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BOARD 21 The streams of Hawaii have been historically dewatered for anthropogenic use, which interrupts the life cycle of several amphidromous stream species. The amphidromous life cycle involves adult reproduction [...]

Deciphering mechanisms that regulate succession on ephemeral resources is critical for elucidating food web dynamics and nutrient recycling. Blow fly (Diptera: Calliphoridae) colonization and utilization of vertebrate carrion serve as a model for such studies, as they are the primary invertebrates that recycle this ephemeral resource. Initial colonization by blow flies often results in heightened attraction and colonization by competing conspecifics and het-erospecifics, thereby regulating associated arthropod succession patterns. We examined the response of Cochliomyia macellaria (F.) and Chrysomya rufifacies (Macquart) to conspecific and heterospecific eggs. Because Ch. rufifacies is facultatively predacious and cannabalistic, we hypothesized that adults would recognize the presence of conspecific and heterospecific eggs, thus avoiding potential predation and competition. Using a Y-tube olfactometer, we measured the residence time response of C. macellaria and Ch. rufifaciesto conspecific and heterospecific eggs of three different age classes (fresh to 9-h-old). Fly responses to surface-sterilized eggs and to an aqueous solution containing egg-associated microbes were then examined. High-throughput sequencing was used to survey egg-associated bacteria from both species. We report that C. macellaria and Ch. rufifacies exhibit differential responses to eggs of conspecifics and heterospecifics, which appear to be a result of microbial volatile-related odors. These behaviors likely influence predator-prey interactions between species. Preliminary high-throughput sequencing revealed Ch. rufifacies had a similar egg-associated fauna as C. macellaria, which may serve as a form of camouflage, allowing it to colonize and thereby attract C. macellaria, a common prey for its larvae. [ABSTRACT FROM AUTHOR]

Necrophagous insect studies have shown that decomposing vertebrate remains are an important ephemeral resource within an ecosystem. However, the microbes (e.g., bacteria and archaea) that were a part of the once living organism and the exogenous taxa that colonize this postmortem resource remain largely underexplored. Also, it is not well understood how these two kingdoms interact to recycle decaying biomass, an important mechanistic question for ecosystem function ecology. To better understand microbial community dynamics throughout decomposition, we used swine carcasses (A/=6) as models for mammalian postmortem decomposition to characterize epinecrotic microbial communities from: the abdominal skin of replicate carcasses; the internal microbiome of individual necrophagous dipteran larvae (maggots); and the microbiome of dipteran larval masses that had colonized the carcasses. Sampling occurred every 12 h for the duration of the decomposition process. We characterized these microbial communities over time using high-throughput 16S amplicon sequencing. The relative abundance of microbial taxa changed over decomposition as well as across sampling locations, suggesting significant interactions between the environment, microbes, and insect larvae. Maggot masses were represented by multiple blow fly species in each mass: Phormia regina (Meigen), Lucilia coerulei-viridis (Macquart), and Cochliomyia macellaria (F.). Relative abundance of these species within the mass also changed as decomposition progressed, suggesting the presence of certain Calliphoridae species within a mass may be associated with temporal shifts of the microbial communities. These results provide new insight into the community ecology of carrion decomposition by providing new data on interactions of microbes and dipteran larvae overtime. [ABSTRACT FROM AUTHOR]

Background: Buruli ulcer (BU), caused by Mycobacterium ulcerans (M. ulcerans), is a necrotizing skin disease found in more than 30 countries worldwide. BU incidence is highest in West Africa; however, cases have substantially increased in coastal regions of southern Australia over the past 30 years. Although the mode of transmission remains uncertain, the spatial pattern of BU emergence in recent years seems to suggest that there is an environmental niche for M. ulcerans and BU prevalence. Methodology/Principal Findings: Network analysis was applied to BU cases in Victoria, Australia, from 1981-2008. Results revealed a non-random spatio-temporal pattern at the regional scale as well as a stable and efficient BU disease network, indicating that deterministic factors influence the occurrence of this disease. Monthly BU incidence reported by locality was analyzed with landscape and climate data using a multilevel Poisson regression approach. The results suggest the highest BU risk areas occur at low elevations with forested land cover, similar to previous studies of BU risk in West Africa. Additionally, climate conditions as far as 1.5 years in advance appear to impact disease incidence. Warmer and wetter conditions 18-19 months prior to case emergence, followed by a dry period approximately 5 months prior to case emergence seem to favor the occurrence of BU. Conclusions/Significance: The BU network structure in Victoria, Australia, suggests external environmental factors favor M. ulcerans transmission and, therefore, BU incidence. A unique combination of environmental conditions, including land cover type, temperature and a wet-dry sequence, may produce habitat characteristics that support M. ulcerans transmission and BU prevalence. These findings imply that future BU research efforts on transmission mechanisms should focus on potential vectors/reservoirs found in those environmental niches. Further, this study is the first to quantitatively estimate environmental lag times associated with BU outbreaks, providing insights for future transmission investigations. [ABSTRACT FROM AUTHOR]

Amphidromous stream fauna represent three phyla that have a tropical distribution among oceanic islands, with a few continental representatives. This lifecycle involves marine larval development, with postlarval migration, growth and reproduction as adults occurring in freshwater streams. Many tropical archipelagoes are on the brink of heavy commercial development, threatening freshwater resources in tropical regions. Because of this threat and the isolated nature of tropical islands, quantitative studies are needed to better understand this unique lifecycle. In this paper, we present the use of two modifications of the original Breder trap to study the migration dynamics of tropical amphidromous fish and shrimp postlarvae. The first modification was used in a cemented and channelized stream. The second modification was used in two streams with natural substrates of large, embedded and immovable boulders and basalt outcrops. Quantitative trapping was standardized by time and numbers of traps used, to give results presented as postlarvae trap-1 h-1. The number of traps used in the natural streams was based on channel width at the trapping location (i.e., equal number of traps per meter), thus providing equivalent trapping effort between streams of different sizes and flow magnitude. Both trap designs were useful for quantitative monitoring of postlarvae over several months and years, among different streams, and were equally practical for assessing diel and species-specific migration dynamics. Postlarval recruitment of Hawaiian amphidromous species showed temporal variation between months and years within the same stream, significant differences between two streams of different flow magnitude, and distinct diel patterns in diurnal and nocturnal fish and shrimp migration, respectively. A direct correlation between stream flow and total fish postlarval migration was documented. [ABSTRACT FROM AUTHOR]

Understanding the interactions of ecosystems, humans and pathogens is important for disease risk estimation. This is particularly true for neglected and newly emerging diseases where modes and efficiencies of transmission leading to epidemics are not well understood. Using a model for other emerging diseases, the neglected tropical skin disease Buruli ulcer (BU), we systematically review the literature on transmission of the etiologic agent, Mycobacterium ulcerans (MU), within a One Health/EcoHealth framework and against Hill's nine criteria and Koch's postulates for making strong inference in disease systems. Using this strong inference approach, we advocate a null hypothesis for MU transmission and other understudied disease systems. The null should be tested against alternative vector or host roles in pathogen transmission to better inform disease management. We propose a re-evaluation of what is necessary to identify and confirm hosts, reservoirs and vectors associated with environmental pathogen replication, dispersal and transmission; critically review alternative environmental sources of MU that may be important for transmission, including invertebrate and vertebrate species, plants and biofilms on aquatic substrates; and conclude with placing BU within the context of other neglected and emerging infectious diseases with intricate ecological relationships that lead to disease in humans, wildlife and domestic animals., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS.)