View source for Heteronema

{{Short description|Genus of algae}}
{{Cleanup|reason=Overreferencing - successive statements sourced to the same reference do not need to be individually sourced, just do it once at the end of the paragraph|date=April 2020}}
{{Automatic taxobox 
| taxon     = Heteronema
| authority = Dujardin, 1841
}}

'''''Heteronema''''' is a genus of [[phagotrophic]], [[flagellate]]d [[euglenoid]]s that are most widely distributed in [[fresh water]] environments.<ref name="Guiry">Guiry, M. D.; Guiry, G. M. (2012). “Heteronema Dujardin, 1841”. Retrieved February 14, 2019, from [http://www.algaebase.org/search/genus/detail/?genus_id=50743]</ref> This genus consists of two very distinguishable morphogroups that are phylogenetically closely related.<ref name="Guiry" /><ref name="Lax">Lax, G.; Simpson, A. G. (2013). “Combining Molecular Data with Classical Morphology for Uncultured Phagotrophic Euglenids (Excavata): A Single-Cell Approach". Journal of Eukaryotic Microbiology. 6: 615-625. [https://doi.org/10.1111/jeu.12068 doi: 10.1111/jeu.12068]</ref><ref name="Lee">Lee, Won J. (2011). “Free-living benthic heterotrophic euglenids from Botany Bay, Australia”. Marine Biology Research. 8 (1): 3-27. [https://doi.org/10.1080/17451000.2011.596545 doi: 10.1080/17451000.2011.596545]</ref> These morphogroups are deciphered based on shape, locomotion, and other ultrastructural traits. However, this genus does pose taxonomic problems due to the varying historical descriptions of ''Heteronema'' species and their similarity to the genus ''[[Peranema]]''.<ref name="Guiry" /> The species ''H. exaratum'' was the first heteronemid with a skidding motion to be sequenced, which led to the discovery that it was not closely related to ''H. scaphrum'', contrary to what was previously assumed, but instead to a sister group of primary [[osmotrophy|osmotrophs]].<ref name="Lax" /> This suggests that skidding heteronemids can also be distinguished phylogenetically, being more closely related to ''Anisoma'', ''[[Dinema (alga)|Dinema]]'', and ''Aphageae'', than to other species within ''Heteronema''.<ref name="Lax" />

==Taxonomy==
The ''Heteronema'' genus was first described by Félix Dujardin, a French zoologist in 1841, as having variable shape, then typified in 1970 by Bourelly as an ''Anisonema''.<ref>Dujardin, F. (1841). “Histoire naturelle des zoophytes. Infusoires, comprenant la physiologie et la classification de ces animaux, et la manière de les étudier à laide du microscope”. doi:10.5962/bhl.title.51143</ref> In 1970, Stein modified the description to include cells with two flagella and the descriptions of two new species  with one containing ingestion rods.<ref name="Guiry" /> It was difficult separating this genus from ''Peranema''; however, in 1967 Leedale described ''Parenema'' to be different based on a more flattened morphology and a trailing flagellum pressed to the side of the cell compared to ''Heteronema''.<ref name="Guiry" /> 

The genus appears to be [[Polyphyly|polyphyletic]], with some species possibly falling into the order of [[Peranemida]] and others into [[Anisonemida]]. A 2021 review of Euglenozoa left it unplaced as to family and order within the clade [[Spirocuta]], and considered that many of its species should be transferred to ''[[Teloprocta]]'', which is placed in Peranemida.<ref name=KostKarnVotyTash21>{{Citation |last1=Kostygov |first1=Alexei Y. |last2=Karnkowska |first2=Anna |last3=Votýpka |first3=Jan |last4=Tashyreva |first4=Daria |last5=Maciszewski |first5=Kacper |last6=Yurchenko |first6=Vyacheslav |last7=Lukeš |first7=Julius |date=2021 |title=Euglenozoa: taxonomy, diversity and ecology, symbioses and viruses |journal=Open Biology |volume=11 |issue=3 |page=200407 |doi=10.1098/rsob.200407 |pmid=33715388 |pmc=8061765 |name-list-style=amp }}</ref>

