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CSU / Botany / BZ 212 / What are the characteristics of xenaxoelomorpha?

What are the characteristics of xenaxoelomorpha?

What are the characteristics of xenaxoelomorpha?


School: Colorado State University
Department: Botany
Course: Animal Biology-Invertebrates
Professor: Corey adam handelsman
Term: Fall 2017
Tags: invertebrates
Cost: 50
Name: BZ 212; Invertebrates Midterm 2 Studyguide
Description: Has a table of the phylum's with common notes, then a full set of detailed notes for all the lectures.
Uploaded: 10/16/2017
16 Pages 193 Views 4 Unlocks

Phyla General Body Plan Support and Locomotion Feeding and Digestion Circulation and Gas exchange Excretion and Osmoregulatin Nervous system and sense organs Reproduction and development Unique Attributes  

What are the characteristics of xenaxoelomorpha?


Triploblastic: cephalization  

and specialization

Musculature and cilia. Has  

circular, diagonoal,  

Circulatory system arised  

from the mesoderm.  

Incomplete digestive  

system. Eats protists,  

Excretory system arised  

from the mesoderm.  

Complete Gut condensed and innervated muscles  Lack excretory organs, so  

Produces assexually through  fission and budding. Gets two  

Xenaxoelomorpha Small, flat marine worms Flat worms. Triploblastic,  

longitudinal, crossover, spiral  and U-shaped muscle fibers

algae, crustaceans, and  larval worms

What are the characteristics of platyhelminthes?

Gas exchange occurs throuhg  diffusion

No specialzied organs and  lack a circulatory system, but  

excretion occurs throuh  diffusion  

Has a cerevral ganglion and 3-5 pairs of  longitudinal nerve cords.  

offspring from fissioning. Also has  sexual reproduction and are  simultaneous hermaphrodites.

sprial cleavage, except in  

parasites. Hermaphroditic.  

Not clearly a  

protosotome or a  deutersotome  We also discuss several other topics like Is ethnicity a biological concept?

non-segmented, bilatteral,  acoelomate,soft-bodied and  dorsoventrally flattend.  

Free living: circular,  

longitudinal and dorsoventral  muscles. Basement membrane  

Complex and complete  

some have hemoglobin. Have  a gastrovascualr cavity and  use diffusion. Endoparsites  

What are the characteristics of chaetognatha?

Reproduce asexually and  sexually. Have a Moller's larva.  Penis fencing. Parasitc flatworms  

Platyhelminthes Chaetognatha

Cephalized. Parasitic: have a  tegumetn with spines  

Body has a head, trunk  segment, and tail segment.  It is covered in a cutivel and  seperated by septa  

Acoelomate. Cuticle covers  body. Has a pair or more of  protonephridia. Has a head  Don't forget about the age old question of How do you find the basis of a vector space?

and cilia. Parasitic: hooks,  adhesive organs, scolices/

No circular muscles. Uses  lateral and caudal fins for  locomotion and stability. Also  is supported by hydrostatic  pressure, collagenous  

basement membrane, and  body wall musculature  

Central cilia. The cuticle  provies protection and rigidity.  Because it is acoelomate it has  hydrosatic support. Moves via  muslces, cilia and adhesive  

gut. Gut can be branched.  Have a pharynx.  

Is an ambush predator.  Has cuticular teeth and  and a mouth. Grasping  spines, neurotoxins from  

vestibular glands, and  digests via a linear  

complete gut

Feed on organim material.  Pump food into complete  cut with a muscular  

pharynx. Digestion and  absorption occur via  

can use anaerobic  


Circulation: hermal system  with sinuses. Gas exchange  and excretion occurs through  diffsuion through the  We also discuss several other topics like How do you get unconscious?

epithelium  Don't forget about the age old question of What is a non superimposable mirror image?

Circulation and gas exchange  

Have protonephridia and  flame celsl

The prtonephridia reomve  metabolic waste.  

Free living: ladder-like nervous system.  Cerebral ganglion. Aurcles

Has ciliary fence receptors that sense  movement in the water. Ventral and  dorsal cerebral ganglion. Paired posterior  nerves to eyes and cilia

Dorsal cerebral ganglion. Has longitudinal  nerve cords. Ringlike commissure around  pharynx. Also has cilia to sene it's  

have secual reprodcution,  

oncomiracidium larva, and  

sometiems an intermediate host

Paired reproductive organs.  

