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African fish live fast, die young

Sept. 3, 2013
Courtesy of BioMed Central
and World Science staff

Af­ri­can an­nu­al fish take the ad­age “live fast, die young” to a whole new lev­el, sci­en­tists have found: their short life­span goes along with the most rap­id sex­u­al matura­t­ion of any ver­te­brate. 

The find is re­ported in the re­search jour­nal EvoDevo as part of a se­ries on ex­treme en­vi­ron­ments.

A nearly dried-out pud­dle in south­west­ern Af­ri­ca in­ha­bi­ted by Af­ri­can an­nual fish with short life­spans. (Courtesy of BioMed Cen­tral)


Af­ri­ca’s ti­ny an­nu­al fish live in tem­po­rary pud­dles cre­at­ed by sea­son­al rain­fall. They must grow and re­pro­duce quickly to lay their har­dy eggs be­fore the wa­ters dry. 

Such fish can grow up to 23 per­cent of their body length in a day, re­port Mar­tin Re­ichard of the In­sti­tute of Ver­te­brate Bi­ol­o­gy in Br­no, Czech Re­pub­lic, and col­leagues, who stud­ied wild-caught fish in cap­ti­vity. 

They found that one spe­cies, Notho­bran­chius kadleci, started re­pro­duc­ing at 17 days old, at a size of just 31 mil­lime­ters (1.2 inch­es), with a re­lat­ed spe­cies, N. furz­eri ma­tur­ing a day lat­er. 

The fish then pro­duced eggs that de­vel­oped to the hatch­ing stage in as few as 15 days, mak­ing the time from one genera­t­ion to the next as lit­tle as month, the re­search­ers found. That, they added, is the most rap­id sex­u­al matura­t­ion time and min­i­mum genera­t­ion time of any known ver­te­brate spe­cies.

A male of the spe­cies No­tho­bran­chius kad­leci. (Cour­tesy of Bio­Med Cen­tral)


When the pools dry up, dor­mant em­bryos can sur­vive in the dried mud for months, un­til the next rains come and the life cy­cle be­gins again. These fish nev­er en­coun­ter their par­ents. In the lab, half of em­bryos were found to skip dor­man­cy when in­cu­bat­ed on peat. In the wild, the in­ves­ti­ga­tors said, they would pop­u­late sec­ond­ary pools pro­duced with­in a sin­gle rainy sea­son af­ter a main pool dried out. 

The find­ings sug­gest that rap­id growth and matura­t­ion don’t com­pro­mise sub­se­quent fe­cund­ity, they added.

An­i­mals with a long life span can af­ford to take things slow. The ti­ny cave-dwelling sal­a­man­der, ol­m (Pro­teus an­gui­nus), which lives for over 100 years, takes 16 years to reach sex­u­al matur­ity. But when the risk of mor­tal­ity is high or life­span shorter, an­i­mals reach sex­u­al matur­ity ear­li­er. The ti­ny go­by, Schind­le­ria, and fe­males of house mouse lab strains (Mus mus­cu­lus) be­come sex­u­ally ma­ture at just 23 days old.

Ear­li­er stud­ies of a lab­o­r­a­to­ry strain of an Af­ri­can an­nu­al fish sug­gested that it took the fish four weeks to ma­ture, but this may have been an overestimate, said Re­ichard and col­leagues. Pre­vi­ous re­ports of early matura­t­ion were based on an­ec­do­tal ev­i­dence, they added, but this study was based on quanti­tative da­ta and in­di­cates that the rap­id growth rate in the lab is still an un­der­es­ti­mate com­pared to that in the wild.


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African annual fish take the adage “live fast, die young” to a whole new level, scientists have found: their short lifespan goes along with the most rapid sexual maturation of any vertebrate. The find is reported in the research journal EvoDevo as part of a series on extreme environments. The tiny annual fish of Africa live in temporary puddles created by seasonal rainfall, and so must grow and reproduce quickly in order to lay their hardy eggs before the waters dry up. Such fish can grow up to 23% of their body length in a day, report Martin Reichard of the Institute of Vertebrate Biology in Brno, Czech Republic, and colleagues, who studied wild-caught fish in captivity. They found that one species, Nothobranchius kadleci started reproducing at 17 days old, at a size of just 31 millimeters (1.2 inches), with a related species, N. furzeri maturing a day later. The fish then produced eggs that developed to the hatching stage in as few as 15 days, making the time from one generation to the next as little as month, the researchers found. That, they added, is the most rapid sexual maturation time and minimum generation time of any known vertebrate species. When the pools dry up, dormant embryos can survive in the dried mud for months, until the next rains come and the life cycle begins again. These fish never encounter their parents. In the lab, half of embryos were found to skip dormancy when incubated on peat in a Petri dish. In the wild, the investigators said, they would populate secondary pools produced within a single rainy season after a main pool dried out. The findings suggest that rapid growth and maturation don’t compromise subsequent fecundity, they added. Animals with a long life span can afford to take things slow. The tiny cave-dwelling salamander, olm (Proteus anguinus), which lives for over 100 years, takes 16 years to reach sexual maturity. But when the risk of mortality is high or lifespan shorter, animals reach sexual maturity earlier. The tiny goby, Schindleria, and females of house mouse lab strains (Mus musculus) become sexually mature at just 23 days old. Earlier studies of a laboratory strain of an African annual fish suggested that it took the fish four weeks to mature, but this may have been an overestimate, said Reichard and colleagues. Previous reports of early maturation were based on anecdotal evidence, they added, but this study was based on quantitative data and indicates that the rapid growth rate in the lab is still an underestimate compared to that in the wild.