Effects of Echinostoma trivolvis metacercariae infection during development and metamorphosis of the wood frog (Lithobates sylvaticus)

Many organisms face energetic trade-offs between defense against parasites and other host processes that may determine overall consequences of infection. These trade-offs may be particularly evident during unfavorable environmental conditions or energetically demanding life history stages. Amphibian metamorphosis, an ecologically important developmental period, is associated with drastic morphological and physiological changes and substantial energetic costs. Effects of the trematode parasite Echinostoma trivolvis have been documented during early amphibian development, but effects during later development and metamorphosis are largely unknown. Using a laboratory experiment, we examined the energetic costs of late development and metamorphosis coupled with E. trivolvis infection in wood frogs, Lithobates [=Rana] sylvaticus. Echinostoma infection intensity did not differ between tadpoles examined prior to and after completing metamorphosis, suggesting that metacercariae were retained through metamorphosis. Infection with E. trivolvis contributed to a slower growth rate and longer development period prior to the initiation of metamorphosis. In contrast, E. trivolvis infection did not affect energy expenditure during late development or metamorphosis. Possible explanations for these results include the presence of parasites not interfering with pronephros degradation during metamorphosis or the mesonephros compensating for any parasite damage. Overall, the energetic costs of metamorphosis for wood frogs were comparable to other species with similar life history traits, but differed from a species with a much shorter duration of metamorphic climax. Our findings contribute to understanding the possible role of energetic trade-offs between parasite defense and host processes by considering parasite infection with simultaneous energetic demands during a sensitive period of development

The Effects of Fluorescent Tracking Powder on Oxygen Consumption in Salamanders Using Either Cutaneous or Bimodal Respiration

Fluorescent powder is gaining attention as an effective method for tracking terrestrial amphibian movements, particularly for species that are too small for conventional tracking equipment. The technique requires coating portions of an animal with fluorescent powder, releasing the animal, and following the trail of powder as it is progressively lost during movement. Recent studies have shown that fluorescent powder has no negative effects on survival or growth. However, a substance that coats the skin, a major respiratory organ in most amphibians, may have sublethal effects on performance and consequently behavior. We tested the effect of fluorescent powder application on the respiration of lungless Red-Backed Salamanders, Plethodon cinereus, and lunged terrestrial Red-Spotted Newts, Notophtholmus viridescens. In comparing species with contrasting skin textures and primary modes of respiration, we expected to find P. cinereus, the species relying solely on cutaneous respiration, more sensitive to fluorescent powder. Standard metabolic rate (SMR) and total oxygen consumption for both species were measured before and after application of the powder. We found no significant differences in respiration between control and powdered salamanders. Independent of treatment, SMR was 6-16% higher during the post-treatment trial in both species, and likewise, total oxygen consumed increased by 8-20% in P. cinereus and by 7-10% in N. viridescens. Our results, in combination with other recent work, suggest that fluorescent powder is a safe technique for tracking amphibians

A new vine snake (Reptilia, Colubridae, Oxybelis) from Peru and redescription of O. acuminatus

The Brown Vine Snake, Oxybelis aeneus, was until recently considered a single species, distributed from southern Arizona through the Neotropics into southeastern Brazil. However, newly conducted research restructured the species with a substantial taxonomic revision, recognizing five additional taxa (i.e. O. koehleri, O. microphthalmus, O. potosiensis, O. rutherfordi, O. vittatus) in this species complex. This revision focused on populations in North America, Central America, and northern South America while neglecting the southern portion of its distribution. Here, we examine the taxonomic history of the complex and use it along with specimen data to resurrect O. acuminatus from southeastern Brazil. Finally, we describe a new species from the Peruvian Amazon based on morphological characters. This work increases the species diversity of the O. aeneus complex to eight, and we expect further increases in biodiversity discoveries with continued exploration of the New World vine snakes

Single-locus species delimitation and ecological niche modeling provide insights into the evolution, historical distribution, and taxonomy of the Pacific Chorus Frogs

The Pacific chorus frogs are a complex of three wide-ranging species (i.e. Hyliola hypochondriaca, Hyliola regilla, Hyliola sierra) whose current taxonomy remains unresolved. We conducted species delimitation analyses of these taxa using fragments of the cytochrome b and 12S–16S mtDNA genes to assess the species diversity. Importantly, we included samples from new locations throughout the range to better understand species distributions and identify potential contact zones among clades. Our analyses revealed three slightly parapatric but distinct species-level clades. Molecular dating revealed that these species began diverging in the Pleistocene c. 1.4 Mya with H. hypochondriaca and H. sierra diverging more recently c. 0.8 Mya. We found that populations from western Montana and Idaho originated recently from populations to the southwest that belong to H. sierra, rather than from H. regilla populations directly to the west. Population sizes of each species expanded c. 130–80 Kya with H. hypochondriaca exhibiting a more pronounced expansion beginning c. 100 Kya than the more gradual expansion of the other two species. The climatic niche models suggest that distributions of the three species were similar during the last interglacial (LIG) as they are today. During the Last Glacial Maximum (LGM), H. hypochondriaca and H. sierra occupied a larger range than they do today whereas H. regilla occupied a smaller refugium, shifted south from the current distribution. This study highlights the continued effectiveness of utilizing single-locus data sets for species delimitation and biogeographic analyses