Seminal vesicles in tail coeloms.  

Internal fertilzation. Different  

species have embryos, eggs,  

marsupial sacs. Hermaphroditic  

but protandrous Protostome  

Can reproduce through  

parthenogenesis or sexual mutual  

cross fertilzation. Their  

development is holoblastic  We also discuss several other topics like What are some truths about texas?


and a trunk


intestin. Cuboidal cellw  have a brush border

Uses chemotaxis to chase  prey. Their proboscis uses  the chemical trey of the  prey to sent them. Some  

occur via diffusion throuh the  body wall.

Osmoregulatses in  

hypoosmotic environments

environment and some species have  ocelli.  

cleavage, but not spiral, and hatye  have direct development

Mouth near cerebral  

ganglion. Has acoleomate  and coelmate characteriscts.  Acoel: mesenchyme and  protonephridia. Coel: clsoed  

Lacks rigid support structures.

inject stylets or toxins into  the prey and eat them  whole. Has a complete  gut. Regional cephilzation.  Ciliated digestive tube.  Gland and nucus cells.  

Asexual: regeneratoin and  fragmentation. Can make multipl  fissions. Sexual: variable, but  most species are gonochroistic  and gonadal develpmbent occurs  If you want to learn more check out What are the three components of the quebec legal system?


circulatory system and  rhynchoceol  

Bilaterally symmetrical,  

Moves with muscle and body  wall. The mesenchyme has  hydrostatic properties

Cilia and musculature  move the food. Has 2-step  digestion  

Closed circulatory system.  Has the Lacun: thin walled  space or cavity.

Has flame bulb  

protonephrida Has nerve spots and cephalix slits

along the body . Can have direct  or indirect deveolpment. Indirect  develpment has a Pilidium larva  


Visceral Mass, and mantle Muscular foot Complete gut, radula on  

coelomate protostomes.  


Introduction of the Bilateria and the Phylum Xenacoelomorpha -Oldest living bilaterians  


All metazoans have eukaryotic cells

A: True

B: False

Tissues evolved before the Metazoa

A: True

B: False

All Triploblastic animals exhibit bilateral symmetry at some point during their life

A: True

B: False

Prokaryotes to modern animals

3 Key innovations

1. Evolution of the eukaryotic cell

2. Emergence of the metazoa

3. 3rd germ layer coupled with bilateral symmetry  

These three innovation explain most of the animal biodiversity  

Strong evidence that Bilateria is a monophyletic clade  

-synapomorphies that we see are symmetry, cephalization, and body with circular and  longitudinal musculature (3rd germ layer)

Triploblastic animals

-3rd germ layer allowed for cephalization and specialization

 -circulatory system, excretory, cynamic gonads all arise from the mesoderm  -facilitated a condensed nervous system and innervating the muscles  -triploblasty came with bilateral symmetry . This resulted in  


 -complete gut

 -excretory organs

Basal Bilaterian


 -small, direct-developing, unsegmented, ciliated worms

 -lack a coelom

 -filled with mesoderm  

 -lack circulatory system

 -have parallel longitude nerve cords

Xenacoelomorpha is the sister group to Nephrozoa

Based on the figure below, the Xenacoelomorpha are likely to have many  synapomorphies that are shared among the…

A: Cnidaria

B: Deuterostomia

C: Protostomia

D: Bilateria  

Protostomes: Mouth formed first from the blastopore

Deuterostomes: Anus formed first from the blastopore

 -old terms that date 100 years ago. Doesn’t hold well for determining relationships for  protostomes. Pretty good for deuterostomes


Synapomorphy: central nervous system with dorsal cerebral ganglion



Protostomia and Deuterostomia

-clades are now based on molecular phylogenetic evidence

-morphological and developmental synapomorphies defining these claseds remains  ambiguous  

