Establishment of a research colony of Marmorkrebs, a parthenogenetic crayfish species

Marmorkrebs, or marbled crayfish, are recently discovered parthenogenetic crayfish. Its origins are unknown, but it has been introduced into natural ecosystems and could become a highly invasive pest species. Marmorkrebs have potential as a model organism for research in many biological fields because they are genetically uniform. A key element of most successful model organisms is maintaining self-sustaining breeding colonies. We report on our efforts find the best conditions for establishing and maintaining a Marmorkrebs breeding colony for research. The colony was founded by four adults of unknown age (P generation). These foundresses were housed communally in standard aquaria and mainly fed vegetables (mostly peas), which were readily eaten. All adults generated multiple large batches of embryos, although three adults died over the course of a year. One daughter of the original adults (F1 generation) had her own offspring (F2 generation). The colony contained 14 descendants of the original adults after one year. The colony was later supplemented with additional 72 juveniles, which experienced 7% mortality in the first month in the colony. High juvenile mortality poses the most significant obstacle to establishing a research colony of Marmorkrebs, although relatively few adults would be needed to supply many viable embryos for developmental research

Assessing threat of introduction of the parthenogenetic marbled crayfish Marmorkrebs into North American waters

Background/Question/Methods Marmorkrebs are parthogenetic crayfish in the genus Procambarus. Their provenance is unknown, but they were discovered in hobbyists\u27 aquaria in Germany in the mid 1990s, and have since been introduced into the North American pet trade. Marmorkrebs are a potential invasive pest species. For example, they have already been introduced into Madagascar, where they may threaten endemic crayfish species. We are trying to estimate the risk, and possible consequences, of any accidental introduction of Marmorkrebs into North American waters. First, we conducted an online survey of hobbyists who keep Marmorkrebs as pets to estimate how widely, and how long, Marmorkrebs have been in distributed in the North American pet trade. Second, we are testing whether Marmorkrebs can successfully compete with other crayfish species during aggressive interactions. Anecdotal information suggests that Marmorkrebs are less aggressive than other crayfish. If Marmorkrebs consistently lose fights with crayfish of other species, this could affect their ability to compete for resources, which might in turn limit the spread of Marmorkrebs through natural ecosystems. To test this, Marmorkrebs and red swamp crayfish (Procambarus clarkii) were isolated for three weeks to place all individuals on an equal social status. A Marmorkrebs was paired in a small tank with either a conspecific or P. clarkii of similar size and their behavior was recorded for 30 minutes or until a clear victor emerged. Results/Conclusions Marmorkrebs are being kept as pets in at least thirteen American states and one Canadian province across North America, with the earliest report dating to 2005. These survey results suggest that an accidental introduction could occur almost anywhere in North America. Preliminary results from aggressive interactions indicate that Marmorkrebs can win fights against similarly sized P. clarkii. Intraspecific interactions were slower to begin and less intense than interspecific interactions. The ability to compete successfully with other species indicate that competition would be unlikely to limit the spread or impact of Marmorkrebs if they were released into North American waters. This, combined with the reproductive potential of a parthenogenetic crayfish where a single isolated individual can reproduce, indicate the threat posed by Marmorkrebs in North America is not trivial

Differential regulation of different human papilloma virus variants by the POU family transcription factor Brn-3a

The Brn-3a POU family transcription factor is over-expressed in human cervical carcinoma biopsies and is able to activate expression of the human papilloma virus type 16 (HPV-16) upstream regulatory region (URR), which drives the expression of the E6 and E7 oncoproteins. Inhibition of Brn-3a expression in human cervical cancer cells inhibits HPV gene expression and reduces cellular growth and anchorage independence in vitro as well as the ability to form tumours in vivo. Here we show that Brn-3a differentially regulates different HPV-16 variants that have previously been shown to be associated with different risks of progression to cervical carcinoma. In human cervical material Brn-3a levels correlate directly with HPV E6 levels in individuals infected with a high risk variant of HPV-16 whereas this is not the case for a low risk variant. Moreover, the URRs of high and intermediate risk variants are activated by Brn-3a in transfection assays whereas the URR of a low risk variant is not. The change of one or two bases in a low risk variant URR to their equivalent in a higher risk URR can render the URR responsive to Brn-3a and vice versa. These results help explain why the specific interplay between viral and cellular factors necessary for the progression to cervical carcinoma, only occurs in a minority of those infected with HPV-16

Evidence for contrasting roles for prolactin in eusocial naked mole-rats, Heterocephalus glaber and Damaraland mole-rats, Fukomys damarensis