FIGURE 1 in A revised molecular phylogeny reveals polyphyly in Schistura (Teleostei: Cypriniformes: Nemacheilidae)

FIGURE 1. Bayesian consensus phylogeny depicting genus- and species-level relationships within the family Nemacheilidae. This tree was derived from a combined analysis of cytochrome b and D-loop gene fragments (1,116 bp and 776 bp, respectively).Published as part of Sgouros, Katherine, Page, Lawrence M., Orlofske, Sarah A. & Jadin, Robert C., 2019, A revised molecular phylogeny reveals polyphyly in Schistura (Teleostei: Cypriniformes: Nemacheilidae), pp. 349-362 in Zootaxa 4559 (2) on page 353, DOI: 10.11646/zootaxa.4559.2.8, http://zenodo.org/record/399343

FIGURE 2 in A revised molecular phylogeny reveals polyphyly in Schistura (Teleostei: Cypriniformes: Nemacheilidae)

FIGURE 2. Phylogenetic estimate of relationships within the family Nemacheilidae generated with a 50% majority-rule consensus for the cytochrome b gene using MrBayes.Published as part of Sgouros, Katherine, Page, Lawrence M., Orlofske, Sarah A. & Jadin, Robert C., 2019, A revised molecular phylogeny reveals polyphyly in Schistura (Teleostei: Cypriniformes: Nemacheilidae), pp. 349-362 in Zootaxa 4559 (2) on page 354, DOI: 10.11646/zootaxa.4559.2.8, http://zenodo.org/record/399343

Data from: Experimental investigation of alternative transmission functions: quantitative evidence for the importance of non-linear transmission dynamics in host-parasite systems

1. Understanding pathogen transmission is crucial for predicting and managing disease. Nonetheless, experimental comparisons of alternative functional forms of transmission remain rare, and those experiments that are conducted are often not designed to test the full range of possible forms. 2. To differentiate among ten candidate transmission functions, we used a novel experimental design in which we independently varied four factors—duration of exposure, numbers of parasites, numbers of hosts, and parasite density—in laboratory infection experiments. 3. We used interactions between amphibian hosts and trematode parasites as a model system and all candidate models incorporated parasite depletion. An additional manipulation involving anesthesia addressed the effects of host behaviour on transmission form. 4. Across all experiments, non-linear transmission forms involving either a power law or a negative binomial function were the best-fitting models and consistently outperformed the linear density-dependent and density-independent functions. By testing previously published data for two other host-macroparasite systems, we also found support for the same non-linear transmission forms. 5. Although manipulations of parasite density are common in transmission studies, the comprehensive set of variables tested in our experiments revealed that variation in density alone was least likely to differentiate among competing transmission functions. Across host-pathogen systems, non-linear functions may often more accurately represent transmission dynamics and thus provide more realistic predictions for infection

Data from: Experimental investigation of alternative transmission functions: quantitative evidence for the importance of non-linear transmission dynamics in host-parasite systems

1. Understanding pathogen transmission is crucial for predicting and managing disease. Nonetheless, experimental comparisons of alternative functional forms of transmission remain rare, and those experiments that are conducted are often not designed to test the full range of possible forms. 2. To differentiate among ten candidate transmission functions, we used a novel experimental design in which we independently varied four factors—duration of exposure, numbers of parasites, numbers of hosts, and parasite density—in laboratory infection experiments. 3. We used interactions between amphibian hosts and trematode parasites as a model system and all candidate models incorporated parasite depletion. An additional manipulation involving anesthesia addressed the effects of host behaviour on transmission form. 4. Across all experiments, non-linear transmission forms involving either a power law or a negative binomial function were the best-fitting models and consistently outperformed the linear density-dependent and density-independent functions. By testing previously published data for two other host-macroparasite systems, we also found support for the same non-linear transmission forms. 5. Although manipulations of parasite density are common in transmission studies, the comprehensive set of variables tested in our experiments revealed that variation in density alone was least likely to differentiate among competing transmission functions. Across host-pathogen systems, non-linear functions may often more accurately represent transmission dynamics and thus provide more realistic predictions for infection

The Scaling of Host Density with Richness Affects the Direction, Shape, and Detectability of Diversity-Disease Relationships

<div><p>Pathogen transmission responds differently to host richness and abundance, two unique components of host diversity. However, the heated debate around whether biodiversity generally increases or decreases disease has not considered the relationships between host richness and abundance that may exist in natural systems. Here we use a multi-species model to study how the scaling of total host community abundance with species richness mediates diversity-disease relationships. For pathogens with density-dependent transmission, non-monotonic trends emerge between pathogen transmission and host richness when host community abundance saturates with richness. Further, host species identity drives high variability in pathogen transmission in depauperate communities, but this effect diminishes as host richness accumulates. Using simulation we show that high variability in low richness communities and the non-monotonic relationship observed with host community saturation may reduce the detectability of trends in empirical data. Our study emphasizes that understanding the patterns and predictability of host community composition and pathogen transmission mode will be crucial for predicting where and when specific diversity-disease relationships should occur in natural systems.</p></div