Alternative conservation outcomes from aquatic fauna translocations: Losing and saving the Running River rainbowfish

1. The translocation of species outside their natural range is a threat to aquatic biodiversity globally, especially freshwater fishes, as most are not only susceptible to predation and competition but readily hybridize with congeners. 2. Running River rainbowfish (RRR, Melanotaenia sp.) is a narrow-ranged, small-bodied freshwater fish that recently became threatened and was subsequently listed as Critically Endangered, owing to introgressive hybridization and competition following the translocation of a congeneric species, the eastern rainbowfish (Melanotaenia splendida). 3. To conserve RRR, wild fish were taken into captivity, genetically confirmed as pure representatives, and successfully bred. As the threat of introgression with translocated eastern rainbowfish could not be mitigated, a plan was devised to translocate captive raised RRR into unoccupied habitats within their native catchment, upstream of natural barriers. The translocation plan involved careful site selection and habitat assessment, predator training (exposure to predators prior to release), soft release (with a gradual transition from captivity to nature), and post-release monitoring, and this approach was ultimately successful. 4. Two populations of RRR were established in two previously unoccupied streams above waterfalls with a combined stream length of 18 km. Post-release monitoring was affected by floods and low sample sizes, but suggested that predation and time of release are important factors to consider in similar conservation recovery programmes for small-bodied, short-lived fishes

Antagonist HIV-1 Gag Peptides Induce Structural Changes in HLA B8

In the cellular immune response, recognition by CTL-TCRs of viral antigens presented as peptides by HLA class I molecules, triggers destruction of the virally infected cell (Townsend, A.R.M., J. Rothbard, F.M. Gotch, G. Bahadur, D. Wraith, and A.J. McMichael. 1986. Cell. 44:959–968). Altered peptide ligands (APLs) which antagonise CTL recognition of infected cells have been reported (Jameson, S.C., F.R. Carbone, and M.J. Bevan. 1993. J. Exp. Med. 177:1541–1550). In one example, lysis of antigen presenting cells by CTLs in response to recognition of an HLA B8–restricted HIV-1 P17 (aa 24–31) epitope can be inhibited by naturally occurring variants of this peptide, which act as TCR antagonists (Klenerman, P., S. Rowland Jones, S. McAdam, J. Edwards, S. Daenke, D. Lalloo, B. Koppe, W. Rosenberg, D. Boyd, A. Edwards, P. Giangrande, R.E. Phillips, and A. McMichael. 1994. Nature (Lond.). 369:403– 407). We have characterised two CTL clones and a CTL line whose interactions with these variants of P17 (aa 24–31) exhibit a variety of responses. We have examined the high resolution crystal structures of four of these APLs in complex with HLA B8 to determine alterations in the shape, chemistry, and local flexibility of the TCR binding surface. The variant peptides cause changes in the recognition surface by three mechanisms: changes contributed directly by the peptide, effects transmitted to the exposed peptide surface, and induced effects on the exposed framework of the peptide binding groove. While the first two mechanisms frequently lead to antagonism, the third has more profound effects on TCR recognition

Barriers to hybridisation and their conservation implications for a highly threatened Australian fish species

Hybridisation and introgression are natural phenomena that may lead to the transfer of adaptive alleles from one species to another and increased species diversity. At the same time, hybridisation and subsequent introgression threaten many species world‐wide through the loss of genetic and species diversity. In Australia, introgressive hybridisation between native and alien species has not typically been considered a significant threat to native biodiversity because of the taxonomic distance between native and alien biota. However, many native fish have been introduced outside their natural range. Recently, four taxa in the genus Melanotaenia have been nationally listed as threatened due to introgressive hybridisation with introduced Melanotaenia splendida. We examined pre‐ and post‐zygotic barriers to hybridisation between M. splendida and one of these threatened taxa—Running River rainbowfish (RRR)—to assess the potential for hybridisation to occur. We used dichotomous mate choice experiments to examine pre‐zygotic barriers and mating experiments to examine post‐zygotic barriers. Size was not a significant predictor of the proportion of time subjects spent with a potential mate, nor was there any significant difference in the amount of time subjects spent with potential mates of their own or the opposite species. Eggs from hybrid pairings with female RRR had a slightly higher hatching rate than those from hybrid pairings with female M. splendida, but neither were significantly different from intraspecies crosses. We could not identify any definite barriers to hybridisation, demonstrating that the introduction of “native” fish species outside their natural range poses a higher risk of hybridisation than previously thought. We call for better education around the consequences of moving “native” fish and the development of rapid response plans to deal with recently established alien populations of Australian fish species in order to prevent future extinctions due to introgressive hybridisation