Do Host-Consumed Resources Increase Endoparasitic But Decrease Ectoparasitic Infections?

Abstract Habitat loss and disease outbreak play a major role in the decline of biodiversity. Habitat degradation is often associated with reduced food resources, which can lead to less investment in host immunity and increased infections. However, pathogens use host resources for replication and pathogen traits, such as infecting hosts internally or short generation times, might allow pathogens to rapidly capitalize on host-consumed nutrients. Thus, it is unclear whether increased food consumption by hosts should reduce or amplify pathogen levels. We conducted experiments on Cuban treefrogs (Osteopilus septentrionalis) to test how food availability affects infection levels of Ranavirus and the fungal pathogen Batrachochytrium dendrobatidis (Bd), which are both associated with mass die-offs of amphibians. Given that Ranavirus is an endoparasite with a much shorter generation time than the ectoparasitic Bd, we postulated that Ranavirus might be able to capitalize on host-consumed resources more quickly than Bd. We hypothesized that increased food availability to hosts might reduce Bd infections more than Ranavirus infections. As predicted, augmenting food access decreased Bd infection intensity, but increased Ranavirus infection intensity. Future work should assess whether pathogen traits, such as generation time and endo- versus ectoparasitism, generally affect whether food resources more positively benefit hosts or pathogens.

Download Full-text

Do host-consumed resources increase endoparasitic but decrease ectoparasitic infections?

10.1101/2021.05.12.443795 ◽

2021 ◽

Author(s):

Brin Shayhorn ◽

Chloe Ramsay ◽

Kristi Medina ◽

Erin Sauer ◽

Jason R. Rohr

Keyword(s):

Food Availability ◽

Fungal Pathogen ◽

Generation Time ◽

Batrachochytrium Dendrobatidis ◽

Habitat Degradation ◽

Infection Intensity ◽

Food Resources ◽

Generation Times ◽

Osteopilus Septentrionalis ◽

Future Work

Habitat loss and disease outbreak play a major role in the decline of biodiversity. Habitat degradation is often associated with reduced food resources, which can lead to less investment in host immunity and increased infections. However, pathogens use host resources for replication and pathogen traits, such as infecting hosts internally or short generation times, might allow pathogens to rapidly capitalize on host-consumed nutrients. Thus, it is unclear whether increased food consumption by hosts should reduce or amplify pathogen levels. conducted experiments on Cuban treefrogs (Osteopilus septentrionalis) to test how food availability affects infection levels of Ranavirus and the fungal pathogen Batrachochytrium dendrobatidis (Bd), which are both associated with mass die-offs of amphibians. Given that Ranavirus is an endoparasite with a much shorter generation time than the ectoparasitic Bd, we postulated that Ranavirus might be able to capitalize on host-consumed resources more quickly than Bd. We hypothesized that increased food availability to hosts might reduce Bd infections more than Ranavirus infections. As predicted, augmenting food access decreased Bd infection intensity, but increased Ranavirus infection intensity. Future work should assess whether pathogen traits, such as generation time and endo- versus ectoparasitism, generally affect whether food resources more positively benefit hosts or pathogens.

Download Full-text

Epidemic and endemic pathogen dynamics correspond to distinct host population microbiomes at a landscape scale

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.0944 ◽

2017 ◽

Vol 284 (1857) ◽

pp. 20170944 ◽

Cited By ~ 28

Author(s):

Andrea J. Jani ◽

Roland A. Knapp ◽

Cheryl J. Briggs

Keyword(s):

