1. 20-1 CHAPTER 20 Crustaceans Crustaceans

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3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-3 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 Probably most abundant animals in the world are members of the copepod genus Calanus Probably most abundant animals in the world are members of the copepod genus Calanus Divided into 5 classes Divided into 5 classes Current molecular phylogenies do not support the monophyly of all classes Current molecular phylogenies do not support the monophyly of all classes Former members of phylum Pentastomida placed in class Maxillopoda, subclass Pentastomida Former members of phylum Pentastomida placed in class Maxillopoda, subclass Pentastomida

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5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-5 Pentastomids Pentastomids Also called tongue worms Also called tongue worms Parasites of vertebrates, living in lungs or nasal cavities Parasites of vertebrates, living in lungs or nasal cavities Closely related to fish lice Closely related to fish lice Overview

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-6 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

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-7 Primitive crustaceans may have up to 60 segments; derived crustaceans have fewer Primitive crustaceans may have up to 60 segments; derived crustaceans have fewer Tagmata are usually head, thorax, and abdomen Tagmata are usually head, thorax, and abdomen Not homologous across taxa Not homologous across taxa 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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9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-9 Anterior end is a non-segmented rostrum Anterior end is a non-segmented rostrum 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

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-10 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 Dorsal tergum and ventral sternum are plates on each somite lacking a carapace Dorsal tergum and ventral sternum are plates on each somite lacking a carapace Telson is not a somite Telson is not a somite Bears anus and may be homologous to the pygidium Bears anus and may be homologous to the pygidium In some species, telson may bear a pair of processes, the caudal furca In some species, telson may bear a pair of processes, the caudal furca Gonopores may be at base of appendages, at the tail, or on somites without legs Gonopores may be at base of appendages, at the tail, or on somites without legs Subphylum Crustacea

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12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-12 Appendages Appendages Members of Malacostraca and Remipedia have appendages on each somite Members of Malacostraca and Remipedia have appendages on each somite Other classes may not bear appendages on abdominal somites Other classes may not bear appendages on abdominal somites Specialization of appendages based on the basic biramous plan Specialization of appendages based on the basic biramous plan Maxilliped has a basal protopod, a lateral exopod, and a medial endopod Maxilliped has a basal protopod, a lateral exopod, and a medial endopod Endites are medial processes, exites are lateral processes and epipod is an exite on the protopod Endites are medial processes, exites are lateral processes and epipod is an exite on the protopod Appendages represent serial homology Appendages represent serial 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

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16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-16 Internal Features Internal Features Muscular and nervous systems and segmentation exhibit metamerism of annelid-like ancestors Muscular and nervous systems and segmentation exhibit metamerism of annelid-like ancestors Hemocoel Hemocoel Persistent blastocoel that becomes filled with blood Persistent blastocoel that becomes filled with blood Coelomic compartments remain as end sacs of excretory organs and gonads Coelomic compartments remain as end sacs of excretory organs and gonads Coelomates only in technical sense of the term Coelomates only in technical sense of the term Subphylum Crustacea

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-17 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 Strong muscles located on each side of stomach control the mandibles Strong muscles located on each side of stomach control the mandibles Subphylum Crustacea

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19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-19 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 Decapod carapace overlaps the gill cavity, leaving anterior and posterior openings Decapod carapace overlaps the gill cavity, leaving anterior and posterior openings “Bailer” of 2 nd maxilla draws water over gill filaments “Bailer” of 2 nd maxilla draws water over gill filaments Gills may project from pleural wall, the articulation of thoracic legs, or thoracic coxae Gills may project from pleural wall, the articulation of thoracic legs, or thoracic coxae Subphylum Crustacea

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21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-21 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 of hemolymph Valves in the arteries prevent backflow of hemolymph Hemolymph conducted to gills, if present, for oxygen and carbon dioxide exchange Hemolymph conducted to gills, if present, for oxygen and carbon dioxide exchange Hemolymph may be colorless, reddish, or bluish Hemolymph may be colorless, reddish, or bluish Contains ameboid cells that may help prevent clotting Contains ameboid cells that may help prevent clotting Hemocyanin and/or hemoglobin are respiratory pigments Hemocyanin and/or hemoglobin are respiratory pigments Subphylum Crustacea

