsshells– Sometimes cover Sometimes cover

shells with sea shells with sea anemones .anemones .

True CrabsTrue Crabs

Abdomen is small and tucked under Abdomen is small and tucked under the compact cephalothorax the compact cephalothorax

V shaped abdomen in males, U V shaped abdomen in males, U shaped in females.shaped in females.

Most are scavengers and predators.Most are scavengers and predators.

Biology of the CrustaceansBiology of the Crustaceans

Feeding and DigestionFeeding and Digestion– In general, digestion is extracellular and In general, digestion is extracellular and

absorbed nutrients are distributed in an absorbed nutrients are distributed in an open circulatory systemopen circulatory system

Nervous systemNervous system– Small simple brainSmall simple brain– Most have compound eyesMost have compound eyes– Sensitive to chemicalsSensitive to chemicals– Pair of statocycst for balancePair of statocycst for balance

BehaviorBehavior

ComplexComplex– Body postures and movements for Body postures and movements for

communicationcommunication– Disputes in territory and courtshipDisputes in territory and courtship

Elaborate courtship behavior.Elaborate courtship behavior.

ReproductionReproduction

Mostly separate sexesMostly separate sexes Males use special appendages to Males use special appendages to

transfer sperm to femalestransfer sperm to females Mating in decapods usually takes place Mating in decapods usually takes place

within a few a hours of the female within a few a hours of the female molting.molting.

Females in many species can save and Females in many species can save and store sperm for different broods of eggs.store sperm for different broods of eggs.

Decapods carry eggs using pleopods.Decapods carry eggs using pleopods.

Marine Crustaceans Growth Marine Crustaceans Growth ChartChart

Weird but True?Weird but True? Do you know that horseshoe crabs are not really crabs at

all? They're actually the only four living species of a group, class Merostomata, that are largely represented by fossils. Horseshoe crabs are in fact living fossils, resembling creatures that went extinct thousands of years ago!

Crabs don’t have ears. Still, they can detect sound which seems a bit of a conundrum. Basically, the hollow hairs on the outside of the crab’s body pick up vibrations created by sounds and vibrations in the water. These hairs are also used for feeling, tasting and smelling. How’s that for multi-tasking.

If a crab loses a claw, it grows back. Don’t you wish you had that quality?

Crab legs and swimming. All crabs have legs. In fact, those are generally the tastiest parts of the crab. Although they live in the water, and have all of those legs, most can’t swim. The Blue and Lady crabs have specialized legs for swimming. These swimming legs are flattened out and act more like paddles. Other than that, the legs are used for walking. These paddle legs move at 20 to 40 revolutions per minute.

Crustaceans turn red when exposed to heat, so while you may Crustaceans turn red when exposed to heat, so while you may see the live ones with a nice blue color, the cooking process see the live ones with a nice blue color, the cooking process will change the color. Similarly, a dead crab on a beach will will change the color. Similarly, a dead crab on a beach will turn red just because of its exposure to the sun’s rays. turn red just because of its exposure to the sun’s rays.

A male crab is called a Jimmy. A male crab is called a Jimmy.

The female crab can only mate during the molting process. The female crab can only mate during the molting process. She emits a powerful aroma to attract the male crab. The She emits a powerful aroma to attract the male crab. The problem is, she may not be in the molting process quite yet, so problem is, she may not be in the molting process quite yet, so the male crab literally stakes his claim by carrying the female the male crab literally stakes his claim by carrying the female crab around underneath his own body until conditions are just crab around underneath his own body until conditions are just right. right.

The female blue crab lays her eggs from 2 to 9 months after The female blue crab lays her eggs from 2 to 9 months after mating, depending upon when the mating took place. mating, depending upon when the mating took place.

The oldest crab industry in the The oldest crab industry in the United StatesUnited States is the blue crab is the blue crab industry of the Chesapeake Bay area, dating back almost to industry of the Chesapeake Bay area, dating back almost to the early 1600s. the early 1600s.

The ghost crab is on record as having the fastest crawling The ghost crab is on record as having the fastest crawling speeds. On firm sand, they have been clocked at 4 miles per speeds. On firm sand, they have been clocked at 4 miles per hour, and 5 miles per hour on a solid, wooden deck. hour, and 5 miles per hour on a solid, wooden deck.

A single Alaskan King Crab can yield over six pounds of meat. A single Alaskan King Crab can yield over six pounds of meat. They can measure up to a 6-foot leg span.They can measure up to a 6-foot leg span.