KINGDOM ANIMALIA
| SYSTEMATIC BIOLOGY |
KINGDOM ANIMALIA |
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| HOME | SYLLABUS | WEEKLY ASSIGNMENTS | J. SYSTEMATIC BIOLOGY | TAXA OF LIFE | |
| PHYLUM ROTIFERA | |||||
Rotifera (ro-TI-fe-ra) is derived from two Latin roots meaning wheel (rota) bearing (fero). The reference is to the turning-wheel appearance of the ciliary pads that surround the mouth.
The rotifers are mainly microscopic free-living aquatic organisms (marine and freshwater). They get their name from the ciliary fields on the anterior end, the motion of which appears to be paired rotating wheels (Figure A). Many are important components of the plankton (Figures B&C) or benthos (Figure A) where they occur. Some are sessile and a few are ectoparasites. Nielsen (2001) considers the Acanthocephala to be within the clade of the rotifers. He supports this by citing the following synapomorphies: the same kind of epidermis with an intracellular lamina, and similarities in the embryological development of Asplanchna (a rotifer) and Macrocanthorhynchus (an acanthocephalan). Also, he says that recent molecular studies support the relationship. However, Brusca and Brusca (2003) dismiss the relationship because the acanthocephalans have no trace of a mastax (Figure D).
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A. A bdelloid rotifer, Philodina, in a typical feeding pose. |
B. Keratella, a common planktonic form has a hardened lorica with spines. |
C. Conochilus, a planktonic colonial rotifer. |
D. A high magnification image of the anterior end of Philodina showing the mastax with its characteristic trophi. |
| Images taken from: A: http://www.ucmp.berkeley.edu/phyla/rotifera/rotifera.html B&C: http://www.microscopy-uk.net/mag/indexmag.html?http://www.microscopy-uk.net/mag/wimsmall/rotidr.html D: http://www.microscopyu.com/galleries/dxm1200/philodinarotiferlarge.html |
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SYNOPTIC DESCRIPTION OF THE ROTIFERA
| The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), and Tudge (2000). |
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I. SYNONYMS: rotifers, rotatoria. II. NUMBER: > 1,800 species known. III. PHYLUM CHARACTERISTICS: A. Structure Symmetry: Bilateral Body Cavity: Small pseudocoelom. Organ systems in parenchymatous mesoderm. Evertible proboscis in a cavity that resembles a rhynchocoel, dorsal to the intestine. Body Covering: Extracellular cuticle and an intracellular skeleton, which forms the lorica of some forms. Support: Hydrostatic skeleton. Digestive System: Complete food tube with mouth and anus. Captures food with anterior ciliary organs (coronae); breaks down the food particles with an elaborate "jaw-like chewing mechanism" (trophi) in the mastax or pharynx. Circulatory System: Absent. Locomotion: Swims with anterior ciliary organs and muscular contractions using adhesive attachments of foot. Excretory System: One pair of protonephridia. Nervous System: Anterior ganglion with 2 major nerves; with sensory eyespots, bristles, etc. Endocrine System: None. B. Reproduction: Reproductive System: Most are dioecious. Can reproduce by parthenogenesis. Oviparous. Development: Zygote develops by spiral cleavage. No larval stage. C. Ecology: Freshwater, or (less so) marine. Usually filter feeders, sometimes carnivores. Planktonic or benthic. |
HIERARCHICAL CLASSIFICATION OF THE ROTIFERA
| Taxonomy of the phylum based on the system of Ruppert and Barnes (1991) and Meglitsch and Schram (1991). Brusca and Brusca (2003) place the Seisonidea and Bdelloidea as orders under the Class Digonata, which is defined by the presence of paired ovaries. The descriptions of the taxa are taken from Margulis and Schwartz (1998), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Ruppert and Barnes (1991) and Meglitsch and Schram (1991). |
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CLASS SEISONIDEA (1 ORDER)
CLASS BDELLOIDEA (1 ORDER)
CLASS MONOGONATA (3 ORDERS)
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This page is maintained by Jack R. Holt. Last modified: 01/05/08
