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ON THE POSSIBLE USE OF ANNUAL KILLIFISHES AS MODELS FOR AGING RESEARCH: A COMMENT ON HERRERA AND JAGADEESWARAN

Scuola Normale Superiore Pisa Italy

Address correspondence to Alessandro Cellerino, Scuola Normale Superiore, Neurobiologia c/o CNR, via Moruzzi 1, Pisa, Tuscany 56100, Italy. E-mail: cellerino{at}in.cnr.it

To the Editor:

In their article, Herrera and Jagadeeswaran have proposed the use of the annual fishes Nothobranchius rachovii and Cynolebias (Austrolebias after the last taxonomic revision) nigripinnis as models for aging research (1). The authors are seemingly unaware of the seminal work of Cooper, Markofsky, and others (2–7) who showed aging-related degenerations in several organs of the annual killifish Nothobranchius guentheri and Nothobranchius korthause and introduced Nothobranchius as a natural model of rapid aging in vertebrates. Herrera and Jagadeeswaran have analyzed the survival curves of Nothobranchius rachovii from a commercial source, and reported a maximum life span of 9.5 months but could not show age-dependent increase in mortality rate or expression of any aging biomarker. If researchers can be enticed to a new model system based on this information, we think that readers of the Journals of Gerontology will be interested to learn that other species of annual fishes exist with much shorter life spans. In 2003, we reported that Nothobranchius furzeri has a maximum survival in laboratory conditions of 12 weeks (8). This life span is comparable to that of wild-type Drosophila, a popular model for aging studies. Moreover, Nothobranchius furzeri has an explosive growth (sexual maturity is attained at 3–4 weeks of age), and its age-dependent mortality rate increases exponentially with age (8).

The huge difference in growth and life span between the two species is not surprising in light of Nothobranchius ecology. Nothobranchius fish are adapted to colonize the temporal ponds of Eastern Africa. When the ponds fill due to the floods, Nothobranchius embryos hatch, reach sexual maturity, and breed before their ephemeral habitat disappears. Extrinsic death probability for Nothobranchius is basically rectangular and is determined by the length of the rainy season. Nothobranchius rachovii originates from the city of Beira (9), with annual rainfall of approximately 1600 mm/year (data from www.worldweather.org). Nothobranchius furzeri, in contrast, originates from the semi-arid lowveld at the border between Mozambique, South Africa, and Zimbabwe (10). Average annual rainfall in that area is about 340 mm/year (data refer to Breitbridge, from www.worldweather.org) but is erratic and can be as low as 200 mm/year in lean years (10). Therefore, the temporal profile of extrinsic mortality rate is drastically different for the two species.

Evolutionary theories of aging predict that an increase in extrinsic mortality rate results in faster growth and, as a consequence, accelerated aging (11). The predictions of the theory perfectly fit the differences in growth rate and life span that we observe by comparing Nothobranchius furzeri and Nothobranchius rachovii. We agree with Herrera and Jagadeeswaran that the short life span of Nothobranchius fishes can represent a decisive advantage for aging research. Even more so, if the correct species is selected.

Footnotes

Decision Editor: James R. Smith, PhD

Received January 29, 2005

Accepted January 30, 2005

REFERENCES

1. Herrera M, Jagadeeswaran P. Annual fish as a genetic model for aging. J Gerontol A Biol Sci Med Sci. 2004;59:101-107.[Medline]
2. Cooper EL, Zapata A, Garcia Barrutia M, Ramirez JA. Aging changes in lymphopoietic and myelopoietic organs of the annual cyprinodont fish, Nothobranchius guentheri. Exp Gerontol. 1983;18:29-38.[Medline]
3. Markofsky J, Perlmutter A. Age at sexual maturity and its relationship to longevity in the male annual cyprinodont fish, Nothobranchius guentheri. Exp Gerontol. 1972;7:131-135.[Medline]
4. Markofsky J, Perlmutter A. Growth differences in subgroups of varying longevities in a laboratory population of the male annual cyprinodont fish, Nothobranchius guentheri (Peters). Exp Gerontol. 1973;8:65-73.[Medline]
5. Markofsky J, Milstoc M. Aging changes in the liver of the male annual cyprinodont fish, Nothobranchius guentheri. Exp Gerontol. 1979;14:11-20.[Medline]
6. Markofsky J, Milstoc M. Histopathological observations of the kidney during aging of the male annual fish Nothobranchius guentheri. Exp Gerontol. 1979;14:149-155.[Medline]
7. Ruijter JM, Peute J, Levels PJ. The relation between pituitary gland and thyroid growth during the lifespan of the annual fish Cynolebias whitei and Nothobranchius korthausae: gonadotropic and thyrotropic cells. Cell Tissue Res. 1987;248:689-697.[Medline]
8. Valdesalici S, Cellerino A. Extremely short lifespan in the annual fish Nothobranchius furzeri. Proc R Soc Lond B Biol Sci. 2003;270:(Suppl 2): S189-S191.
9. Ahl E. Neue oder selten importierte Fische III. Blaetter fuer Aquarien und Terrarienkunde 1926;37:346-348.
10. Jubb RA. A new Nothobranchius (Pisces, Cyprinodontidae) from Southeastern Rhodesia. J Am Killifish Assoc. 1971;8:12-19.
11. Stearns SC, Ackermann M, Doebeli M. The experimental evolution of aging in fruitflies. Exp Gerontol. 1998;33:785-792.[Medline]

This article has been cited by other articles:

				P. Jagadeeswaran RESPONSE TO CELLERINO ON ANNUAL KILLIFISHES J. Gerontol. A Biol. Sci. Med. Sci., December 1, 2005; 60(12): 1492 - 1492. [Full Text] [PDF]

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