Epitopes Of Tilapia Red Blood Cells. I. Species-Specific Antibodies For The Control Of Tilapia Breeding Stocks

Specific antisera against red blood cells of some tilapia species were obtained by reciprocal inter- specific and intergeneric immunizations. The antisera were used to confirm co-dominant expres- sion of epitopes in F1 interspecific hybrids and to identify the parental origin of three red tilapia strains. The antisera in all hybrids (Oreochromis niloticus x O. mossambicus, O. aureus x O. horno- rum, O. niloticus x S. galilaeus and O. niloticus x O. aureus) were positive to both parental strains. However, while all F1 hybrids of O. mossambicus x O. hornorum were positive to anti-O. mossambi- cus antiserum, only 50% were positive to anti-O. hornorum antiserum. In most cases, these results point to co-dominant expression of the species-specific epitopes in hybrids. In addition, the triple parental origins of the Philippine red tilapia (positive for O. aureus, O. mossambicus and O. niloticus epitopes) and of mossambicus red tilapia (positive for O. hornorum, O. mossambicus and O. niloticus epitopes) were assessed. The O. niloticus red tilapia, described as a purebred red variant of O. niloticus, was positive for both anti-O. niloticus and anti-O. aureus antibodies, with a significantly more intense reaction to the latter. A possible genetic basis of this last finding is discussed

Full-Sib Mating Can Reduce Deleterious Effects Associated With Residual Sperm Inheritance In Gynogenotes

Fertilization of Oreochromis aureus eggs with UV-irradiated sperm from the closely related species O. niloticus, followed by diploidy restoration, produced offspring with lower embryo viability and higher skeletal deformation rates than siblings generated with sperm from a genetically distant species (Tilapia zillii). Results showed that: (a) deleterious effects due to O. niloticus sperm accu- mulate in gynogenetic fish over generations; (b) such effects are eliminated when using T. zillii sperm to fertilize eggs from gynogenetic mothers produced by full-sib matings. These results sug- gest that: (a) deleterious effects are associated with residual male DNA fragments which may be passed on to descendent offspring; (b) such fragments are significantly purged following full-sib mating. These findings suggest that biparental reproduction may play an important role in the con- trol of genome integrality by purging supernumerary chromosome fragments

A deleterious effect associated with UNH159 is attenuated in twin embryos of an inbred line of blue tilapia \u3ci\u3eOreochromis aureus\u3c/i\u3e

Offspring of a highly inbred gynogenetic line of Oreochromis aureus displayed 12-fold increase in twinning rate compared to the outbred population. Asymmetric conjoined twins, which consist of a normal embryo attached to a malformed-atrophic twin, were frequently encountered in both gynogenetic (90·7%) and outbred (38·2%) embryos. The monozygotic origin of these twins was determined using five microsatellite markers. Progeny of heterozygous parents for the microsatellite UNH159 were separated into sub-sets of twins and normal full-sibs. Consistent with previous reports, the normal embryo sub-set exhibited elimination of both types of homozygotes for the UNH159 genetic marker at 2–8 days after fertilization. Unexpectedly, this elimination was less frequent in twins. The UNH159 marker as well as RNA-binding motif protein, X-linked (rbmx), SRY-box containing gene 3 (sox3) and alpha-thalassemia/mental retardation syndrome X-linked (atrx) genes were mapped to linkage group 2. These gene orthologues are all located on the mammalian X chromosome and atrx is necessary for the X-chromosome inactivation

Viral encephalitis of tilapia larvae: Primary characterization of a novel herpes-like virus

AbstractWe report here an outbreak of an acute disease that caused high mortality rate in laboratory-reared tilapia larvae. The disease was initially observed in inbred gynogenetic line of blue tilapia larvae (Oreochromis aureus) and could be transmitted to larvae of other tilapia species. Based on the clinical manifestation (a whirling syndrome), we refer to the disease as viral encephalitis of tilapia larvae. The disease-associated DNA virus is described and accordingly designated tilapia larvae encephalitis virus (TLEV). A primary morphological, biophysical and molecular characterization of TLEV is presented. By virtue of these properties, the newly discovered virus is a herpes-like virus. Phylogenetic analysis, albeit limited, confirms this assumption and places TLEV within the family of Herpesviridae and distantly from the families Alloherpesviridae and Iridoviridae. By using PCR with virus-specific primers, diseased larvae and adult TLEV carriers were also identified in tilapia delivered from external hatcheries