Conflicting preferences within females: sexual selection versus species recognition

Preferences for mates within and between species are often harmonious, as traits that females prefer are usually more developed in conspecifics than heterospecifics. This need not be the case, however. When it is not, conflict between these arenas of mate choice can be resolved if females attend to different cues for each task. But this raises the potential for correlations among preferences to limit the opportunity for these two processes to operate independently. Here, we show that, within individual female pygmy swordtails (Xiphophorus pygmaeus), directional preferences for conspicuous ornamentation are inversely associated with discrimination against a sympatric heterospecific, Xiphophorus cortezi. Thus, mate choice among and within species need not be separate, independent processes; instead, they can be mechanistically intertwined. As a consequence, different arenas of mate choice can constrain one another, even when females assess multiple cues.     

剑尾鱼卵子发生的组织学观察

应用光学显微镜对卵胎生硬骨鱼类剑尾鱼(Xiphophorus helleri)卵巢的组织结构进行了观察。结果显示,剑尾鱼卵子的发育过程可划分为6个时相。Ⅰ时相的卵母细胞呈原始分化状态,细胞外具一层细胞质膜。Ⅱ时相卵母细胞外不仅具有质膜,而且还包绕一层滤泡细胞。Ⅲ时相和Ⅳ时相的卵母细胞分化明显,胞质内开始积累脂滴和卵黄颗粒。Ⅴ时相为成熟卵子,卵子的卵膜极薄,胞质内含有丰富的脂滴和卵黄。Ⅵ时相卵母细胞进入退化期,滤泡细胞从卵周向中央突入,卵黄被完全吸收,滤泡细胞自身也变得肥大。结果表明,剑尾鱼卵巢中卵母细胞的发育是不同步的。     

Offspring production with cryopreserved sperm from a live-bearing fish Xiphophorus maculatus and implications for female fecundity

Xiphophorus fishes are well-established models for biomedical research of spontaneous or induced tumors, and their use in research dates back to the 1930s. Currently, 58 well-pedigreed lines exist among 24 Xiphophorus species housed as live animals at the Xiphophorus Genetic Stock Center. The technique of sperm cryopreservation has been applied to preserve these valuable genetic resources, and production of offspring has been reported with cryopreserved sperm in two species (X. helleri and X. couchianus). The goal of this research was to establish protocols for sperm cryopreservation and artificial insemination that yield live young in X. maculatus, a widely used research species. The objectives were to: 1) collect basic biological characteristics of males, and quantify the sperm production yield after crushing of dissected testis; 2) cryopreserve sperm from X. maculatus by adapting as necessary the protocols for sperm cryopreservation of X. helleri and X. couchianus; 3) use cryopreserved sperm to inseminate virgin females of X maculatus and other species (X. helleri and X. couchianus), and 4) compare experimental trials over a 3-year period to identify opportunities for improving female fecundity. In total, 117 males were used in this study with a standard length of 2.5 ± 0.3 cm (mean ± SD), body weight of 0.474 ± 0.149 g, and dissected testis weight of 7.1 ± 3.7 mg. Calculation of sperm availability showed 5.9 ± 2.8 × 10(6) sperm cells per mg of testis weight. Offspring were produced from cryopreserved sperm. Male-to-male variation (1-70%) was observed in post-thaw motility despite little variation in motility before freezing (60-90%) or genetic variation (~100 generations of sib-mating). Comparisons of biological factors of males did not have significant correlations with the production of live young, and the influence of females on production of young was identified from the comparison of artificial insemination over 3 years. Overall, this study describes offspring production from cryopreserved sperm in a third species of Xiphophorus fishes, and identifies the opportunities for improving female fecundity which is essential for establishment of germplasm repositories for Xiphophorus fishes.     

Unification of the genera Nonlabens, Persicivirga, Sandarakinotalea and Stenothermobacter into a single emended genus, Nonlabens, and description of Nonlabens agnitus sp. nov

Phylogenetic analyses based on 16S rRNA gene sequences showed that a bacterial isolate, designated JC2678(T), represents a distinct phyletic line within the suprageneric monophyletic clade containing the genera Nonlabens, Persicivirga, Stenothermobacter and Sandarakinotalea. The polyphasic data presented in this study demonstrated that the members belonging to the Nonlabens-like clade overall constitute a single genus. Therefore, it is proposed to transfer the members of genera Persicivirga O'Sullivan et al. 2006, Stenothermobacter Lau et al. 2006 and Sandarakinotalea Khan et al. 2006 to the genus Nonlabens Lau et al. 2005. Thus, P. dokdonensis (Yoon et al. 2006) Nedashkovskaya et al. 2009, P. ulvanivorans Barbeyron et al. 2010, P. xylanidelens O'Sullivan et al. 2006, Sandarakinotalea sediminis Khan et al. 2006 and Stenothermobacter spongiae Lau et al. 2006 should be transferred to Nonlabens dokdonensis comb. nov., Nonlabens ulvanivorans comb. nov., Nonlabens xylanidelens comb. nov., Nonlabens sediminis comb. nov. and Nonlabens spongiae comb. nov., respectively. In addition, strain JC2678(T) (=KACC 14155(T)=JCM 17109(T)) is proposed to constitute a novel species belonging to the genus Nonlabens with the name of Nonlabens agnitus sp. nov.     

