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

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.

The Louisiana Amphibian Monitoring Program from 1997 to 2017: Results, analyses, and lessons learned

To determine trends in either frog distribution or abundance in the State of Louisiana, we reviewed and analyzed frog call data from the Louisiana Amphibian Monitoring Program (LAMP). The data were collected between 1997 and 2017 using North American Amphibian Monitoring Program protocols. Louisiana was divided into three survey regions for administration and analysis: the Florida Parishes, and 2 areas west of the Florida parishes called North and South. Fifty-four routes were surveyed with over 12,792 stops and 1,066 hours of observation. Observers heard 26 species of the 31 species reported to be in Louisiana. Three of the species not heard were natives with ranges that did not overlap with survey routes. The other two species were introduced species, the Rio Grande Chirping Frog (Eleutherodactylus cystignathoides) and the Cuban Treefrog (Osteopilus septentrionalis). Both seem to be limited to urban areas with little to no route coverage. The 15 most commonly occurring species were examined in detail using the percentage of stops at which they observed along a given survey and their call indices. Most species exhibited a multimodal, concave, or convex pattern of abundance over a 15-year period. Among LAMP survey regions, none of the species had synchronous population trends. Only one group of species, winter callers, regularly co-occur. Based on the species lists, the North region could be seen as a subset of the South. However, based on relative abundance, the North was more similar to Florida parishes for both the winter and summer survey runs. Our analyses demonstrate that long-term monitoring (10 years or more) may be necessary to determine population and occupancy trends, and that frog species may have different local demographic patterns across large geographic areas.

Asymmetric cross-strain protection for amphibians exposed to a fungal-metabolite prophylactic treatment

Chytridiomycosis, an infectious disease of amphibians caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), poses an imminent conservation threat. The global spread of Bd has led to mass mortality events in many amphibian species, resulting in at least 90 species' extinctions to date. Exposure to Bd metabolites (i.e. non-infectious antigenic chemicals released by Bd) partially protects frogs during subsequent challenges with live Bd, suggesting its use as a prophylactic treatment and potential vaccine. However, we do not know whether Bd metabolite exposure protects against strains beyond the one used for treatment. To address this knowledge gap, we conducted a 3 × 2 experiment where we exposed adult Cuban treefrogs, Osteopilus septentrionalis , to one of three treatments (Bd metabolites from California-isolated strain JEL-270, Panamá-isolated strain JEL-419, or an artificial spring water control) and then challenged individuals with live Bd from either strain. We found that exposure to Bd metabolites from the California-isolated strain significantly reduced Bd loads of frogs challenged with the live Panamá-isolated strain, but no other treatments were found to confer protective effects. These findings demonstrate asymmetric cross-protection of a Bd metabolite prophylaxis and suggest that work investigating multiple, diverse strains is urgently needed.

Diet of a community of frogs in an agroecosystem in western Cuba

The study of frog diets in agricultural areas enables us to recognize their role in terrestrial food webs as predators of invertebrates, which can become crop pests or disease transmission vectors for humans. The present study examines the diet composition of three syntopic frog species occurring in one agroecosystem in Cuba, and their interspecific trophic interactions. The fieldwork was in Zea mays and Colocasia esculenta crops in Pinar del Río province, Cuba, in August, 2020. The frogs were measured and stomach-flushed in situ, and released at the site of capture. Niche overlap between species was calculated. Fifty-two frogs were captured and 43 (82.7%) had prey in their stomachs. Eleutherodactylus goini had the highest rate of prey/stomach and the broadest diet diversity while Osteopilus septentrionalis had the lowest rate and the narrowest diet diversity. High diet overlap was detected between Eleutherodactylus species. The most consumed prey were Lepidoptera, Hymenoptera, and Blattodea. The diet data suggests that these species could be important biological controls of the invertebrate community in the studied agroecosystems. This indicates a positive impact of these native frogs to the crops by controlling noxious and damaging invertebrates.

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

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.

Invasive Cuban Treefrogs (Osteopilus septentrionalis) Have More Robust Locomotor Performance Than Two Native Treefrogs (Hyla spp.) in Florida, USA, in Response to Temperature and Parasitic Infections

Introduced species pose a threat to biodiversity, and ecological and physiological factors are important in determining whether an introduced species becomes successfully established in a new region. Locomotor performance is one such factor that can influence the abundance and distribution of an introduced species. We investigated the effects of temperature and parasitism by the intestinal nematode Aplectana hamatospicula on the maximum jump distance and endurance in one invasive and two native treefrogs in Florida, USA. We collected frogs from the wild, estimated their parasite loads, and tested their locomotor performance at three temperatures. Contrary to expectations, invasive Cuban treefrogs (Osteopilus septentrionalis), which are adapted to a warmer climate in the Caribbean, outperformed pinewoods treefrogs (Hyla femoralis) and squirrel treefrogs (H. squirella) at each temperature, even when controlling for body size differences. In all three species, maximum jump distance was positively related to temperature, and this relationship was stronger for larger frogs. Parasites influenced both the maximum jump distance and endurance of frogs. In all three species, larger frogs jumped farther maximum distances than smaller frogs, but this relationship was stronger when frogs had lower, rather than higher, parasite loads. Parasitism had little effect on endurance in invasive frogs, but it tended to decrease the endurance of native frogs at high temperatures. Furthermore, at low temperatures, the lengths of consecutive jumps of infected native frogs tended to increase, suggesting that parasites limited the distances of initial jumps. Effects of temperature and parasites on the locomotor performance of frogs could influence their abilities to forage, escape predators, and disperse. The tremendous locomotor performance of O. septentrionalis, which is maintained across temperatures and parasite loads, likely contributes to the invasion success of this species.

UNA RANA ARBORÍCOLA (Osteopilus septentrionalis, HYLIDAE) DEPREDANDO A UN TOMEGUÍN DE LA TIERRA ENJAULADO (Tiaris olivaceus) EN CUBA

Abstract.-We are reporting the first case of predation of a Cuban Treefrog (Osteopilus septentrionalis) on a confined caged bird, a Yellow-faced Grassquit, (Tiaris oilivaceus) in central Cuba. We comment about predation on aquarium fish too. Both cases of predation are not reported previously.

La RANA LECHERA (Trachycephalus typhonius) EN COSTA RICA

Trachycephalus typhonius es una especie común y con amplia distribución. Sus registros en Costa Rica son limitados a las zonas bajas, sin registros previos en la cuenca alta del Río Grande de Térraba. Aquí, reportamos la Rana Lechera para esta cuenca, y extendemos su rango altitudinal a través de registros participativos de la comunidad local. El individuo de la Rana Lechera fue encontrado en la comunidad de Fila Tigre, Coto Brus. Sus características diagnósticas como el patrón reticulado del iris, falta de barras oscuras verticales en sus labios y piel glandular pueden ser confirmadas a través de fotografías y nos permiten diferenciarla de especies similares como Smislica baudinii y Osteopilus septentrionalis. Por lo tanto, apoyamos la importancia de los esfuerzos de la comunidad local por conocer su biodiversidad, dado que enriquecen el conocimiento de la fauna y permiten enfocar esfuerzos futuros de exploración e investigación en la zona