Jonathan T. Fingerut

Bio: Jonathan T. Fingerut is an academic researcher from Saint Joseph's University. The author has contributed to research in topics: Settlement (structural) & Population. The author has an hindex of 6, co-authored 16 publications receiving 206 citations. Previous affiliations of Jonathan T. Fingerut include University of California, Los Angeles & Academy of Natural Sciences of Drexel University.

Patterns and processes of larval emergence in an estuarine parasite system.

Abstract: Trematode parasites in intertidal estuaries ex- perience constantly varying conditions, with the presence or absence of water potentially limiting larval transport be- tween hosts. Given the short life spans (24 h) of cercariae, emergence timing should be optimized to enhance the prob- ability of successful transmission. In the present study, field measurements and laboratory experiments identified pro- cesses that regulate the emergence of cercariae from their first intermediate snail hosts in an intertidal marsh. Larvae emerged over species-specific temperature ranges, exclu- sively during daylight hours, and only when snails were submerged. The three factors operate over different tempo- ral scales: temperature monthly, light diurnally (24-h pe- riod), and water depth tidally (12-h period). Each stimulus creates a necessary condition for the next, forming a hier- archy of environmental cues. Emergence as the tide floods would favor transport within the estuary, and light may trigger direct (downward or upward) swimming toward host habitats. Abbreviated dispersal would retain asexually re- produced cercariae within the marsh, and local mixing would diversify the gene pool of larvae encysting on sub- sequent hosts. In contrast to the timing of cercarial release, emergence duration was under endogenous control. Dura- tion of emergence decreased from sunrise to sunset, perhaps in response to the diminishing lighted interval as the day progresses. Circadian rhythms that control cercarial emer- gence of freshwater species (including schistosomes) are often set by the activity patterns of subsequent hosts. In this estuary, however, the synchronizing agent is the tides. To-

Larval swimming overpowers turbulent mixing and facilitates transmission of a marine parasite

Abstract: Planktonic cercariae (parasite larvae) of digenetic flatworms (Himasthla rhigedana) encyst up to 100% of intermediate host populations. Toward explaining such high prevalence, larval behavior and passive-transport processes were evaluated experimentally for their roles in waterborne parasite transmission. Using a new application of laser and digital video imaging technologies, we quantified cercarial movements in still water and in simulated field flows. In still water, downward swimming in response to light, irrespective of intensity or source, and gravity brought larvae to the bottom three-times faster than gravitational sinking alone. A 33% elevation in temperature (18–24°C) caused a 71% increase in swim speed. In flume flows characteristic of southern California salt marshes (u* = 0.2 cm/s, occurring >80% of the time), vertical larval distributions were highly bottom skewed. The mean downward swim speed (0.59 cm/s at 24°C) was three times faster than turbulent fluctuations (w′ = 0.23 cm/s), indicating...

Dispersal pathways, seed rains, and the dynamics of larval behavior

Abstract: Dispersing propagules (larvae, seeds, and spores) establish and maintain populations, which serve as templates for subsequent species interactions. Connectivity among demes derives, in large part, from connectivity between consecutive steps, release, transport, and settlement, in dispersal pathways. Concurrent measurements of individuals in each step are a necessary precursor to identifying governing mechanisms. Here we directly and definitively resolved the roles of physics and behavior in mediating dispersal pathways of an estuarine parasite between its intermediate hosts. Planktonic cercariae of Himasthla rhigedana, a parasitic flatworm, are functionally similar to lecithotrophic larvae of many free-living marine invertebrates. The combination of parasite life cycle characteristics and the relatively simple tidal flows in their habitat renders this system an effective model for dispersal studies. Simultaneous field measurements of larval release, transport, settlement, and the flow regime, together with mechanistic experiments, led to empirical understanding of host colonization. All dispersal steps were highly and significantly correlated over time and in space. This tight coupling resulted, unequivocally, from a suite of larval behaviors. Cercariae emerged from first intermediate host snails only during daytime flood tides, enhancing larval retention in the marsh. Daylight triggered downward swimming, and within seconds, cercariae overpowered turbulent mixing, landing in benthic habitat of second intermediate host snails and crabs. Larvae settled (encysted) on external regions of snails/crabs that, presumably, were most vulnerable to ingestion by definitive host shorebirds. In total, cercarial behaviors greatly foreshortened dispersal distances, magnified local parasite prevalence, and increased the likelihood of large-scale transmission by definitive hosts. Cracking open the black box of dispersal thus revealed mechanisms, connectivity, and ecological consequences of the larval stage.

