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Crayfish Prelab

2010United streaming: crayfish 10:44 Youtube- crayfish external anatomyhttp://www.youtube.com/watch?v=rZ-7LF5AkGs 6.21 internalhttp://www.youtube.com/watch?v=rpkiNLhCBMU&feature=related 9.47 Crayfish Review http://biog-101-104.bio.cornell.edu/BioG101_104/tutorials/animals/crayfish.html Label digrams Prelab questions

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Taxonomic Classification• Kingdom-Animalia• Phylum-Arthropoda• Class-Crustacea• Order-Decapoda (10 feet)• Family-Astacidea• Genus-Cambarus• Species-affinis

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What do crayfish look like?External Anatomy (Dorsal View)

• Body is divided into 2 regions:• 1. Cephalothorax (the head and carapace)• 2. Abdomen (posterior portion of body)• Label the uropods, chelipeds, antennae, and antennules

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External Anatomy (Ventral View)Appendages:• Crayfish appendages are biramus – branched – and

jointed• 7 pairs of feeding appendages, including the mandibles

and chelipeds.• Antennules contain hearing and balancing mechanisms• Antennae contain organs of touch, taste and smell• Swimmerets are abdominal structures for swimming• Walking legs are thoracic structures for walking

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Where do they live?

• In nearly all bodies of fresh water that contain lime

• Why would lime be important to the crayfish?

--used to harden the exoskeleton of chitin • What adaptations do crayfish show for their

aquatic habitat?

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Respiration

• They have gills as their respiratory organs. Gills take in oxygen from water and pass carbon dioxide back to the water

• The gills can hold oxygen for a long time once the crayfish is out of the water

What are the gills attached to? –the walking legs

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How do crayfish move?• Use telson, uropods, & swimmerets to swim

backwards

• Use walking legs (4 pairs) to crawl over the bottom

• 5th pair of walking legs (crayfish aredecapods) is modified as the chelipeds (pincers/claws)

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What do crayfish eat?

• Omnivorous• fish & shrimp larvae• pond vegetation• small water insects

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Tracing food through the crayfish1. Mandibles move from side to side to crush food

as 2.it enters the mouth3.Food then passes through the esophagus to the4.cardiac stomach, where it is ground up (part of

the stomach is lined with “teeth”).5.Food then passes through the digestive glands

and for digestion and temporary storage.6.Undigested food travels through the intestine and

is eliminated through the anus

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Excretory System: The Green Gland• The green gland is located internally just behind

each antenna and right under the brain. These structures filter fluid waste from the blood

• The green glands are analogous to what human structure? _kidneys_

• Based on the crayfish’s habitat, do you think the green gland retains salt in the body of the crayfish, or excretes salt to osmoregulate?

Retain salt• Nitrogenous waste exits the body through

nephridiopores into the surrounding water.

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Reproduction

• reproduce sexually, sexes are separate, and fertilization is internal:

Males – testes (white) produce sperm that exit the body through a pore at the base of the 5th pair of walking legs

Females – ovaries (orange) produce eggs which are released after internal fertilization through a pore at the base of the 3rd pair of walking legs

• Females usually have 10-800 eggs, which hatch in 2-20 weeks, depending on the water temperature.

• Eggs are retained until mature on the swimmerets of the female

• An average crayfish life span is 3-4 years

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Swimmerets role in Reproduction

• located on the ventral side of abdomen (used for swimming and for reproduction)

• Difference between males and females:• Females: crescent shaped slit; are all soft to

the touch• Males: sperm duct opening (actual pore); hard

to the touch

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Internal Male & Female structures

• The male’s gonads are very difficult to find (they are located underneath the heart)

• The ovaries are yellow/orange. They are located just below the carapace.

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Circulation of the Crawfish• Heart – located on dorsal side just below

digestive glands • Open circulatory system

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Nervous System

• Large nerves travel from brain to ventral part of body

• A _ventral nerve cord is present• Compound Eyes with more than 2,000 lenses

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