Pseudoperanema Christen, 1962

Holotype species: Pseudoperanema hyalinum Christen

Currently accepted name for the type species: Peranema hyalinum Christen

Description: Colorless, phagotrophic flagellates, with special ingestion apparatus consisting of separate rods associated with a subapical cytostome independent of canal and reservoir; cell non-rigid, euglenoid movement violent in non-swimming cells, cell slightly flattened when swimming, pellicular striations coarse. Two emergent flagella, unequal in length and thickness, heterodynamic, the longer, thicker one directed anteriorly during swimming, the shorter, thinner one curving posteriorly and pressed closely to the cell (usually difficult to see). Cells swim in several different ways: one is a gliding locomotion with the long flagellum held straight while the beating tip traces a funnel shape; another is swimming with a cilium-like beat and recovery stroke of 80% of the flagellar length; a third is gliding against a substratum with a snapping action of the anterior 30% of the thick flagellum.

Information kindly contributed by G.F. Leedale & M.D. Guiry but may now be outdated.

Taxonomic status: This name is currently regarded as a synonym of Peranema.

Comments: Different species vary from 8 to 200 µm in length but the type species is also very variable, with size varieties from 20-80 x 10-25 µm and a chromosome number of ca. 175 for the large form. P. trichophorum normally ingests food particles and living organisms (bacteria, yeasts, algae and even Euglena cells as big as itself) by engulfing them whole into food vacuoles. The ingestion rods are protruded and hooked onto the prey which is then pulled through the cytostome in conjunction with a wave of euglenoid movement. In the case of a large prey the rods are detached, moved and attached again further along so that more of the prey can be pulled into the predator. A whole Euglena gracilis will be engulfed in 15 minutes. Alternatively, Peranema will feed by cutting and sucking. Several individuals converge on the prey (filamentous algae such as Cladophora, or a very large Euglena such as E. ehrenbergii), protrude their ingestion rods and rasp a way through the prey's wall or periplast. Cladophora walls can be cut through in about 15 minutes and the cell contents are then sucked into a food canal below the cytostome. If the prey is big enough, more than one Peranema will enter the cell and engulf the remaining contents, withdrawing when fully charged with food vacuoles. These decrease in size as digestion proceeds and indigestible remains are finally ejected from the cell posterior, a whole Euglena gracilis being digested in 24 hours. Peranema can digest fat, protein and starch, ultimate conversion to paramylon and oil being indicated by the accumulation of these inclusions in the feeding cell. The chemotactic response of Peranema to its prey can be demonstrated by bursting open living algal cells in a suspension of hungry Peranema individuals; the predators stream in for the meal from all directions like microscopic sharks. Freshwater and marine, common in ponds, ditches, marshes, sediments and marine sands; cosmopolitan.

Under the genus name of Peranema, taxonomic and nomenclatural problems abound. In the International Code of Botanical Nomenclature (ICBN) the name Peranema is occupied by a genus of ferns described by Don in 1825 (Silva, 1980). Some phycologists (e.g. Bourrelly, 1985) therefore adopt the name Pseudoperanema, originally proposed by Christen (1962) for P. trichophorum which has a second emergent flagellum that was not recorded in the original description. In the International Code of Zoological Nomenclature (ICZN) the name Peranema is not preoccupied and protozoologists often retain the name or propose a double naming system (Larsen and Patterson, 1991). Lackey (1940) created the genus Peranemopsis for a Peranema-like species which genuinely lacks the trailing flagellum (and therefore fulfills exactly the original description of Peranema trichophorum). To add to the confusion, Bourrelly (1970) sees no distinction between Peranema and Heteronema and merges the latter genus into the former.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 02 April 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 30 September 2022

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