Phylum Xenacoelomorpha

-small flat marine worms

-incomplete digstive system

-lacking excretory organs

 -subphylum Acoelmorpha

 -Class Acoela

 -Class Nemertodermatida

 -subphylum Xenotrubellida

Class Acoela

-tiny worms

-move in between sediments feeding on bacteria  

-some have photosynthetic symbionts. Could be diatoms or algae

 -some of the symbionts are acquired through feeding, other through vertical  transmission where the symbiont is passed from parent ot offspring

Body Plan

-covered in cilia

-no extracellular matrix that binds the epidermis

-rhabdoid glands produce mucus and allow them to glide with the cilia  -have statocyst

-apical organ  

-sagittocyst: used for prey capture and reproduction

Support and locomotion

-musculature + cilia = movement

-muscle fibers crisscross the body and allows them to expand, contract, and force food  in many different ways  


Eat protists, algae, crustaceans, larval worms

-glide over prey and cover prey in mucus and cover their body around the prey -avoid dead material, this means they pursue life prey

Rely on diffusion for gas exchange and excretion  

Nervous system and sense organs

-cerebral ganglion: cluster of nerve cells

-3-5 pairs of longitudinal nerve cords  

-peripheral neurons

 -epidermal sensory cells

 -anterior light-sensitive cells  



 -both fission and budding  

 -unlike what we’ve seen in other organisms

 -transferous fission. When it reaches a butterfly stage, it goes through longitudinal  fission and two individuals reproduce  


 -more common


 -pierce epidermis of mate and release sperm: 2 individuals can inseminate each  other

No larva stage → direct development  

Not clearly Deuterostome or protostome

-has radial cleavage up through the 4 cell stage and there are rotations after the 4 cell  stage

 -blastopore does not from the mouth: possible this was the origin of the protostomes  

Class Nemertodermatida

Anterior statocyst has 2 statoliths

-bodies covered in cilia  

-reproduce sexually

-similar to Acoela, but there is still unknown about their nerbous and repdoctuve system -has a proboscis: elongated head of the animal

 -muscular pharynx that protrudes the proboscis

 -proboscis can be retracted

-live in fine sand

Subphylum Xenoturbellida

-simple nervous system  

-not well studied: not much known  

-similiar locomotion to subphylum Acoelomorpha


Acoeomoprhs represent a shift frokm the readiats (Cnidear, Ctenophora) in that their  nervous system is…

A: not cephalized and nonspecific  

B: not cephalized but highly specialized

C: cephalized and associated with specialized neurons

D: cephalized but lacks concentrations of nerve cells (ganglia)

Phylum Platyhelminthes



-dorsoventrally flattened

-range in size can be up to 30ft long  

-can be parasitic  

-spiral cleavage (except the parasites)






-complex, complete gut → still one opening → gastrovascular cavity  -cephalized



Phylum Platyhelminthes

 Subphylum: Catenulidea

 Subphylum Rhabditophora

 Class Acenstrosomoata: parasitic flatworms

 Cohort Trematoda: monogenean, liver and blood flukes

 Superorder Digenea

 Cohort Monogenea

Body plan


-bilateral symmetric

-plumbing: organ and organ systems that are elaborate that we haven’t seen before   -more nerves than previous groups

 -branched digestive system

 -body gets support from lots of mesoderm: precise locomotion and muscle  contractions  

-Active lifestyle  

-Don’t have a circulatory system: provides some constraints  

-Flat body: diffusion → maintain high surface to volume ratio

 -have issues with ionic balance, osmoregulation, and desiccation because of a flat  body

 -can live in damp terrestrial environments


Body wall

-epidermis complex



-basement membrane: extracellular matrix  

-circular muscles

Parasitic Platyhelminthes

-specialized structures

-some don’t have complete guts

-oral suckers, some have hooks

-special attachment organs to attach to parts of the host

Body wall of parasitic flatworms

-robust outer covering

-comprised of protective outer surface to protect from digestive enzymes -some have spines as reinforcement structure

-longitudinal muscles

-pinocytocic vsicles: collect resources from the outside and bring it into the organsim  Cestodes

-have a scolex: attach to intestine of host

-proglottids: absorbs energy from host  

Support and locomotion

-ventral cilia

 -cilia powered gliding

-pedal waves: muscular undulations  

-du-glands, releaser gland, and adhesive gland

 -biological glue is secreted to attach. Some muscles break this secretion so they can  continue to move along  


REading assignment 2 postponed until after exam. Will post on 10/20

Exam will cover







Review guide will be psoted on 10/13


What was a key innovation in the evolution of modern animals? A: the 3rd germ layer

B: the acoelomate condition

C: Neurons

D: Gastrulation  

Which phlum is definetly a bilaterian but does not alighn with protostomes or  deuterostomes?

