A new species of cichlid fish, Lethrinops atrilabris is described from specimens collected by trawling at a depth of around 90 m off Monkey Bay, southern Lake Malawi. It is assigned to the genus ...Lethrinops on the basis of its vertical flank barring, lack of enlarged cephalic lateral line canal pores and the form of the lower jaw dental arcade. It can be distinguished from congeneric species by its male breeding dress of contrasting flank barring and dark ventral surface, most strikingly on the lips, throat and chest, its relatively small known maximum size <75 mm standard length (SL), large eyes (38%–41% head length), laterally compressed body (depth 2.5–2.7 times max head width) and lower gill raker count (13–14).
Null geodesics in conformal gravity Turner, George E; Horne, Keith
Classical and quantum gravity,
05/2020, Letnik:
37, Številka:
9
Journal Article
Recenzirano
Odprti dostop
We present an analysis of the null geodesics of the static, spherically symmetric, vacuum solution to the equations of conformal (Weyl) gravity. We classify the full range of exotic spacetimes ...arising from the parameter space of the metric. The nature of various notable features of these spacetimes is investigated including light spheres, horizons and physical singularities.
The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here we report the discovery and detailed characterization of early-stage adaptive ...divergence of two cichlid fish ecomorphs in a small (700 meters in diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet, and trophic morphology. With whole-genome sequences of 146 fish, we identified 98 clearly demarcated genomic "islands" of high differentiation and demonstrated the association of genotypes across these islands with divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight-vision–associated genes), hormone signaling, and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi.
Abstract
The adaptive radiation of cichlid fishes in East African Lake Malawi encompasses over 500 species that are believed to have evolved within the last 800,000 years from a common founder ...population. It has been proposed that hybridization between ancestral lineages can provide the genetic raw material to fuel such exceptionally high diversification rates, and evidence for this has recently been presented for the Lake Victoria region cichlid superflock. Here, we report that Lake Malawi cichlid genomes also show evidence of hybridization between two lineages that split 3–4 Ma, today represented by Lake Victoria cichlids and the riverine Astatotilapia sp. “ruaha blue.” The two ancestries in Malawi cichlid genomes are present in large blocks of several kilobases, but there is little variation in this pattern between Malawi cichlid species, suggesting that the large-scale mosaic structure of the genomes was largely established prior to the radiation. Nevertheless, tens of thousands of polymorphic variants apparently derived from the hybridization are interspersed in the genomes. These loci show a striking excess of differentiation across ecological subgroups in the Lake Malawi cichlid assemblage, and parental alleles sort differentially into benthic and pelagic Malawi cichlid lineages, consistent with strong differential selection on these loci during species divergence. Furthermore, these loci are enriched for genes involved in immune response and vision, including opsin genes previously identified as important for speciation. Our results reinforce the role of ancestral hybridization in explosive diversification by demonstrating its significance in one of the largest recent vertebrate adaptive radiations.
The hundreds of cichlid fish species in Lake Malawi constitute the most extensive recent vertebrate adaptive radiation. Here we characterize its genomic diversity by sequencing 134 individuals ...covering 73 species across all major lineages. The average sequence divergence between species pairs is only 0.1-0.25%. These divergence values overlap diversity within species, with 82% of heterozygosity shared between species. Phylogenetic analyses suggest that diversification initially proceeded by serial branching from a generalist Astatotilapia-like ancestor. However, no single species tree adequately represents all species relationships, with evidence for substantial gene flow at multiple times. Common signatures of selection on visual and oxygen transport genes shared by distantly related deep-water species point to both adaptive introgression and independent selection. These findings enhance our understanding of genomic processes underlying rapid species diversification, and provide a platform for future genetic analysis of the Malawi radiation.
