Chapter 7 Marine Animals Without a Backbone II

Arthopods: the armored achievers (進步者 ) o o o Phylum Arthopoda Largest phylum of animal; insects dominate on land but rare in sea Morphological characters: (1) segmented and bilaterally symmetry, (2) jointed appendages, (3) exoskeleton; protection, support, flexible, attachment Molt Limitation in size and growth 2

Figure 7. 27 Crustaceans

Crustaceans • Subphulum Crustacea • Characters: (1) most marine, (2) have gill, (3) chitinous skeleton hardened by calcium carbonate, (4) specialized appendages, (5) two pairs of antennae • 68000 species with additional 150000 undescribed species 4

Figure 7. 28 Copepods -- extremely abundant and important -- filter feeding, parasitism, carnivores

Figure 7. 29 a Barnacles -- Attach to surface, have cirri (蔓足 ) -- filter feeding

Figure 7. 30 Amphipods

Amphipods • Laterally compressed body • < 2 cm in length, planktonic life • Common in shore debris • Over 5000 species 8

Figure 7. 31 Isopods

Isopods • About same size as amphipods • Flat body, legs similar in size 10

Fish lice

Krill (euphausiids)

Krill (euphausiids) • • • Planktonic shrimp-like crustaceans Size up to 6 cm Distinctive carapace Filter feeder; diatom and planktons Extremely common in polar waters 13

Decapoda

Decapoda o The largest group and largest size of crustaceans o About 10000 species o Five pairs of walking legs o Three pairs of maxillipeds(顎足); filtering device o Cephalothorax and abdomen o Shrimp scavenger, lobster nocturnal 15

Colorful shrimp in tropics

Hermit crab

Coconut crab

Figure 7. 36 True crab

True crab • abdomen is small and typically broad cephalothorax • Abdomen is V-shape in male and Ushape in female • The largest and most diverse group of decopoda • scavengers and predators 20

Biology of Crustaceans -- diverse form paralleled by diverse functional features • Feeding and digestion • Nervous system and behavior • Reproduction and Life history 21

Feeding and digestion o o o Filter feeding is common for small planktonic crustaceans Chitinous teeth for grinding and bristle for shifting Stomach; two-chambered in decapods, connected to digestible glands Digestion is essentially extracellular Open circulatory system Gills 22

Nervous system and behavior o o o A small, relatively simple brain Sensory organs are well developed, most have compound eyes Keen sense of “smell” A pair of statocyst The most behaviorally complex invertebrates 23

Reproduction and Life history o o o Internal fertilization Mating takes place immediately after the female molts In amphipods and isopods, eggs are brooded in a chamber In decapods and others, carry eggs in pleopods Nauplius(無節幼蟲) 24

Other marine arthopods Horseshore crab

Horseshore crab • Class Merostomata • The “living fossil” • Live on soft bottom in shallow waters 26

Sea spiders

Sea spiders • Class Pycnogonida • 4 or more pair of jointed legs • A large proboscis with the mouth at the tip • Most common in cold waters ; occur throughout the oceans 28

Insects

Insects • • Class Insecta Have three pairs of legs rare in the sea Live at water’s edge; decaying seaweed accumulate at high tide mark • scavenger 30

Lophophorates o o Unit feeding structure Characters; (1) suspension feeding, (2) lack of segmentation, (3) bilateral symmetry, (4) have a coelomic cavity and a U-shaped gut 31

Brozoans

Brozoans • • • Phylum Ectoporcta Moss animal, form delicate colonies About 4500 species, almost all marine Zooids (個蟲) Lophophore is retractable, and ectoprocta 33

Phoronids

Phoronids • Phylum Phoronida • Worm-like and tube-build animal • Have a lophophore, and gut is Ushpaed • 20 species, all marine, shallow waters • Burrow in sand or attaching tubes 35

Lamp shells

Lamp shells • Phylum Brachipod • Close to 350 species • Have a shell with two parts; dorsal and ventral • Have a conspicuous lophophore • Found attached to rocks or burrowing in soft sediment 37

Arrow worm

Arrow worm Phylum Chaetognatha n About 100 species, all marine n Important members of the plankton n Almost transparent streamlined n Head had eyes, spines and teeth n Voracious carnivores n 39

Arrow worm Size from few mm to 10 cm n Voracious carnivores n Motionless in water n 40