A: Platyhelminthes

B: Ctenophora

C: Cnidaria

D: Xenacoelomorpha

What is the external protective covering exhibited by flukes and tapeworms? A: Prohaptor

B: Tegument

C: epidermis

D: basement membrane

Support and locomotion on Parasitic Platyhelminthes

Dignean Fluke

-oral sucker



-has a scolex

-can have varying shapes

Onogenean fluke

-Buccal sucker

-Opisthaptor: posterior succker, primary source of attachment Lack ventral cilia

What structures would you expect to find in all parasitic platyhelminthes? A: an intestine

B: attachment organs

C: locomotor ventral cilia

D: specialized cephalic sensory organs  

Feeding and Digestion

Free-living flatworms

-predators or scavengers

-use pharynx to feed and is the only opening into the gastrovascular cavity  -cilia sweep food into the pharynx

 -different pharynx structures

 -can be reversible

 -can be inverted

 -use body to force food into the pharynx  

-guts vary

 -can be simple, tribranched, or multi-branched gut

-retractro muscles can pull pharynx into the gut

-specialeds cell are in gut and enxymatic lgand cell secretes enxaymes to break down  nutrients and the Phagocytic nutritive cell take up the broken down protiens and further  break them down intracellulary in food vacuoles  


Smaller free-living flatworms are likely to have a ...gut, while the largest sflatworms are  likely to have a ...gut

A: tribranched; multibranched

B: mulitvranched;saclike

C: tribranched; saclike

D: saclike; multibranched  

If you large, it is difficult to transport nutrients thorugh diffuiosn, which is why htey are  multibranched beause it increases he surface area

Parasitic flatwomrs

-feed on host tissue of hose fluids

Monogenean fluke

-oral xucker

 -pharynx and mouth have muschles to “pump” and bring fluid into the mouth  Cestodes: abandon a digestive tract

 -fill body with reproductiv eorgans and absorb nutrients from the host  -absorb nutrients acrosss the tegumnet  

Circulation and GAs Exchange

-No specialized organs

-lack circulatory system

 -some have hemoglobin

-Gastrovascular cavity and diffusion  

-endoparasites capable of anaerobic metabolism  


-metabolic waste will leave mostphy by diffuion, but also by protonephridia -protonephridia: seen in othe rgroups as well

 -used for osmoregulation

 -specialized organs of flame cells.

 -protonephridia poor that goes through epidermis

 -flame bulb are like ciliated canals, and the cilia collect thign sthat need to be  exvreted and send stuff to the nephridiopoere  

Parasites excretion

-protonoephridia are found in nearly all flatworms  

Nervous system

-vary from simple to nerve net to lakker-like nervou system

-ladder -like nerbous systme

 -paired lateral nerve cords that run ventrally and dorsally

 -transvers commissure that connect the dorsal and ventral nerve cords  -cebreal ganglion  

-anteriory sensory organs htat are little more sophisticated

 -auricles: protude from the head


 -allow the flatworms to orinate themsleves and track down prey  -optic nerve: run from cebeal ganlgion  

 -ocellus: eye spots

Parasitic flatworms nervous system

 -nervous system reduced becasue not as neccessary for their sednetary life  -neurons associated with the sucker

Reproduction and development of free-living flatworms


 -fission planes  

 -regenerate and generate copies of itself  




 -mating usually occurs through mutual cross fertilization

 -cirrus: male repoductive organ

 -after cross fertilization, some lay egg capules and others partially develop th elarva  inside them

 -some undergo a larva stage

 -Mueller’s larva: undergo metamorphosis and is free-living  

 -penis fencing

 -hypodermic fertilization

 -don’t want to bear burdern of reproduction  

Reproduction and development of parasitic flukes

 -hermaphroditic and cross-ferlizaton

 -usually don’t self-fertilize  

 -high fecundity and high mortalitytand complex life cycles  

 -produce up to 100,000 more eggs as free-living species

 -some have to have an intermidate host

-need ot know life cycles fo rlab bu tnot for lecture  

 -every proglotid is capable of reproducing

Parasitc Helminths an dHuman Health  

-micro and macro organism play a criticla role in dribing immunoregulation  -”old friends: exposure to microbes and other organims during critical phases of human  devleopment  

