Gregarines
| Gregarines | ||||||||||||
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Gregarine |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Gregarinasina | ||||||||||||
| Dufour , 1828 |
The gregarines are a group endoparasitär living protozoa and belong to the tribe of the Apicomplexa . They live in the intestines or other body cavities of various invertebrate hosts and occur both terrestrially, for example in many species of beetles, as well as marine and limnic in other arthropods or tunicates .
anatomy
Gregarines are divided into two sections, the smaller protomerites and the larger deutomerites . In between there is a transverse septum that can be seen under the light microscope. The cell nucleus is located in the deutomerite, the main section of the Gregarine . Some Gregarine species have an additional section on their protomerite, which is called epimerite , and which they can use to attach themselves to surfaces, for example in the intestine of their host.
Unlike other unicellular organisms, gregarines have neither a cell mouth nor a cell juvenile , nor food vacuoles or contractile vacuoles . Instead, there are micropores , called microcytostomes, at the bottom of the wrinkled surface, with which they can absorb vital nutrients. The surface, which is longitudinally striped by the parallel elevations, consists of three membranes, which are collectively known as the pellicula and which represent the outer layer of the Gregarine. The ectoplasm (outer cytoplasm ), which contains numerous microfilaments and microtubules , connects to the inside . The endoplasm (inner cytoplasm) contains reserve substances such as fats and proteins as well as amylopectin .
The Gregarine have a large size variance and can be from a few micrometers to a maximum of 15 millimeters in size. The latter is unusually large for protozoa .
Locomotion
The locomotion of the Gregarine appears evenly and takes place through microfilaments and microtubules in the ectoplasm within the pellicle. The surface of the Gregarine does not seem to change.
Reproduction and development
Gregarines show an alternation between asexual reproduction and sexual reproduction . The latter begins with gamontogamy , in which two single-celled individuals of different sexes ( gamonts ) attach to each other. The female and male Gregarines differed morphologically and in color. One gregarine hangs with the front end to the rear end of the other, and both surround each other with a common cyst and are from now on called the gamontic cyst . In the cyst, nuclear divisions ( mitoses ) take place in both gamonts , and finally a number of gametes (sex cells ) emerge from each gamont . The gametes are the surviving component within the cyst; the remaining plasma complex (residual body) of the gamonts no longer functions and dies. The gametes that now leave the cyst can all look the same (isogametes) or different depending on their sex (anisogametes).
Only now do gametes of different sexes fuse in pairs to form diploid zygotes . These can either turn into spores or develop into a sporocyst. In the latter case, eight haploid sporozoites emerge from the diploid zygote ( sporogony ), in which the contents are divided into eight sporozoites. In this form, as a spore or within the sporocyst, the parasites leave the host in order to be ingested outside by a new host animal, for example with food. If the parasites get into a new host, they leave the sporocyst and grow from the trophozoite (vegetative form) to the gamont (generative form). With the entry of the gamontogamy begins a new gamontogamy and the reproductive cycle is completed.
In juvenile form, Gregarines can live intracellularly (within the cells of their hosts); above a certain size they only live extracellularly in the intestine or in other body cavities of the host.
Taxonomy
The group was discovered in 1828 (as "Gregarines") by the French naturalist Léon Dufour in the intestines of insects he studied and first described. Depending on the assigned rank , different names are in use today on this basis, which differ only in the respectively assigned ending: e.g. B. Gregarinida (as a class), Gregarinasida. The most commonly used name is Gregarinasina, formally the name form for a subclass. Since numerous authors now attach little importance to the rank-based, classical taxonomy and nomenclature, the name Gregarinasina is sometimes retained to describe a non-ranked taxon; for example by Sina Adl and colleagues in their much-used taxonomic overview.
The group includes about 1800 described species, but it is assumed that a multiple of this number is still undescribed. As parasites of invertebrates, most Gregarines are economically insignificant and therefore very poorly researched.
swell
- Storch, V. & U. Welsch (2009): Kükenthal - Zoological internship. 26th edition. Spektrum Akademischer Verlag. Heidelberg. Chapter 1 - Protozoa. Chapter 15 - Systematic Organization of the Animal Kingdom.
- Purves, WK et al. (2006): Biology. 6th edition. Spectrum Academic Publishing House. Heidelberg.
- Alarcon, ME et al. (2011): Life Cycle and Morphology of Steinina ctenocephali (Ross 1909) comb. nov (Eugregarinorida: Actinocephalidae), a Gregarine of Ctenocephalides felis (Siphonaptera: Pulicidae) in Taiwan. Zoological Studies.
- Forbes, MR, Mlynarek, JJ, Allison, J. & KK Hecker (2011): Seasonality of gregarine parasitism in the damselfly, Nehalennia irene: understanding unimodal patterns. Springer publishing house.
- Takov, D., Daychev, D., Linde, A., Draganova, S. & D. Pilarska (2011): Pathogens of bark beetles (Coleoptera: Curculionidae) in Bulgarian forests. Springer publishing house.
- Michalková, V., Krascsenitsvá, E. & M. Kozánek (2011): On the pathogens of the spruce bark beetle Ips typographus (Coleoptera: Scolytinae) in the Western Carpathians. Institute of Zoology, Slovak Academy of Sciences.
- Menard, R. (2001): Gliding Motility and Cell Invasion by Apicomplexa: Insights from the Plasmodium sporozoite. Published in: Cellular Microbiology. Volume 3. Blackwell Science Ltd .: pp. 63-73.
- Walker, MM, Mackenzie, M., Bainbridge, SP and C. Orme (1979): A Study of the Structure and Gliding Movement of Gregarina Garnhami. Published in: Journal of Eukaryotic Microbiology. Volume 26: pp. 566-574.
- Rueckert, SI & BS Leander (2008): Gregarina Dufour 1828. Gregarines. Published in: The Tree of Life Web Project. (Page: http://tolweb.org/Gregarina/124806 (2012/3/10))
Individual evidence
- ↑ cf. about WoRMS World Register of Marine Species (2019). Gregarinasina , accessed May 2, 2019.
- ↑ Gregarinasina Dufour 1828 (classified according to the rank of a tribe (Phylum, P)) in: Sina M. Adl et al. (2018): Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes. Journal of Eukaryotic Microbiology 66: 4-119. doi: 10.1111 / jeu.12691 .