Gastrotricha
Presented by:
Kalana Rupasinghe
Jilllian Savoy
James Schumacher
Taxonomic Grouping
Kingdom
Animalia
Phylum
Gastrotricha
Class
Gastrotricha
Order
Macrodasyida
Chaetonotidae
Gastrotricha Structure and Anatomy
Spiny Bristles:
Thorny structures
used as a means of
intimidation as well
as being about to
grapple to objects as
a means of
locomotion.
Anus:
Small opening in
which waste is
excreted as very
small castings.
Esophagus:
Tube-like structure in which
mineral foods pass from the mouth
to the intestine
Salivary Gland:
Secretes sticky
acidic
substance used
to breakdown
the small foods
that it
consumes.
Usually less that
1mm, rarely up to
3mm.
Intestinal Track:
Structure in which consumed
minerals are broken down into vital
nutrients before secretion.
Gastrotricha - Diet
Gastrotricha are very small marine flatworms that will feed on
small organisms or materials, such as:
• Blue or Green Algae
• Protists
- Slime molds, amoebas, planktons
• Unicellular Algae
- Chlorella
• Bacteria
- algae, and other such bacteria
• Detritus
- Decomposes dead matter
Environment
• Commonly found in marine and benthic
environments
-as such, they are huge contributors in their community
• Can be found in terrestrial areas, typically in lotic water areas.
• Notably found in organic sediment in eutrophic
and lentic biotopes.
• Also found in loose sediment or
epi-benthic, compacted into mud or
layered organisms
Evolution
• Little is known of the evolution of gastrotricha, but recent
research did come to light
• Over time, the Splanchnic muscles developed in a circular
pattern.
- Result of better digestion of prey, namely diatoms.
- Allowed better mobility
• Additionally, the longitudinal muscle and radial dilutions
developed in the gut tube
Evolution (Cont.)
• Main problem of the lack of information of
Gastrotricha is the non-existence of fossil
evidence
• Morphologically belong to a protostome
(clade) that consist of other phylum's
Gastrotricha
based on molecular evidence:
- Nematodes + Nematomorpha +
Gastrotricha
• The common ancestor that the protostome
arose from, is debated from either freeliving turbellarian flatworms or coelomates
• Ally themselves with lophotrochozouns
based on SSU rRNA sequences
lophotrochozouns
Nematoda
Nematomorpha
Evolution (Cont.)
• Being more closely related to the phlum nematoda,
what differs between them can be seen in their
embryonic stages
- Gastrotricha’s cell cleavage results to being radial
holobolistic pattern
- Nematoda’s cell cleavage
results to being spiral
holobolistic pattern
Reproduction: Marine Species
• Marine species are mostly hermaphroditic: possess both male
and female sex organs (with only one being functional at a
time)
• Sperm is transferred via a spermatophore through internal
fertilization
• Eggs are produced in small numbers at a time
• No larval stage; hatch as small Gastrotrichs and reach sexual
maturity within 2-3 days
Reproduction: Freshwater Species
• Freshwater species are mostly parthenogenic; all
functionally female (asexual reproduction)
• Produce two types of eggs:
1. - The quick-to-hatch egg(1-4 days) also seen in marine
species
2. - A tougher overwintering egg that can withstand extreme
temperatures, allowing it to exist in unstable
environments
Order: Macrodasyida
•
•
•
•
•
•
•
•
•
310 species; 6 families
Mainly marine (and hermaphroditic)
Elongate body
A complex distribution of adhesive
tubes
Myoepithelial pharynx with
inverted Y-shaped lumen
Presence of pharyngeal pores
Cellular epidermis surrounded by a soft cuticle
Internal circular musculature
Order: Chaetonotidae
• Uniform body covered with a thick layer of soft
homogenous cuticle
• Overall shape : ten-pin or bottle-shaped
• Commonly found in epi-benthic , interstitial , and
marine
environments
- Can be found in brackish estuaries
• Contained within excretory system lie
rapidly beating cilia as a way of removing
excretory waste (protonephrida)
• Under order: consist of 450 different species
Thank You for Listening!!!
And we hope you have enjoyed this
presentation!!!
See references
References
Balsamo, Maria, Jean-Loup d’Hondt, Jacek Kisielewski, and Lara Pierboni. "Global
diversity of gastrotrichs (Gastrotricha) in fresh waters." Hydrobiologia The International
Journal of Aquatic Sciences (2007). Web. 6 Mar. 2013.
Hochberg, R. "Musculature of the primitive gastrotrich Neodasys (Chaetonotida):."
Marine Biology (2004): 316-22. Web. 4 Mar. 2013.
Litvaitis, Marianne K., and Rick Hochberg. "Macrodasyida (Gastrotricha): A Cladistic
Analysis of Morphology." Invertebrate Biology 120.2 (2001): 124-35. Print.
Litvaitis, Marianne K., and Rick Hochberg. "The musculature of Draculiciteria tessalata
(Chaetonotida,." Hydrobiologia (2001): 155-61. Web. 6 Mar. 2013.
Paps, Jordi, and Marta Riutort. "Molecular phylogeny of the phylum Gastrotricha: New
data brings together molecules and morphology." Molecular Phylogenetics and
Evolution 63.1 (2012): 208-12. Print.
Valentine, James W. On the Origin of Phyla. Chicago: The University of Chicago Press,
2004. 361-78. Print.