 -alergies are rare among farmers

 -urban living reduced contacts of humanes with microbes and worms and lead to  more people being susceptible to sclerosis , diabetes, and allergies  -it is belived that there is a disruption in immunoregulatory circuits, likley reflecting  reduced exposures to “old friend “ organims with hich humans coevolved  -clinical trails are testing these concepts

 -can renewed old friends restore immune systmes

Microbes and helminths compete with each other and blaance each other out  

Enigmatic Protostome Phyla

 Chaetognatha and Gastrotricha  

-Polytomy: related in some way but we really don’t know whn and where they started  divergin and why

-Chaetognatha mya be a sister group/taxa of protostomes or basal protostomes. Could  be the ancelstra state of Spiralia  

 -have protosotme like affinity, but don’t know where they lie and aren’t really a  protstome

Phylum Chaetoagnatha

-”Bristle Jaws”

-typically marin, planktonic and predatory

-not deuterostomes nor a sister group

 -more affiliated wiht protostome

-ecologiclaly important

 -feed copepods and small zooplankton  

-date back to carbonifeous peried 20 mya

Body Plan

-Lateral and caudal fins for locomotion and stability

-externally, have bilateral symmetry  

-body covered in cuticle

-body divided by septa

-no circular muscles  

-cilia don’t beat but do sense movement in water and help orinatate the Chaetoagnatha  -translucent

-spend time motionless in water column  



-vestibul/opening: mouth position back of vestibule

-hood can be drawn over the head for streamlining

-grasping spines and cuticular teeth used for prey capture and food handling  


-mouth connect to long intesting that terminates at the trunk

 -complete digestive system  

-ovaries are also in the trunk

-seminal vesicle is in the tail: seperation of female and male organisms

Support and locomotion

Support: hydrostatic pressure

 -coelomanic cavity

 -collagenous basement membrane

 -body wlal mulculature  

 -Septa: 2 coeleom  

-Tripartite coelom  


I-clicker question

All Bilateria are triploblastic

A: True

B: False

Which of the following can be considered synapomorphies in all protostomes? A: schizocoely; spiral cleavage

B: enterocoely; radial cleavage

C: a central nervous system with dorsal cerebral ganglion

D: a mouth that arises from the blastopore during embryonic development E: trimeric coelom; gill slits  

Enterocoely and Schizocoely are developmental processes that give rise to A: the formation of the epidermis and cuticle

B: the endodermis and gut

C: a fluid filled cavity

D: the acoelomate condition

E: the mesodermal germ layer and musculature

Chaetognath Body Plan

-Cuticular teeth: can pierce prey and insert venom  

-Cilia are not’ used for movement, are used for detecting movement in the wat -tail fin used for stability when they swim  

-intestine runs from the mouth to the anus  

Support and locomotion

-Swim by contracting the longitudinal muscles in the body  

-fluid filled coelom and hydrostatic skeleton  

 -undulate through the water  

-basement membrane of the epidermis is full of collagenous fibers -Septa divide the organsim, you end up with a right and life coelom compartment:  tripartite coelom

-1:2:2 tripartite coelom

 -1 coelom in head, 2 in trunk, 2 in tail

Feeding and digestion

-ambush predators  

-motionless in water column

-ciliary receptors sense movements

-Grasping spines

-Neurotoxins from vestibular glands  

 -slow or paralyze prey while they try and shove them in the mouth -digestion via linear complete guy

 -extracellular in gut lumen  

Chaetognath Behavior

-diurmanl movments

 -close to the surface there’s not a lot of them

 -as time goes to noonto night the amount of chaetognaths increase  -feed mostly on copepods  