Silk filaments enhance the settlement of stream insect larvae

Abstract: Many aquatic organisms need to settle in suitable benthic habitats while being transported via water currents. Such settlement is especially challenging for organisms that encounter complex benthic topography and lack the ability to move easily from the water column to the bed (e.g., via swimming). We conducted flume studies to examine whether the settlement of drifting stream insects is facilitated by adhesive filaments that extend from their bodies. Using a new tripwire visualization technique, we found that neonatal black flies (Simuliumtribulatum) drifted with silk threads averaging six times their body length. These threads allowed larvae to contact or snag the bed from a greater height than would be possible through direct body-to-bed contact alone, and instantly arrested their downstream movement. Thus, silk increased their probability of settlement. We then performed an experiment to examine how settlement varied with bed topography and velocity. We tested whether settlement rate differed between a flat bed and an irregular bed that mimicked key aspects of their natural cobble-bed habitat. Velocities were similar for both bed treatments. Settlement on the irregular bed was 40 times greater than on the flat bed due to silk use. Settlement rate also exhibited a marginally significant decline with increasingly velocity on the flat bed, but not on the irregular bed. Silk threads should greatly increase the settlement rate of these nonswimming larvae on coarse-grained stream beds. Thus, silk snagging can potentially reduce the downstream distance that individuals are transported during a drift event, although the effects of silk on other phases of larval dispersal may differ.

Local modification of benthic flow environments by suspension-feeding stream insects

Abstract: Larval black flies often exhibit spatially aggregated distributions, and individuals within patches can potentially reduce the supply of suspended food particles to downstream neighbors by modifying local flow characteristics. We used hot-film anemometry to quantify the magnitude and spatial extent of flow modifications downstream from feeding Simulium vittatum larvae in a laboratory flume, and to determine whether temporal patterns of flow variation are related to movements of the larval feeding appendages. Mean velocity 1 mm downstream from feeding larvae was reduced by 75%, and the percent reduction in velocity diminished asymptotically with downstream distance. Reduced velocities were evident as much as 60 mm downstream from, and 3 mm to either side of, larvae. Turbulence intensity (i.e., the SD of the velocity time series) was generally higher in this region relative to control flow conditions. Three results demonstrate the major contribution of the larval feeding appendages (i.e., labral fans) to such flow modification. First, there was a minimal reduction in mean velocity 5 mm downstream from non-feeding larvae (i.e., with closed labral fans), whereas mean velocity at the same location was reduced markedly when larvae were feeding. Second, the power spectrum of the velocity time series exhibited greatest power at frequencies that corresponded to the frequency of labral fan motions. Third, fan flick times accounted for most of the variance in the velocity power spectrum. The large local flow modifications that we documented have potentially important consequences for the feeding performance and growth of individuals located within larval aggregations, and are likely to influence behavioral interactions and spacing patterns.