Work on the Lake Victoria cichlids Pundamilia nyererei (red dorsum males, deeper water), Pundamilia pundamilia (blue males, shallower water) and related species pairs has provided insights into ...processes of speciation. Here, we investigate the female mating behaviour of 5 Pundamilia species and 4 of their F1 hybrids through mate choice trials and paternity testing. Complete assortative mating was observed among all sympatric species. Parapatric species with similar depth habitat distributions interbred whereas other parapatric and allopatric species showed complete assortative mating. F1 hybrids mated exclusively with species accepted by females of the parental species. The existence of complete assortative mating among some currently allopatric species suggests that pre-existing mating barriers could be sufficient to explain current patterns of co-existence, although, of course, many other factors may be involved. Regardless of the mechanism, mating preferences may influence species distribution in potentially hybridizing taxa, such as in the adaptive radiation of cichlid fish. We suggest that this at least partly explains why some species fail to establish breeding populations in locations where they are occasionally recorded. Our results support the notion that the mating preferences of potentially cross-breeding species ought to be included in coexistence theory.
Abstract
Moving human sexuality beyond a specialty focus and establishing a sexuality discourse within social work’s foundation may be challenging. Group process and reflection, hallmarks of social ...work, may be a way to integrate this sometimes overlooked and often taboo conversation into social work coursework. Undergrad students from two Mid-western universities reflected on the usefulness of an established experiential sex education activity . Qualitative analysis of student narratives resulted in seven themes describing the usefulness of this activity including: (i) emotional intimacy; (ii) connection; (iii) power of personal stories; (iv) normalising; (v) healing; (vi) clinical profile and (vii) RE-storying. These themes demonstrate that this activity has clear benefits and enriches the overall learning of the topic of human sexuality. Further, these themes fit nicely within a social work pedagogy teaching clinical practice skills such as group process, rapport building and use of self. Implications for social work are discussed.
The purpose of this qualitative case study research was to explore how adults with mild intellectual disabilities (ID) live out their social-sexual lives. Findings revealed the importance of both ...physical and emotional pleasure to five adults with ID. Research and educational efforts with this population have focused largely on reproduction and abuse prevention, emphasizing safety over the possibilities of human connectedness. Data sources included observations and a series of interviews. Findings in five areas – sensuality, intimacy, sexual experience, sexual attitudes, and sexual self-identity – demonstrate the richness of data that can be obtained with this population using qualitative research. Participants’ own words about their social-sexual lives are poignant, mirroring core social work pillars: self-determination and strengths perspective. Discussion includes recommendations for ways that social workers, as well as, sexuality and disability professionals can support individuals’ quality of life by addressing sexual pleasure as a key component of sexual health services.
Abstract
Social work students must advance their social work skills gaining practice competencies. And, whilst practice learning takes place in field education placements, social work students often ...also enrol in a dedicated unit/ course whereby the teaching of practice skills is facilitated in class. A practice skills class is another learning space to imbue practice wisdom. Adjunct teaching staff are often employed on short-term university contracts to teach social work students in the area of practice skills. Whilst these practitioners can bring a wealth of experience and expertise to the under-graduate classroom, it cannot be assumed that adjunct teaching staff have formal training in curricula development nor pedagogical delivery. The goal of this article is to identify the critical elements of teaching practice skills and to examine the ways in which teaching content is delivered. This article presents the ‘teaching the teacher’ experience of three social work educators at an Australian university. A collaborative autoethnography identified three themes from the inductive analysis: (i) teaching best practices, (ii) teaching role and (iii) teaching practice skills. Finally, implications for social work are discussed and recommendations shared.
Practice skills are essential for social work students. In addition to the practice learning gleaned from field placements, social work students often enrol in a dedicated unit/ course teaching practice skills. These instructors teaching in-class practice skills units/courses are often practitioners with rich experience; however, no formal training on how to teach. Three Australian social work educators examine the process, highlighting best practices for and educators’ multiple roles inside in-class instruction/teaching of practice skills. Most importantly, they identify critical skills identified as the art of social work practice.
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