Infectious Disease ◽

Fungal Pathogen ◽

Batrachochytrium Dendrobatidis ◽

Infection Intensity ◽

Host Population ◽

Symbiotic Bacteria ◽

Skin Microbiome ◽

Pathogen Infection ◽

Microbiome Composition ◽

Pathogen Invasion

Infectious diseases have serious impacts on human and wildlife populations, but the effects of a disease can vary, even among individuals or populations of the same host species. Identifying the reasons for this variation is key to understanding disease dynamics and mitigating infectious disease impacts, but disentangling cause and correlation during natural outbreaks is extremely challenging. This study aims to understand associations between symbiotic bacterial communities and an infectious disease, and examines multiple host populations before or after pathogen invasion to infer likely causal links. The results show that symbiotic bacteria are linked to fundamentally different outcomes of pathogen infection: host–pathogen coexistence (endemic infection) or host population extirpation (epidemic infection). Diversity and composition of skin-associated bacteria differed between populations of the frog, Rana sierrae , that coexist with or were extirpated by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). Data from multiple populations sampled before or after pathogen invasion were used to infer cause and effect in the relationship between the fungal pathogen and symbiotic bacteria. Among host populations, variation in the composition of the skin microbiome was most strongly predicted by pathogen infection severity, even in analyses where the outcome of infection did not vary. This result suggests that pathogen infection shapes variation in the skin microbiome across host populations that coexist with or are driven to extirpation by the pathogen. By contrast, microbiome richness was largely unaffected by pathogen infection intensity, but was strongly predicted by geographical region of the host population, indicating the importance of environmental or host genetic factors in shaping microbiome richness. Thus, while both richness and composition of the microbiome differed between endemic and epidemic host populations, the underlying causes are most likely different: pathogen infection appears to shape microbiome composition, while microbiome richness was less sensitive to pathogen-induced disturbance. Because higher richness was correlated with host persistence in the presence of Bd, and richness appeared relatively stable to Bd infection, microbiome richness may contribute to disease resistance, although the latter remains to be directly tested.

Download Full-text

Optimal digestion theory does not predict the effect of pathogens on intestinal plasticity

Biology Letters ◽

10.1098/rsbl.2013.0038 ◽

2013 ◽

Vol 9 (2) ◽

pp. 20130038 ◽

Cited By ~ 6

Author(s):

Matthew D. Venesky ◽

Shane M. Hanlon ◽

Kyle Lynch ◽

Matthew J. Parris ◽

Jason R. Rohr

Keyword(s):

Body Size ◽

Food Consumption ◽

Fungal Pathogen ◽

Batrachochytrium Dendrobatidis ◽

Relative Length ◽

Food Resources

One prediction of optimal digestion theory is that organisms will increase the relative length of their digestive tracts when food resources become limited. We used theory of optimal digestion to test whether tadpoles can adjust the relative length of their intestines when challenged with the fungal pathogen Batrachochytrium dendrobatidis ( Bd ). The degree of tadpole mouthpart damage, a symptom of Bd infections that reduces food consumption, was associated positively with the length of tadpole intestines relative to their body size, consistent with optimal digestion theory. After controlling for mouthpart damage, tadpoles exposed to Bd had shorter intestines relative to their body size, opposite to the predictions of optimal digestion theory. One explanation of why tadpoles with higher Bd loads have shorter relative intestinal lengths is that they divert energy from maintaining intestinal and overall growth towards anti-parasite defences.

Download Full-text

Behaviour ofStreptococcus lactisin heat treated (80 °C for 30 min) or sterilized cow's and ewe's milk

Journal of Dairy Research ◽

10.1017/s0022029900023190 ◽

1983 ◽

Vol 50 (3) ◽

pp. 357-363 ◽

Cited By ~ 5

Author(s):

Francisco J. Chavarri ◽

Jose A. Nuñez ◽

Manuel Nuñez

Keyword(s):

Acid Production ◽

Generation Time ◽

Buffer Capacity ◽

Cow’S Milk ◽

Cow's Milk ◽

Vitamin Content ◽

Streptococcus Lactis ◽

Generation Times ◽

Heat Treated ◽

Ewe's Milk

SummaryGeneration times and acid production after 6 and 24 h by 20 strains ofStreptococcus lactisof dairy origin were determined in heat treated (80 °C for 30 min) and sterilized cow's and ewe's milk. Ewe's milk enhanced growth of the streptococci, with significantly (P< 0·001) shorter generation times and higher acid production after 6 h incubation than cow's milk, probably due to its higher vitamin content. The stronger buffer capacity of ewe's milk allowed a higher (P< 0·001) acid production after 24 h than cow's milk. A stimulatory effect of sterilization on generation time and acid production after 24 h was observed in cow's milk. However, the heat treated ewe's milk was shown to be a better substrate than sterilized ewe's milk forStr. lactis.

