20-1 CHAPTER 20 Crustaceans Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Sally Lightfoot Crab, from the Galapagos

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Overview Over 67,000 living species Over 67,000 living species Insects and crustacea compose over 80% of all named animal species Insects and crustacea compose over 80% of all named animal species Divided into 5 classes Divided into 5 classes We will study 3 classes, Branchiopoda and Malacostraca, Maxillopoda We will study 3 classes, Branchiopoda and Malacostraca, Maxillopoda Branchiopoda = water fleas, brine shrimp Branchiopoda = water fleas, brine shrimp Malacostaca = isopods, krill, crab, lobster, etc. Malacostaca = isopods, krill, crab, lobster, etc. Maxillopoda = barnacles Maxillopoda = barnacles

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Subphylum Crustacea General Nature of a Crustacean Main distinguishing characteristic of crustaceans Main distinguishing characteristic of crustaceans Two pairs of antennae Two pairs of antennae Head also has a pair of mandibles and 2 pairs of maxillae Head also has a pair of mandibles and 2 pairs of maxillae One pair of appendages on each of the additional segments One pair of appendages on each of the additional segments Some segments may lack appendages Some segments may lack appendages All appendages, except perhaps first antennae, are biramous All appendages, except perhaps first antennae, are biramous

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Tagmata (segments) are usually head, thorax, and abdomen Tagmata (segments) are usually head, thorax, and abdomen In most one or more thoracic segments are fused with the head as a cephalothorax In most one or more thoracic segments are fused with the head as a cephalothorax Arrangement of tagmata in Malacostraca is the ancestral plan Arrangement of tagmata in Malacostraca is the ancestral plan Head has 5 fused somites Head has 5 fused somites Thorax has 8 Thorax has 8 Abdomen has 6 Abdomen has 6 Subphylum Crustacea

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Anterior end is a non-segmented rostrum (covers eyes in some) Anterior end is a non-segmented rostrum (covers eyes in some) Telson, with the last abdominal somite and uropods, forms a tail Telson, with the last abdominal somite and uropods, forms a tail Dorsal covering is the carapace Dorsal covering is the carapace May cover most of body or just cephalothorax May cover most of body or just cephalothorax Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Form and Function External Features External Features Secreted cuticle is made of chitin, protein, and calcareous material Secreted cuticle is made of chitin, protein, and calcareous material Heavy plates have more calcareous deposits Heavy plates have more calcareous deposits Joints are soft and thin, allowing flexibility Joints are soft and thin, allowing flexibility Telson is not a somite Telson is not a somite Bears anus Bears anus Subphylum Crustacea

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Appendages Appendages Most have appendages on each somite Most have appendages on each somite Appendages represent homology Appendages represent homology Have evolved a wide variety of walking legs, mouthparts, swimmerets, etc. from modification of the basic biramous appendage Have evolved a wide variety of walking legs, mouthparts, swimmerets, etc. from modification of the basic biramous appendage Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Appendages of crayfish: 3 main parts to each appendage Protopod = brownEndopod = blueExopod = yellow

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. AppendageFunction# of pairs AntennaTouch, taste, equilibrium2 MandibleCrushing food1 MaxillaHandling food, drawing water currents to gills 2 MaxillipedTouch, taste, handling food3 Walking legsOffense, Defense, walking (cheliped is 1st, with pincer) 5 SwimmeretTransfer sperm, create water currents, carrying eggs and young 5 UropodSwimming, egg protection in females 1 Crawyfish Appendage and Function (Number if pairs)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Internal Features Internal Features Coelomates - reduced Coelomates - reduced Persistent blastocoel that becomes filled with blood Hemocoel Persistent blastocoel that becomes filled with blood Hemocoel Protostomes (mouth first) Protostomes (mouth first) Complete Gut Complete Gut Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Muscular System Muscular System Striated muscles Striated muscles Make up a major portion of crustacean body Make up a major portion of crustacean body Most muscles arranged as antagonistic groups Most muscles arranged as antagonistic groups Flexors draw a limb toward the body and extensors straighten a limb out Flexors draw a limb toward the body and extensors straighten a limb out Abdominal flexors of a crayfish allow it to swim backward Abdominal flexors of a crayfish allow it to swim backward Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Internal Anatomy of the crayfish. Green Gland = Kidney