Female bias for enlarged male body and dorsal fins in Xiphophorus variatus

Female preference for male fin elaborations in Poeciliid fishes may be driven by a sensory bias for increased lateral projection area (LPA) that has existed since the lineages diverged from a common ancestor. Previous research supports this hypothesis demonstrating female Poecilia latipinna, Poecilia mexicana, and Poecilia reticulata prefer males of larger body and dorsal fin size, but exhibit no such preferences when controlling for total LPA. In the current study, we further tested this hypothesis by presenting female platys, Xiphophorus variatus, with pairs of dummy males differing in: (1) body size (holding dorsal fin size constant); (2) dorsal fin size (holding body size constant); and (3) dorsal fin: body size ratio (holding total LPA constant). Females spent more time near dummies of greater body and dorsal fin size; however, in the third experiment, neither fin size, body size, nor any particular dorsal fin + body size combination was preferred. These results provide additional support for the LPA and sensory bias hypotheses, demonstrating that female X. variatus not only prefer males with “swords”, but sailfin-like dorsal fins as well when body size is held constant. Shared preference for increased LPA is consistent with common ancestry of the sensory/neural systems in females of all four species.     

Parasites, emerging disease and wildlife conservation

In this review some emerging issues of parasite infections in wildlife, particularly in Australia, are considered. We discuss the importance of understanding parasite biodiversity in wildlife in terms of conservation, the role of wildlife as reservoirs of parasite infection, and the role of parasites within the broader context of the ecosystem. Using a number of parasite species, the value of undertaking longitudinal surveillance in natural systems using non-invasive sampling and molecular tools to characterise infectious agents is illustrated in terms of wildlife health, parasite biodiversity and ecology.     

Middle Pleistocene fossil Cercopithecidae from Asbole, Afar Region, Ethiopia

A sample of 117 fossil cercopithecids has been collected from the Middle Pleistocene site of Asbole, Afar Region, Ethiopia. A minimum of five species is present. There are two species of Cercopithecini, here recognized as cf. Chlorocebus aff. aethiops, and cf. Chlorocebus cf. patas. There are also two species of Papionini: Papio hamadryas ssp. indet. and Theropithecus oswaldi leakeyi. Finally, there is a single species of colobine present, Colobus sp. indet. The assemblage is chronologically constrained and is derived from sediments dated to approximately 600 ka. Within this sample Colobus sp. is by far the most common species present, outnumbering the other four species combined. The cercopithecid assemblage is most consistent with a woodland habitat, corroborating an earlier interpretation based on the non-primate fauna. Taxonomic, biogeographic, and evolutionary implications of the assemblage are also discussed.     

Relationships of plant pathogenic enterobacteria based on partial atpD, carA, and recA as individual and concatenated nucleotide and peptide sequences

Relationships of the genera in the Enterobacteriaceae containing plant pathogenic species: Brenneria, Dickeya, Enterobacter, Erwinia, Pantoea, Pectobacterium, and Samsonia, were investigated by comparison of their nucleotide and peptide sequences of atpD, carA, recA, and the concatenated sequences. Erwinia spp. and Pantoea spp., with Pectobacterium cypripedii, formed a group distinct from other pathogenic taxa. Pectobacterium, Brenneria, Dickeya, and Samsonia formed a contiguous clade. Samsonia was usually concurrent with Pectobacterium. Most Brenneria were also close to Pectobacterium, suggesting that these three taxa might be better represented as a single genus. Brenneria quercina was not closely associated with other members of this genus and may represent a separate genus. The sequences representing Dickeya were distinct, further supporting the generic status of the taxon. Plant pathogenic Enterobacter spp. display such sequence variability that few definite conclusions as to their specific placement could be made. These data highlight the difficulty of drawing reliable and robust taxonomic conclusions based on comparative analysis of sequence data without some independent criterion to calibrate a scale for diversity.     

Gene expression in spider appendages reveals reversal of exd/hth spatial specificity, altered leg gap gene dynamics, and suggests divergent distal morphogen signaling

Leg development in Drosophila has been studied in much detail. However, Drosophila limbs form in the larva as imaginal discs and not during embryogenesis as in most other arthropods. Here, we analyze appendage genes in the spider Cupiennius salei and the beetle Tribolium castaneum. Differences in decapentaplegic (dpp) expression suggest a different mode of distal morphogen signaling suitable for the specific geometry of growing limb buds. Also, expression of the proximal genes homothorax (hth) and extradenticle (exd) is significantly altered: in the spider, exd is restricted to the proximal leg and hth expression extends distally, while in insects, exd is expressed in the entire leg and hth is restricted to proximal parts. This reversal of spatial specificity demonstrates an evolutionary shift, which is nevertheless compatible with a conserved role of this gene pair as instructor of proximal fate. Different expression dynamics of dachshund and Distal-less point to modifications in the regulation of the leg gap gene system. We comment on the significance of this finding for attempts to homologize leg segments in different arthropod classes. Comparison of the expression profiles of H15 and optomotor-blind to the Drosophila patterns suggests modifications also in the dorsal-ventral patterning system of the legs. Together, our results suggest alterations in many components of the leg developmental system, namely proximal-distal and dorsal-ventral patterning, and leg segmentation. Thus, the leg developmental system exhibits a propensity to evolutionary change, which probably forms the basis for the impressive diversity of arthropod leg morphologies.