22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-22 Excretory System Excretory System Antennal or maxillary glands Antennal or maxillary glands Called green glands in decapods Called green glands in decapods End sac of antennal gland has a small vesicle and a spongy labyrinth End sac of antennal 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 Resorption of salts and amino acids occurs as the filtrate passes the excretory tubule and bladder Resorption of salts and amino acids occurs as the filtrate passes the excretory tubule and bladder Mainly regulates the ionic and osmotic composition of body fluids Mainly regulates the ionic and osmotic composition of body fluids Subphylum Crustacea

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24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-24 Nitrogenous wastes excreted across thin areas of cuticle in the gills Nitrogenous wastes excreted across thin areas of cuticle in the gills Freshwater crustaceans constantly threatened by over-dilution with water Freshwater crustaceans constantly threatened by over-dilution with water Gills must actively absorb Na + and Cl - Gills must actively absorb Na + and Cl - Marine crustaceans have urine that is isosmotic with blood Marine crustaceans have urine that is isosmotic with blood Subphylum Crustacea

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-25 Nervous and Sensory Systems Nervous and Sensory Systems More fused ganglia than in other arthropods More fused ganglia than in other arthropods Pair of supra-esophageal ganglia connects to eyes and two pairs of antennae Pair of supra-esophageal ganglia connects to eyes and two pairs of antennae Neuron connectives join this brain to the subesophageal ganglion Neuron connectives join this brain to the subesophageal ganglion Supplies nerves to mouth, appendages, esophagus, and antennal glands Supplies nerves to mouth, appendages, esophagus, and antennal glands Double ventral nerve cord has a pair of ganglia for each somite to control appendages Double ventral nerve cord has a pair of ganglia for each somite to control appendages Eyes and statocysts are largest sensory organs Eyes and statocysts are largest sensory organs 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 Subphylum Crustacea

26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-26 Statocyst opens at base of first antenna in crayfish Statocyst opens at base of first antenna in crayfish Statocyst lined with sensory hairs that detect position of grains of sand Statocyst lined with sensory hairs that detect position of grains of sand Compound eyes, made of many units called ommatidia Compound eyes, made of many units called ommatidia Cornea focuses light down the columnar ommatidium Cornea focuses light down the columnar ommatidium Distal retinal, proximal retinal, and reflecting pigment cells form a sleeve around each ommatidium Distal retinal, proximal retinal, and reflecting pigment cells form a sleeve around each ommatidium Each ommatidium detects a restricted area of objects, a mosaic, in bright light Each ommatidium detects a restricted area of objects, a mosaic, in bright light In dim light, the distal and proximal pigments separate and produce a continuous image In dim light, the distal and proximal pigments separate and produce a continuous image Subphylum Crustacea

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28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-28 Reproduction, Life Cycles, and Endocrine Function Reproduction, Life Cycles, and Endocrine Function Diversity of Reproduction Diversity of Reproduction Barnacles are monoecious but generally cross- fertilize Barnacles are monoecious but generally cross- fertilize In some ostracods, males are scarce and reproduction is by parthenogenesis In some ostracods, males are scarce and reproduction is by parthenogenesis Most crustaceans brood eggs in brood chambers, in brood sacs attached to the abdomen, or attached to abdominal appendages Most crustaceans brood 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

29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-29 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 with uniramous first antennae, and biramous second antennae and mandibles that all aid in swimming The nauplius is a common larval form with uniramous first antennae, and biramous second antennae and mandibles that all aid in swimming 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

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31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-31 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 is made of a very thin lipid- impregnated protein Outermost epicuticle is made of a very thin lipid- impregnated protein Most of the cuticle is composed of several layers of the procuticle Most of the cuticle is composed of several layers of the procuticle Exocuticle, beneath the epicuticle, contains protein, calcium salts, and chitin Exocuticle, beneath the epicuticle, contains protein, calcium salts, and chitin Subphylum Crustacea

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33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-33 Endocuticle has a heavily calcified principal layer and an uncalcified membranous layer Endocuticle has a heavily calcified principal layer and an uncalcified membranous layer Molting animals grow in the intermolt phases, or instars Molting animals grow in the intermolt phases, or instars Soft tissue increases in size until there is no space within the cuticle Soft tissue increases in size until there is no space within the cuticle When body fills the cuticle, animal is in the premolt phase When body fills the cuticle, animal is in the premolt phase Epidermal cells enlarge before ecdysis Epidermal cells enlarge before ecdysis Subphylum Crustacea