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Respiratory System Respiratory System Smaller crustaceans may exchange gases across thinner areas of cuticle Smaller crustaceans may exchange gases across thinner areas of cuticle Larger crustaceans use featherlike gills for gas exchange Larger crustaceans use featherlike gills for gas exchange Circulatory Circulatory Open circulatory system Open circulatory system No system of veins to separate blood from interstitial fluid No system of veins to separate blood from interstitial fluid Hemolymph exits heart through arteries Hemolymph exits heart through arteries Passes to hemocoel to return to the heart via sinuses Passes to hemocoel to return to the heart via sinuses Dorsal heart Dorsal heart Single-chambered sac of striated muscle Single-chambered sac of striated muscle Valves in the arteries prevent backflow Valves in the arteries prevent backflow Hemolymph conducted to gills, if present, for oxygen and carbon dioxide exchange Hemolymph conducted to gills, if present, for oxygen and carbon dioxide exchange Hemocyanin and/or hemoglobin are respiratory pigments Hemocyanin and/or hemoglobin are respiratory pigments Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hemolymph travel: Heart, Body, Sinus, Gills, Heart via Ostium (opening)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Excretory System Excretory System Antennal or maxillary glands Antennal or maxillary glands Called “green glands” Called “green glands” End sac of green gland has a small vesicle and a spongy labyrinth End sac of green gland has a small vesicle and a spongy labyrinth Labyrinth connects by an excretory tubule to dorsal bladder that opens to exterior pore Labyrinth connects by an excretory tubule to dorsal bladder that opens to exterior pore Hydrostatic pressure within a hemocoel provides a force for filtration of fluid into the end sac Hydrostatic pressure within a hemocoel provides a force for filtration of fluid into the end sac Subphylum Crustacea

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Nervous and Sensory Systems Nervous and Sensory Systems More fused ganglia than in other arthropods More fused ganglia than in other arthropods Pair of ganglia connects to eyes and two pairs of antennae Pair of ganglia connects to eyes and two pairs of antennae Nerves join this brain to the mouth, appendages, esophagus, and antennal glands Nerves join this brain to the mouth, appendages, esophagus, and antennal glands Ventral nerve cord has a pair of ganglia for each somite to control appendages Ventral nerve cord has a pair of ganglia for each somite to control appendages Tactile hairs occur on the body, especially on chelae, mouthparts and telson Tactile hairs occur on the body, especially on chelae, mouthparts and telson Chemical sensing of taste and smell occurs in hairs on antennae and mouth Chemical sensing of taste and smell occurs in hairs on antennae and mouth Compound eye migrates pigments for day or night vision Compound eye migrates pigments for day or night vision Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Compound eyes work differently during day and night. Pigment cells will expand or constrict to allow different amounts of light to hit the photoreceptor cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Reproduction, Life Cycles, and Endocrine Function Reproduction, Life Cycles, and Endocrine Function Diversity of Reproduction Diversity of Reproduction Most crustaceans group eggs in brood chambers, in brood sacs attached to the abdomen, or attached to abdominal appendages Most crustaceans group eggs in brood chambers, in brood sacs attached to the abdomen, or attached to abdominal appendages Crayfishes develop directly without a larval form Crayfishes develop directly without a larval form Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Most crustaceans have a larva unlike the adult in form, and undergo metamorphosis Most crustaceans have a larva unlike the adult in form, and undergo metamorphosis The nauplius is a common larval form The nauplius is a common larval form Appendages and somites are added in a series of molts Appendages and somites are added in a series of molts Metamorphosis of a barnacle proceeds from a free-swimming nauplius to a larva with a bivalve carapace and finally to a sessile adult with plates Metamorphosis of a barnacle proceeds from a free-swimming nauplius to a larva with a bivalve carapace and finally to a sessile adult with plates Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Life cycle of a Gulf Shrimp Metamorphosis

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Ecdysis Ecdysis Necessary for a crustacean to increase in size the Necessary for a crustacean to increase in size the Exoskeleton does not grow Exoskeleton does not grow Physiology of molting affects reproduction, behavior, and many metabolic processes Physiology of molting affects reproduction, behavior, and many metabolic processes Underlying epidermis secretes cuticle Underlying epidermis secretes cuticle Outermost epicuticle and 2 layer procuticle dissolve and are discarded. Outermost epicuticle and 2 layer procuticle dissolve and are discarded. Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Pre-molt Stage: Protocuticle sperates from epidermis. Epidermis secretes new epicuticle. Pre-molt Continued: Molting fluid dissolves endocuticle, and Solutions are rebsorbed. New exocuticle develops Ecdysis Stage: Old epicuticle and exocuticle are discarded. Post-ecdysis: New cuticle is stretched and hardens. Endocuticle is secreted.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A.Membrane between carapace and abdomen ruptures (2 hours) B.Head Thorax and Abdomen withdraw (15 minutes) C.Lobster continues rapid absorption of water to increase length by 20% and weight by 50%. Tissue water will be replaced by protein later. (weeks) Lobster Molt

