BIOLOGY 453 - COMPARATIVE VERT. ANATOMY WEEK 1, LAB 2: Embryology of Frog & Chick

Learning Goals

1. Know both the traditional taxonomy & major clades to which the frog & chick embryos belong. a. Know at least 1 shared derived trait that can “define” each clade.

2. Be able to identify the following in a frog & chick embryo: a. Relative amount of yolk in eggs: microlecithal, mesolecithal, macrolecithal b. Cleavage patterns: holoblastic, meroblastic & discoidal. c. Identify these developmental stages & associated structures in embryonic frog development:

i. Fertilized egg or zygote: animal & vegetal pole ii. Blastula (blastocoel, micromeres & macromeres) iii. Gastrula (blastocoel, archenteron, notochord, yolk plug, blastopore, anterior vs posterior regions) iv. Neurula (neural plate & neural folds, anterior vs posterior regions)

d. In the chick find these homologous structures to the blastopore: Hensen’s node & primitive streak. e. Primary germ layers (ectoderm, mesoderm or endoderm) & examples of adult tissues each may form.

i. Identify the 3 major types of mesoderm: epimere (somites), mesomere (intermediate) & hypomere (lateral plate mesoderm). Give an example of an adult tissue that is derived from each type.

f. Identify these structures or organs in both frog & chick embryos, as noted: eye, lens, otic capsule, notochord, somites, neural tube or neural folds, brain, pharyngeal arches and heart.

g. Identify these additional organs in the tadpole (they remain small or difficult to see in early chick stages): liver, kidney, and gut or intestine.

3. Compare the lamprey larva & amphioxus specimens to the frog & chick embryos. What traits do the frog & chick embryos share with the lamprey larva & Amphioxus?

Specimens to Examine

Misc. 35 mm slides Microscope slide: Whole mount Microscope slide: Sagittal Sec. Frog embryo X X X Chick embryo X X X

Traditional Taxonomy & Major Clades

Traditional Taxonomy Major Clades Subphylum Vertebrata (Craniata)

Class Lissamphibia (frogs, salamanders...) Class Aves (birds) & more!!

Clade Vertebrata: fishes, amphibians, “reptiles”, birds & mammals Shared derived trait: vertebral column surrounds spinal cord

Clade Tetrapoda: amphibian, lizard, snake, alligator, bird, mammal

Shared derived traits: digits on limbs, loss of internal gills... Clade Amniota: lizards, snakes, alligators, birds & mammals

Shared derived traits: amniotic egg with new extra-embryonic membranes amnion, chorion & allantois

Additional Sources of Information

Topic Egg type Cleavage Coelom formation Mesoderm diff. Neurulation

Kardong (text) pg. 159-160 162-165 165, 168-170 170-175 167, 170-174

GENERAL Cell & Developmental Biology Online! 2009. Univ. of Guelph, Zoology Dept.

http://www.uoguelph.ca/zoology/devobio/dbindex.htm Mallery, C. 2009. Animal Development. Biol. 150. Univ. of Miami.

http://www.bio.miami.edu/~cmallery/150/devel/animal_development.htm Nouvelles Technologies Educatives del l'universite de Lyon1. 2000. Atlas d'embryologie descriptive des vertébrés.

http://nte-serveur.univ-lyon1.fr/nte/embryon/tp2000/correction.htm PBS. 2008. Morphing Embryos. Odyssey of Life. (Quicktime videos of embryos)

http://www.pbs.org/wgbh/nova/odyssey/clips/ Slonczewski, J. 2009. Chapter 14. Gastrulation & Neurulation. Biology 114, Biology Dept., Kenyon College

http://biology.kenyon.edu/courses/biol114/Chap14/Chapter_14.html Univ. of Calgary. 2000. The Virtual Embryo.

http://people.ucalgary.ca/~browder/virtualembryo/db_tutorial.html Wasserman, B. Movies/Pics. Bill Wasserman’s Developmental Biology Page, Loyola Univ., Chicago.

http://www.luc.edu/faculty/wwasser/dev/devm.htm

CHICK ONLY Burke, AC. 2009. Body wall formation in the chick embryo. Learning Objects Team, Wesleyan University.

http://learningobjects.wesleyan.edu/musc_dev/ Cebra-Thomas, J. 2003. Chick Embryo Staging. Developmental Biology, Swarthmore Univ.

http://www.swarthmore.edu/NatSci/sgilber1/DB_lab/Chick/chick_stage.html DevBio.com 2009. Coelom Formation (animation). Developmental Biology Online. Companion to Developmental Biology,

8th Edition by Scott F. Gilbert, Sinauer Associates. http://8e.devbio.com/article.php?ch=15&id=138 Gilbert, SF. 2000. Early Development in Birds. Cleavage in Bird Eggs. Developmental Biology, 6th Ed.

http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=dbio&part=A2581 Hill, M. 2008. Embryology: Chicken Development Stages. Univ. of New South Whales Embryology.

