\u3ci\u3eParavitellotrema overstreeti\u3c/i\u3e Sp. n. (Digenea: Hemiuridae) from the Colombian Freshwater Stingray \u3ci\u3ePotamotrygon magdalenae\u3c/i\u3e Dumeri

Paravitellotrema overstreeti from the freshwater stingray Potamotrygon magdalenae in northern Colombia most closely resembles P. thorsoni by possessing a muscular sinus organ and sinus sac as well as exhibiting a saccate rather than elongate prostatic vesicle, It differs by possessing lobate rather than spherical vitellaria, a smaller sinus organ and sinus sac, elongate rather than diamond-shaped prostatic cells enclosed in a delicate membrane rather than free in the parenchyma, and a metraterm joining the hermaphroditic duct immediately anterior to the prostatic vesicle rather than at the base of the sinus organ

Two New Species of \u3ci\u3eAcanthobothrium\u3c/i\u3e Van Beneden 1849 (Cestoidea: Tetraphyllidea) from Freshwater Stingrays in South America

Two new species of Acanthobothrium are reported from freshwater stingrays in northern South America. Acanthobothrium quinonesi sp. n. is described from Potamotrygon magdalenae Dumeril collected from the Magdalena River in northern Colombia and A. amazonensis sp. n. from P. circularis Garman collected in the Itacuai River of northwestern Brazil. Acanthobothrium quinonesi differs from A. amazonensis by having a smaller and anteriorly-curved cirrus sac, 43-60 rather than 50-72 testes, and bothridial hooks 100-142 μm long rather than 145-184 μm long. Characters used in the taxonomy of Acanthobothrium species are listed to show that the new species resemble each other and A. terezae, also from a South American freshwater stingray, more than they do any other members of the genus

Two New Tetraphyllidean Cestodes from \u3ci\u3ePotamotrygon circularis\u3c/i\u3e Garman (Chondrichthyes: Potamotrygonidae) in the Itacnai River, Brazill

The new genus Rhinebothroides is proposed to include three species of Rhinebothriumlike cestodes parasitizing freshwater stingrays in South America. They differ from Rhinebothrium species by having squared rather than elongate bothridia, by possessing internal seminal vesicles, and by exhibiting terminal genitalia at the ovarian level. Rhinebothroides circularisi sp. n. in Potamotrygon circularis from the Itacuai River in northwestern Brazil differs from R. moralarai by having more testes and bothridial loculi and differs from R. scorzai by lacking vitelline follicles proximate to the genital pore, by having a straight rather than coiled vagina, and by possessing craspedote rather than acraspedote proglottids. Potamotrygon circularis from the Itacuai River also hosted Potamotrygonocestus amazonensis sp. n. which differs from the only other member of the genus, P. magdalenensis, by having bothridial hooks 58-78µm long rather than 43-55 µm long, by possessing a shallow genital atrium rather than lacking one, and by having follicular rather than compact vitellaria

\u3ci\u3eParavitellotrema overstreeti\u3c/i\u3e Sp. n. (Digenea: Hemiuridae) from the Colombian Freshwater Stingray \u3ci\u3ePotamotrygon magdalenae\u3c/i\u3e Dumeri

Paravitellotrema overstreeti from the freshwater stingray Potamotrygon magdalenae in northern Colombia most closely resembles P. thorsoni by possessing a muscular sinus organ and sinus sac as well as exhibiting a saccate rather than elongate prostatic vesicle, It differs by possessing lobate rather than spherical vitellaria, a smaller sinus organ and sinus sac, elongate rather than diamond-shaped prostatic cells enclosed in a delicate membrane rather than free in the parenchyma, and a metraterm joining the hermaphroditic duct immediately anterior to the prostatic vesicle rather than at the base of the sinus organ

Like-minded sources on Facebook are prevalent but not polarizing

Many critics raise concerns about the prevalence of ‘echo chambers’ on social media and their potential role in increasing political polarization. However, the lack of available data and the challenges of conducting large-scale field experiments have made it difficult to assess the scope of the problem 1,2. Here we present data from 2020 for the entire population of active adult Facebook users in the USA showing that content from ‘like-minded’ sources constitutes the majority of what people see on the platform, although political information and news represent only a small fraction of these exposures. To evaluate a potential response to concerns about the effects of echo chambers, we conducted a multi-wave field experiment on Facebook among 23,377 users for whom we reduced exposure to content from like-minded sources during the 2020 US presidential election by about one-third. We found that the intervention increased their exposure to content from cross-cutting sources and decreased exposure to uncivil language, but had no measurable effects on eight preregistered attitudinal measures such as affective polarization, ideological extremity, candidate evaluations and belief in false claims. These precisely estimated results suggest that although exposure to content from like-minded sources on social media is common, reducing its prevalence during the 2020 US presidential election did not correspondingly reduce polarization in beliefs or attitudes

Effects of Elevated Temperature and Carbon Dioxide on the Growth and Survival of Larvae and Juveniles of Three Species of Northwest Atlantic Bivalves

Rising CO2 concentrations and water temperatures this century are likely to have transformative effects on many coastal marine organisms. Here, we compared the responses of two life history stages (larval, juvenile) of three species of calcifying bivalves (Mercenaria mercenaria, Crassostrea virginica, and Argopecten irradians) to temperatures (24 and 28°C) and CO2 concentrations (∼250, 390, and 750 ppm) representative of past, present, and future summer conditions in temperate estuaries. Results demonstrated that increases in temperature and CO2 each significantly depressed survival, development, growth, and lipid synthesis of M. mercenaria and A. irradians larvae and that the effects were additive. Juvenile M. mercenaria and A. irradians were negatively impacted by higher temperatures while C. virginica juveniles were not. C. virginica and A. irradians juveniles were negatively affected by higher CO2 concentrations, while M. mercenaria was not. Larvae were substantially more vulnerable to elevated CO2 than juvenile stages. These findings suggest that current and future increases in temperature and CO2 are likely to have negative consequences for coastal bivalve populations

Secondary Metabolites of Marine Microbes: From Natural Products Chemistry to Chemical Ecology

Marine natural products (MNPs) exhibit a wide range of pharmaceutically relevant bioactivities, including antibiotic, antiviral, anticancer, or anti-inflammatory properties. Besides marine macroorganisms such as sponges, algae, or corals, specifically marine bacteria and fungi have shown to produce novel secondary metabolites (SMs) with unique and diverse chemical structures that may hold the key for the development of novel drugs or drug leads. Apart from highlighting their potential benefit to humankind, this review is focusing on the manifold functions of SMs in the marine ecosystem. For example, potent MNPs have the ability to exile predators and competing organisms, act as attractants for mating purposes, or serve as dye for the expulsion or attraction of other organisms. A large compilation of literature on the role of MNPs in marine ecology is available, and several reviews evaluated the function of MNPs for the aforementioned topics. Therefore, we focused the second part of this review on the importance of bioactive compounds from crustose coralline algae (CCA) and their role during coral settlement, a topic that has received less attention. It has been shown that certain SMs derived from CCA and their associated bacteria are able to induce attachment and/or metamorphosis of many benthic invertebrate larvae, including globally threatened reef-building scleractinian corals. This review provides an overview on bioactivities of MNPs from marine microbes and their potential use in medicine as well as on the latest findings of the chemical ecology and settlement process of scleractinian corals and other invertebrate larvae