Echinoderms: five-way symmetry

Echinoderms: five-way symmetry • Phylum Echinodermata. • Radially symmetry is a secondary development • Most have pentamerous radial symmetry 42

-- Lack head -- no anterior, posterior, dorsal, ventral size

-- Have complete digestive tract and endoskeleton -- endoskeleton; covered by thin layer of ciliated tissue -- Have water vascular system

-- Tube feet are muscular extension of these canal; ampullae (壺) -- Tube feet often end in a sucker; madreporite (篩板) -- tube for locomotion and receive stimuli

Type of Echinoderms About 7000 species, all marine Benthic animal, widely distributed Sea stars Brittle stars Sea urchins Sea Cucumbers Crinoids 46

Sea stars

Sea stars q. Class Asteroidea q. Ambulacral groove (步帶溝) q. Endoskeleton q. Carnivores 48

-- pincer-like pedicellariae (叉棘)

Brittle stars

Brittle stars ¨Class Ophiuroidae ¨Snake-like movement of the arms ¨Tube feet have not suckers, lack anus ¨Detritivore and carnivore ¨About 2000 species; widely distributed 51

Sea urchins

Sea urchins • Class Echinoidae • The endoskeleton form a test • Mouth on the bottom and the anus on top • Bands of pores • Detritivore and carnivore • Aristotle’s lantern • About 1000 species; rocky shore 53

Sand dollar -- Flattened bodies, short spines, deposit feeder, -- live in soft bottom

Sea Cucumbers

Sea cucumber Class Holothuridae Five rows of tube feet are concentrated Oral and aboral surface at the end Tube feet extend from mouth to anus Do not have spines and lack obvious radial symmetry Calcareous spicules; endoskeleton Deposit feeder Secrete toxic substance or evisceration 56

Crinoids

Crinoids Class Crinoidae q Suspension feeder, about 600 species q Body plan is upside-down brittle star q Tube feet along the arm secrete mucus q 58

Sea lilies Feather star

Biology of Echinoderms -- Radial symmetry associated with sedentary life style Feeding and Digestion o Nervous system and Behavior o Reproduction and Life History o 60

Feeding and Digestion q Digestive system is relatively simple q Most sea stars are carnivores; everting stomach, intestine is short or missing, no anus q Gut of sea urchins and sea cucumbers is long and coiled q Coelomic fluid, transport oxygen and nutrients; lack distinct circulatory system q Small, branched projection of the body wall in sea stars and sea urchin q Water is drawn through the anus in sea urchin; respiratory trees 61

Nervous system and Behavior q. Coordinates movements in the absence of brain 62

Reproduction and Life history q. Sex are separate and external fertilization q. Bilateral ciliated larva, metamorphosis inot radial symmetry q. Asexual reproduction by separate central disk or body into two pieces q. Regeneration 63

Hemichorodates: a missing link? -- echinoderms and chordate share several feature related to development of embryos -- hemichorodate have basic developmental characteristics of chordates and echinoderms

Hemichorodates • Phylum Hemichordata • Morphology characters: (1) have a nerve cord, (2) openings along the anterior part of the gut • About 85 species, most are enteropneusts; acron worm • Mucus-secreting proboscis 65

Enteropneusts 66

Chordates without a backbone o o Phylum Chordata; protochordates About 49000 species Characters of (1) a single, hollow nerve cord, (2) have gill (or pharyngeal) slits, (3) a notochord, (4) a post-anal tail, and a ventral heart No backbone 67

Tunicates

Tunicates Subphylum Urochordatea About 3000 species, all marine Class Ascidiacea Attached to hard surface, the only sessile or attached chordates Body is protected by a tunic Filter feeders; incurrent siphon and excurrent siphon Colonial 69

Tunicates (cont. ) Adult posses neither a notochord nor a dorsal nerve cord Tadpole larvae display the fundamental chordate traits; have an eye After metamorphosis, the notochord and tail are reabsorbed 70

Class Thaliacea; salp

Ascidian

Sea squirt

Class Larvcea, Larvceans

Figure 7. 49 Lancelets

Lancelets

Lancelets ¨Subphylum Cephalochordata ¨Inhabitant of soft bottom, and filter feeder ¨Using gill to capture and concentrate organic particles 77