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Deuterostomes and Chordates: An Introduction to Echinoderms and Lower Chordates, Lab Reports of Biology

Shippensburg University of Pennsylvania (SU)Biology

An overview of the phyla echinodermata and chordata, focusing on their characteristics, subphyla, and key features. It includes information on the body symmetry, coelom, and specific traits of echinoderms and chordates, as well as the development and functions of their various subphyla. Students are encouraged to examine and label diagrams of sea stars and other specimens, as well as observe live and preserved echinoderms and chordates.

Typology: Lab Reports

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BIO 1

Section 3

Dr. Pablo Delis

Joe Lahovski

11/12/09

Taxonomy & Morphology: Echinoderms & Lower Chordates

Objective:

•Familiarize us with the diversity of deuterostome animals and some

characteristics that define the structure of the phylogenetic tree

•Recognize the two deuterostome phyla, and subphyla of chordates

•Identify the key characteristics of echinoderms and chordates

•Appreciate the diversity of these phyla and be able to identify them to class

The lab instructs us to answer questions about each phylum, which are answered here:

Phylum Echinodermata

1. Secondary pentameric radial symmetry; most are sessile or very slow-moving

because of their body symmetry type; in the larval stage, they are bilateral

2. Coelom

3. Network of hydraulic canals; branching into extensions of tube feet; used for

locomotion, feeding, and gas exchange

Phylum Chordata

1. Bilaterally symmetrical, coelomates

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BIO 1

Section 3 Dr. Pablo Delis Joe Lahovski 11/12/

Taxonomy & Morphology: Echinoderms & Lower Chordates

Objective:

Familiarize us with the diversity of deuterostome animals and some characteristics that define the structure of the phylogenetic tree
Recognize the two deuterostome phyla, and subphyla of chordates
Identify the key characteristics of echinoderms and chordates
Appreciate the diversity of these phyla and be able to identify them to class The lab instructs us to answer questions about each phylum, which are answered here: Phylum Echinodermata

Secondary pentameric radial symmetry; most are sessile or very slow-moving because of their body symmetry type; in the larval stage, they are bilateral
Coelom
Network of hydraulic canals; branching into extensions of tube feet; used for locomotion, feeding, and gas exchange Phylum Chordata
Bilaterally symmetrical, coelomates

Notochord; dorsal, hollow nerve cord; pharyngeal slits of clefts; muscular, post- anal tail Phylum Echinodermata

Have "spiny skins"
- Dermal endoskeleton is comprised of numerous calcareous ossicles and spines
Well developed coelom and are all marine
Although they develop bilaterally as larvae, they transform into adults that exhibit pentaradiate symmetry
Water-vascular system, tube feet, pincerlike pedicellariae, and skin gills (dermal branchiae)
Nervous system and sensory organs are primitive, no excretory organs
A definite head is absent
Class Crinoidea- sea lilies and sea stars
- Very abundant in prehistoric oceans
- Most forms have a stalk for aboral attachment to the substrate
- Mouth and anus are on the oral surface
Class Asteroidea- sea stars
- Body is star-shaped with arms not sharply marked off from the central disc
- Ambulacral groove is open with tube feet on the oral side
- Anus and madreporite on the aboral side
Class Ophiuroidea- brittle stars and basket stars

Make an incision such that you can remove the dorsal skin from the body disc and from at least one arm
Notice that the stomach is divided into two parts, the pyloric (dorsal) and cardiac (ventral) stomach
Pyloric stomach receives enzymes from the pyloric cecae
Cardiac stomach can be everted during feeding
Understand the arrangement of the water-vascular system
The madreporite connects to the stone canal which in turn connects to the circular ring canal located within the body disc
Five radial canals branching off the ring canal; one ring canal per arm
Lateral canals branch from the radial canals and lead to the ampullae
Ampullae- muscular sac-like structures; when they contract, water is forced into the tube feet causing them to expand; when muscles in the tube feet contract, water returns to the ampullae and the tube feet retract, generating suction
In the arms, identify the pyloric cecae and gonads
A hard ambulacral ridge is evident in each arm and contains the radial canal
Radial and lateral canals may be difficult to identify
Observe the ampullae within the arm and the tube feet on the outside
A radial nerve also runs through the ambulacral ridge
Also observe the arm of the sea star from a cross-sectional view
Diagram and label your sea start dissection in your lab notebook
Examine the dry and bottled echinoderms available on the side counter

Note any comments on the accompanying index cards
Make a written record of the specimens in your lab notebook Phylum Chordata
Most complex organisms are represented in this phylum
Highly evolved nervous system is chiefly responsible for giving this phylum its eminence among animals
Some certain key characteristics may only be represented during embryological development and then disappear as development progresses
Notochord, pharyngeal gill slits, dorsal hollow nerve cord, and a post-anal tail
Identify the key characteristics of chordate biology on the specimens we observe
Subphylum Urochordata- tunicates, sea squirts
Only larval tunicates possess all chordate characteristics
Larvae resemble a frog tadpole in body form; also have a dorsal hollow nerve cord, gill slits and post-anal tail
Larva transforms into a sessile, sac-like form that loses the tail, the notochord and nerve cord become vestigial and the pharyngeal gill slits persist to function in a filter-feeding capacity
Body is enclosed in a tunic (covering)
Subphylum Cephalochordata
Have a fish-like form in that they possess dorsal and ventral fins for stabilizing themselves in their marine environment
Notochord extends into the head region

