GNATHANS

1. PHYLUM
CHAETOGNATHA

2.  General Description
 Mode of Nutrition
 Reproduction
 Locomotion
 Habitat
 Classification

3. ThenameChaetognatha (ke-tog-na-tha)comes fromthe
Greekword( Chaite– meanslongflowinghair,+Gnathos– means
Jaw)
Chaetognatha

4. PhylumChaetognatha meaningBristle-jaws.
- commonly know
n as “a
rro
w w
o
rm
s”.
Are coelomateanimalsofrelativelysmallsize,with
straight,slender,transparentbodydisplaying
perfectbilateral symmetry
.
*theyareusuallycolorless,slightlyopaque.
General
Description

6. * THE BODY IS DIVIDED IN THREE PARTS BY
INTERNAL PARTITIONING: HEAD, TRUNKAND TAIL.
- Finsonboththetailandthebody
.
- The head has eyes with photoreceptive cells,
Eachsideoftheheadbearsagroupofcurved
graspinghooksandoneortworowsofteeth.

7. *calledtheanteriorandposteriorteeth.
*thehooksandteetharemadeofchitin.
- Thetrunkbearsoneortwopairsoflateralfins
incorporatingstructuressuperficiallysimilar to
the fin rays of fish, with which they are not
homologous.
- They are generally less than an inch (2.5
centimeters)insize.

8.  Chaetognathsarecarnivorouspredators.
 These voracious meat-eaters catch large
numbers of copepods, larval fish,
crustaceans,swallowingthemwhole
.
- The largespines aroundtheir mouthhelps
them grab and restrain their prey and
immobilizethemwithneurotoxins.
Mode Of
Nutrition

9. Allknow
nChaetognathaareHermaphrodites.
* meaning they possess both male
andfemalesexorgans.
-Thefemaleorgan(theovaries)
*arejustbehindthemid-body
mark(trunk)
-Themaleorgan(thetestis)
*areinthetail
Reproducti
on

10.  The sperm mature before the ova
(eggs) which ma
y help avoid self
fertilizationtosameextent.
Fertilizationisinternalanddependingon
the species fertilized eggs ma
y be
brooded, deposited on the seafloor
, or
releasedintotheocean.

11.  Their torpedo-like body shape
allowsthemtomov
equicklythroughthe
water
.
-Chaetognatha alternatebetw
een
swim
ming andfloating.
- Thefinsalongtheirbodyarenotusedto
swim,butrathertohelpthemfloat.
- Theyusuallyswimtothesurfaceatnight
anddescendduringdaytime.
Locomotion

12. They arefoundin all marinewaters, from
surface tropical waters and shallow tide
pools to the deep sea and polar regions,
most species are planktonic, but a small
numberofspeciesareBenthic.
*about 20%, live just above the ocean
floorandcanattachtoseaweedorrocks.
Habitat

13. Chaetognatha are traditionally
classed by an (embryologist) as
De
ute
rostom
e
s and by
(phylogenists) asProtostom
e
s.
Classification
Animalia
Chaetognath
aSagittoidea
 Kingdom:
Phylum
:
Class:
Order:
Aphragmophor
aPhragmophora

14. The embryologist Lynn Margulis and
K.V Schwartz placed chaetognaths in
deuterostomes in their five kingdom
classification.
Deuterostomes - The name
deuterostomes means "second mouth."
The name is derived from the embryo
developingtheanusfirst,followedbythe
mouth.

15. The phylogenists Thomas Cavalier-
Smith placed them in the
protostomes in his six kingdom
classification.
Protostomes – means “first
mouth” embryos develop the mouth
firstandthentheanus,

16. Referen
ce
 Animaldiversity.org/accounts/chaetognatha
 www.earthlife.net/inverts/chaetognatha.html
 www.newworldencyclopedia.org/entry/Chaetognatha
 https://en.Wikipedia.orh/wiki/Chaetognatha
 eol.org/pages/1740/overview
 Species-identification.org
 www.polarlife.ca/organisms/inverts/marine_inverts/chaet
ognatha.htm