===List of species===
{{As of|2023|May}}, [[AlgaeBase]] recognized the following species:<ref>{{AlgaeBase taxon|name=''Heteronema'' Dujardin, 1841|id=50743|access-date=2023-05-22}}</ref>  <!-- The formatting (font and size) does not look the same as the species names in red font. -->
{{div col}}
*''[[Heteronema abruptum]]'' <small>Skuja</small>
*''[[Heteronema aciforme]]'' <small>Z.X.Shi</small>
*''[[Heteronema acus]]'' <small>(Ehrenberg) F.Stein</small>
*''[[Heteronema acuta]]'' <small>Wawrik</small>
*''[[Heteronema acutissimum]]'' <small>Lemmermann</small>
*''[[Heteronema aquae]]'' <small>Skvortzov</small>
*''[[Heteronema bifurcata]]'' <small>H.Silva</small>
*''[[Heteronema capitatum]]'' <small>Z.X.Shi</small>
*''[[Heteronema citriformis]]'' <small>Wawrik</small>
*''[[Heteronema diaphanum]]'' <small>Skuja</small>
*''[[Heteronema discomorphum]]'' <small>Skuja</small>
*''[[Heteronema distigmoides]]'' <small>Christen</small>
*''[[Heteronema eneydae]]'' <small>Skvortzov</small>
*''[[Heteronema fidalgae]]'' <small>Skvortzov</small>
*''[[Heteronema fusiforme]]'' <small>Skvortzov</small>
*''[[Heteronema globuliferum]]'' <small>(Ehrenberg) F.Stein</small>
*''[[Heteronema hexagonum]]'' <small>(Playfair) Skuja</small>
*''[[Heteronema invaginata]]'' <small>Prowse</small>
*''[[Heteronema klebsii]]'' <small>Senn</small>
*''[[Heteronema leptosomum]]'' <small>Skuja</small>
*''[[Heteronema longiovata]]'' <small>H.Silva</small>
*''[[Heteronema marina]]'' <small>Dujardin</small>
*''[[Heteronema medusae]]'' <small>Skvortzov</small>
*''[[Heteronema metabolissimum]]'' <small>Wawrik</small>
*''[[Heteronema mutabile]]'' <small>(A.Stokes) Lemmermann</small>
*''[[Heteronema nebuloglabrum]]'' <small>H.Silva</small>
*''[[Heteronema ovalis]]'' <small>Kahl</small>
*''[[Heteronema palmeri]]'' <small>Skvortzov</small>
*''[[Heteronema plicatum]]'' <small>Skuja</small>
*''[[Heteronema polymorphum]]'' <small>Deflandre</small>
*''[[Heteronema proteus]]'' <small>Christen</small>
*''[[Heteronema pterbica]]'' <small>Schroeckh, W.J.Lee & D.J.Patterson</small>
*''[[Heteronema punctato]]'' <small>Skvortzov</small>
*''[[Heteronema robusta]]'' <small>Skvortzov</small>
*''[[Heteronema rosae-mariae]]'' <small>Skvortzov</small>
*''[[Heteronema sacculus]]'' <small>Skuja</small>
*''[[Heteronema saopaulensis]]'' <small>Skvortzov</small>
*''[[Heteronema scabra]]'' <small>Z.Cyrus</small>
*''[[Heteronema shii]]'' <small>Kapustin & D.Davydov</small>
*''[[Heteronema similis]]'' <small>Skvortzov</small>
*''[[Heteronema spirale]]'' <small>Klebs</small>
*''[[Heteronema spirogyra]]'' <small>Skuja</small>
*''[[Heteronema splendens]]'' <small>J.Larsen & D.J.Patterson</small>
*''[[Heteronema subsucculus]]'' <small>Z.Shi</small>
*''[[Heteronema taurica]]'' <small>Vetrova</small>
*''[[Heteronema tortum]]'' <small>Z.Shi</small>
*''[[Heteronema tortuosum]]'' <small>Christen</small>
*''[[Heteronema trachelomonades]]'' <small>Skvortzov</small>
*''[[Heteronema tremulum]]'' <small>Zacharias</small>
*''[[Heteronema trispira]]'' <small>Matvienko</small>
*''[[Heteronema vetrovae]]'' <small>Kapustin & D.Davydov</small>
{{div col end}}

