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Keratella , like all rotifers are pseudocoelomates. This is a paedomorphic condition in which the blastocoel remains even once the animal has reached maturity. It is thought that this condition is secondarily derived Brusca and Brusca, Keratella is a footless rotifer which posesses a protective covering, or lorica.
Keratella cochlearis occur in two body forms. The tecta form exists without the posterior spine displayed by the typica form.
Generally, spines are present on those Keratella which are born in the presence of predators such as cladocerans, Asplanchna and cyclopoid copepods. The typica form can be born from a tecta mother and vice versa Gilbert and MacIsaac, Keratella cochlearis is a nearly ubiquitous species, found in almost any body of water imaginable.
Indeed, memberes of the genus Keratella are found throughout the entire world. Because Keratella is able to survive with low amounts of food, it is often found in food-poor environments which cannot sustain larger zooplankton. The small size of Keratella , however, means that its populations can be greatly impacted by the presence of predators Thorpe, The ciliated corona is the source of locomotion for Keratella ,creating the appearance of spinning which gave rotifers their name.
However, the main function of the corona is to provide the current necessary for highly efficient filter feeding. The cilia of the corona direct food particles into the buccal funnel and down into the mastax where they are crushed by the trophi. This feeding mechanism allows Keratella to eat a variety of shapes and sizes of food, primarily consisting of phytoplankton such as Cryptomonas and Chlamydomonas Bogdan and Gilbert, Reproduction of rotifers is generally achieved parthenogenetically.
For this to occur, the female produces a 2n egg via mitosis which will then hatch into a 2n clone of the mother. A noticable feature of the cloning of Keratella is the fact that the offspring may vary in body form from that of their mother.
Sexual reproduction occurs periodically in response to unknown stimuli. In sexual reproduction the female undergoes meiosis and produces 1n eggs, some of which hatch into 1n males.
These males then undergo mitosis to create 1n sperm which will fertilize a 1n egg. The fertilized egg will hatch into a 2n female and sexual reproduction will be complete. Figure 1. The lorica and posterior spine of this typica form of Keratella cochlearis offer a measure of protection against predators. Bogdan, Kenneth G. Seasonal patterns of feeding by natural populations of Keratella, Polyarthra, and Bosmina : Clearance rater, selectivities and contributions to community grazing.
Limnology and Oceanography v27 5 Brusca, R. Sinauer Associates, Inc. Sunderland, Massachusettes, USA. Gilbert, John J. The susceptibility of Keratella cochlearis to interference from small cladocerans. Freshwater Biology v22 pp Thorp, J. Ecology and classification of North American freshwater invertebrates. Academic Press, Orlando, Florida. Growth and Reproduction Reproduction of rotifers is generally achieved parthenogenetically.
Keratella cochlearis Figure 1. Figure 2. The ciliated corona directs food into the gut tract. Figure 3. This Keratella is carrying an egg. Works Cited Bogdan, Kenneth G.
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Rotifer Symposium V pp Cite as. Vertical distribution of the rotifer Keratella cochlearis in stratified water columns of mesotrophic and eutrophic lakes during summer stagnation has been studied. Coexisting morphs K. The distribution of morph abundance and reproductive potential indicate that substitution of morphs within the vertical water column may be due to trophic conditions. The maximum population productivity is observed at the epi-metalimnion border. The maximum density zone lies below the zone of the highest productivity.
We'd like to understand how you use our websites in order to improve them. Register your interest. Rotifers are ubiquitous freshwater animals for which many complexes of cryptic species i. Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region Italy and investigated mitochondrial genetic diversity in K. We sequenced the mitochondrial cytochrome c oxidase subunit I and used the generalised mixed Yule coalescent approach, Poisson tree process model and automatic barcode gap discovery to delimit mitochondrial groups, associated with putative evolutionary significant units ESUs. Based on sequences, eight putative ESUs were indicated that could only partially be delimited by lorica morphology.