Parasite-mediated enemy release and low biotic resistance may facilitate invasion of Atlantic coral reefs by Pacific red lionfish (Pterois volitans)

NEW INSIGHTS BASED ON MORPHOLOGICAL AND MOLECULAR DATA REVEAL THE TAXONOMIC STATUS OF HALIOTREMA PTEROISI (MONOGENOIDEA: DACTYLOGYRIDAE) INFECTING DEVIL FIREFISH PTEROIS MILES (PERCIFORMES: SCORPAENOIDEI: SCORPAENIDAE) IN THE RED SEA OFF EGYPT

HALIOTREMA PTEROISI

Paperna, 1972 (Monogenoidea: Dactylogyridae) was found parasitizing the gill lamellae of devil firefish, Pterois miles (Bennet) (Perciformes: Scorpaenidae), in the Red Sea off Safaga (26°44'N, 33°56'E), Egypt. The parasite species was described based on morphological features of available specimens and transferred to PlatycephalotremaKritsky and Nitta, 2019 (Dactylogyridae) as Platycephalotrema pteroisi (Paperna, 1972) n. comb. The occurrence of Pl. pteroisi off Safaga, Egypt, represented a range extension for the helminth of about 160 km to the southwest of the southern end of the Gulf of Aqaba. The transfer of the species to Platycephalotrema based on an evaluation of morphological features was supported by an analysis of molecular sequences of the 28S rDNA gene of Pl. pteroisi and 49 other dactylogyrid species. Maximum-likelihood, Bayesian inference, and maximum parsimony analyses of this dactylogyrid sequence data revealed H. pteroisi to nest with significant support within the clade of Platycephalotrema spp. During the literature review of dactylogyrid species infecting scorpionfishes, it was determined that Ancyrocephalus sp. of Dyer et al. from luna lion fish Pterois lunulata Temminck and Schlegel collected off Okinawa-jima, Japan represented an undescribed species of Platycephalotrema.

Parasite and genetic diversity of big-scale sand smelt (Atherina boyeri Risso, 1810) populations in their natural and expansion ranges in Ukraine

The big-scale sand smelt (Atherina boyeri) is an Atlanto-Mediterranean amphidromous fish species found within the Black Sea. Here, we assess differences in the parasite fauna of big-scale sand smelt populations from their natural range in the northwestern Black Sea and from their expansion range in the Lower and Middle River Dnipro. In addition, we undertook a microsatellite analysis to assess the genetic similarity of fish from the different locations. We found that the parasite community of fish in their natural range was wider than that from their expansion range. While the Gulf of Odesa was most distant from all other localities by parasite community composition and the Dnipro Reservoir was characterised by an absence of parasites (newest and most distant expansion locality), only fish from the Danube Delta showed a significant genetic difference. Our results suggest that the parasite community of big-scale sand smelt is primarily influenced by environmental factors, such as habitat type, water salinity and/or prey composition. Both microsatellite analysis and parasite community species composition (e.g. the presence of the marine Telosentis exiguus in the Kakhovka Reservoir and freshwater Raphidascaris sp. in the Gulf of Odesa) confirmed that populations in the River Dnipro reservoirs had, at some time, been connected with native marine populations, thus also confirming the species' amphidromous nature.

Epidemics in native species influence the outcome of a species invasion

Invasive species can have large effects on native communities. When native and invasive species share parasites, an epidemic in a native species could facilitate or inhibit the invasion. We sought to understand how the incidence and timing of epidemics in native species caused by a generalist parasite influenced the success and impact of an invasive species. We focused on North American native and invasive species of zooplankton (Daphnia dentifera and Daphnia lumholtzi, respectively), that can both become infected with a fungal parasite (Metschnikowia bicuspidata). In a laboratory microcosm experiment, we exposed the native species to varying parasite inocula (none, low, high) and two invasive species introduction times (before or during an epidemic in the native species). We found that the invasive species density in treatments with the parasite was higher compared to uninfected treatments, though only the early invasion, low-parasite and uninfected treatments exhibited significant pairwise differences. However, invasive resting eggs were only found in the uninfected treatments. The density of the native species was lowest with a combination of the parasite present, and the invasive species introduced during the epidemic. Native infection prevalence in these treatments (late invasion, parasite present) was also higher than prevalence in treatments where the invasive species was introduced before the epidemic. Therefore, the timing of an invasion relative to an epidemic can affect both the native and invasive species. Our results suggest that the occurrence and timing of epidemics in native species can influence the impacts of a species invasion.

