Comparison of growth performance among channel-blue hybrid catfish, ccGH transgenic channel catfish, and channel catfish in a tank culture system

Fish is an essential source of high-quality protein for people worldwide. The present study was designed to compare the growth performance among the channel-blue hybrid catfish, channel catfish transgenic for the channel catfish growth hormone (ccGH) cDNA driven by the antifreeze protein promoter from an ocean pout Zoarces americanus (opAFP-ccGH), and non-transgenic channel catfish control. Mean body weight of channel-blue hybrid catfish was 15.80 and 24.06% larger than non-transgenic channel catfish control at 4 and 18 months of age, respectively. However, transgenic opAFP-ccGH channel catfish were 5.52 and 43.41% larger than channel-blue hybrid catfish and 22.19 and 77.91% larger than their controls at 4 and 18 months of age, respectively. Significant differences in mean body weight between the sexes within all genetic types were found. Males were larger than females (P < 0.001). However, mean body weight of non-transgenic males was not larger than transgenic opAFP-ccGH females or male and female hybrid catfish. Condition factor of transgenic opAFP-ccGH channel catfish was higher (P < 0.05) than that of full-sibling, non-transgenic channel catfish and hybrid catfish. The mean percentage body weight gain of GH transgenic channel catfish was 559%, the channel-blue hybrid catfish was 384.9% and their non-transgenic controls channel catfish was 352.6%.

Evaluation of Crossability between Nicotiana benthamiana and Nicotiana excelsior

Wild tobacco species in the Nicotiana section Suaveolentes are promising genetic resources to introduce their disease resistance to cultivated tobacco, Nicotiana tabacum. However, hybrid lethality is observed in hybrid seedlings from crosses between most Suaveolentes species and N. tabacum. In particular, N. benthamiana belonging to the section Suaveolentes produces only viable hybrids after crossing with N. tabacum. In the present study, crossability between N. benthamiana and N. excelsior (section Suaveolentes) was investigated to test the possible usefulness of N. benthamiana as the bridge parent to transfer desirable genes of N. excelsior to N. tabacum via bridge crossing. After reciprocal crosses using three accessions of N. benthamiana and N. excelsior each, several crossing barriers such as cross-incompatibility, seed abortion, and male and female hybrid sterility were observed. Although reciprocal hybrids between N. benthamiana and N. excelsior showed a high degree of chromosome pairing in meiosis, univalents and multivalents, as well as chromosome bridges and lagging chromosomes, were observed. These meiotic abnormalities were thought to cause hybrid sterility. The possible usefulness of reciprocal hybrids between N. benthamiana and N. excelsior is discussed.

Uniparental genome elimination in Australian carp gudgeons

Metazoans usually reproduce sexually, blending the unique identity of parental genomes for the next generation through functional crossing-over and recombination in meiosis. However, some metazoan lineages have evolved reproductive systems where offspring are either full (clonal) or partial (hemiclonal) genetic replicas. In the latter group, the process of uniparental genome elimination selectively eliminates either the maternal or paternal genome from germ cells, and only one parental genome is selected for transmission. Although fairly common in plants, hybridogenesis (i.e. clonal haploidization via chromosome elimination) remains a poorly understood process in animals. Here, we explore the proximal cytogenomic mechanisms of somatic and germ cell chromosomes in sexual and hybrid genotypes of Australian carp gudgeons (Hypseleotris) by tracing the fate of each set during mitosis (in somatic tissues) and meiosis (in gonads). Our comparative study of diploid hybrid and sexual individuals revealed visually functional gonads in male and female hybrid genotypes and generally high karyotype variability, although the number of chromosome arms remains constant. Our results delivered direct evidence for classic hybridogenesis as a reproductive mode in carp gudgeons. Two parental sets with integral structure in the hybrid soma (the F1 constitution) contrasted with uniparental chromosomal inheritance detected in gonads. The inheritance mode happens through pre-meiotic genome duplication of the parental genome to be transmitted, while the second parental genome is likely gradually eliminated already in juvenile individuals. The role of metacentric chromosomes in hybrid evolution is also discussed.

