Epitoky: Difference between revisions
Mccullermi (talk | contribs) Revised much of the article and included references. |
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[[File:Syllid polychaete undergoing epitoky.jpg|thumb|Syllid [[polychaete]] budding epitokes for the purpose of sexual reproduction.]] |
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[[File:Alitta succinea (epitoke).jpg|thumb|right|200px|''[[Alitta|Alitta succinea]]'' (common clam worm) in Epitoky stage]] |
[[File:Alitta succinea (epitoke).jpg|thumb|right|200px|''[[Alitta|Alitta succinea]]'' (common clam worm) in Epitoky stage]] |
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'''Epitoky''' is a process that occurs in many species of [[polychaete]] marine worms wherein a sexually immature worm (the '''atoke''') is modified or transformed into a sexually mature worm (the '''epitoke'''). Epitokes are [[pelagic]] [[morph (zoology)|morphs]] capable of [[sexual reproduction]].<ref>{{cite book|last=Pechenik|first=Jan I.|title=Biology of the Invertebrates, Seventh Edition|year=2015|publisher=McGraw-Hill Education|location=New York, NY|isbn=978-0-07-352418-4|pages=302–304}}</ref> Unlike the immature form, which is typically [[benthic]] (live on the bottom), epitokes are specialized for swimming as well as reproducing. The primary benefit to epitoky is increased chances of finding other members of the same species for reproduction. |
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'''Epitoky''' is a form of [[reproduction]] observed in [[polychaete]] marine worms. The worms undergo a partial or complete transformation into an '''epitoke''', a [[pelagic]] [[morph (zoology)|morph]] capable of [[sexual reproduction]]. |
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There are two methods in which epitoky can occur: '''schizogamy''' and '''epigamy'''. Many species go through '''schizogamy''', where the atoke uses [[asexual reproduction]] to produce buds from its posterior end. Each bud develops into an epitoke and, once fully formed, will then break off from the atoke and become free-swimming. Many genetically identical epitokes are formed in this way, thus allowing a higher chance of finding a mate of the same species and subsequent passing of genes to the next generation. Atokes may then live through another season to form more epitokes. |
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Often an epitoke is the posterior part of the worm, which separates from the anterior part (called the '''atoke'''); [[gamete]]s are produced inside the epitoke. The epitoke may also form by asexual [[budding]] from the posterior. |
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'''Epigamy''' is another common way to form epitokes. For species that use this method, the atoke undergoes physiological and morphological modifications as it transforms into the epitoke.<ref name="Chatelain">{{cite journal |doi=10.1016/j.cbpb.2007.09.006 |last=Chatelain|first=Étienne Hébert|last2=Breton|first2=Sophie|last3=Lemieux|first3=Hélène|last4=Blier|first4=Pierre U.|title=Epitoky in ''Nereis'' (''Neanthes'') ''virens'' (Polychaeta: Nereididae): A story about sex and death |journal=Comparative Biochemistry and Physiology, Part B |volume=149 |issue=2008 |pages=202-208 |year=2008}}</ref> Typically, male worms undergo a more pronounced transformation from atoke to epitoke. Modifications may include an increase in size of [[parapodia]] and the development of paddle-like [[chaeta]]e for enhanced swimming ability, [[atrophy]] of the gut, filling of the body cavity with [[gametes]] ([[eggs]] or [[sperm]]), the development of large eyes, and the musculature may even change to perform swimming movements instead of feeding movements.<ref name="Chatelain" /><ref name="Dorresteign">{{cite book|last=Dorresteijn|first=Adriaan W.C.|last2=Westheide|first2=Wilfried|title=Reproductive Strategies and Developmental Patterns in Annelids|year=2013|publisher=Springer Science & Business Media|isbn=9789401728874}}</ref> The majority of species that undergo epigamy are unable to revert back to the atoke form and die after reproducing. |
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There are two methods in which this can occur, '''epigamy''' and '''schizogamy'''. In epigamy, the whole worm transforms into a swarming epitoke. It rises and sheds its eggs and sperm. After reproduction, it dies. In schizogamy, the sexual forms are budded from the posterior or from the parapodia to swarm. This is effectively asexual reproduction of the epitoke. |
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Male and female epitokes are produced and swim to the water's surface only at certain times of the year and are often synchronized with moon cycles in a behavior called '''swarming'''. Swarming brings individuals of the same species together so that there is an increased rate of fertilization <ref>{{cite book|last=Karleskint|first=George|last2=Turner|first2=Richard|last3=Small|first3=James|title=Introduction to Marine Biology, Third Edition|year=2009|publisher=Cengage Learning|isbn=9780495561972|pages=237}}</ref>. Some polychaete species have been found to use [[bioluminescence]], presumably to compact and maintain swarms.<ref name="Dorresteign" /> Both schizogamous and epigamous epitokes are non-feeding individuals that die once [[gametes]] have been released into the water. |