==Description==
The ''Heteronema'' genus consists of diverse, colorless euglenoids that range in size from 8 - 75 micrometer (<math>\mu</math>m).<ref name="Guiry" /><ref name="Lax" /> Euglenoids are assigned to this genus if they have characteristics such as an ingestion apparatus, a capacity for flagellar movement, and a recurrent flagellum that is not adpressed to the ventral side of the cell.<ref name="Guiry" /><ref name="Breglia">Breglia, Susana A.; Yubuki, Naoji; Leander, Brian S. (2013). “Ultrastructure and Molecular Phylogenetic Position of Heteronema scaphrum: A Eukaryovorous Euglenid with a Cytoproct”. Journal of Eukaryotic Microbiology. 2: 107-120. [https://doi.org/10.1186/1471-2180-10-145 doi: 10.1111/jeu.12014]</ref> The cells are covered with a large number of proteinaceous [[pellicle (biology)|pellicle]] strips with [[microtubule]]s lined underneath.<ref name="Lax" /> These pellicle strips are a distinguishing feature of the euglenoids, that allows the cells to undergo [[metaboly]], giving the cell flexibility and movement.<ref name="Lax" /> ''Heteronema'', under the light microscope, is morphologically similar to ''Peranema'', where both groups are metabolic, have the ability to glide, have visible feedings rods, and two different flagellum on opposite ends of the cell.<ref name="Breglia" /> <!-- Consider describing or explaining "where both groups are metabolic". -->''Heteronema'' is separated into two specific morphogroups, one consisting of elongate and very flexible cells that move by gliding, holding the [[anterior]] flagellum out in front of the cell.<ref name="Lax" /> This morphogroup includes the species ''H. scaphrum''.<ref name="Lax" /> In contrast, the second group consists of ovoid, more rigid cells that have a characteristic rapid “skidding” swimming behavior.<ref name="Lax" /> Examples of species within this group are ''H. ovale'' and ''H. exaratum''.<ref name="Lax" /> The skidding behavior is very similar to the primary osmotrophs, where the motion is powered by the beating of the anterior flagellum, positioned in a curve to the right of the cell, in a sinusoidal pattern.<ref>Larsen, Jacob; Patterson, David J. (1990). “Some flagellates (Protista) from tropical marine sediments”. Journal of Natural History. 24 (4): 801-937. [https://doi.org/10.1080/00222939000770571 doi:10.1080/00222939000770571]</ref><ref name="Lax" /> This may also reflect the evolution of ancestral phagotrophic euglenoids, where almost all species swam poorly and relied on gliding instead of flagellar movement.<ref name="Lax" /> The flagella are hollow with heteromorphic paraxonemal rods, covered with sheaths of hairs.<ref name="Lee" /> In accordance to its name, the anterior emergent flagella is longer and thicker, directed anteriorly and used for locomotion, and the shorter, thinner flagellum is directed [[posterior (anatomy)|posterior]]ly.<ref name="Lee" /> The feeding apparatus is usually quite small, composed of separate microtubule rods and surrounded by spiral striations at the anterior end of the cell.<ref>Schroeckh, Sabrina; Lee Won J.; Patterson, David J. (2006). “Free-living heterotrophic euglenids from freshwater sites in mainland Australia”. Hydrobiologia. 493:1-3. [https://doi.org/10.1023/A:1025457801420 doi: 10.1023/A:1025457801420]</ref><ref name="Breglia" /> <!-- Consider adding images of the two specific morphogroups. -->

==Habitat and ecology==
''Heteronema'' is generally widespread and commonly found in [[brackish]] pools and fresh water ponds; however, some species are observed to exist in [[marine biology|marine]] environments.<ref name="Guiry" /> These euglenoids are phagotrophic, making them important in [[benthic]] systems and [[microbial food web]]s.<ref name="Guiry" /><ref name="Lax" />

==Life history==
There is no [[sexual reproduction]] observed in the euglenoids; however, [[asexual reproduction]] can occur through [[mitosis]] followed by [[cytokinesis]], where [[basal bodies]] and flagellar systems replicate first, followed by the feeding system.<ref name="Esson"> Esson, H. J.; Leander, B. S. (2006). “A model for the morphogenesis of strip reduction patterns in phototrophic euglenids: Evidence for heterochrony in pellicle evolution”. Evolution Development, 8 (4): 378-388. [https://doi.org/10.1111/j.1525-142x.2006.00110.x doi:10.1111/j.1525-142x.2006.00110.x]</ref> After the duplication of the [[Cell nucleus|nucleus]] and [[cytoskeleton]], a cleavage furrow appears, migrating from the flagellar pocket to the anterior opening, and then to the posterior end, separating the parent from the [[daughter cell]].<ref name="Esson" />  <!-- Consider adding an imaging showing the asexual reproduction process. --> 

== References ==
{{reflist}}

{{Taxonbar|from=Q26157861}}
[[Category:Euglenozoa]]