Robert C. Jadin

Parasite transmission in complex communities: Predators and alternative hosts alter pathogenic infections in amphibians

While often studied in isolation, host-parasite interactions are typically embedded within complex communities. Other community members, including predators and alternative hosts, can therefore alter parasite transmission (e.g., the dilution effect), yet few studies have experimentally evaluated more than one such mechanism. Here, we used data from natural wetlands to design experiments investigating how alternative hosts and predators of parasites mediate trematode (Ribeiroia ondatrae) infection in a focal amphibian host (Pseudacris regilla). In short-term predation bioassays involving mollusks, zooplankton, fish, larval insects, or newts, four of seven tested species removed 62-93% of infectious stages. In transmission experiments, damselfly nymphs (predators) and newt larvae (alternative hosts) reduced infection in P. regilla tadpoles by -50%, whereas mosquitofish (potential predators and alternative hosts) did not significantly influence transmission. Additional bioassays indicated that predators consumed parasites even in the presence of alternative prey. In natural wetlands, newts had similar infection intensities as P. regilla, suggesting that they commonly function as alternative hosts despite their unpalatability to downstream hosts, whereas mosquitofish had substantially lower infection intensities and are unlikely to function as hosts. These results underscore the importance of studying host-parasite interactions in complex communities and of broadly linking research on predation, biodiversity loss, and infectious diseases.

It's a predator-eat-parasite world: how characteristics of predator, parasite and environment affect consumption.

Understanding the effects of predation on disease dynamics is increasingly important in light of the role ecological communities can play in host–parasite interactions. Surprisingly, however, few studies have characterized direct predation of parasites. Here we used an experimental approach to show that consumption of free-living parasite stages is highly context dependent, with significant influences of parasite size, predator size and foraging mode, as well as environmental condition. Among the four species of larval trematodes and two types of predators (fish and larval damselflies) studied here, parasites with larger infective stages (size >1,000xa0μm) were most vulnerable to predation by fish, while small-bodied fish and damselflies (size <10xa0mm) consumed the most infectious stages. Small parasite species (size approx. 500xa0μm) were less frequently consumed by both fish and larval damselflies. However, these results depended strongly on light availability; trials conducted in the dark led to significantly fewer parasites consumed overall, especially those with a size of <1,000xa0μm, emphasizing the importance of circadian shedding times of parasite free-living stages for predation risk. Intriguingly, active predation functioned to help limit fishes’ infection by directly penetrating parasite species. Our results are consistent with established theory developed for predation on zooplankton that emphasizes the roles of body size, visibility and predation modes and further suggest that consumer–resource theory may provide a predictive framework for when predators should significantly influence parasite transmission. These results contribute to our understanding of transmission in natural systems, the role of predator–parasite links in food webs and the evolution of parasite morphology and behavior.

Cryptic diversity in disjunct populations of Middle American Montane Pitvipers: a systematic reassessment of Cerrophidion godmani

Jadin, R.C., Townsend, J.H., Castoe, T.A. & Campbell, J.A. (2012). Cryptic diversity in disjunct populations of Middle American Montane Pitvipers: a systematic reassessment of Cerrophidion godmani. —Zoologica Scripta, 41, 455–470.

Biomphalaria straminea (Mollusca: Planorbidae) as an Intermediate Host of Ribeiroia sp. (Trematoda: Psilostomidae) in Brazil

Abstract: Species of Ribeiroia are trematode parasites of birds and mammals that have acquired notoriety since Ribeiroia ondatrae was identified as a cause of mortality and malformations in North American amphibians. Although species of Ribeiroia have been reported in vertebrate hosts in South America, the snails involved in its transmission remain unknown in Brazil. During malacological studies conducted at Pampulha Reservoir, Belo Horizonte, Minas Gerais, Brazil, between January 2009 and February 2012, in total 14,264 specimens of Biomphalaria straminea were collected, of which 192 (1.35%) were infected with gymnocephalous cercariae. The larvae were used for experimental infection of laboratory-reared guppies (Poecilia reticulata); metacercariae obtained in these fishes were orally administered to domestic ducks (Cairina moschata); and adult parasites were obtained from the proventriculus 10 days after infection. Based on morphological and molecular analyses, the parasite was identified as Ribeiroia sp., a species morphologically similar to R. ondatrae, but distinctly different at the molecular level. This is the first report of larvae of Ribeiroia in Brazil and B. straminea as a new intermediate host for this genus.

A relict lineage and new species of green palm-pitviper (Squamata, Viperidae,Bothriechis) from the Chortís Highlands of Mesoamerica

A new species of palm-pitviper of the genus Bothriechis is described from Refugio de Vida Silvestre Texíguat in northern Honduras. The new species differs from congeners by having 19 dorsal scale rows at midbody, a bright green dorsal coloration in adults, the prelacunal scale fused to the second supralabial, and in representing a northern lineage that is sister to Bothriechis lateralis, which is distributed in Costa Rica and western Panama and is isolated from the new taxon by the Nicaraguan Depression. This represents the 15th endemic species occurring in Refugio de Vida Silvestre Texíguat, one of the richest herpetofaunal sites in Honduras, itself being the country with the highest degree of herpetofaunal endemism in Central America. We name this new species in honor of a Honduran conservationist slain in fighting against illegal logging, highlighting the sacrifices of rural activists in battling these issues and the critical importance of conservation in these areas.

First record of the common house gecko (Hemidactylus frenatus) in Ecuador

Key data Hemidactylus frenatus; Gekkonidae; Common House Gecko; Ecuador; Provincias Esmeraldas and Manabi; population; San Lorenzo & Pedernales. UTA R-55986–88 & DHMECN 04606; verified by Carl J. Franklin, Amphibian and Reptile Diversity Research Center, University of Texas at Arlington, and Cecilia Tobar, Division de Herpetologia, Museo Ecuatoriano de Ciencias Naturales, Quito, Ecuador.

Ontogenetic Effects on Snake Hemipenial Morphology

Abstract In this study we investigate hemipenial variation through ontogeny by preparing specimens of known-aged individuals from captive-bred Plains Gartersnakes, Thamnophis radix, descended from a wild population in northern Illinois, USA. We examined males at two different ages (215–254 days, N = 9) and (829–867 days, N = 12) to compare both juvenile and adult morphologies. Hemipenis length increased isometrically with tail length, and there were no significant differences detected between right and left hemipenis length or width. In addition, this study is the first to explore variation in hemipenial morphology within and among litters. We found significant litter effects on hemipenis length, on the elevation (but not the slope) of the relationship between hemipenis length and tail length, and on number of basal hooks, suggesting a possible genetic basis to these characteristics. These results highlight the importance of examining multiple males through ontogeny, as well as reporting body-size measurements for all specimens, to obtain an accurate representation of the hemipenis morphology of a species for comparative ecological, taxonomic, and evolutionary studies.