Dileptus
Encyclopedia
Dileptus is a genus of unicellular ciliate
protists, belonging to the class Litostomatea
. Members of the genus are found in fresh and salt water. Like most of the free-living Litostomes, Dileptus is an aggressive predator, carrying an arsenal of toxin-bearing trichocyst
s (toxicysts) in a prehensile proboscis, with which it stuns its microscopic victims before consuming them.
Dileptus was first seen and described by O. F. Müller
in 1773, who reports having found the creature "in water where duckweed dwells" ('"in aquis, ubi lemna hospitatur"). He describes the organism in detail, recording its sharp posterior and its "long neck," which has a tendency to assume a spiral shape. The species Müller named Vibrio anser is generally understood to be a synonym of Dileptus anser
. In a later work, Animalcula Infusoria, published posthumously in 1786, he repeats the earlier description of the creature and adds several illustrations of it
Dileptus has become a model organism, used in the study of ciliary patterns, ontogenesis, conjugation and food acquisition
In 1841, M. Félix Dujardin created the genus Dileptus and moved Müller's Vibrio anser to it. By the time a full revision of the genus was published in 1963, the genus included about 50 species.
In 1974, John O. Corliss proposed the order Haptorida, to which Dileptus has generally been assigned under the subclass Haptoria.
However, in 2006, Strüder-Kypke et al. published the results of a molecular analysis of the Litostomes, which indicated that Dileptus is genetically, as well as morphologically, distinct from other Haptorian ciliates, and that they are, in fact, phylogenetically basal
to that group.
Recent research, combining genetic analysis with a study of physical characteristics (morphology), suggests that the Dileptids and their sister clade
the Tracheliids belong in a subclass of their own. For this purpose, Vd'ačný et al. resurrect a subclass of Litostomatea first proposed by the Russian researcher A.W. Jankowski in 1980: Rhynchostomata, which they amend to Rhynchostomatia.
As a result, the class Litostomatea, which previously had two recognized subclasses, now has three: Haptoria. Trichostomatia and Rhynchomstomatia.
In addition, the authors of the study divide the order Dileptida among two families: the Dimacrocaryonidae, most of whose members have a double macronucleus, and the Dileptidae, which have a multiple macronucleus (the nodes of which may be either scattered or arranged like a string of beads). Most of the known species of Dileptus fall into the latter group, although two were moved to the genus Rimaleptus within Dimacrocaryonidae.
Ciliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...
protists, belonging to the class Litostomatea
Litostomatea
The Litostomatea are a class of ciliate protists. Until recently, the class Litostomatea was divided into two groups, the Haptoria and the Trichostomatia. However, new genetic information has resulted in the resurrection of a third subclass, Rhynchostomatia, first proposed by A. W. Jankowski in...
. Members of the genus are found in fresh and salt water. Like most of the free-living Litostomes, Dileptus is an aggressive predator, carrying an arsenal of toxin-bearing trichocyst
Trichocyst
http://media-2.web.britannica.com/eb-media/68/8968-004-A94DB3DF.jpg A trichocyst is a structure in the cortex of certain ciliate and flagellate protozoans consisting of a cavity and long, thin threads that can be ejected in response to certain stimuli...
s (toxicysts) in a prehensile proboscis, with which it stuns its microscopic victims before consuming them.
Dileptus was first seen and described by O. F. Müller
Otto Friedrich Müller
Otto Friedrich Müller, also Mueller was a Danish naturalist.-Biography:Müller was born in Copenhagen. He was educated for the church, became tutor to a young nobleman, and after several years' travel with him settled in Copenhagen in 1767, and married a lady of wealth.His first important works,...
in 1773, who reports having found the creature "in water where duckweed dwells" ('"in aquis, ubi lemna hospitatur"). He describes the organism in detail, recording its sharp posterior and its "long neck," which has a tendency to assume a spiral shape. The species Müller named Vibrio anser is generally understood to be a synonym of Dileptus anser
Dileptus anser
Dileptus anser is a unicellular ciliate protozoan belonging to the genus Dileptus. Specimens range in size between 0.24 and 0.60 mm long, and are found in freshwater streams, lakes and ponds.-Morphology:...
. In a later work, Animalcula Infusoria, published posthumously in 1786, he repeats the earlier description of the creature and adds several illustrations of it
Dileptus has become a model organism, used in the study of ciliary patterns, ontogenesis, conjugation and food acquisition
Appearance and characteristics
Dileptus cell bodies are elongate, with a well-developed prehensile proboscis at the front end. The cytostome is at the base of the neck and is well fortified with stiff microtubular rods (nematodesmata). The surface of the cell is uniformly covered with cilia arranged in longitudinal rows. The body may narrow at the posterior, forming something like a tail. Multiple contractile vacuoles lie in a row along the dorsal surface.Classification
Müller named the creature he observed in 1773 Vibrio anser (anser being Latin for "goose"), placing it in a genus of long necked ciliates that included, among other species, the "swan-necked" ciliate Lacrymaria olor.In 1841, M. Félix Dujardin created the genus Dileptus and moved Müller's Vibrio anser to it. By the time a full revision of the genus was published in 1963, the genus included about 50 species.
In 1974, John O. Corliss proposed the order Haptorida, to which Dileptus has generally been assigned under the subclass Haptoria.
However, in 2006, Strüder-Kypke et al. published the results of a molecular analysis of the Litostomes, which indicated that Dileptus is genetically, as well as morphologically, distinct from other Haptorian ciliates, and that they are, in fact, phylogenetically basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
to that group.
Recent research, combining genetic analysis with a study of physical characteristics (morphology), suggests that the Dileptids and their sister clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
the Tracheliids belong in a subclass of their own. For this purpose, Vd'ačný et al. resurrect a subclass of Litostomatea first proposed by the Russian researcher A.W. Jankowski in 1980: Rhynchostomata, which they amend to Rhynchostomatia.
As a result, the class Litostomatea, which previously had two recognized subclasses, now has three: Haptoria. Trichostomatia and Rhynchomstomatia.
In addition, the authors of the study divide the order Dileptida among two families: the Dimacrocaryonidae, most of whose members have a double macronucleus, and the Dileptidae, which have a multiple macronucleus (the nodes of which may be either scattered or arranged like a string of beads). Most of the known species of Dileptus fall into the latter group, although two were moved to the genus Rimaleptus within Dimacrocaryonidae.