Echinodermata I Bio 2 I Exam 4

Protostome or Deuterostome?

Deuterostome

Deuterostome

mesodermal cells form pockets that pinch off, or bud, from the endodermal lining of the primitive (embryonic) gut to create the coelom cavity. Anus forms first then the mouth forms second.

Symmetry

larvae are bilateral but adult are pentaradial symmetry (divided into 5 parts on the central axis)

Coelom absent or present

present- this is because echinoderms have a true coelom, that is, they are triploblastic (3 germ layers: endoderm, ectoderm, mesoderm)

Degree of cephalization (distinct- present; indistinct; absent)

absent, their symmetry prevents this

Eumatazoa

true tissues

How is echinodermata classified under bilateria if they’re adult form is in pentaradial symmetry?

larvae starts of bilaterial

How does the blastopore form

blastula formation begins with radial cleavage of the zygote into a solid ball of cells (morula). As cells continue to divide, they migrate to the outer edge, leaving a fluid-filled central cavity called the blastocoel. This hollow sphere becomes a single-layered, ciliated blastula

How does blastapore formation differentiate clades/groups/domains/protostome vs. deuterostome

During gastrulation, the blastopore is the first opening that forms in the embryo; its fate—whether it becomes the mouth or the anus—determines the animal's developmental pathway and evolutionary classification

Examples of Echinodermata

Starfish, sea urchins, sea cucumbers

Classes of Echinodermata

Asteroidea, Crinoidea, Ophiuroidea, Echinoidea, Holothuroidea

Unifying traits of Class Asteroidea- specific to just this class

• have gonads and gut in arms

• suckered tube feet used for locomotion

• individual control of tube feet

• evertible stomach (ability for stomach to leave arm, digest food, and then return back into the arm)

• Open Ambulacral Grooves: The ambulacral grooves, which contain the tube feet, are wide open along the oral surface of the arms (uncovered by ossicles)

• Marginal Anus and Madreporite Location:The anus is generally located on the dorsal (aboral) surface, and a single, often conspicuous, madreporite (the water inlet for the vascular system) is located aborally, typically on the edge of the disc

Pentaradial is a specialized form of

radial symmetry

Pentaradial symmetry is specialized to

Echinodermata

Echinodermata have bilaterial symmetry just like their

common ancestors

Protostome or Deuterostome Body Plan

Protostome

Protostome or Deuterostome

Deuterostome

Unifying traits of Echinodermata - ONLY echinodermata have these unique traits

• ability to regenerate limbs

• calcium carbonate plates= spiny skin “ossicles”

• water vascular system with madreporite and tube feet

• Pentaradial Symmetry in Adults: Adult echinoderms possess a body arrangement based on five parts (or multiples of five) surrounding a central axis. Note: Larvae are bilaterally symmetrical..

• smart connective tissue liquifies under neural control

• ambulacral zones where tube feet emerge from body wall

• loss of cerebral ganglion

• Aboral Madreporite: A sieve-like plate located on the aboral (upper) surface that acts as the entrance to the water vascular system

Unifying traits of Class Crinoidea

• tube feet lack suckers

• madreporite absent

Unifying traits of class Ophiuroidea

• articulated arms

• no anus

• madreporite on oral side

• loss of suckers

• tube feet lack suckers

• ambulacral grves are completely closed and covered by bony plates (c/e lack of suckers on tube feet)

• tube feet are significantly reduced (small), lack suckers, and function primarily as sensory organs that detect light and odors instead of locomotion

Unifying traits of class Echinoidea

• moveable spines used for defense, locomotion, and camouflage.

• Aristotle’s Lantern: Most echinoids feature a complex, five-toothed chewing structure located on the underside of their body for scraping algae and food

• fused calcium carbonate plates forming a test

• tube feet with suckers

• presence of an anus

Unifying traits of the class Holothuroidea

• retractable oral tentacles

• internal madreporite

• reduced endoskeleton

• elongated body

• Many can eject sticky filaments or expel their internal organs (evisceration) as a distraction when threatened

• can regrow digestive tract

how are sea urchins and sand dollars related

have no split appendages so tube feet are on the outside of ball/urchin (sand dollars appendages are just squished)

A unique trait of echinoidea is that they are negatively phototaxic meaning they

move away from light to avoid predators

Traits of Eukaryotes

linear DNA, endoplasmic reticulum

How do tube feet and appendages separate each class of Echinodermata

• Asteroidea

  • tube feet: along ambulacral grove, oral side (which is aboral), suction cups on end for locomotion

  • appendages: small, snapper-like, jaw-like structures called pedicellariae on the skin surface, used to keep the surface clear of debris and small settlers

• Crinoidea:

  • tube feet: Located on the pinnules (side branches) of the arms and are used solely for feeding

  • appendages: feathery arms are lined with extensions called pinnules.Feather stars have small, flexible, hook-like appendages called cirri at their base, allowing them to cling to the substrate or move around

• Ophiuroidea:

  • tube feet: pointed, tentacle like projections that lack suction cups. Used for feeding

  • appendages:often have movable spines along their thin, jointed, snakelike arms to help anchor in crevices

• Echinoidea:

  • tube feet:end in suction cups for climbing and holding onto surfaces

  • appendages:They possess numerous long, movable spines articulated on the test, which are used for protection and locomotion

• Holothuroidea:

  • tube feet:tube feet on the dorsal side are reduced, while those on the ventral side are used for crawling

  • appendages: tube feet surrounding the mouth are highly modified into feeding tentacles (ranging from 10 to 30) that catch food particles in the water or deposit feed on the sand.Some species can expel sticky threads called Cuvierian tubules from the anus for defense

Draw and Label Asteroidea Anatomy

Draw and label Asteroidea larva

Draw and label arm anatomy of adult Asteroidea

Identify

Crinoidea

Identify

Crinoidea

Identify

Asteroidea

Identify

Ophiuroidea

Identify

Echinoidea

Describe this image

tube feet and clamer claw have allowed an echinoidea to grab objects and use attach them to its body for protection

Identify

Holothuroidea