Zoology

• spatulate = spatula-shaped -- (of a leaf shape; having a broad rounded apex and a narrow base)
• therian mammals
• albumen = egg white, ovalbumin
• bastula
• blastomeres - (any cell resulting from cleavage of a fertilized egg)
• vegetal (hemisphere) - (of reproduction) characterized by asexual processes
• Hox genes - homeotic
• meroblastic - partial cleavage of macroleithal eggs
• distend = dilate -- (become wider; "His pupils were dilated")
• distend -- (swell from or as if from internal pressure; "The distended bellies of the starving cows")
• allantois (=umbilical?) -- (vascular fetal membrane that develops from the hindgut in embryonic higher vertebrates (reptiles, birds and mammals))
• chorion -- (outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals))
• foramina = hiatus -- (a natural opening or perforation through a bone or a membranous structure)
• otic = auricular -- (of or relating to near the ear)
• tuberosity - a protuberance on a bone especially for attachment of a muscle or ligament
• ectodermal - the outer germ layer that develops into skin and nervous tissue
• cyclostomes - primitive aquatic vertebrate
• teleost = teleostan -- (a bony fish of the subclass Teleostei)
• hypophysis = pituitary gland -- (the master gland of the endocrine system; located at the base of the brain)
• somites = epimeres, metamere -- (one of a series of similar body segments into which some animals are divided longitudinally)
• cartilage - cells (chondrocytes), within spaces (lacunae) of matrix of proteoglycans and fibers. Formed at the surface membrane of tissue (perichondrium).
• hyaline cartilage - lubrication of joints and formation of long bones -- (translucent cartilage that is common in joints and the respiratory passages; forms most of the fetal skeleton). Can transform into: fibrous cartilage (vertibrae discs), elastic cartilage (with fat cells, external ear and epiglottis), calcified cartilage (skeletons of elasmobranchs. not remodelled once formed).
• endochondral bone (or replacement bone), dermal bone, membrane bone
• osteons = Haversian system -- A central canal and the concentric osseous lamellae encircling it, occurring in compact bone.
• glycoproteins are found in cartilage
• hydroxyapatite is found in bones
• calcium phosphate crystals
• neural crests
• placodes, ectodermal
• somitomeres (form muscle)
• primordia =anlage -- (an organ in its earliest stage of development; the foundation for subsequent development)

skull parts

chondrocranium

• supports brain and special sense organs
• A portion of the embryonic cranium forming the bones of the base of the skull and eventually undergoing ossification.
• only in fetal life
• except in cyclostomes and sharks
• notochord's cartilaginous sheath usually joins the chondrocranium.
• trabeculae pair of "small beams", anterior to the notochord, with hypophysis located between posterior ends. Related to the forebrain, nasal capsules, orbis, and rostrum. Trabeculae can have different conditions: widely separated (platytrabic), joined, fused anteriorly (Y shape, tropitrabic).
• parachordal cartilages - fuse to form the basal plate by surrounding the notochord
• basal plate is of segmental origin from the sclerotomes of embryonic head somites
• occipital condyles, which articulate the first free vertebra of the spine. (chapter 9)

visceral skeleton

• (or splanchnocranium)
• gill arch support

dermal elements

• (or dermatocranium)
• superficial framework of the skull

Vertebrate structure and morphology

Concepts:

• phylogenetic homology (unlike serial homology)
• analogy
• homeobox genes (shared by all multicellular animals)
• Form and function
• Preadaption (Form before function)
• biomechanics, study of biological function
• vestigial organ or degenerate organ, vestigial eyes
• differential reproduction
• punctuated equilibrium vs phyletic gradualism
• linear evolution
• branching evolution
• Adaptive radiation, radiating evolution, evolution radiation, radiation

Questions?

• metamerism vs serial homology

Primative animals:

• Mountain beaver, most primative living rodent (not really a beaver)

Retained primative features:

• Polypterus, fish
• Sphenodon, reptile
• Platypus, mammal

Shared characters

Characters shared by related phyla:

• Multicellular animals
• Embryos with three tissue (germ) layers -- ectoderm, mesoderm, endoderm
• Bilateral symmetry
• Gut is complete (seperate openings for mouth and anus in blastopore)
• Internal skeleton from mesoderm
• Mesoderm is formed (at least in part) from dissue derived from embryonic gut

Related "phyla":

• Echinodermata* -- except only larvae are bilateral. (phylum of starfishes, sea urchins, sea cucumbers, etc)
• Hemichordata* (wormlike, burrowing animals)
• Pogonophora (now considered a family of annelids)
• Chaetognatha

Except: one group has no internal skeleton, another: no digestive tract. Another: lacks a coelom (body cavity).