34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-34 Secrete a new epicuticle and then begin secreting a new exocuticle Secrete a new epicuticle and then begin secreting a new exocuticle Enzymes released into the area above new epicuticle dissolve the old endocuticle Enzymes released into the area above new epicuticle dissolve the old endocuticle When only the old exocuticle and epicuticle remain, the animal swallows water to expand and burst the old cuticle When only the old exocuticle and epicuticle remain, the animal swallows water to expand and burst the old cuticle Soft new cuticle stretches and then hardens with the deposition of inorganic salts Soft new cuticle stretches and then hardens with the deposition of inorganic salts Molting occurs often in young animals and may cease in adults Molting occurs often in young animals and may cease in adults Subphylum Crustacea

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36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-36 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 X-organ Central nervous system decreases production of molt-inhibiting hormone by the X-organ Promotes release of molting hormone from the Y-organs which promotes ecdysis Promotes release of molting hormone from the Y-organs which promotes ecdysis Subphylum Crustacea

37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-37 Other Endocrine Functions Other Endocrine Functions Removing eyestalks accelerates molting and prevents color changes to match background Removing eyestalks accelerates molting and prevents color changes to match background Hormones from neurosecretory cells in eyestalk control dispersal of cell pigment Hormones from neurosecretory cells in eyestalk control dispersal of cell pigment Neurosecretions from pericardial organs stimulate increase in heartbeat Neurosecretions from pericardial organs stimulate increase in heartbeat Androgenic glands in male amphipods stimulate expression of male characteristics Androgenic glands in male amphipods stimulate expression of male characteristics Subphylum Crustacea

38. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-38 Feeding Habits Feeding Habits Same fundamental mouthparts are adapted to a wide array of feeding habits Same fundamental mouthparts are adapted to a wide array of 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

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40. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-40 Brief Survey of Crustaceans Class Remipedia Only 10 described species Only 10 described species All found in caves connected to the sea All found in caves connected to the sea Primitive features include 25–38 segments with similar, paired, biramous, swimming appendages Primitive features include 25–38 segments with similar, paired, biramous, swimming appendages Antennules also biramous Antennules also biramous Maxillae and maxillipeds are prehensile and specialized for feeding Maxillae and maxillipeds are prehensile and specialized for feeding Swimming legs are directed laterally rather than ventrally as is found in copepods and cephalocarids Swimming legs are directed laterally rather than ventrally as is found in copepods and cephalocarids

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42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-42 Class Cephalocarida Only 9 species described Only 9 species described Live in coastal bottom sediments from intertidal zones to 300 meters depth Live in coastal bottom sediments from intertidal zones to 300 meters depth Thoracic limbs and 2 nd maxillae are very similar Thoracic limbs and 2 nd maxillae are very similar Lack eyes, a carapace, and abdominal appendages Lack eyes, a carapace, and abdominal appendages True hermaphrodites and unique in discharging eggs and sperm through same duct True hermaphrodites and unique in discharging eggs and sperm through same duct Brief Survey of Crustaceans

43. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-43 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 Notostraca, includes tadpole shrimp Order Notostraca, includes tadpole shrimp Carapace forms a large dorsal shield Carapace forms a large dorsal shield Order Conchostraca, includes clam shrimp Order Conchostraca, includes clam shrimp Enclosed by a bivalved carapace Enclosed by a bivalved carapace Order Cladocera, includes water fleas Order Cladocera, includes water fleas Carapace encloses the body but not the head Carapace encloses the body but not the head Brief Survey of Crustaceans

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45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-45 In all flattened, leaf-like legs serve as respiratory organs, assist in suspension feeding, and, (except for cladocerans), locomotion In all flattened, leaf-like legs serve as respiratory organs, assist in suspension feeding, and, (except for cladocerans), 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 Brief Survey of Crustaceans

46. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-46 Fertilized eggs highly resistant to cold Fertilized eggs highly resistant to cold Critical for winter survival of population Critical for winter survival of population Cladocerans: Development mostly direct Cladocerans: Development mostly direct Other branchiopods: Gradual metamorphosis Other branchiopods: Gradual metamorphosis Brief Survey of Crustaceans

47. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-47 Class Ostracoda 6,000 known species 6,000 known species Most are dioecious Most are dioecious Enclosed in a bivalve carapace Enclosed in a bivalve carapace 0.25–8.0 mm long 0.25–8.0 mm long Fusion of trunk somites Fusion of trunk somites Thoracic appendages are reduced to two or one Thoracic appendages are reduced to two or one Most are benthic or climb onto plants, but some are planktonic, parasitic, or burrowing Most are benthic or climb onto plants, but some are planktonic, parasitic, or burrowing Widespread in both marine and freshwater habitats Widespread in both marine and freshwater habitats Development by gradual metamorphosis Development by gradual metamorphosis Brief Survey of Crustaceans

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49. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-49 Class Maxillopoda General body plan General body plan Five cephalic, six thoracic and four abdominal somites plus a telson Five cephalic, six thoracic and four abdominal somites plus a telson No appendages on abdomen No appendages on abdomen When present, the eye is unique in structure and called a maxillopodan eye When present, the eye is unique in structure and called a maxillopodan eye Brief Survey of Crustaceans

50. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-50 Subclass Mystacocarida Less than 0.5 mm long Less than 0.5 mm long Live in interstitial water between sand grains Live in interstitial water between sand grains 10 species have been described from around the world 10 species have been described from around the world Primitive in several characteristics Primitive in several characteristics Brief Survey of Crustaceans

51. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-51 Subclass Copepoda Third in numbers of species Third in numbers of species Lack a carapace and retain simple, median, nauplius eye in the adult Lack a carapace and retain simple, median, nauplius eye in the adult Single pair of uniramous maxillipeds and four pairs of flattened, biramous, thoracic swimming appendages Single pair of uniramous maxillipeds and four pairs of flattened, biramous, thoracic swimming appendages A major articulation separates the posterior from the anterior, appendage-bearing portion of the body A major articulation separates the posterior from the anterior, appendage-bearing portion of the body Antennules often longer than other appendages Antennules often longer than other appendages Brief Survey of Crustaceans

52. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-52 Parasitic forms highly modified and reduced Parasitic forms highly modified and reduced Often unrecognizable as arthropods Often unrecognizable as arthropods Free-living copepods may be the dominant consumer Free-living copepods may be the dominant consumer Marine copepod Calanus is most abundant organism in zooplankton by biomass Marine copepod Calanus is most abundant organism in zooplankton by biomass Cyclops and Diaptomus important elements of freshwater plankton Cyclops and Diaptomus important elements of freshwater plankton Some free-living copepods are intermediate hosts of human parasitic tapeworms and nematodes Some free-living copepods are intermediate hosts of human parasitic tapeworms and nematodes Brief Survey of Crustaceans

53. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-53 Development is indirect Development is indirect Some highly modified parasites have unusual metamorphoses Some highly modified parasites have unusual metamorphoses Brief Survey of Crustaceans

54. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-54 Subclass Tantulocarida Only recently described Only recently described Approximately 12 species Approximately 12 species Tiny copepod-like ectoparasites of deep-sea benthic crustaceans Tiny copepod-like ectoparasites of deep-sea benthic crustaceans No head appendages beyond one pair of antennae in sexual females No head appendages beyond one pair of antennae in sexual females Likely alternate between a parthenogenetic cycle and a bisexual cycle with fertilization Likely alternate between a parthenogenetic cycle and a bisexual cycle with fertilization Tantalus larvae penetrate cuticle of host by mouth tube Tantalus larvae penetrate cuticle of host by mouth tube Abdomen and all thoracic limbs are lost during metamorphosis to an adult Abdomen and all thoracic limbs are lost during metamorphosis to an adult Brief Survey of Crustaceans

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56. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-56 Subclass Branchiura Lack gills Lack gills Most are ectoparasites of marine and freshwater fish Most are ectoparasites of marine and freshwater fish 5–10 mm long 5–10 mm long Broad, shield-like carapace, compound eyes, four biramous thoracic swimming appendages, and a short unsegmented abdomen Broad, shield-like carapace, compound eyes, four biramous thoracic swimming appendages, and a short unsegmented abdomen Second maxillae are modified as suction cups to attach to host fish Second maxillae are modified as suction cups to attach to host fish Development is direct Development is direct Brief Survey of Crustaceans

