Zoology 200
Chapter 6 & 7
Dr. Bob Moeng
Diversity of Marine Animals
Classification
• Dependent on physical, physiological and behavioral characteristics
Cells
• Single (protozoans) vs multicellular
• Single celled organism must carry on all functions of the animal individually including
feeding, reproduction and locomotion (flagella or cilia)
– Asexual reproduction is typical
More Cells
– Means of locomotion frequently determines phylum
• Sarcomastigophora - have flagella or pseudopodia or both
– Foraminiferans (shelled (CaC03 or cemented sand grains and planktonic or
benthic) amoebae) and radiolarians (silica skeleton and planktonic) in this
phylum
• Ciliophora - have cilia
– Most parasitic
• Labyrinthomorpha - colonial network of cells
Multiple Cells
• Typical of animals though the transition is vague between colonial protozoans and
loosely organized multicellular organisms
• Leads to contractile muscles and conducting nerve tissue
More Multiple Cells
• Includes sexual reproduction with meiotic production of haploid sex cells
– Frequently includes larval stage (distribution for benthic organisms)
• Developmental formation of blastula - process of layering tissue
• Requires skeletal support - internal or external
Porifera
• Multicellular with minimum of cell specialization
– Pinacocyte - exterior protection
– Chaonocytes - interior water movement and food collection
– Amoebocyte - establish the spongin and/or spicule skeleton and distribute
nutrients
• Benthic and do have short-lived larval stage
– Also asexually reproduce by budding
Symmetry
• Radial vs. bilateral
• Some Porifera are radial, others not
• Cnidaria are the largest group that highlight radial symmetry
– Class Hydrozoa - hydroids and man-of-war (colonies are not radial…individual
specialization of responsibility)
– Class Scyphozoa - jellyfishes
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Zoology 200
Chapter 6 & 7
Dr. Bob Moeng
– Class Anthozoa - corals and anemones
– Medusa vs Polyp stages
• Oral and aboral surfaces
More Symmetry
• Ctenophora also radial symmetry (all marine and usually planktonic)
– Ctenes - bands of cilia
– Have digestive tract with mouth and anus
Bilateral
• Platyhelminthes and above
• Left and right, front and back
• True body cavity - coelom (Ectoprocta and above)
• Cephalization and increased development of sensory apparatus
– Highlighted by the mollusks (cephalopods)
– Simplest forms are a range of small or microscopic benthic worms (seven phyla)
More Bilateral
• Skeleton - external, hydrostatic (two layers of muscle), internal
– Hydrostatic skeleton based on two layers of muscle surrounding a space sipuncula (peanut worms) - all marine, benthic and usually intertidal
• Segmentation (Annelida and above)
– Annelida - polychaete worms (5000 in Class Polychaeta)
Even More Bilateral
– Arthropods - exoskeletons made of chitin
• Class Insecta - few related to marine environment
• Class Merostomata - Horseshoe crab
• Class Crustacea - two pairs of antennae (barnacles, crabs, shrimps, lobsters)
– Subclass Copeopoda
Still More Bilateral
– Echinoderms secondarily radial (pentaradial)
• Much more advanced than other radial animals
• Tube feet system for locomotion, respiration, excretion and sensation
• Larval forms that are bilateral
• Class Echinoidea - sea urchins and sand dollars
• Class Crinoidea - seal lilies
• Class Ophiuroidea - brittle stars
• Class Holothuroidea - sea cucumbers
• Class Asteroidea - starfishes
Chordata
• Notochord, hollow dorsal nerve cord and pharyngeal arches
– Subphylum Urochordata - sea squirts and salps
– Subphylum Cephalochordata - lancelet (Branchistoma)
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Zoology 200
Chapter 6 & 7
Dr. Bob Moeng
– Subphylum Vertebrata - spinal column (with hollow nerve tube)replaces
notochord, post-anal tail, pharyngeal pouches, sensory structures and brain
Marine Fishes
• Class Agnatha - jawless fishes - hagfishes and lampreys
• Class Chondricthyes - (or cartilaginous fishes) sharks and rays
– Paired fins, biting jaws with teeth, most marine
– Like other vertebrates, salt conc 50% of seawater…osmotic problem
• Concentrations of urea, and trimethylamine oxide (TMAO) protects proteins
from urea
– Cartilaginous skeleton
More Marine Fishes
• Class Osteichthyes - bony fishes
– Subclass Sarcopterygii - (lobe-finned fishes) coelacanth
– Subclass Actinopterygii - (ray-finned fishes)
• Infraclass Teleostei - about 58% are marine
– Hypoosmotic to seawater
– Many with swim bladder
• Other infraclasses - sturgeons and gars
Tetrapods
• Four Legged, air breathing (terrestrial ancestor and must return to surface), period in
water variable but usually at least for food
• Marine Amphibians
– Absent
Marine Reptiles
• Class Reptilia - snakes, turtles and iguana
– Oviparous vs. ovoviviparous (sea snakes)
• Both require internal fertilization
– Hypoosmotic - nasal glands near eyes secrete salt at twice concentration of
seawater and kidneys produce uric acid (almost non-toxic) to conserve water
• Able to drink seawater due to efficiency
Marine Birds
• Class Aves
– Feathers, flight adaptations, deal with osmotic problems much like reptiles,
oviparous, homeothermic (insulation and countercurrent)
– Some with little time in marine environment, others a good deal of their life
Marine Mammals
• Class Mammalia
– Order Carnivora - seals, sea lions, walruses, sea otters, polar bears
– Order Cetacea - whales, dolphins, porpoises
• Toothed (suborder Odontoceti) vs. baleen (suborder Mysticeti) whales
– Order Sirenia - manatees, dugongs
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Zoology 200
Chapter 6 & 7
Dr. Bob Moeng
– Homeothermic, viviparous, mammary glands, body hair, reproductive tract
separate from digestive tract
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