AboutZoos, Since 2008


New type of repro­duc­tive hor­mones appli­ca­tion could save endan­gered frogs from going extinct

pub­lished 24 Decem­ber 2018 | mod­i­fied 24 Decem­ber 2018

Assisted breed­ing tech­nique pro­duced hun­dreds of north­ern cor­ro­boree frog offspring

Northern Corroboree frogsNorth­ern Cor­ro­boree frogs (Pseudophryne pengilleyi).
Image credit: Aimee Silla

In a world first, repro­duc­tive biol­o­gists at the Uni­ver­sity of Wol­lon­gong (UOW) have suc­cess­fully applied hor­mones top­i­cally to the abdomens of north­ern cor­ro­boree frogs to get breed­ing pairs of the endan­gered frog ‘in the mood’ to mate. The pro­gramme has enabled the gen­er­a­tion of hun­dreds of off­spring, with more than 800 viable eggs pro­duced using hormone-​assisted breed­ing tech­niques over the past four years.

North­ern cor­ro­boree frog off­spring of dif­fer­ent devel­op­men­tal stages (eggs, tad­poles and juve­nile frogs) have been released into sites in the north­ern Brind­abella Ranges, with more than 100 juve­nile frogs released in recent weeks by her­peto­fauna experts from UOW and Taronga Zoo.

Dr Aimee Silla and Dr Phillip Byrne from UOW’s Cen­tre for Sus­tain­able Ecosys­tem Solu­tions led the research project, team­ing up with Taronga Con­ser­va­tion Soci­ety Aus­tralia Her­peto­fauna Super­vi­sor Dr Michael McFad­den. The results have been pub­lished on 26 April in the jour­nal Repro­duc­tion, Fer­til­ity and Devel­op­ment.

We are delighted with the suc­cess of our breed­ing pro­to­cols,” Dr Silla said.

Repro­duc­tive hor­mones are admin­is­tered to male and female north­ern cor­ro­boree frogs prior to putting pairs in breed­ing tanks. The hor­mones help encour­age the frogs to mate, get­ting them in the right ‘mood’ for courtship and reproduction.”

Top­i­cal appli­ca­tion of repro­duc­tive hor­mones elim­i­nates the need for spe­cialised train­ing in amphib­ian injec­tion, one of the main rea­sons why repro­duc­tive tech­nolo­gies have not been widely adopted by cap­tive breed­ing facilities.

Amphib­ians have highly per­me­able skin, so we were able to squirt the hor­mones onto the ven­tral pelvic region of the frogs and it soaked right in,” Dr Silla said.

Although the north­ern cor­ro­boree frog has been bred suc­cess­fully in cap­tiv­ity for a num­ber of years, cap­tive pop­u­la­tions dis­play strong mat­ing bias (where a small pro­por­tion of desir­able males gain the major­ity of mat­ings, while a large num­ber of males don’t mate and there­fore don’t pass on their genes).

Dr Byrne said that in north­ern cor­ro­boree frog cap­tive breed­ing pro­grammes, typ­i­cally less than a third of avail­able males con­tribute to mat­ing suc­cess annually.

Over time, such cap­tive mat­ing biases may lead to a loss of genetic vari­a­tion and adap­tive poten­tial that could com­pro­mise long-​term re-​introduction suc­cess,” Dr Byrne said.

The research team used the hormone-​assisted breed­ing tech­niques to assist the genetic man­age­ment of the species by boost­ing breed­ing suc­cess and increas­ing the genetic diver­sity of offspring.

Dr Silla said she hoped their devel­op­ment of a user-​friendly, cost-​effective method for hor­mone appli­ca­tion would lead to more cap­tive breed­ing facil­i­ties using hor­mone treat­ment to boost the breed­ing suc­cess of endan­gered frogs.

The method could prove par­tic­u­larly impor­tant in devel­op­ing coun­tries in trop­i­cal and sub-​tropical regions of Africa, Asia and Cen­tral and South Amer­ica, which col­lec­tively are home to more than 80 per cent of endan­gered amphibians.

The North­ern Cor­ro­boree frog

The north­ern cor­ro­boree frog (Pseudophryne pengilleyi) is marked by yellowish-​green and black stripes on its back, as dis­tinct from the closely related south­ern cor­ro­boree frog (Pseudophryne cor­ro­boree) which has bright yel­low and black stripes. The north­ern cor­ro­boree frog is clas­si­fied as Endan­gered by the IUCN Red List of Threat­ened Species.

The north­ern cor­ro­boree frog grows to about 2.5 to 3cms in length and is endemic to the Aus­tralian Alps (the Brind­abella Ranges in the ACT and adja­cent Fiery Ranges and Bogong Moun­tains in New South Wales).

Threats to the species include: cli­mate change; dam­age to breed­ing sites by feral pigs and horses, fire, drought, inva­sive weeds, and forestry oper­a­tions; and infec­tion by the amphib­ian chytrid fungus.

(Source: Uni­ver­sity of Wol­lon­gong media release, 06.12.2018)

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