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GastrotrichaPresented by:

Kalana Rupasinghe Jilllian SavoyJames Schumacher

Taxonomic GroupingKingdom Animalia

Phylum Gastrotricha

Class Gastrotricha

Order Macrodasyida Chaetonotidae

Gastrotricha Structure and AnatomyIntestinal Track:Structure in which consumed minerals are broken down into vital nutrients before secretion.Anus:Small opening in which waste is excreted as very small castings.Spiny Bristles:Thorny structures used as a means of intimidation as well as being about to grapple to objects as a means of locomotion.Esophagus:Tube-like structure in which mineral foods pass from the mouth to the intestineUsually less that 1mm, rarely up to 3mm.Salivary Gland:Secretes sticky acidic substance used to breakdown the small foods that it consumes.

3Gastrotricha - DietGastrotricha are very small marine flatworms that will feed on small organisms or materials, such as:Blue or Green AlgaeProtists- Slime molds, amoebas, planktonsUnicellular Algae- ChlorellaBacteria- algae, and other such bacteriaDetritus- Decomposes dead matter

EnvironmentCommonly 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

EvolutionLittle is known of the evolution of gastrotricha, but recent research did come to lightOver 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 evidenceMorphologically belong to a protostome (clade) that consist of other phylum's based on molecular evidence: Nematodes + Nematomorpha + GastrotrichaThe common ancestor that the protostome arose from, is debated from either free-living turbellarian flatworms or coelomatesAlly themselves with lophotrochozouns based on SSU rRNA sequences

Gastrotricha

NematodaNematomorphalophotrochozouns

Evolution (Cont.)Being more closely related to the phlum nematoda, what differs between them can be seen in their embryonic stagesGastrotrichas cell cleavage results to being radial holobolistic patternNematodas cell cleavage results to being spiral holobolistic pattern

Reproduction: Marine SpeciesMarine 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 timeNo larval stage; hatch as small Gastrotrichs and reach sexual maturity within 2-3 days

Reproduction: Freshwater SpeciesFreshwater species are mostly parthenogenic; all functionally female (asexual reproduction)

Produce two types of eggs:- The quick-to-hatch egg(1-4 days) also seen in marine species- A tougher overwintering egg that can withstand extreme temperatures, allowing it to exist in unstable environments

Order: Macrodasyida310 species; 6 familiesMainly marine (and hermaphroditic)Elongate bodyA complex distribution of adhesive tubesMyoepithelial pharynx with inverted Y-shaped lumenPresence of pharyngeal poresCellular epidermis surrounded by a soft cuticleInternal circular musculature

Order: ChaetonotidaeUniform 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 environmentsCan 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

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See references

ReferencesBalsamo, Maria, Jean-Loup dHondt, 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.

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