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58. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-58 Subclass Pentastomida Tongue worms Tongue worms Consist of about 90 species of parasites of vertebrate respiratory systems Consist of about 90 species of parasites of vertebrate respiratory systems Most infect reptile lungs, a few infect air sacs of birds or mammals Most infect reptile lungs, a few infect air sacs of birds or mammals More common in tropical regions extending out to North America, Europe, and Australia More common in tropical regions extending out to North America, Europe, and Australia Range from 1 to 13 cm in length Range from 1 to 13 cm in length Chitinous cuticle regularly molted Chitinous cuticle regularly molted Brief Survey of Crustaceans

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60. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-60 Five protuberances on the anterior end provide the phylum name Five protuberances on the anterior end provide the phylum name Four of the protuberances bear claws Four of the protuberances bear claws Fifth contains the mouth and two pairs of hooks Fifth contains the mouth and two pairs of hooks Simple straight digestive system Simple straight digestive system Nervous system has paired ganglia along the ventral nerve cord Nervous system has paired ganglia along the ventral nerve cord Lack any circulatory, excretory, or respiratory organs Lack any circulatory, excretory, or respiratory organs Sexes are separate Sexes are separate Brief Survey of Crustaceans

61. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-61 Females larger than males Females larger than males Produces millions of eggs that pass up the host trachea, are swallowed and leave host with feces Produces millions of eggs that pass up the host trachea, are swallowed and leave host with feces Larvae hatch out as oval, tailed creatures with four stumpy legs Larvae hatch out as oval, tailed creatures with four stumpy legs Most life cycles require an intermediate vertebrate host, usually a fish or reptile Most life cycles require an intermediate vertebrate host, usually a fish or reptile After ingestion by an intermediate host After ingestion by an intermediate host Larva penetrates intestine and migrates until it changes to a nymph Larva penetrates intestine and migrates until it changes to a nymph Nymph becomes encapsulated and remains dormant until eaten Nymph becomes encapsulated and remains dormant until eaten When eaten, juvenile migrates to lung, feeds on blood and tissue, and matures When eaten, juvenile migrates to lung, feeds on blood and tissue, and matures Brief Survey of Crustaceans

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63. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-63 Subclass Cirripedia Includes barnacles in order Thoracica and three orders of burrowing or parasitic forms Includes barnacles in order Thoracica 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, and thoracic legs are long with hairlike setae Head is reduced, abdomen is absent, and thoracic legs are long with hairlike setae Jointed cirri bear setae and extend from the plates to feed on small particles Jointed cirri bear setae and extend from the plates to feed on small particles In barnacles in intertidal zones, plates close to protect against dessication In barnacles in intertidal zones, plates close to protect against dessication Brief Survey of Crustaceans

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65. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-65 Most non-parasitic barnacles are hermaphroditic and undergo metamorphosis during development Most non-parasitic barnacles are hermaphroditic and undergo metamorphosis during development Most hatch as nauplii and become cyprid larvae with a bivalve carapace and compound eyes Most hatch as nauplii and become cyprid larvae with a bivalve carapace and compound eyes Attach to substrate by first antennae and adhesive glands Attach to substrate by first antennae and adhesive glands Secrete calcareous plates, lose eyes, and transformation of swimming appendages to filtering cirri Secrete calcareous plates, lose eyes, and transformation of swimming appendages to filtering cirri Parasitic forms may have a kentrogon stage that injects cells into the hemocoel of host Parasitic forms may have a kentrogon stage that injects cells into the hemocoel of host Brief Survey of Crustaceans

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67. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-67 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 Brief Survey of Crustaceans

68. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-68 1 st pair of thoracic limbs are maxillipeds 1 st pair of thoracic limbs are maxillipeds Remaining thoracic limbs lack exopods Remaining thoracic limbs lack exopods Abdominal appendages bear gills, except for uropods Abdominal appendages bear gills, except for uropods Common land forms include sow bugs and pill bugs Common land forms include sow bugs and pill bugs Cuticle lacks protection of insect cuticle Cuticle lacks protection of insect cuticle Must live in moist habitats Must live in moist habitats Some isopods are highly modified as parasites of fishes or crustaceans Some isopods are highly modified as parasites of fishes or crustaceans Development typically direct but may be metamorphic in parasitic forms Development typically direct but may be metamorphic in parasitic forms Brief Survey of Crustaceans

