Presented by: Kalana Rupasinghe Jilllian Savoy James Schumacher
Taxonomic Grouping Kingdom Animalia Phylum Gastrotricha Class Gastrotricha Order Macrodasyida Chaetonotidae
Gastrotricha Structure and Anatomy Intestinal 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 intestine Usually less that 1mm, rarely up to 3mm. Salivary Gland: Secretes sticky acidic substance used to breakdown the small foods that it consumes.
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 based on molecular evidence: -Nematodes + Nematomorpha + Gastrotricha The common ancestor that the protostome arose from, is debated from either free- living turbellarian flatworms or coelomates Ally themselves with lophotrochozouns based on SSU rRNA sequences Gastrotricha Nematoda Nematomorpha lophotrochozouns
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
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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.