[Annelida] metamerism

[David Weisblat]

Geoff is right that metamerism and segmentation are often used 
synonymously. But since there are two nice distinct words, they can also 
be used to distingush different degrees of regularity in body 
organization as follows:

Segmentation: body plan in which two or more tissues or organs systems 
(such as nervous, muscular, excretory, circulatory and/or integumental) 
are organized metamerically along the A-P axis of the animal; metamers 
of different systems have the same repeat length.

Metamerism: body plan organization featuring repeating units along the 
A-P axis but falling short of the rigorous definition of segmentation, 
e.g., only one organ system is arranged into repeating subunits, or the 
spatial repeat lengths are different between systems.

With this set of definitions, one can perhaps distinguish metamerism 
(in  flatworm, molluscs, nematodes) from segmentation (in most annelids, 
arthropods and vertebrates).

Best,
David Weisblat



 
Geoff Read wrote:
>>>> On 5/09/2020 at 4:59 p.m., "anil sharma" <asanilsharma3 from gmail.com>
>>>>         
> wrote:
>   
>> Give me details about metamerism in annelids
>>     
>
> Simply a term for a segmented body. 
>
> Metamerism summarised (somewhat unreliably) here:
> http://www.iaszoology.com/?page_id=339
>
> Some of these papers may provide more depth. To obtain consult a
> library.
>
> Almeida, W.d.O.; Christoffersen, M.L.; Amorim, D.d.S.; Garraffoni,
> A.R.S.; Silva, G.S. (2003). Polychaeta, Annelida, and Articulata are not
> monophyletic: Articulating the Metameria (Metazoa, Coelomata). Revista
> Brasileira de Zoologia 20(1): 23-57. 
>
> Bernard, H.M. (1900). A suggested origin of the segmented worms, and
> the problem of metamerism. Annals and Magazine of Natural History,
> London  6: 509-520. 
>
> Chaudonneret, J. (1980). Les diverses modalités de la métamérie chez
> les invertébrés. 1. Polychètes aberrantes: les myzostomides. Bulletin
> Soc. zool. Fr. 104(3): 271-272. 
>
> Clark, R.B. (1964). Dynamics in Metazoan Evolution. The origin of the
> coelom and segments. Clarendon Oxford University Press, Oxford. x and
> 313 p.
>
> Fischer, A. (1999). Reproductive and developmental phenomena in
> annelids: a source of exemplary research problems. Hydrobiologia 402:
> 1–20. 
>
> Giangrande, A.; Gambi, M.C. (1998). Metamerism and life-style within
> polychaetes: morpho-functional aspects and evolutionary implications.
> Italian Journal of Zoology 65(1): 39-50. 
>
> Malakhov, V.V. (2004). Origin of bilateria. Zhurnal Obshchei Biologii
> 65(5): 371-388. 
>
> Malaquin, A. (1904). La cephalisation chez les Annelides et la question
> du metamerisme. Comptes Rendu, Academie des Sciences, Paris 138:
> 821-824. 
>
> Malikova, I.G.; Sokolova, I.O. (1992 (1994)). Development metamerism in
>  Pygospio elegans Claparede (Polychaeta: Spionidae). Explorations of the
> Fauna of the Seas 43(51): 43-47. 
>
> Morgan, H. (1892). Spiral modification of metamerism. Journal of
> Morphology, Boston 7: 245-251. 
>
> Sedgwick, A. (1884). On the origin of metameric segmentation. Quarterly
> Journal of Microscopical Science 24: 43-82,plates42-43. 
>
> Shimizu, T.; Nakamoto, A. (2001). Segmentation in annelids: Cellular
> and molecular basis for metameric body plan. Zoological Science (Tokyo)
> 18(3): 285-298. 
>
> Westheide, W. (1997). The direction of evolution within the polychaeta.
> Journal of Natural History. 31(1): 1-15. 
>
> Zrzavy, J.; Stys, P. (1995). Evolution Of Metamerism In Arthropoda -
> Developmental And Morphological Perspectives. Quarterly Review of
> Biology 70(3): 279-295. 
>
>
>
>   

-- 
--------------------------------------------------------------------------------
David A. Weisblat
Professor, Cell & Developmental Biology

MCB, 385 LSA
University of California
Berkeley, CA 94720-3200, USA

510-642-8309 phone
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