Elevated prolactin (PRL) has been associated with the expression of social and cooperative behaviours in a number of vertebrate species, as well as suppression of reproduction. As social mole-rats exhibit both of these traits, PRL is a prime candidate in mediating their social phenotype. While naked and Damaraland mole-rats (NMRs and DMRs) have evolved eusociality independently within their family, both species exhibit an extreme skew in lifetime reproductive success, with breeding restricted to a single female and one or two males. Non-breeding NMRs of both sexes are physiologically inhibited from reproducing, while in DMRs only the non-breeding females are physiologically suppressed. Newly emerging work has implicated the dopamine system and PRL as a component in socially induced reproductive suppression and eusociality in NMR, but the DMR remains unstudied in this context. To investigate evolutionary convergence in the role of PRL in shaping African mole-rat eusociality, we determined plasma PRL concentrations in breeders and non-breeders of both sexes, comparing DMRs with NMRs. Among samples from non-breeding NMRs 80% had detectable plasma PRL concentrations. As a benchmark, these often (37%) exceeding those considered clinically hyperprolactinaemic (25 ng ml−1) in humans: mean ± s.e.m.: 34.81 ± 5.87 ngml−1; range 0.00–330.30 ng ml−1. Conversely, 85% of non-breeding DMR samples had undetectable values and none had concentrations above 25 ng ml−1: 0.71 ± 0.38 ng ml−1; 0.00–23.87 ngml−1. Breeders in both species had the expected variance in plasma PRL concentrations as part of normal reproductive function, with lactating queens having significantly higher values. These results suggest that while elevated PRL in non-breeders is implicated in NMR eusociality, this may not be the case in DMRs, and suggests a lack of evolutionary convergence in the proximate control of the social phenotype in these mole-rats.SARCHI Chair to NCB (Grant N64756)http://rsbl.royalsocietypublishing2019-05-01hj2018Anatomy and PhysiologyMammal Research InstituteZoology and Entomolog

Nonadiabatic charged spherical gravitational collapse

We present a complete set of the equations and matching conditions required for the description of physically meaningful charged, dissipative, spherically symmetric gravitational collapse with shear. Dissipation is described with both free-streaming and diffusion approximations. The effects of viscosity are also taken into account. The roles of different terms in the dynamical equation are analyzed in detail. The dynamical equation is coupled to a causal transport equation in the context of Israel-Stewart theory. The decrease of the inertial mass density of the fluid, by a factor which depends on its internal thermodynamic state, is reobtained, with the viscosity terms included. In accordance with the equivalence principle, the same decrease factor is obtained for the gravitational force term. The effect of the electric charge on the relation between the Weyl tensor and the inhomogeneity of energy density is discussed.Comment: 23 pages, Latex. To appear in Phys. Rev. D. Some references correcte

Self-similar and charged spheres in the diffusion approximation

We study spherical, charged and self--similar distributions of matter in the diffusion approximation. We propose a simple, dynamic but physically meaningful solution. For such a solution we obtain a model in which the distribution becomes static and changes to dust. The collapse is halted with damped mass oscillations about the absolute value of the total charge.Comment: 15 pages, 7 figure

Social Structure Predicts Genital Morphology in African Mole-Rats

BACKGROUND:African mole-rats (Bathyergidae, Rodentia) exhibit a wide range of social structures, from solitary to eusocial. We previously found a lack of sex differences in the external genitalia and morphology of the perineal muscles associated with the phallus in the eusocial naked mole-rat. This was quite surprising, as the external genitalia and perineal muscles are sexually dimorphic in all other mammals examined. We hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure. METHODOLOGY/PRINCIPAL FINDINGS:We compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. Our findings support a relationship between social structure, mating system, and sexual differentiation. Naked mole-rats lack sex differences in genitalia and perineal morphology, silvery mole-rats exhibit sex differences, and Damaraland mole-rats are intermediate. CONCLUSIONS/SIGNIFICANCE:The lack of sex differences in naked mole-rats is not an attribute of all African mole-rats, but appears to have evolved in relation to their unusual social structure and reproductive biology

Ten strategies for avoiding and overcoming authorship conflicts in academic publishing

For better or for worse, authorship is a currency in scholarly research and advancement. In scholarly writing, authorship is widely acknowledged as a means of conferring credit but is also tied to concepts such as responsibility and accountability. Authorship is one of the most divisive topics both at the level of the research team and more broadly in the academy and beyond. At present, authorship is often the primary way to assert and receive credit in many scholarly pursuits and domains. Debates rage, publicly but mostly privately, regarding authorship. Here we attempt to clarify key concepts related to authorship informed by our collective experiences and anchored in relevant contemporary literature. Rather than dwelling on the problems, we focus on proactive strategies for creating more just, equitable, and transparent avenues for minimizing conflict around authorship and where there is adequate recognition of the entire process of knowledge generation, synthesis, sharing, and application with partners within and beyond the academy. We frame our ideas around 10 strategies that collectively constitute a roadmap for avoiding and overcoming challenges associated with authorship decisions

Ageing-associated DNA methylation dynamics are a molecular readout of lifespan variation among mammalian species.

BACKGROUND: Mammalian species exhibit a wide range of lifespans. To date, a robust and dynamic molecular readout of these lifespan differences has not yet been identified. Recent studies have established the existence of ageing-associated differentially methylated positions (aDMPs) in human and mouse. These are CpG sites at which DNA methylation dynamics show significant correlations with age. We hypothesise that aDMPs are pan-mammalian and are a dynamic molecular readout of lifespan variation among different mammalian species. RESULTS: A large-scale integrated analysis of aDMPs in six different mammals reveals a strong negative relationship between rate of change of methylation levels at aDMPs and lifespan. This relationship also holds when comparing two different dog breeds with known differences in lifespans. In an ageing cohort of aneuploid mice carrying a complete copy of human chromosome 21, aDMPs accumulate far more rapidly than is seen in human tissues, revealing that DNA methylation at aDMP sites is largely shaped by the nuclear trans-environment and represents a robust molecular readout of the ageing cellular milieu. CONCLUSIONS: Overall, we define the first dynamic molecular readout of lifespan differences among mammalian species and propose that aDMPs will be an invaluable molecular tool for future evolutionary and mechanistic studies aimed at understanding the biological factors that determine lifespan in mammals