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The first form is characteristic of ''[[Nereidae]]'' where the whole worm becomes an epitoke. This form may be accompanied by partial or full degeneracy of [[digestion|digestive]] organs (causing the animal to die quickly) and enhancement of motor and sensory organs; in particular, whereas in its nonreproductive form the worm is a crawling animal, when it becomes an epitoke the worm develops swimming appendages, such as broad [[parapodia]] with paddle-shaped [[chaeta]]e. |
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Epitokes swim to the [[plankton]]-rich surface region, where the gametes erupt from the body and the [[larva]]e hatch. This action is often synchronized with moon cycles, and epitokes swim in swarms. |
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== References == |
== References == |
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{{reflist}} |
{{reflist}} |
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* Brusca, Gary and Brusca, Richard: Invertebrates (2nd edition) |
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[[Category:Reproduction in animals]] |
[[Category:Reproduction in animals]] |
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Revision as of 22:26, 17 May 2016
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Epitoky is a process that occurs in many species of polychaete marine worms wherein a sexually immature worm (the atoke) is modified or transformed into a sexually mature worm (the epitoke). Epitokes are pelagic morphs capable of sexual reproduction.[1] Unlike the immature form, which is typically benthic (live on the bottom), epitokes are specialized for swimming as well as reproducing. The primary benefit to epitoky is increased chances of finding other members of the same species for reproduction.
There are two methods in which epitoky can occur: schizogamy and epigamy. Many species go through schizogamy, where the atoke uses asexual reproduction to produce buds from its posterior end. Each bud develops into an epitoke and, once fully formed, will then break off from the atoke and become free-swimming. Many genetically identical epitokes are formed in this way, thus allowing a higher chance of finding a mate of the same species and subsequent passing of genes to the next generation. Atokes may then live through another season to form more epitokes.
Epigamy is another common way to form epitokes. For species that use this method, the atoke undergoes physiological and morphological modifications as it transforms into the epitoke.[2] Typically, male worms undergo a more pronounced transformation from atoke to epitoke. Modifications may include an increase in size of parapodia and the development of paddle-like chaetae for enhanced swimming ability, atrophy of the gut, filling of the body cavity with gametes (eggs or sperm), the development of large eyes, and the musculature may even change to perform swimming movements instead of feeding movements.[2][3] The majority of species that undergo epigamy are unable to revert back to the atoke form and die after reproducing.
Male and female epitokes are produced and swim to the water's surface only at certain times of the year and are often synchronized with moon cycles in a behavior called swarming. Swarming brings individuals of the same species together so that there is an increased rate of fertilization [4]. Some polychaete species have been found to use bioluminescence, presumably to compact and maintain swarms.[3] Both schizogamous and epigamous epitokes are non-feeding individuals that die once gametes have been released into the water.
Since epitokous individuals may look much different than atokous individuals, in the past it was thought that epitokes were a separate group of polychaete marine worms.
References
- ^ Pechenik, Jan I. (2015). Biology of the Invertebrates, Seventh Edition. New York, NY: McGraw-Hill Education. pp. 302–304. ISBN 978-0-07-352418-4.
- ^ a b Chatelain, Étienne Hébert; Breton, Sophie; Lemieux, Hélène; Blier, Pierre U. (2008). "Epitoky in Nereis (Neanthes) virens (Polychaeta: Nereididae): A story about sex and death". Comparative Biochemistry and Physiology, Part B. 149 (2008): 202–208. doi:10.1016/j.cbpb.2007.09.006.
- ^ a b Dorresteijn, Adriaan W.C.; Westheide, Wilfried (2013). Reproductive Strategies and Developmental Patterns in Annelids. Springer Science & Business Media. ISBN 9789401728874.
- ^ Karleskint, George; Turner, Richard; Small, James (2009). Introduction to Marine Biology, Third Edition. Cengage Learning. p. 237. ISBN 9780495561972.
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