REPRODUCTION IN BRITISH SEA ANEMONES

Cnidaria

Sea Anemones   Page 2


Sea Anemones found in the seas around the British Isles reproduce in a variety of ways. Scientific papers on this subject should be treated with caution as some of them are incorrect.

Methods:

Longitudinal Fission. Some species including the common southern and western species the Snakelocks Anemone, Anemonia viridis (=A. sulcata), reproduce by literally tearing itself into two anemones. Further observations.

Snakelocks Anemone Reproducing

Baceral Laceration: Fragments of tissue break off from the base and develop into new sea anemones, notably by the Plumose Anemones, Metridium senile, which is also reported to reproduce sexually.  Another picture.

Sexual Reproduction: Sperm and eggs discharged into the sea. This occurs in the Pimplet Anemone, Anthopleura ballii.


Beadlet Anemones are the most widespread of the British sea anemones, found the length of the British Isles on rocky shores and anywhere where there is a hard surface to attach to. Red, green and brown varieties occur. The best explanation of their reproduction is by parthenogenesis.

However, the author of this piece (Andy Horton) considers the likelihood that they break off internally to be a strong possibility. No evidence of sexual reproduction has been observed despite extensive study.
 

Beadlet Anemone, Actinia equina,  spurting out a young anemone.

 

 Parthenogenesis.

Transverse Fission.
Budding

 

Dahlia Anemone, Urticina felina.

The method of reproduction of the large, common and widespread sea anemone is not known.



LIFE SPANS OF SEA ANEMONES

Sea Anemones have not been kept in aquaria long enough to establish with any certainty how long sea anemones naturally live, if not predated upon or dying from causes other than old age. However, there are records of large tropical display anemones living for several decades in Public Aquaria, housing several generations of commensal Clownfish, Amphiprion ocellaris. AH

John Ottaway and Ken Sebens have made actuarial tables for anemones.Since they came up with potential lifespans on the order of several centuries, personal experience is unlikely to be a good guide. (Daphne Fautin).

Daphne G. Fautin
Professor, Biological Sciences
Curator, Natural History Museum and Biodiversity Research Center
Haworth Hall
University of Kansas
Lawrence, Kansas 66045  USA

telephone 1-785-864-3062
fax 1-785-864-5321
for e-mail, please use fautin@ukans.edu

lab web page: http://www.nhm.ukans.edu/~inverts
direct to sea anemone database version 2.1: biocomplexity.nhm.ukans.edu/
         anemones/images/Version.html
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"Sir John Dalyell at his time kept a well-known specimen of Actinia equina named "Granny" in captivity for decades and at his decease Charles Peach inherited the animal, which in this way happened to live in Edinburgh for more than 50 years, so at least certain species seem to be able to have a very long potential life span. Certain very deep-living animals like bivalves are known of being able to live for several hundred years and I guess it is likely that certain deep-living sea anemones also could reach such ages."
(from Hans.G.Hansson@TMBL.GU.SE **** Tjaernoe Marine Biological Lab. ****
http://www.tmbl.gu.se   Phone: +46 526 686 36   Fax: +46 526 686 07
Personal home page: http://www.tmbl.gu.se/staff/HansGHanssonP.html  )
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I have kept a specimen of the "strawberry" Beadlet Actinia fragacea from the NE Atlantic Ocean that lived for 10 years (without showing any sign of reproducing) and it may have lived much longer. I got the specimens muddled up when transferring them to another tank. AH
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"It is said that they are essentially immortal, showing no obvious senescence either at the individual or the cellular levels, and certainly not at the clone level in clonal species (but of course they do die from other causes, e.g. predation and disease).

A couple anecdotal examples:

Bob Paine has been watching the same Urticina crassicornis at Tatoosh Island since 1968, and it has not moved nor changed in size.

There is the story of the legendary anemone kept in Edinburgh, I think, for something like 90 years; the anemone died of a seawater system malfunction, not old age.  This is reported in Ricketts and Calvin among other places.

I know that John Pearse has kept Anthopleura artemesia in captivity for well over 10 years and they're doing just fine.

Ken Sebens calculated from population-level data (observed field mortality rates) that the average age of Anthopleura xanthogrammica on the Washington coast must be around 500 years with some individuals, theoretically anyway, having been around since the Pleistocene (this is heresay from Bob Paine based on Ken's calculations).

Hope these help!  I would very much appreciate hearing about any other responses you receive."  Good luck!  Dave

DAVID L. SECORD, PhD
Assistant Professor of Biology & Environmental Science Coordinator (UWT)
and Adjunct Assistant Professor of Zoology (UW Seattle)

University of Washington, Tacoma  TEL: 253-692-5659
Interdisciplinary Arts & Sciences  FAX: 253-692-5612
1900 Commerce Street (MS 358436)  TDD: 253-692-4413
Tacoma, WA 98402-3100 USA   EMAIL: dave@u.washington.edu

GALAPAGOS 2000 TRIP INFORMATION AND APPLICATION:
http://www.tacoma.washington.edu/liberal/study-abroad/galapagos.html

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LIFE  SPANS

Among single-celled organisms, which reproduce by cell division, the concept of an individual life span loses some validity, as in a sense the individual continues to exist indefinitely. Thus arbitrary definitions of individual lives, such as the period between reproductive divisions, may be used to estimate life span, but such estimates are not comparable to those for sexually reproducing organisms.

In most species the maximum life span can be estimated from the longest observed survival of individual members of the
species. The maximum human life span is reported to be between 115 and 150 years. In many animals, the maximum life span
has been calculated from survival in captivity, where safety from predators allows many individuals to live to an advanced old
age seldom reached in the wild.

Extract from Encyclopaedia Britannica  (Life Spans)

Anemones are multi-celled organisms, but in some respects (reproduction) may resemble unicellular organisms. However, even sea anemones not observed to reproduce sexually could do so on occasions. AH



More Information & Speculation on the Life Spans of Cnidarians



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