Lampreys have a round mouth with rasping tongue and horny tooth-like structures in the oral funnel used for grasping prey
Class Myxini- hagfish
Scavenger agnathans
Feed on debris on the ocean floor and have whisker-like barbels for detecting food in the mud
Gnathostomes- jawed vertebrates
Functional jaws and two sets of paired appendages
Class Chondrichthyes- sharks, skates, rays, chimeras
Almost exclusively marine
Skeleton entirely of cartilage; vertebrae well developed
Well-developed jaws; calcification of cartilage results in bone-like integrity
Typical "fish" arrangement of fins present
Paired pectoral and pelvic and unpaired dorsal caudal and anal fins
Scales are tiny and tooth-like and composed of dentin
No air (swim) bladder is present and most lack an operculum covering gills
Osteichthyes
Most successful group of vertebrates in terms of number and species
Skeleton composed almost entirely of bon
Operculum covers the gills
Air (swim) bladder to regulate buoyancy
Original role of air bladder was respiration

Still evident in primitive body fish such as lungfish
Class Actinopterygii- ray finned fishes; most familiar fishes
Class Actinistia- coelacanths; primitive lobed finned fishes with robust fleshy fins inhabiting relatively deep sea waters; only two species exist today
Class Dipnoi- lungfishes; primitive freshwater fishes with flimsy fleshy fins and dual respiration (gills and lungs); five species exist today
Tetrapods- amphibians, reptiles, birds, mammals
Class Amphibia- frogs, toads, salamanders, caecilians
Metamorphosis and very think permeable skin
Larval stage is typically aquatic and the adult stage is typically terrestrial
Adults have legs, lungs; larvae have gills
Fertilization is typically external in frogs and toads and internal in salamanders and caecilians
Heart is three-chambered; two atria and one ventricle
Amniotes
Set of extra-embryonic membranes; amnion, chorion, and allantois
Membranes made their first appearance in reptiles and are adaptations that enable the development of the embryo in a shelled egg on the land
Class/Clade Reptilia- lizards, snakes, turtles, crocodilians, tuatara, birds*
Dry skin (very few glands), epidermal scales
Heart is typically three-chambered with partial diversion of the ventricle
Crocodilians have a four-chambered heart

Include the majority of the living members of class Mammalia
Tremendous diversity in a large number of orders
Examination of the Aquatic Lower Chordates
Subphylum Urochordata- Tunicates
Identify the excurrent siphon, incurrent siphon, bronchial (gill) basket and digestive tract in the preserved specimens
The ascidian (larval) stage demonstrates all chordate characteristics:
Dorsal hollow nerve cord, notochord, gill slits, post-anal tail, and a ventral heart
Examine the slide mounted ascidian larva
Subphylum Cephalochordata- Amphioxus (w.m., slide)
Be able to identify Phylum characteristics in specimen
Examine two cross-sections (slide) of amphioxus
One anterior and one posterior
Identify nerve cord, gills, gill slits, and pharynx on the anterior
Identify dorsal fin, nerve cord, and notochord on the posterior
Subphylum Vertebrata- Cephaloaspidomorphi
Examine an intact lamprey
Observe that the cylindrical body has a funnle-like mouth, buccal funnel
Inside the funnel, observe the horny teeth it uses to attach itself to the side of larger fish

A rasping tongue is used to etch flesh from the side of the prey, leaving the prey with a gaping wound and the fate of infection and death
Lampreys do not possess paired fins
The single fins include the dorsal fin (split into anterior dorsal and posterior dorsal) and the caudal fin
Identify the rudimentary eyes and the seven pairs of external gill slits
Examine a specimen that has been cut in the mid-sagittal plane
Observe teeth, bronchial tube with internal gill slits, notochord, and spinal cord
Annular cartilage is a ring of cartilage that supports the circular, jawless mouth
Spinal cord is dorsal to the notochord
Examine a cross-section of the lamprey taken through the mid to posterior portion of the body
Review the positional relationships of the spinal cord and notochord
Class Chondrichthyes
Locate the lateral line
Identify the paired nostrils, five pairs of external gill slits, dorsal fins, caudal fin, and paired pectoral and pelvic fins
Examine the living and preserved specimens of the remaining classes of Vertebrata; identify characteristics of the classes mentioned in this unit

Deuterostomes and Chordates: An Introduction to Echinoderms and Lower Chordates, Lab Reports of Biology

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BIO 1

Taxonomy & Morphology: Echinoderms & Lower Chordates