Aisha Muhammad
Phylum Gastrotricha
“Stomach
Hair”
or “Hairy Belly”
General
Characteristics
o
Aquatic worms
o
Cilia on ventral
surface of head and trunk
o
Bilateral symmetry
o
Forked tail for
toes/feet
o
Acoelomate
o
Complete gut with
anus
o
Cuticle with
numerous scales and spines
o
Nervous system with
ganglia
o
No circulatory
system
o
Marine or freshwater
habitats
o
Range 0.5mm to 4mm
in size
Are Gastrotrichs important?
To most people, Gastrotrichs probably seem unimportant. However, to
aquatic systems they are very important. Gastrotrichs consume various bacteria,
microalgae and protozoans; and serve as food for larger organisms. Gastrotrichs
also play a vital role in researching the origin of pseudocoelomates,
the history of life and the connectedness of organisms.
G A S T
R O T R I C H A
The Phylum Gastrotricha
is made up of 765 species. Organisms in the Phylum Gastrotricha
can be identified easily by their defining characteristics. Like their name
suggests, the Gastrotrichs appear to have a “hairy belly”. Their ventral
surface is covered in cilia especially the head and trunk. The four tufts of
beating cilia on the head pull in organic matter for the animal to consume.
Their bodies are elongated and flattened and have a forked tail for the
toes/feet. They have adhesive tubes
that aid in attaching to vegetation or other substrates. Depending on the
species, Gastrotrichs can have anywhere from 2-250 adhesive tubes. Gastrotrichs
are functionally acoelomate; but have a complete gut. They have no gas exchange
or circulatory systems; although some species have protonephridia.
Gastrotrichs have a nervous system comprised of a small brain (ganglia) and a
pair of longitudinal nerve cords.
Life cycle and
Reproduction
Members
of the Phylum Gastrotricha are either female only or hermaphrodites.
Freshwater species tend to be all female. They produce a tough egg that will
experience such conditions as drought or excessive heat or excessive cold in
order to hatch. This is so the species will be able to survive in an unstable
environment. A second egg type will hatch almost immediately which will be a
small Gastrotrich.
Marine species tend to be hermaphrodites with only one set of
gonads functional at a time (meaning that each individual is either
functionally male or functionally female). A functional male Gastrotrich
transfers sperm to a functionally female Gastrotrich via a spermatophore.
There
is no larval stage. The young hatch out and feed and grow quickly and may reach
sexual maturity in as little as 2 days. The average life span of a Gastrotrich
is very short, about 3 to 21 days.
Taxonomy
The exact taxonomy of the Phylum Gastrotricha
is as follows:
o Kingdom: Animalia
o Subkingdom: Eumetazoa
o Superphylum: Platyzoa
o Phylum: Gastrotricha
Under the Phylum Gastrotricha, there is the Class Gastrotricha
and there are two Orders, both with seven Families:
o Order Macrodasyida
(310 species)
·
Family Dactylopdolidae
·
Family Lepidodasyidae
·
Family Macrodasyidae
·
Family Planodasyidae
·
Family Thaumastodermatidae
·
Family Turbanellidae
·
Family Xenodasyidae
o Order Chaetonotida
(455 species)
·
Family Chaetonotidae
·
Family Dasydytidae
·
Family Dichaeturidae
·
Family Neodasyidae
·
Family Neogosseidae
·
Family Proichthydidae
·
Family Xenotrichulidae
The above
organism is Dactylopodola agadasys
The taxonomy
for Dactylopodola agadasys is as follows:
o
Kingdom Animalia
o
Phylum Gastrotricha
o
Class Gastrotricha
o
Order Macrodasyida
o
Family Dactylopdolidae
o
Genus Dactylopodola
o
Species agadasys
Dactylopodola agadasys has been
reported in fine sediments around Macleay Island,
Queensland, Australia. This species is characterized by the abundant cilia
distributed around the lateral, dorsolateral and dorsal portions of the body.
The head region is distinct in juveniles but indistinct in adults.
So…WHY Gastrotrichs??
When I found out that Gastrotricha meant “hairy belly” it instantly became one of
my favorite Phyla. The name meaning something funny is what initially sparked
my interest in these animals, and it is why I chose to do my webpage on them.
As I learned more and more about them and their lifestyle I grew more and more
intrigued. It amazed me that something so microscopic was not only a free
living animal, but that it even had structures that humans have. When I
observed a live Gastrotrich it was fascinating watching it eat and swim around
so quickly. Seeing all of the cilia beating was one of my favorite things.
Going into this project my knowledge of Gastrotrichs was somewhat limited, but
I’ve learned tons of awesome information.
work cited
o
Ramel, Gordon. The Phylum Gastrotricha. The
Gastrotrichs (Phylum Gastrotricha). Web. 10 Apr.
2012. http://www.earthlife.net/inverts/gastrotricha.html.
o
Todaro, Antonio. "Gastrotricha
Overview." Gastrotricha Homepage. Antonio Todaro. Web. 11 Apr. 2012.
<http://www.gastrotricha.unimore.it/overview.htm>.
o
"Gastrotricha."
- New World Encyclopedia. Web. 10 Apr. 2012.
<http://www.newworldencyclopedia.org/entry/Gastrotricha>.
o
Hochberg, Rick. "STRI
- Office of Bioinformatics - Metas." Smithsonian
Tropical Research Institute-obio Root. Rick Hochberg.
Web. 10 Apr. 2012. <http://biogeodb.stri.si.edu/bioinformatics/dfm/metas/view/44263>.
o
Wxfix. "Gastrotrichiae." YouTube.
YouTube, 04 Dec. 2007. Web. 13 Apr. 2012.
<http://www.youtube.com/watch?v=fBJvRTs1pi4>.
o
"Smithsonian Tropical
Research Institute-Dactylopodola Agadasys."
Smithsonian Tropical Research Institute-obio Root.
Web. 10 Apr. 2012.
<http://biogeodb.stri.si.edu/bocas_database/search/species/3433>.
o
Any information not from
the cited locations above was from the lecture notes given in class.