http://embryology.med.unsw.edu.au/OtherEmb/chick2.htm Muneoka, K. 2006. Online Developmental Atlas. CELL 413 - Embryology Lab., Dept. of Cell & Mol. Biol., Tulane Univ.

http://www.tulane.edu/~embryo/labsyllabus.htm Shaw, M. 2005. Gametogenesis & Development. Univ. of Manitoba - series of labeled chick slides with descriptions

http://www.umanitoba.ca/faculties/science/biological_sciences/lab14/biolab14_4.html Temkin, M. 2001. Atlas of Developmental Stages, Developmental Biology - 31 St. Lawrence Univ.

http://it.stlawu.edu/~mtem/devbiol/db99atlas.htm Univ. of Illinois Urbana-Champaign. 1998. Chickscope (Go into a stage to find great microscopic views!)

http://chickscope.beckman.uiuc.edu/explore/embryology/ FROG ONLY Cebra-Thomas, J. 2003. Xenopus Embryo Staging. Developmental Biology, Swarthmore Univ.

http://www.swarthmore.edu/NatSci/sgilber1/DB_lab/Frog/frog_staging.html Frontiers in Bioscience. 2007. Germ Layer Derivatives. Atlas of Xenopus Embryology

http://www.bioscience.org/atlases/fert/htm/develhum/5germper.htm Kimball, J. 2009. Frog Embryology. Kimball’s Biology Pages.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FrogEmbryology.html Munson, D. 2009. Histology. (frog images) MCB 116: Experimental Embryology. Harvard Univ.

http://www.courses.fas.harvard.edu/~mcb116/topics/histology.html Sievert, L. 2004. Frog Development Models. Vertebrate Structure and Development, ZO 515 - 516. Emporia State Univ.

http://academic.emporia.edu/sievertl/verstruc/frmodel.htm Univ. of Wisconsin. 2002. Amphibian Embryology Tutorial! (QuickTime movie & more)

http://worms.zoology.wisc.edu/frogs/welcome.html

Embryology Basics EGG TYPES Eggs vary in size primarily because of differences in the amount of yolk, but eggs of similar size may also vary in the proportionate amount of yolk. Eggs are described in the table.

Microlecithal [lecith = yolk] Mesolecithal Macrolecithal small amount of yolk moderate amount of yolk large amount of yolk

In fact, eggs within some taxa such as amphibians and fishes show a wide range of size & yolk proportion. Technically, they fall into a continuum of variation rather than absolute categories. Most vertebrate eggs have an unequal distribution of yolk in the egg. These eggs have separate regions with non-yolky material at one end of the egg & yolk concentrated at the opposite side. This type of egg is called telolecithal [telo = end] with separate animal & "vegetal" or yolk poles. CLEAVAGE PATTERNS Cleavage (mitotic cell division) through yolk is slower than cleavage through the animal pole. As a result, cells may get smaller in the animal pole region than in the vegetal pole. If cleavage occurs through both the animal & vegetal poles it is called holoblastic [holo = whole; blast = bud] cleavage. It will be equal & holoblastic in microlecithal eggs but there is usually unequal, holoblastic cleavage in mesolecithal eggs with more yolk. These eggs produce smaller animal pole cells & larger, yolk filled cells. If the vegetal pole has a very large mass of yolk, i.e. its a macrolecithal egg, the egg doesn't cleave completely. If only the animal pole undergoes cleavage this is called meroblastic [mero = a part] cleavage. A specialized form of meroblastic cleavage is called discoidal cleavage [disc = round plate]: the animal pole cells are extremely small & the yolk amount is huge. GERM LAYER INTRODUCTION Ectoderm forms the epidermis of the skin, the lens of the eye & neural ectoderm forms brain & spinal cord. Mesoderm divides into 4 major regions that form specific tissues of the body:

Chordamesoderm - forms the notochord Epimere (Paraxial mesoderm) - forms segmented blocks called somites Mesomere (Intermediate mesoderm) - forms the kidneys & gonads Hypomere (Lateral plate mesoderm) - forms smooth muscle, heart, coelomic cavity

Endoderm forms the epithelial lining of the gut or archenteron, epithelial lining of the lungs & the yolk, if present. The mesodermal somites form in pairs along either side of the notochord in young embryos. Each somite divides into 3 subdivisions that form some of the segmented structures of the body & part of the skin:

Sclerotome - vertebrae Dermatome - dermis of skin Myotome - skeletal or somatic muscle Myotomes develop into a series of V-shaped, segmentally arranged muscles or myomeres that are visible in the tail of the frog embryo. Myomeres form segmentally arranged muscles in all vertebrates although the pattern may be modified. Myosepta are connective tissue layers that separate the myomeres.

Germ layer development in a

transversely sectioned amniote.

Class Lissamphibia - Frog Embryos Identify the listed structures for each slide. More features may be present; you are responsible for only those listed.