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71. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-71 Order Amphipoda Amphipods resemble isopods Amphipods resemble isopods Lack a carapace, have sessile compound eyes, and one pair of maxillipeds Lack a carapace, have sessile compound eyes, and one pair of maxillipeds However, they are compressed laterally, and gills are in the thoracic region However, they are compressed laterally, and gills are in the thoracic region Abdominal and thoracic limbs are grouped for jumping and swimming Abdominal and thoracic limbs are grouped for jumping and swimming Many are marine, others are beach-dwelling, freshwater, or parasitic Many are marine, others are beach-dwelling, freshwater, or parasitic Development is direct Development is direct Brief Survey of Crustaceans

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74. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-74 Order Euphausiacea Approximately 90 species Approximately 90 species Includes important ocean plankton called krill Includes important ocean plankton called krill Carapace does not completely enclose gills Carapace does not completely enclose gills Lack maxillipeds and all limbs have exopods Lack maxillipeds and all limbs have exopods Most are bioluminescent with a light- producing organ called a photophore Most are bioluminescent with a light- producing organ called a photophore Form a major component of the diet of baleen whales and of many fishes Form a major component of the diet of baleen whales and of many fishes Eggs hatch as nauplii Eggs hatch as nauplii Development is direct Development is direct Brief Survey of Crustaceans

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76. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-76 Order Decapoda 5 pairs of walking legs and 3 pairs of maxillipeds 5 pairs of walking legs and 3 pairs of maxillipeds In crabs, first pair of walking legs form pincers In crabs, first pair of walking legs form pincers Range from a few millimeters to the Japanese crab with a 4 m leg-span Range from a few millimeters to the Japanese crab with a 4 m leg-span Approximately 18,000 species Approximately 18,000 species Includes crayfishes, lobsters, crabs, and true shrimp Includes crayfishes, lobsters, crabs, and true shrimp Crabs have a broader cephalothorax and reduced abdomen, compared to crayfish or lobsters Crabs have a broader cephalothorax and reduced abdomen, compared to crayfish or lobsters Brief Survey of Crustaceans

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79. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-79 Phylogeny and Adaptive Diversification Phylogeny Remipedia appear to be the most primitive of Crustacea Remipedia appear to be the most primitive of Crustacea Fossils of an arthropod in the Mississippian are likely the sister group to remipedians Fossils of an arthropod in the Mississippian are likely the sister group to remipedians One theory is that each modern somite represents two ancestral somites that fused together, forming the biramous appendage One theory is that each modern somite represents two ancestral somites that fused together, forming the biramous appendage The pentastomids were placed in Ecdysozoa because of the similarities in larvae, molting of the cuticle, and sperm morphology The pentastomids were placed in Ecdysozoa because of the similarities in larvae, molting of the cuticle, and sperm morphology Phylogenies based on rRNA genes and affirmed in sequences of mitochondrial DNA indicate that pentastomids are crustaceans Phylogenies based on rRNA genes and affirmed in sequences of mitochondrial DNA indicate that pentastomids are crustaceans

80. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-80 Adaptive Diversification Crustaceans are unquestionably the dominant arthropod in marine environments Crustaceans are unquestionably the dominant arthropod in marine environments They also share dominance in freshwater environments with the insects They also share dominance in freshwater environments with the insects The class Malacostraca is most diverse and members of Copepoda are most abundant The class Malacostraca is most diverse and members of Copepoda are most abundant Copepods are particularly successful as parasites of both vertebrates and invertebrates Copepods are particularly successful as parasites of both vertebrates and invertebrates Phylogeny and Adaptive Diversification

81. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-81 Classification Class Remipedia Class Remipedia Class Cephalocarida Class Cephalocarida Class Branchiopoda Class Branchiopoda Order Anostraca Order Anostraca Order Notostraca Order Notostraca Order Cladocera Order Cladocera Order Conchostraca Order Conchostraca Phylogeny and Adaptive Diversification

82. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-82 Class Ostracoda Class Ostracoda Subclass Maxillopoda Subclass Maxillopoda Subclass Mystacocarida Subclass Mystacocarida Subclass Copepoda Subclass Copepoda Subclass Tantulocarida Subclass Tantulocarida Subclass Branchiura Subclass Branchiura Subclass Pentastomida Subclass Pentastomida Subclass Cirripedia Subclass Cirripedia Phylogeny and Adaptive Diversification

83. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20-83 Class Malacostraca Class Malacostraca Order Isopoda Order Isopoda Order Amphipoda Order Amphipoda Order Euphausiacea Order Euphausiacea Order Decapoda Order Decapoda Phylogeny and Adaptive Diversification