Parasite Transmission in Social Interacting Hosts: Monogenean Epidemics in Guppies

Background: Infection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally. Methodology/Principal Findings: Here, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata). Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria), and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling. Conclusions/Significance: These findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density

‘Nothing about us without us’ : disabled people determining their human rights through the UNCRPD

The human rights and fundamental freedoms of disabled persons are set out in the United Nations Convention on the Rights of Persons with Disabilities (UNCRPD). This paper firstly focuses on the importance of the involvement of disabled people at all levels of decision-making. The second part of the paper identifies those aspects of the UNCRPD that reflect the direct involvement of disabled people. Finally, it considers how human rights bodies can best build on this specific aspect of the UNCRPD in order to realize the potential of the Convention as a determining factor in affirming disabled people rights in an effective and meaningful manner.peer-reviewe

Biological and trophic consequences of genetic introgression between endemic and invasive Barbus fishes.

Genetic introgression with native species is recognized as a detrimental impact resulting from biological invasions involving taxonomically similar invaders. Whilst the underlying genetic mechanisms are increasingly understood, the ecological consequences of introgression are relatively less studied, despite their utility for increasing knowledge on how invasion impacts can manifest. Here, the ecological consequences of genetic introgression from an invasive congener were tested using the endemic barbel populations of central Italy, where the invader was the European barbel Barbus barbus. Four populations of native Barbus species (B. plebejus and B. tyberinus) were studied: two purebred and two completely introgressed with alien B. barbus. Across the four populations, differences in their biological traits (growth, body condition and population demographic structure) and trophic ecology (gut content analysis and stable isotope analysis) were tested. While all populations had similar body condition and were dominated by fish up to 2 years of age, the introgressed fish had substantially greater lengths at the same age, with maximum lengths 410-460 mm in hybrids versus 340-360 mm in native purebred barbel. The population characterized by the highest number of introgressed B. barbus alleles (81 %) had the largest trophic niche and a substantially lower trophic position than the other populations through its exploitation of a wider range of resources (e.g. small fishes and plants). These results attest that the genetic introgression of an invasive congener with native species can result in substantial ecological consequences, including the potential for cascading effects. Supplementary Information: The online version contains supplementary material available at 10.1007/s10530-021-02577-6

How Do They Do It? – Understanding the Success of Marine Invasive Species

From the depths of the oceans to the shallow estuaries and wetlands of our coasts, organisms of the marine environment are teeming with unique adaptations to cope with a multitude of varying environmental conditions. With millions of years and a vast volume of water to call their home, they have become quite adept at developing specialized and unique techniques for survival and – given increasing human mediated transport – biological invasions. A growing world human population and a global economy drives the transportation of goods across the oceans and with them invasive species via ballast water and attached to ship hulls. In any given 24-hour period, there are about 10,000 species being transported across different biogeographic regions. If any of them manage to take hold and establish a range in an exotic habitat, the implications for local ecosystems can be costly. This review on marine invasions highlights trends among successful non-indigenous species (NIS), from vectors of transport to ecological and physiological plasticity. Apart from summarizing patterns of successful invasions, it discusses the implications of how successfully established NIS impact the local environment, economy and human health. Finally, it looks to the future and discusses what questions need to be addressed and what models can tell us about what the outlook on future marine invasions is

Stable isotope ratios of egg albumen of three waterbird species nesting in the Colorado River Delta indicate differences in foraging ground and isotopic niche breadth

The Colorado River Delta is one of the most impacted wetland systems in the world and has experienced massive habitat loss owing to severe restrictions in freshwater inflow as a result of dam construction and diversion of water for irrigation. However, the delta still offers nesting and foraging habitats for waterbirds, although the habitats available are highly fragmented and limited. Stable isotope ratio (SIR) analysis was used to assess quantitatively isotopic niche width of gull-billed terns (Gelochelidon nilotica), laughing gulls (Leucophaeus atricilla) and snowy egrets (Egreta thula) that nest at an inland and coastal location. The variance in carbon and nitrogen SIR of egg albumen indicated that inland colonies have a much broader isotope niche width (range 2.9 to 23.9) than coastal colonies (<0.1 to 1.4).Species-specific mean albumen δ13C values from inland nests were significantly more depleted in 13C than coastal colonies (-19.5 to -23.1‰ and -10.4 to -14.9‰, respectively). Comparison of albumen δ13C values corrected for trophic fractionation with those of potential prey and primary producers collected at 10 potential foraging grounds indicates that females of the three species that nest in inland colonies did not feed in habitats located in the vicinity of their nesting site, while coastal colonies had distinct isotopic signatures reflecting marine primary production. Inland colonies probably forage in a variety of habitats and for different prey, relying on food webs based mostly on C3 terrestrial plants. Differences in the isotopic composition of eggs from species nesting in the same area and between conspecifics nesting in different habitats indicate that foraging habitats vary substantially, suggesting that feeding varies as a function of local resource availability. These results suggest that a variety of habitat types fulfill the foraging needs of this suite of nesting waterbird species, especially in inland colonies. Since the specific feeding areas of nesting females from the inland colonies have not been identified, protection of the remaining wetlands within the Colorado River Delta is warranted. © 2013 John Wiley & Sons, Ltd

Stable isotope ratios of egg albumen of three waterbird species nesting in the Colorado River Delta indicate differences in foraging ground and isotopic niche breadth

The Colorado River Delta is one of the most impacted wetland systems in the world and has experienced massive habitat loss owing to severe restrictions in freshwater inflow as a result of dam construction and diversion of water for irrigation. However, the delta still offers nesting and foraging habitats for waterbirds, although the habitats available are highly fragmented and limited. Stable isotope ratio (SIR) analysis was used to assess quantitatively isotopic niche width of gull-billed terns (Gelochelidon nilotica), laughing gulls (Leucophaeus atricilla) and snowy egrets (Egreta thula) that nest at an inland and coastal location. The variance in carbon and nitrogen SIR of egg albumen indicated that inland colonies have a much broader isotope niche width (range 2.9 to 23.9) than coastal colonies (<0.1 to 1.4).Species-specific mean albumen δ13C values from inland nests were significantly more depleted in 13C than coastal colonies (-19.5 to -23.1‰ and -10.4 to -14.9‰, respectively). Comparison of albumen δ13C values corrected for trophic fractionation with those of potential prey and primary producers collected at 10 potential foraging grounds indicates that females of the three species that nest in inland colonies did not feed in habitats located in the vicinity of their nesting site, while coastal colonies had distinct isotopic signatures reflecting marine primary production. Inland colonies probably forage in a variety of habitats and for different prey, relying on food webs based mostly on C3 terrestrial plants. Differences in the isotopic composition of eggs from species nesting in the same area and between conspecifics nesting in different habitats indicate that foraging habitats vary substantially, suggesting that feeding varies as a function of local resource availability. These results suggest that a variety of habitat types fulfill the foraging needs of this suite of nesting waterbird species, especially in inland colonies. Since the specific feeding areas of nesting females from the inland colonies have not been identified, protection of the remaining wetlands within the Colorado River Delta is warranted. © 2013 John Wiley & Sons, Ltd