Costs of dispersal

Abstract: Dispersal costs can be classified into energetic, time, risk and opportunity costs and may be levied directly or deferred during departure, transfer and settlement. They may equally be incurred during life stages before the actual dispersal event through investments in special morphologies. Because costs will eventually determine the performance of dispersing individuals and the evolution of dispersal, we here provide an extensive review on the different cost types that occur during dispersal in a wide array of organisms, ranging from micro-organisms to plants, invertebrates and vertebrates. In general, costs of transfer have been more widely documented in actively dispersing organisms, in contrast to a greater focus on costs during departure and settlement in plants and animals with a passive transfer phase. Costs related to the development of specific dispersal attributes appear to be much more prominent than previously accepted. Because costs induce trade-offs, they give rise to covariation between dispersal and other life-history traits at different scales of organismal organisation. The consequences of (i) the presence and magnitude of different costs during different phases of the dispersal process, and (ii) their internal organisation through covariation with other life-history traits, are synthesised with respect to potential consequences for species conservation and the need for development of a new generation of spatial simulation models.

Ecosystem energetic implications of parasite and free-living biomass in three estuaries

Abstract: Parasites can have strong impacts but are thought to contribute little biomass to ecosystems. We quantified the biomass of free-living and parasitic species in three estuaries on the Pacific coast of California and Baja California. Here we show that parasites have substantial biomass in these ecosystems. We found that parasite biomass exceeded that of top predators. The biomass of trematodes was particularly high, being comparable to that of the abundant birds, fishes, burrowing shrimps and polychaetes. Trophically transmitted parasites and parasitic castrators subsumed more biomass than did other parasitic functional groups. The extended phenotype biomass controlled by parasitic castrators sometimes exceeded that of their uninfected hosts. The annual production of free-swimming trematode transmission stages was greater than the combined biomass of all quantified parasites and was also greater than bird biomass. This biomass and productivity of parasites implies a profound role for infectious processes in these estuaries.

Ecology of sea lice parasitic on farmed and wild fish

Abstract: Sea lice, especially Lepeophtheirus salmonis and Caligus spp., have the greatest economic impact of any parasite in salmonid fish farming and are also a threat to wild salmonids. Here, I review how the biology and ecology of various louse and host species influence their pathogenicity and epidemiology. Recent discoveries of new species and genotypes emphasize the need for more basic research on louse taxonomy and host preferences. Louse development rates are strongly dependent on temperature, and increasing mean sea temperatures are likely to increase infestation pressure on farms and wild fish, as well as affecting the geographical distribution of hosts and parasites. Despite progress in finding L. salmonis larvae in the plankton and in modelling louse production in several countries, more data on larval behaviour and distribution are required to develop dispersal and transmission models for both L. salmonis and Caligus spp. This knowledge could be used to take measures to reduce the risks of lice affecting farmed and wild fish.

Global warming and temperature-mediated increases in cercarial emergence in trematode parasites.

Abstract: Global warming can affect the world's biota and the functioning of ecosystems in many indirect ways. Recent evidence indicates that climate change can alter the geographical distribution of parasitic diseases, with potentially drastic consequences for their hosts. It is also possible that warmer conditions could promote the transmission of parasites and raise their local abundance. Here I have compiled experimental data on the effect of temperature on the emergence of infective stages (cercariae) of trematode parasites from their snail intermediate hosts. Temperature-mediated changes in cercarial output varied widely among trematode species, from small reductions to 200-fold increases in response to a 10 degrees C rise in temperature, with a geometric mean suggesting an almost 8-fold increase. Overall, the observed temperature-mediated increases in cercarial output are much more substantial than those expected from basic physiological processes, for which 2- to 3-fold increases are normally seen. Some of the most extreme increases in cercarial output may be artefacts of the methods used in the original studies; however, exclusion of these extreme values has little impact on the preceding conclusion. Across both species values and phylogenetically independent contrasts, neither the magnitude of the initial cercarial output nor the shell size of the snail host correlated with the relative increase in cercarial production mediated by rising temperature. In contrast, the latitude from which the snail-trematode association originated correlated negatively with temperature-mediated increases in cercarial production: within the 20 degrees to 55 degrees latitude range, trematodes from lower latitudes showed more pronounced temperature-driven increases in cercarial output than those from higher latitudes. These results suggest that the small increases in air and water temperature forecast by many climate models will not only influence the geographical distribution of some diseases, but may also promote the proliferation of their infective stages in many ecosystems.