• *Deuterostomia (second + mouth: blastopore forms no mouth)

Chordata

• Chordata subphylums:
  • Vertebrata
  • Urochordata (tunicates and sea squirts)
  • Cephalochordata (lancelets, or amphioxus)

Characters:

1. notochord (= back + cord)
2. dorsal hollow nerve cord (nerve cord)
   • derived from ectoderm by neurulation
3. pharynx
   • outside of the plylum, pharyngeal slits found only in hemichordates
4. ventral heart
   • (or ventral pulsating vessel in cephalochordates).
   • Blood vascular system is closed (blood does not enter tissue space)
5. cephalization
   • sense organs in the head
   • (urochordates have no head)
6. tail extending posterior to the anus
   • (except urochordates)
7. metamerism
   • segmentation of some features of the body

Primative vs derived

• early lineage characters: primitive, general, plesiomorphic (= close + form), basal, ancestral state, ancestral order, unspecialized/unspecialised, the proposed (metazoan) condition
• character-states that evolved later: advanced, derived, apomorphic (= separate + form)
• sharing primative character-states: symplesiomorphy (= with + close + form)
• sharing derived character-states: synapomorphy (= with + separate + form)
• other descriptions: vestigial, persistant, secondary, pioneered by

Agnatha

• Agnatha are Vertebrata but are without jaws. Not monophyletic.
• pl. Agnathans
• first known vertebrates to evolve
• all extinct 200 myo (except lampreys and hagfish)
• most primative body plan of a living vertebrate is ammocoetes, lamprey larva.
• advanced over (other?) protochordates
• characters: cranium, brain, paired organs of sight, large persistant notochord, usually have vertebrae, usually cartilaginous skeletons, often have pectoral spikes, folds, or lobes.
• first evolution of dentine, enamel. bone.
• characters that came later: jaws, true teeth, girdles, typical appendages, pelvic fins
• more than a dozen orders

Cyclostomata

• Cyclostomata (= round + mouth)
• Lampreys and Hagfishes

Hagfishes

Hagfish

• exclusively marine
• evolved Lower cambrian, at least 550 myo, probably.
• eyes are vestigial
• gills in pouches
• primarily scavengers
• sister group of all animals to follow
• craniata (phylum) is hagfishes combined with sister group vertebrata (subphylum)
• Myxinoidea (Myx = slime) is the first subclass of Agnatha (the dubious class)

Lamprey

Lamprey

• larva called ammocoetes
• Petromyzontia
• no close relatives, though perhaps near anaspids in the same cubclass Cephalaspidomorpha
• more primitive than any other agnathans except hagfish (Donoghue, Forey, Aldridge, 2000)
• gills in pouches (but different to hagfish)
• semiparasidic upon bony fishes
• ammoceotes (larva) more ancestral characters than adult. Especially for mouth parts, pharynx, gonads, and some digestive organs.
• larva become adult by metamorphosis

Pteraspidomorpha

Pteraspidomorpha (= wing + shield + form)

• appear 500myo, before any other vertebrates except conodonts
• principal representative: pteraspids (order Heterostraci)
• pteraspids have heavy armour covering head and anterior of body.
• most have rostrum projecting over the mouth
• bizarre spines on the shield
• no paired fins
• lateral eyes
• two nostrils, common exit from all of the gill pouches (unlike other agnathans)
• possibly slow swimmers, but not bottom feeders
• most were marine

Anaspids

• Anaspid (= without + shield)
• Order: Anaspida
• long exinct
• only jawless vert with streamlined form.
• small, platelike scales
• no head armor
• active swimmers
• pectoral spikes
• long, thin, paired fins (may have undulated)
• many gill openings (like cephalaspids and cyclostomes
• lateral gill openings (unlike cephalaspids' ventral ones)

Chordata species ranking

• Animal phyla, by # species: arthropoda, nematoda, mollusca, chordata, protozoa, cnidaria, annelida, echinodermata, porifera, bryozoa...

Other agnathans

• Ostracoderms (= shell skins), extinct, bony scales
• Arandaspida and Astraspida: Flourished in the Ordovician. Large head shields, no fins except caudal fin.
• Galeaspida, massive one piece shields
• Pituriaspida, long rostrum on the head armour.
• Thelodonti. sharklike scales over whole body. unknown phylogenetic position.

Actinopterygii

Actinopterygii, the ray-finned fishes. Most bony fishes belong to this subclass, but they do not include the ancestors of land vertebrates. We know from cranial bone patterns, and the nature of the venous system and reproductive ducts.

Panderichthyida

• "Panderichthyida is virtually an amphibian with fins." or Panderichthys

Mesoderm

Mesoderm formed by:

• separation from the gut tube
• by delamination
• by primative streak
• cells detach from existing tissue layers and migrate individually as mesenchyme.

see: embryogenesis

Recommended references:

• Gilbert, and Ranio (eds.). 1997. Embryology: constructing the organism One of the few comparative texts. Invertebrate embryology is followed by chapters on cephalochordates, fishes, amphibians, reptiles, and birds, and mammals. (amazon)

Secretory glands

Secretory gland

mucous cell: (epidermal)

• mucus
• poisonous secretion
• photophore - light producing

proteinaceous cell: (epidermal)

• keratins - feathers, hair, claws, reptilian scales, stratum corneum (dead outermost layer)
• slime
• poison
• substances eliciting alarm reactions
• enamel
• possibly photophores

Pigment cells

chromatophores of the epidermis:

• derived from neural crest cells
• any layer of the skin (according to taxon)
• melanophore (endotherms, epidermis)
• melanosomes (migratory organelles)
• melanin (black, brown, red)
• morphological color change

chromatophores of the dermis:

• almost exclsuively in ectotherms
• constant, morphological, or physiological color change.
• Iridophores - large cells. crystaline deposits of mostly guanine.
• Xanthophores, large, yellow
• erythrophores, red, pigments: pteridines and carotenoids in organelles called pterinosomes