Molecular phylogenetics of the freshwater gastropod genus Juga (Cerithioidea: Semisulcospiridae)

Trematode parasites exceed aquatic insect biomass in Oregon stream food webs

Although parasites are increasingly recognized for their ecosystem roles, it is often assumed that free-living organisms dominate animal biomass in most ecosystems and therefore provide the primary pathways for energy transfer. To examine the contributions of parasites to ecosystem energetics in freshwater streams, we quantified the standing biomass of trematodes and free-living organisms at nine sites in three streams in western Oregon, USA. We then compared the rates of biomass flow from snails Juga plicifera into trematode parasites relative to aquatic vertebrate predators (sculpin, cutthroat trout and Pacific giant salamanders). The trematode parasite community had the fifth highest dry biomass density among stream organisms (0.40 g/m² ) and exceeded the combined biomass of aquatic insects. Only host snails (3.88 g/m² ), sculpin (1.11 g/m² ), trout (0.73 g/m² ) and crayfish (0.43 g/m² ) had a greater biomass. The parasite 'extended phenotype', consisting of trematode plus castrated host biomass, exceeded the individual biomass of every taxonomic group other than snails. The substantial parasite biomass stemmed from the high snail density and infection prevalence, and the large proportional mass of infected hosts that consisted of trematode tissue (M = 31% per snail). Estimates of yearly biomass transfer from snails into trematodes were slightly higher than the combined estimate of snail biomass transfer into the three vertebrate predators. Pacific giant salamanders accounted for 90% of the snail biomass consumed by predators. These results demonstrate that trematode parasites play underappreciated roles in the ecosystem energetics of some freshwater streams.

Intra-Annual Changes in Waterborne Nanophyetus salmincola

An analysis of daily water samples collected from an index site on Big Soos Creek, Washington indicated intra-annual differences in the concentrations of waterborne Nanophyetus salmincola. Waterborne concentrations, quantified as gene copies/L, peaked during the fall (October-November 2016), decreased to very low concentrations over the winter (January-March 2017), and then increased in the spring and throughout the summer. High waterborne concentrations of N. salmincola DNA (2 × 10⁶ gene copies/L) corresponded with live N. salmincola cercariae (mean = 3 cercariae/L) that were detected in companion water samples. Spikes in waterborne N. salmincola concentrations in October and November typically coincided with increases in streamflow; this combination resulted in elevated infection pressures during high water events in the fall. The peak in waterborne N. salmincola concentrations corresponded with an accompanying peak in tissue parasite density (metacercariae/posterior kidney) in Coho Salmon Oncorhynchus kisutch that were reared in the untreated water.

Assessing the diversity of Western North American Juga (Semisulcospiridae, Gastropoda)

Juga is a genus of freshwater gastropods distributed in Pacific and Interior drainages of the Pacific Northwest from central California to northern Washington. The current classification has relied heavily on features of the shell, which vary within and across drainages, and often intergrade without sharp distinctions between species. The only previous molecular analysis included limited population sampling, which did not allow robust assessment of intra- versus interspecific levels of genetic diversity, and concluded almost every sampled population to be a distinct OTU. We assembled a multilocus mitochondrial (COI, 16S) and nuclear gene (ITS1) dataset for ∼100 populations collected across the range of the genus. We generated primary species hypotheses using ABGD with best-fit model-corrected distances and further explored our data, both individual gene partitions and concatenated datasets, using a diversity of phylogenetic and species delimitation methods (Bayesian inference, maximum likelihood estimation, StarBEAST2, bGMYC, bPTP, BP&P). Our secondary species delimitation hypotheses, based primarily on the criterion of reciprocal monophyly, and informed by a combination of geography and morphology, support the interpretation that Juga comprises a mixture of geographically widespread species and narrow range endemics. As might be expected in taxa with low vagility and poor dispersal capacities, analysis of molecular variance (AMOVA) revealed highly structured populations with up to 80% of the observed genetic variance explained by variation between populations. Analyses with bGMYC, bPTP, and BP&P appeared sensitive to this genetic structure and returned highly dissected species hypotheses that are likely oversplit. The species diversity of Juga is concluded to be lower than presently recognized, and the systematics to require extensive revision. Features of the teleoconch considered significant in species-level and subgeneric classification were found to be variable within some species, sometimes at a single site. Of a number of potentially new species identified in non-peer reviewed reports and field guides, only one was supported as a distinct OTU.

Phylogenetic analysis of the Lancinae (Gastropoda, Lymnaeidae) with a description of the U.S. federally endangered Banbury Springs lanx

We examined the patelliform snails of the subfamily Lancinae, endemic to northwestern North America, to test whether morphological variation correlated with genetic and anatomical differences. Molecular analyses using cox1, 16S, calmodulin intron, and 28S rDNA partial sequences and anatomical data supported recognition of four species in three genera. The relationships of lancines within Lymnaeidae are not yet well-resolved. The federally endangered Banbury Springs lanx is described as a new genus and species, Idaholanxfresti, confirming its distinctiveness and narrow endemicity.

Against the odds of unusual mtDNA inheritance, introgressive hybridisation and phenotypic plasticity: systematic revision of Korean freshwater gastropods (Semisulcospiridae, Cerithioidea)

The systematics of Semisulcospiridae in Korea is critically revised by means of comparative anatomy, including comprehensive review of type material and mitochondrial phylogenetics (sequences of COI and 16S). The family is represented by two genera with different reproductive modes: Semisulcospira Boettger, 1886 is viviparous and contains three species (S. coreana (Martens, 1886), S. gottschei (Martens, 1886) and S. forticosta (Martens, 1886)) while Koreoleptoxis Burch & Jung, 1988 is oviparous and also contains three species (K. globus (Martens, 1886), K. nodifila (Martens, 1886), K. tegulata (Martens, 1894)). Koreanomelania Burch & Jung, 1988 is synonymised with Koreoleptoxis. Species can be distinguished by differences in shell shape and sculpture. They form well-differentiated clusters in the mitochondrial phylogeny, consistently revealing lower intraspecific than interspecific genetic distances. Sequences of Japanese Semisulcospira species fall into three distinct major clades (A–C), rendering Semisulcospira non-monophyletic in the mitochondrial tree. Only a small number of Japanese samples were closely related to the Korean clade (Clade C). The numerically predominant Japanese mitochondrial Clade B exhibited increased lineage divergence and, when translated into amino acids, significantly more amino acid substitutions in comparison with Korean species. I conclude that these Japanese sequences may be paralogous and/or may undergo non-neutral evolution. Hence, they are not suitable for inferring phylogenetic relationships.