Hemal system with sinus

 -fairly primitive

 -sinuses intween between intestine

 -allow nutrients to flow through the musculature  

Gas exchange and excretion

 -diffusion through epithelium

 -not much specialization

Nervous system and sense organs

-ventral ganglion

-dorsal cerebral ganglion

-paired posterior nerves to eyes and cilia  

-eye spots: perceive light

-cluster of cilia that are associated with ventral nerves that are going to run ot he ventral  ganglion  


-Spatial separation of male and female structures

-structures are paired

-developing eggs, oviducts in the trunk

-testis are in the tail

-sperm develop in the tial and will congregate in a sperm mass  

-internal fertilization  

-hermaphroditic but protandrous: male reproductive structures form first, which avoids  self-fertilization  


-deposit eggs on substrate

-some species shed egg capsules  

-some broups will brood the eggs through maturation  

-used to be grouped with deuterostomes, but are actually protostomes  -neither the mouth or the anus from from the blastopore  


Considering chaetognath embryology and molecular evidence that they represent basal  protostomes or an early branching phylum with protostome affinity,  A: secondary formation of the mouth is a synapomorphic deuterostome characteristic B: secondary formation of the mouth is a plesiomorphic of the Bilateria  Plesiomorphy is ancestral

C: secondary formation of the mouth arose independently multiple times in the Bilateria D: secondary formation of the mouth evolved after the Deuterostomia diverged from the  Protostomia  

-All the Deuterostomes show the same characteristic, which would be plesiomorphic

Phylum Gastrotricha  

Marine, brackish and freshwater

-Cuticle covers body

-Functionally acoelomate

 -densely packed mesoderm

-duo-gland adhesive tubes

-Ventral cilia >1 pair of protonephridia  

Order Chaetonotida

-primarily freshwater

-syncytial epidermis  

Order macrodantin

-primarily maine

-cellular epidermis

Body Plan Chaetonotida

-adhesive tubes

-bowling pin body structure

-divide body into a head a trunk

-adheisve tube

Body Plan Cacro Doshida?

-more tubular shape

-internal structure similar to Chaetonotida

Support and locomotion

-acoelomate construction: hydrostatic support

-cuticle: protection and rigidity

-move with muscles, cilia and adhesive tubes

Feeding and digestion

-feed on nearly any organic material  

-pump food into guys with muscular pharynx

-complete gut

-digestion and absorption via intestinal

-cuboidal cells with brush border  

Circulation and Gas Exchange

-protonephridia: remove metabolic waste

-osmoregulation in hypoosmotic environments

 -big deal in freshwater

-diffusion through body wall

 -fusional distances small becaue organsim is pretty flat

Nervous system and sense organs

-dorsal cerebral ganglion (brain)

-Longitudinal nerve cords

-ringlike commissure around pharynx

-cilia around head and body  

-ocelli: eyepsots for photosensitivity  

Reproduction and development

-fairly complex

- most species reproduce sexually through mutual cross fertilization  -each one is outcrossing and rearing offspring



-poorly studied

-Cleavage holoblastic but is not spiral

-direct development, aka not larval form  

PHylum Nemertea: Ribbon worms

-functionally acoelomate, but have two coeloms

 -used to be associated with platyhelminthes

 -actually more closely related to eh molluscs and annelids  -morphological structure

-complete gut

-closed circulatory system

-unsegmented worms


-dorsoventrally flattened  


-most are in the Nemertean

-proboscis armature

-layering of body wall musculature

-position of longitudinal nerve cords  


What characteristics are associated with the acoelomate condition? A: closed circulatory system

B: complete through gut

C: mesenchyme/parenchyma

D: metanephridia  





 Closed circulatory system


Body Plan

-Peidermis, dermis, Nesenchyme and Rhyncocoel

-Above the gut you have the provusics and the rhyncocoel  -rhynchocoel is a true coelom  

-ciliated epidermal cell

-gland cell

-sensory cell  

-mucus gland cell  

Support and Locomotion

-Lack rigid support structures

-muscle and body wall, hydrostatic properties of mesenchymal  -proboscis can be used for predator evasion

Feeding and digestion  

-Chemotaxis utilized to pursue prey

 -proboscis scents prey and then wraps around prey  -use stylets to pierce prey, some use toxins  -ingest prey whole


-elongated reversible tube associated with the foregut  -contains tubes, musculature and hydraulic system   -controlled by retractor muscles  



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