Invasive brown widow spiders avoid parasitism despite high densities

Invasive species are sometimes less susceptible to natural enemies compared to native species, but the mechanism is often unclear. Here we tested two potential mechanisms for lower parasitism of invasive species: density-dependent parasitism and preference for human-dominated habitats. We investigated how variation in host density and habitat type affect egg sac parasitism in two widow spider species (family Theridiidae). We compared parasitism on the egg sac of the brown widow, Latrodectus geometricus, an urban invasive species, and the white widow, Latrodectus pallidus, a species native to Israel. To investigate variation in host and parasitoid density, we measured nearest-neighbor distance between spider webs and parasitism rates in 16 sites, and in a single site monthly throughout a year. In L. pallidus, denser sites were more heavily parasitized (up to 55%) and parasitism rate increased with population density throughout the season. Extremely dense L. geometricus populations, however, had very low rates of parasitism (0-5%). We then conducted an egg sac transplant experiment in human-dominated and natural habitats. We found no parasitism of either species in the human-dominated habitat, compared to 30% parasitism of both species in the natural habitat. In addition, we found evidence for higher predation of L. pallidus than of L. geometricus egg sacs, particularly in the natural habitat. These combined results suggest that the human-dominated habitats inhabited by L. geometricus have a lower abundance of predators and parasites. We conclude that lower parasitism and predation in human-dominated habitats could contribute to the invasion success of L. geometricus.

Biotic Interactions and the Future of Fishes on Coral Reefs: The Importance of Trait-Based Approaches

Biotic interactions govern the structure and function of coral reef ecosystems. As environmental conditions change, reef-associated fish populations can persist by tracking their preferred niche or adapting to new conditions. Biotic interactions will affect how these responses proceed and whether they are successful. Yet, our understanding of these effects is currently limited. Ecological and evolutionary theories make explicit predictions about the effects of biotic interactions, but many remain untested. Here, we argue that large-scale functional trait datasets enable us to investigate how biotic interactions have shaped the assembly of contemporary reef fish communities and the evolution of species within them, thus improving our ability to predict future changes. Importantly, the effects of biotic interactions on these processes have occurred simultaneously within dynamic environments. Functional traits provide a means to integrate the effects of both ecological and evolutionary processes, as well as a way to overcome some of the challenges of studying biotic interactions. Moreover, functional trait data can enhance predictive modeling of future reef fish distributions and evolvability. We hope that our vision for an integrative approach, focused on quantifying functionally relevant traits and how they mediate biotic interactions in different environmental contexts, will catalyze new research on the future of reef fishes in a changing environment.

Comparison of Whole Blood Fatty Acid Profiles between Lionfish (Pterois spp.) in Wild and Managed Care Environments

Suboptimal nutrition may contribute to lionfish (Pterois volitans and Pterois miles) health issues in managed care environments. This study’s objective was to establish and compare whole blood fatty acid profiles in wild and aquarium lionfish. Whole blood samples were dried onto specialized high-quality paper cards from wild, invasive lionfish harvested off the North Carolina coast (n = 16) and lionfish managed by the North Carolina Aquariums (n = 12). Blood fatty acid profiles were analyzed from dried blood spots. Aquarium lionfish had significantly (p < 0.05) higher linoleic (18:2ω6) and eicosapentaenoic (20:5ω3) acid levels than wild lionfish. Similarly, aquarium lionfish had significantly (p < 0.05) lower saturated fatty acids and arachidonic (20:4ω6) to eicosapentaenoic acid (20:5ω3) ratios than wild lionfish. Total omega-3 and omega-6 fatty acids, as well as the ratio of these two fatty acid groups, were similar between wild and aquarium lionfish. Gut content analysis of wild lionfish diets included reef-dependent and schooling fish while aquarium lionfish diets were pelagic fish, crustaceans, mollusks, and commercial gel diets with nutrient supplements. This study reports whole blood fatty acid profiles in lionfish, providing comparative macronutrient data that may be useful for improving their nutrition and welfare in aquariums.

