Celebrate diversity: The fish that fertilizes itself

It’s almost another marbled clone.

There are parthenogenetic vertebrates (some of which have been featured on this blog), but the Mangrove killifish, Kryptolebias marmoratus, is the only vertebrate that regularly self-fertilizes. Most individuals have male and female reproductive organs. Obviously, this allows you to have individuals that are not quite clones, but certainly have much more limited variation than most sexual species.

But, because sex is rarely simple, some individuals in this species are just male.

And that little detail means that the hope that all these individuals will create nice, neat, clone lineages gets shot down. So Tatarenkov and colleagues decided to investigate how genetically similar these fish are to each other.

Some findings are depressingly familiar. Cell biologists have often found that what they thought was one type of cell cultures has been contaminated by nearby strains of other immortal cells. HeLa cells are particularly notorious in this regard. Similarly, Tatarenkov and company found about 20% of their marbled killifish did not have the expected genes. Incomplete record keeping meant that many sources of error, or sources of new variation they found, could not be traced back to its source.

They did find new genetic variation that appeared to have cropped up since the animals had been collected for the lab, which they attributed to new mutations. In fact, one gene seemed to be a mutational “hotspot,” mutating several times in different lines.

The major source of genetic variation, however, was the original source of the lab population. This fish has a wide distribution, and stocks collected from different locations did not resemble each other. Thus, this fish has a nice combination of being able to maintain genetic similarity within a lineage, but there remains some variation across lineages.

P.S. – If this fish’s specific name, “marmoratus,” looks a bit familiar, it’s because it is Latin for “marbled.” And that’s undoubtedly the same root for the word, “Marmorkrebs.”

Reference

Tatarenkov A, Ring B, Elder J, Bechler D, Avise J. 2010. Genetic Composition of Laboratory Stocks of the Self-Fertilizing Fish Kryptolebias marmoratus: A Valuable Resource for Experimental Research PLoS ONE 5(9): e12863. DOI: 10.1371/journal.pone.0012863

Picture from here.

Martin and colleagues, 2010

Martin P, Dorn NJ, Kawai T, van der Heiden C, Scholtz G. 2010. The enigmatic Marmorkrebs (marbled crayfish) is the parthenogenetic form of Procambarus fallax (Hagen, 1870). Contributions to Zoology 79(3): 107-118. http://www.ctoz.nl/vol79/nr03/a03

Abstract

A mysterious parthenogenetic cambarid crayfish (the Marmorkrebs) has been spreading across the globe for the past decade. We compare this crayfish directly to two other cambarids, Procambarus fallax and P. alleni, that have been suggested to be related or even identical to the Marmorkrebs. Using external morphology and sequences of two mitochondrial genes we show clear correspondences between Marmorkrebs and P. fallax, a species found natively throughout peninsular Florida, USA. Based on these congruent results we suggest that the Marmorkrebs is the parthenogenetic form of P. fallax. This finding has potential evolutionary and ecological implications at several levels. The Marmorkrebs might be a type of geographical parthenogenesis, but a natural population in the wild is so far unknown. Furthermore, challenges arise in regard to the respective species status of the Marmorkrebs. Taxonomically we suggest that the Marmorkrebs is treated as “form” of P. fallax. Last but not least, the identity of this animal and its ecology has an impact for considering potential spread and effects of this species across the globe.

Keywords: 12S rRNA, annulus ventralis, COI, DNA barcoding, species concept, thelytoky

Edit, 29 December 2018: Link to article updated. Really wishing more journals used DOIs...

Crayfish at World Aquaculture Society conference

Tthe World Aquaculture Society meeting will be holding a special session on crayfish at the next meeting in New Orleans in March 2011. The organizing committee is still accepting abstracts for this session until 30 September 2010. The session will be chaired by Julie Delabbio and Ray McClain.

To submit an abstract, go to https://www.was.org and click on the New Orleans meeting logo.

If ever there was a place to present a paper on crayfish aquaculture, New Orleans is it.

First report of Marmorkrebs in Asian ecosystems

Japan becomes the latest addition to the map of where Marmorkrebs have been found in natural ecosystems. Tadashi Kawai, the co-editor of The Biology of Freshwater Crayfish, provided me with this brief translated excerpt from the book.

The marbled crayfish was found as pet in Japanese aquarium trade. In 2006, Sapporo Salmon Museum (Sapporo City, Hokkaido) accepted the unknown crayfish from volunteer conservationists. They collected from a river from Sapporo City. As the crayfish show marble color patter on their carapace and their juvenile are all female, it identified as parthenogenetic Marmorkrebs.

The Google Map that I maintain of Marmorkrebs introductions has been updated accordingly.

Reference

Kawai T, Takahata M (eds.). 2010. Biology of Crayfish. Sapporo: Hokkaido University Press. 556 pgs. ISBN: 978-4-8329-8194-2.

http://www.hup.gr.jp/details/ISBN978-4-8329-8194-2.htm

Sapporo Salmon Museum picture from here.

Hybridization

In vertebrates, nearly every case of parthenogenetic species can be traced back to a hybridization event. Does this mean it’s important to evolution generally? Jerry Coyne, whose main research is speciation, looks at this question.

Could Maryland be next?

Candus Thomson, writing on the Outdoors Girl blog for the Baltimore Sun, reports that Maryland is considering adding Marmorkrebs to Maryland’s “Nuisance Species” list. I’d previously mentioned Maryland had a fact sheet about Marmorkrebs, but hadn’t realized that it was probably prepared as part of this move to consider Marmorkrebs for regulation.

The meeting happened last Wednesday, with Candus noting there were six biologists for every member of the public(!).

The public can comment on the proposed regulations by visiting here until 30 September 2010.

Breakthrough?

If you read this blog, but don’t visit the home page every time, you might not have noticed another set of new papers in press that are now listed on the home page.

There are more papers in press right now than were published all of last year. Some of those might not make it to final publication (with volume and page numbers) this year, but I’m expecting most will. Which is quite an lovely surge in Marmorkrebs research.

Photo by ViaMoi on Flickr, used under a Creative Commons license.