Download Full-text

Fungal infection, decline and persistence in the only obligate troglodytic Neotropical salamander

PeerJ ◽

10.7717/peerj.9763 ◽

2020 ◽

Vol 8 ◽

pp. e9763

Author(s):

Mizraim Olivares-Miranda ◽

Vance T. Vredenburg ◽

Julio C. García-Sánchez ◽

Allison Q. Byrne ◽

Erica B. Rosenblum ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

Infection Intensity ◽

Sampling Technique ◽

Sympatric Species ◽

Amphibian Declines ◽

Small Range ◽

Museum Specimens ◽

Amphibian Species ◽

Extant Population ◽

Epidemic Wave

The fungal pathogen Batrachochytrium dendrobatidis (Bd) is implicated in global mass die-offs and declines in amphibians. In Mesoamerica, the Bd epidemic wave hypothesis is supported by detection of Bd in historic museum specimens collected over the last century, yet the timing and impact of the early stages of the wave remain poorly understood. Chiropterotriton magnipes, the only obligate troglodytic Neotropical salamander, was abundant in its small range in the decade following its description in 1965, but subsequently disappeared from known localities and was not seen for 34 years. Its decline is roughly coincident with that of other populations of Neotropical salamanders associated with the invasion and spread of Bd. To determine the presence and infection intensity of Bd on C. magnipes and sympatric amphibian species (which are also Bd hosts), we used a noninvasive sampling technique and qPCR assay to detect Bd on museum specimens of C. magnipes collected from 1952 to 2012, and from extant populations of C. magnipes and sympatric species of amphibians. We also tested for the presence of the recently discovered Batrachochytrium salamandivorans (Bsal), another fungal chytridiomycete pathogen of salamanders, using a similar technique specific for Bsal. We did not detect Bd in populations of C. magnipes before 1969, while Bd was detected at low to moderate prevalence just prior to and during declines. This pattern is consistent with Bd-caused epizootics followed by host declines and extirpations described in other hosts. We did not detect Bsal in any extant population of C. magnipes. We obtained one of the earliest positive records of the fungus to date in Latin America, providing additional historical evidence consistent with the Bd epidemic wave hypothesis. Genotyping results show that at least one population is currently infected with the Global Panzootic Lineage of Bd, but our genotyping of the historical positive samples was unsuccessful. The lack of large samples from some years and the difficulty in genotyping historical Bd samples illustrate some of the difficulties inherent in assigning causality to historical amphibian declines. These data also provide an important historical baseline for actions to preserve the few known remaining populations of C. magnipes.

Download Full-text

Body length of Hylodes cf. ornatus and Lithobates catesbeianus tadpoles, depigmentation of mouthparts, and presence of Batrachochytrium dendrobatidis are related

Brazilian Journal of Biology ◽

10.1590/s1519-69842013000100021 ◽

2013 ◽

Vol 73 (1) ◽

pp. 195-199 ◽

Cited By ~ 10

Author(s):

CA. Vieira ◽

LF. Toledo ◽

JE. Longcore ◽

JR. Longcore

Keyword(s):

North America ◽

South America ◽

Body Length ◽

Fungal Pathogen ◽

Batrachochytrium Dendrobatidis ◽

Strong Association ◽

Experimental Studies ◽

Sao Paulo ◽

Lithobates Catesbeianus ◽

Pure Cultures

A fungal pathogen Batrachochytrium dendrobatidis (Bd), which can cause morbidity and death of anurans, has affected amphibian populations on a worldwide basis. Availability of pure cultures of Bd isolates is essential for experimental studies to understand the ecology of this pathogen. We evaluated the relationships of body length of Hylodes cf. ornatus and Lithobates catesbeianus tadpoles to depigmentation of mouthparts and determined if dekeratinization indicated an infection by Batrachochytrium dendrobatidis. A strong association existed for both species, one from South America (Brazil: São Paulo) and one from North America (USA: Maine). We believe it prudent not to kill adult amphibians if avoidable, thus obtaining tissue for isolating Bd from tadpoles is reasonable because infected specimens of some species can be selectively collected based on depigmentation of mouthparts.