35 mm Slides: Images from

http://www.swarthmore.edu/NatSci/sgilber1/DB_lab/Frog/frog_staging.html Whole views Various sectioned views

Fertilized egg: Mesolecithal (moderately yolked). Telolecithal egg with animal (pigmented) & vegetal poles

Cleavage: Eight cell stage or slightly higher. Holoblastic (complete cleavage) Radial cleavage: Describe this term. Meroblastic cleavage: means unequal sized blastomeres. Label the micromeres: animal cells & macromeres: yolk-filled cells.

Blastula stage: Identify the animal pole & vegetal pole. Label the blastula cavity.

Early gastrulation: Find the dorsal lip of the blastopore, as animal pole cells begin to migrate over yolk & into interior space of embryo. Cells migrating inward will form endoderm, mesoderm. Remnant of blastocoel still apparent in Sagittal section.

Late Gastrulation: Find the blastopore filled with the yolk plug. Label the gut (archenteron). Label germ layers: ectoderm, mesoderm & endoderm.

Early Neurulation: Label the neural folds & neural groove. In the transverse section, label notochord, somites & gut.

Late Neurulation: Neural tube has closed. In the transverse section find & label the 3 primary germ layers; neural tube, notochord, archenteron & somites

Whole Mount Frog Embryo (4-8 mm) Microscope Slide

Identify the following: eye, otic vesicle (future ear), brain, spinal cord, notochord, pharyngeal arches, heart, & myomeres. Otic vesicle & pharyngeal arches may be hard to see on some slides.

Sagittal Section 10 mm Frog Embryo Microscope slide

Each slide has a series of sagittal sections. Identify the following structures (they won't all be visible on any given section or perhaps any 1 slide): eye & lens, otic vesicle, brain, spinal cord, notochord, pharynx, heart, kidney, liver, intestine, myomeres.

http://www.uoguelph.ca/zoology/devobio/210labs/34frogwm.htm

B

What type of sectional view is this? Is this more or less mature than the drawing in figure B? Label the brain, spinal cord,

notochord, yolk, pharynx, myotomes, anus & heart. C

What type of sectional view is this? Find & label the notochord, neural tube, intestines, liver & kidney tissue.

Make your own drawings of the specimens showing para-sagittal views here:

A

D

Class Aves - Chick Embryos

Use these diagrams & illustrations to help you label the images on the following pages. 24 hr stage

33 hr hour stage

72 hour stage

96 hr stage

Identify the listed structures for each slide. More features may be present; you are responsible for only those listed.

35 mm slides - Whole View Chick Embryo Images from http://www.swarthmore.edu/NatSci/sgilber1/DB_lab/Chick/chick_stage.html

18 hr. Gastrulation

Find notochord, Hensen's node & the primitive streak.

21 hr. Early neurulation

Find neural groove & neural folds, somites, primitive streak & Hensen's node

28-33 hr.

Find the neural tube, brain, somites, blood islands in extra-embryonic region & posterior portion of heart.

48 hr.

Find the optic capsule, otic vesicle/capsule, heart, somites, brain & neural tube.

72 hr.

Find the eye, lens, otic capsule, brain, spinal cord (neural tube), pharyngeal grooves or arches, heart, somites, limb buds.

84 hr.

Find the eye, lens, otic capsule, brain, spinal cord (neural tube), pharyngeal grooves or arches, heart, somites & limb buds. The transparent sac near the tail is the allantois, one of the extra-embryonic membranes unique to amniotes.

Whole Mount Microscope slide 48-72 hour chick embryo Identify the following: optic cup (eye), lens, otic capsule, brain, spinal cord, pharyngeal arches, heart, somites & limb buds.

Make your own drawing here:

Sagittal Section Microscope slide 48 hour chick embryo Each slide has a series of sagittal sections. Identify the following (not all are visible on any given section or any 1 slide): eye (lens &

eye cup shows a pigmented retina forming), otic capsule, brain, spinal cord, pharynx, heart & somites Sagittal section of a 48 hour chick embryo.

Sagittal section of a 72 hour chick embryo.

Make your own para-sagittal drawing here:

48 hour embryo at left 72 hour embryo below

35 mm slides - Transverse Sections of Chick #1 Gastrulation: This is a section through the primitive streak showing the formation of ectoderm, mesoderm & endoderm.

#2 Early neurulation: Label the neural plate, notochord, somites. Identify the germ layers endoderm, mesoderm & ectoderm.

#3 Late neurulation: find the neural tube, notochord, somites.

#4 Higher magnification: find somites, coelomic cavity, paired dorsal aortae, notochord & neural tube, "future" archenteron/gut Identify the germ layers - ectoderm, mesoderm, and endoderm. Then identify the 2 divisions of the somite visible in this slide - dermatome-myotome (darker line of tissue, dorsal to rest of somite) & sclerotome division (lateral to neural tube & notochord).