Chromosomal evolution in Raphicerus antelope suggests divergent X chromosomes may drive speciation through females, rather than males, contrary to Haldane's rule

Chromosome structural change has long been considered important in the evolution of post-zygotic reproductive isolation. The premise that karyotypic variation can serve as a possible barrier to gene flow is founded on the expectation that heterozygotes for structurally distinct chromosomal forms would be partially sterile (negatively heterotic) or show reduced recombination. We report the outcome of a detailed comparative molecular cytogenetic study of three antelope species, genus Raphicerus, that have undergone a rapid radiation. The species are largely conserved with respect to their euchromatic regions but the X chromosomes, in marked contrast, show distinct patterns of heterochromatic amplification and localization of repeats that have occurred independently in each lineage. We argue a novel hypothesis that postulates that the expansion of heterochromatic blocks in the homogametic sex can, with certain conditions, contribute to post-zygotic isolation. i.e., female hybrid incompatibility, the converse of Haldane’s rule. This is based on the expectation that hybrids incur a selective disadvantage due to impaired meiosis resulting from the meiotic checkpoint network’s surveillance of the asymmetric expansions of heterochromatic blocks in the homogametic sex. Asynapsis of these heterochromatic regions would result in meiotic silencing of unsynapsed chromatin and, if this persists, germline apoptosis and female infertility.

The Effect of Emulsifier on Growth Performance and Fat Digestibility in Turkeys

The present study investigated the effect of an emulsifier with very high hydrophilic-to-lipophilic balance (HLB) value (18) on growth performance and fat digestibility in turkeys. A total of 1120 day-old female Hybrid Converter turkeys were randomly divided into four treatment groups with 7 replicates (pens) of 40 birds each. Control group (T1) turkeys were fed a basal diet (BD), while turkeys from experimental groups received different levels of the commercial emulsifier VE added to diets with standard or reduced metabolizable energy (ME) content: T2 – BD + 500 ppm of VE; T3 – BD + 500 ppm of VE until 8 weeks of age, and 250 ppm from 9 to 16 weeks; T4 – BD – 3% ME + 500 ppm of VE until 8 weeks of age, and 250 ppm from 9 to 16 weeks. Regardless of its dietary inclusion level (500 g/ton and 500/250 g/ton feed), the emulsifier positively influenced the body weights (BW) and body weight gains (BWG) of birds. On days 56 and 112, significant differences in the values of these parameters were noted between the control treatment (T1) vs. groups T2 and T3. Emulsifier addition even contributed to an increase in the BWG and BW of birds receiving diets with 3% lower ME content, as compared with turkeys fed control diets. This shows that the emulsifier more than compensated the reduction in ME in T4. The turkeys from group T3 were characterized by significantly higher feed efficiency than T1 and T4 birds. The highest fat digestibility was noted in turkeys fed diets with a standard ME level and emulsifier addition (T2 and T3). In conclusion, the use of dietary emulsifier positively influences the growth performance of turkeys, and improves fat digestibility.

A wood-warbler produced through both interspecific and intergeneric hybridization

Hybridization between divergent taxa can provide insight into the breakdown of characters used in mate choice, as well as reproductive compatibility across deep evolutionary timescales. Hybridization can also occur more frequently in declining populations, as there is a smaller pool of conspecific mates from which to choose. Here, we report an unusual combination of factors that has resulted in a rare, three-species hybridization event among two genera of warblers, one of which is experiencing significant population declines. We use bioacoustic, morphometric and genetic data, to demonstrate that an early generation female hybrid between a golden-winged warbler ( Vermivora chrysoptera ) and a blue-winged warbler ( V. cyanoptera ) went on to mate and successfully reproduce with a chestnut-sided warbler ( Setophaga pensylvanica ) . We studied the product of this event—a putative chrysoptera × cyanoptera × pensylvanica hybrid—and show that this male offspring sang songs like S. pensylvanica , but had morphometric traits similar to Vermivora warblers. The hybrid's maternal parent had V. chrysoptera mitochondrial DNA and , with six plumage-associated loci, we predicted the maternal parent's phenotype to show that it was likely an early generation Vermivora hybrid . That this hybridization event occurred within a population of Vermivora warblers in significant decline suggests that females may be making the best of a bad situation, and that wood-warblers in general have remained genetically compatible long after they evolved major phenotypic differences.

The Vengeful Lioness in Greek Tragedy: A Posthumanist Perspective1

This chapter reinterprets the animal metaphors used in ancient Greek tragedy to describe revenging women from a posthumanist perspective. Whereas critics have commonly regarded such metaphors as indicating the female revenger’s inhuman savagery and otherness (whereby a woman’s attempt to assume a male heroic role transforms her instead into a monstrous beast), posthumanism challenges conventional distinctions between animal and human, male and female. Drawing on the work of Rosi Braidotti, it argues that female revengers similarly challenge these distinctions. The metaphorical metamorphosis of Aeschylus’ Clytemnestra and Euripides’ Medea into lionesses reveals their complex figuration as male-female hybrid beings, recalling the tragic suffering and protective violence of the Homeric lion within a new context of interfamilial conflicts. These transformations engender terror but also compassion, evoking new ways of conceptualising humans-as-animals that invite recognition of our own unstable and hybrid nature.