Download Full-text

A review of the life cycles and life-history adaptations of pelagic tunicates to environmental conditions

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr159 ◽

2011 ◽

Vol 69 (3) ◽

pp. 358-369 ◽

Cited By ~ 33

Author(s):

Don Deibel ◽

Ben Lowen

Keyword(s):

Life History ◽

Environmental Conditions ◽

Generation Time ◽

Egg Production ◽

Food Concentration ◽

Life Cycles ◽

Population Doubling ◽

Event Scale ◽

Generation Times ◽

Doubling Times

Abstract Deibel, D., and Lowen, B. 2012. A review of the life cycles and life-history adaptations of pelagic tunicates to environmental conditions. – ICES Journal of Marine Science, 69: 358–369. Phylogeny, life cycles, and life-history adaptations of pelagic tunicates to temperature and food concentration are reviewed. Using literature data on lifetime egg production and generation time of appendicularians, salps, and doliolids, rmax, the maximum rate of lifetime reproductive fitness, is calculated as a common metric of adaptation to environmental conditions. The rmax values are high for all three groups, ranging from ∼0.1 to 1.9 d−1, so population doubling times range from ∼8 h to 1 week. These high values of rmax are attributable primarily to short generation times, ranging from 2 to 50 d. Clearly, pelagic tunicates are adapted to event-scale (i.e. days to weeks) rather than seasonal-scale changes in environmental conditions. Although they are not closely related phylogenetically, all three groups have a unique life-history adaptation promoting high lifetime fitness. Appendicularians have late oocyte selection, salps are viviparous, and doliolids possess a polymorphic asexual phase. There has been little research on hermaphroditic appendicularians, on large oceanic salps, and on doliolids generally. Research is needed on factors regulating generation time, on the heritability of life-history traits, and on age- and size-specific rates of mortality.

Download Full-text

Rapid juvenile development in old forest lichens

Botany ◽

10.1139/b10-086 ◽

2011 ◽

Vol 89 (1) ◽

pp. 65-72 ◽

Cited By ~ 39

Author(s):

Per Larsson ◽

Yngvar Gauslaa

Keyword(s):

Growth Rates ◽

Generation Time ◽

Population Biology ◽

Limiting Factors ◽

Noninvasive Method ◽

Relative Growth ◽

Relative Growth Rates ◽

Generation Times ◽

Young Forests ◽

Juvenile Development

Generation time and juvenile growth rates are important but poorly known parameters in lichen population biology. By using a noninvasive method, we aimed to quantify these variables in juvenile thalli of Lobaria pulmonaria (L.) Hoffm., L. scrobiculata (Scop.) D.C., and Pseudocyphellaria crocata (L.) Vain., in situ, on twigs of Picea abies (L.) H. Karst in boreal rainforests. Growth was monitored during the summer months (May–August, 106 d), as well as in the remaining part of the year (259 d), for each of two sequential years, by means of repeated photography and imaging analysis. The mean relative thallus-area growth rates were 0.53 ± 0.02, 0.41 ± 0.02, and 0.57 ± 0.04 mm2·mm–2·year–1 (mean ±SE), respectively, in the three species, equivalent to a yearly growth of 101 ± 5%, 70 ± 6%, and 121 ± 12%. Growth was much slower during the winter (0.09–0.12 mm2·cm–2·d–1) than in summer (0.19–0.27 mm2·cm–2·d–1). Relative growth rates significantly declined with increasing thallus size. Estimated generation times in L. scrobiculata and P. crocata, based upon the first observed formation of reproductive structures, were 15–22 and 9–13 years, respectively. Studied L. pulmonaria thalli produced no diaspores during the experiment, consistent with a generation time >17 years. The relative growth rates we measured and our estimated generation times are faster than those earlier recorded. Thus, our noninvasive method can estimate parameters needed to model population growth within a reasonable period of time. The rapid juvenile development implies that the growth rates and generation times are unlikely to be the limiting factors that exclude these lichens from young forests.

Download Full-text