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Hormonal Control of Ecdysis Hormonal Control of Ecdysis Temperature, day length, or other stimuli trigger central nervous system to begin ecdysis Temperature, day length, or other stimuli trigger central nervous system to begin ecdysis Central nervous system decreases production of molt-inhibiting hormone by the medulla region of the brain Central nervous system decreases production of molt-inhibiting hormone by the medulla region of the brain Promotes release of molting hormone from the glands near mandible which promotes ecdysis Promotes release of molting hormone from the glands near mandible which promotes ecdysis Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Feeding Habits Feeding Habits Suspension feeders generate water currents in order to feed on plankton, detritus,and bacteria Suspension feeders generate water currents in order to feed on plankton, detritus,and bacteria Predators consume larvae, worms, crustaceans, snails, and fishes Predators consume larvae, worms, crustaceans, snails, and fishes Scavengers eat dead animal and plant matter Scavengers eat dead animal and plant matter Crayfishes have a two-part stomach Crayfishes have a two-part stomach Gastric mill grinds up food in 1 st compartment Gastric mill grinds up food in 1 st compartment Subphylum Crustacea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Diplopoda have a 2 part stomach: Cardiac and Pyloric Contain teeth for mastication and setae for straining

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Class Branchiopoda Over 10,000 species, 4 orders Over 10,000 species, 4 orders Order Anostraca, includes fairy shrimp and brine shrimp Order Anostraca, includes fairy shrimp and brine shrimp Lack a carapace Lack a carapace Order Cladocera, includes water fleas (daphnia) Order Cladocera, includes water fleas (daphnia) Carapace encloses the body but not the head Carapace encloses the body but not the head Brief Survey of Crustaceans

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display In all, legs serve as respiratory organs, assist in suspension feeding, and locomotion In all, legs serve as respiratory organs, assist in suspension feeding, and locomotion Most are freshwater Most are freshwater Important component of freshwater zooplankton Important component of freshwater zooplankton May reproduce by parthenogenesis to rapidly boost summer populations and then by sexual reproduction with the onset of unfavorable conditions May reproduce by parthenogenesis to rapidly boost summer populations and then by sexual reproduction with the onset of unfavorable conditions Fertilized eggs highly resistant to cold Fertilized eggs highly resistant to cold Critical for winter survival of population Critical for winter survival of population Brief Survey of Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Class Maxillopoda General body plan General body plan No appendages on abdomen No appendages on abdomen Subclass Cirripedia - barnacles Subclass Cirripedia - barnacles Brief Survey of Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Subclass Cirripedia Includes barnacles and three orders of burrowing or parasitic forms Includes barnacles and three orders of burrowing or parasitic forms Adults are sessile and attach directly (acorn barnacles) or by a stalk (goose barnacles) Adults are sessile and attach directly (acorn barnacles) or by a stalk (goose barnacles) Carapace surrounds body and secretes a set of calcareous plates Carapace surrounds body and secretes a set of calcareous plates Head is reduced, abdomen is absent Head is reduced, abdomen is absent Jointed feeding legs bear setae and extend from the plates to feed on small particles Jointed feeding legs bear setae and extend from the plates to feed on small particles Brief Survey of Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A. Acorn BarnacleB. Gooseneck Barnacle

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Barnacles on healthy grey whale Contains commensalistic barnacles And parasitic amphipods (arrows)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Life cycle of parasitic barnacle. Enters crab, root-like processes grow throughout body. Reproductive structure develops externally.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Class Malacostraca Largest and most diverse class of Crustacea with over 20,000 species Largest and most diverse class of Crustacea with over 20,000 species Contains three subclasses, 14 orders, and many suborders Contains three subclasses, 14 orders, and many suborders Order Isopoda Only truly terrestrial crustaceans Only truly terrestrial crustaceans Also have marine and freshwater forms Also have marine and freshwater forms Dorsoventrally flattened, lack a carapace, and have sessile compound eyes Dorsoventrally flattened, lack a carapace, and have sessile compound eyes Common land forms include sow bugs and pill bugs Common land forms include sow bugs and pill bugs Some isopods are highly modified as parasites of fishes or crustaceans Some isopods are highly modified as parasites of fishes or crustaceans Brief Survey of Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A.Pill Bugs B.Freshwater Sow bug - aquatic isopod

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Order Euphausiacea Approximately 90 species Approximately 90 species Includes important ocean plankton called krill Includes important ocean plankton called krill Brief Survey of Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Order Decapoda 5 pairs of walking legs 5 pairs of walking legs In crabs, first pair of walking legs form pincers (Chelipeds) In crabs, first pair of walking legs form pincers (Chelipeds) Approximately 18,000 species Approximately 18,000 species Includes crayfishes, lobsters, crabs, and true shrimp (size of cephalothorax and abdomen vary) Includes crayfishes, lobsters, crabs, and true shrimp (size of cephalothorax and abdomen vary) Brief Survey of Crustaceans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display A.Tropical Rock Crab B.Hermit Crab C.Male Fiddler Crab D.Red Night Shrimp E.Spiny Lobster

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Sponge Crab - masks itself with materials from environment, sponge