Macrostomum hystrix is a free-living flatworm in the family Macrostomidae. It is small, transparent, and a simultaneous hermaphrodite.
| Macrostomum hystrix | |
|---|---|
| |
| Adult | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Platyhelminthes |
| Order: | Macrostomida |
| Family: | Macrostomidae |
| Genus: | Macrostomum |
| Species: | M. hystrix
|
| Binomial name | |
| Macrostomum hystrix Luther, 1905[1]
| |
Biology
editMacrostomum hystrix is capable of hypodermic insemination. In this process, sperm is injected through the epidermis into the parenchyma of the mating partner. This is done by a needle-like stylet, which is the male copulatory organ. The stylet has a rigid and pointed distal thickening, as well as a subterminal stylet opening which can puncture the epidermis of the mating partner. The sperm are highly motile, small and simple, but have no flagellates. The female antrum shows a simple anatomy and is only involved in laying eggs.[2]
In isolated worms, it has been shown that Macrostomum hystrix does not only use hypodermic insemination for outbreeding but also self-fertilization, or "selfing". To achieve this, they inject their sperm into themselves — mainly into their own heads, due to physical constraints. From there, the sperm apparently migrate to the site of fertilization. Worms that were isolated showed significantly more sperm in their heads, compared to worms that had the opportunity to cross-fertilize.[3] Macrostomum hystrix prefers outbreeding if partners are available because selfing also has costs. The amount of offspring of worms that selfed is reduced, as is the offspring's survival. As a consequence, Macrostomum hystrix only begins selfing in the extended absence of mating partners: delayed selfing represents a conditional reproductive strategy which allows them to deal with periodic conditions of low mate abundance.[4]
References
edit- ^ Luther, A. (1905). "Zur Kenntnis der Gattung Macrostoma" (PDF). Festschrift für Palmén, Helsingfors.
- ^ Schärer, Lukas; Littlewood, D. Timothy J.; Waeschenbach, Andrea; Yoshida, Wataru; Vizoso, Dita B. (2011-01-25). "Mating behavior and the evolution of sperm design". Proceedings of the National Academy of Sciences. 108 (4): 1490–1495. doi:10.1073/pnas.1013892108. ISSN 0027-8424. PMC 3029721. PMID 21220334.
- ^ Ramm, Steven A.; Schlatter, Aline; Poirier, Maude; Schärer, Lukas (2015-07-22). "Hypodermic self-insemination as a reproductive assurance strategy". Proceedings: Biological Sciences. 282 (1811): 20150660. doi:10.1098/rspb.2015.0660. ISSN 1471-2954. PMC 4528547. PMID 26136446.
- ^ Ramm, S. A.; Vizoso, D. B.; Schärer, L. (2012-12-01). "Occurrence, costs and heritability of delayed selfing in a free-living flatworm". Journal of Evolutionary Biology. 25 (12): 2559–2568. CiteSeerX 10.1.1.702.7627. doi:10.1111/jeb.12012. ISSN 1420-9101. PMID 23110716. S2CID 23561102.