First record and molecular characterisation of two Gnathia species (Crustacea, Isopoda, Gnathiidae) from Philippine coral reefs, including a summary of all Central-Indo Pacific Gnathia species

Due to their unusual life cycle that includes parasitic larval and free living adult stages, gnathiid isopods are typically overlooked in biodiversity surveys, even those that focus on parasites. While the Philippines sits within the region of highest marine biodiversity in the world, the coral triangle, no gnathiid species have been identified or described from that region. Here we present the first records of two gnathiid species collected from the Visayas, central Philippines: Gnathia malaysiensis Müller, 1993, previously described from Malaysia, and G. camuripenis Tanaka, 2004, previously described from southern Japan. This paper provides detailed morphological redescriptions, drawings and scanning electron microscope images as well as the first molecular characterisation of both species, Furthermore, a summary of the Central-Indo Pacific Gnathia species is provided.

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Morphological description of two gnathiid species collected from the central Philippines, along with molecular data, are presented.

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Gnathia malaysiensis was previously described from Malaysia and G. camuripenis was previously described from southern Japan.

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Although the Philippines is in the highly biodiverse coral triangle, this is the first gnathiid description from this region.

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The wide geographic range of G. camuripenis suggests dispersal via large, highly mobile fishes, and/or tropical cyclones.

Pulse Heat Stress and Parasitism in a Warming World

Infectious disease outbreaks emerged across the globe during the recent 2015-2016 El Niño event, re-igniting research interest in how climate events influence disease dynamics. While the relationship between long-term warming and the transmission of disease-causing parasites has received substantial attention, we do not yet know how pulse heat events - common phenomena in a warming world - will alter parasite transmission. The effects of pulse warming on ecological and evolutionary processes are complex and context dependent, motivating research to understand how climate oscillations drive host health and disease. Here, we develop a framework for evaluating and predicting the effects of pulse warming on parasitic infection. Specifically, we synthesize how pulse heat stress affects hosts, parasites, and the ecological interactions between them.

Precipitous Declines in Northern Gulf of Mexico Invasive Lionfish Populations Following the Emergence of an Ulcerative Skin Disease

Invasive Indo-Pacific lionfish Pterois volitans/miles have become well-established in many western Atlantic marine habitats and regions. However, high densities and low genetic diversity could make their populations susceptible to disease. We examined changes in northern Gulf of Mexico (nGOM) lionfish populations following the emergence of an ulcerative skin disease in August 2017, when estimated disease prevalence was as high as 40%. Ulcerated female lionfish had 9% lower relative condition compared to non-ulcerated females. Changes in lionfish size composition indicated a potential recruitment failure in early summer 2018, when the proportion of new recruits declined by >80%. Remotely operated vehicle surveys during 2016–2018 indicated lionfish population density declined in 2018 by 75% on natural reefs. The strongest declines (77–79%) in lionfish density were on high-density (>25 lionfish per 100 m²) artificial reefs, which declined to similar levels as low-density (<15 lionfish per 100 m²) artificial reefs that had prior lionfish removals. Fisheries-dependent sampling indicated lionfish commercial spearfishing landings, commercial catch per unit effort (CPUE), and lionfish tournament CPUE also declined approximately 50% in 2018. Collectively, these results provide correlative evidence for density-dependent epizootic population control, have implications for managing lionfish and impacted native species, and improve our understanding of biological invasions.

Dactylogyrids (Platyhelminthes: Monogenoidea) Infecting the Gill Lamellae of Flatheads (Scorpaeniformes: Platycephalidae), with Proposal of Platycephalotrema n. gen. and Descriptions of New Species from Australia and Japan

Platycephalotrema n. gen. (Dactylogyridae) is proposed for four new species and 5 previously described species parasitizing the gills of flatheads (Scorpaeniformes: Platycephalidae) as follows: Platycephalotrema ogawai n. sp. (type species) from Platycephalus sp. 1 (type host) and Platycephalus sp. 2, both of Nakabo & Kai (2013) (locally known as “Yoshino-gochi” and “Ma-gochi,” respectively) (Japan); Platycephalotrema austrinum n. sp. from Platycephalus endrachtensis Quoy & Gaimard (type host) and Platycephalus sp. (Australia); Platycephalotrema bassensis (Hughes, 1928) n. comb. from Platycephalus bassensis Cuvier (Australia); Platycephalotrema koppa n. sp. from Platycephalus fuscus Cuvier (Australia); Platycephalotrema macassarensis (Yamaguti, 1963) n. comb. from Platycephalus indicus (Linnaeus) (China, Macassar); Platycephalotrema mastix n. sp. from P. fuscus and P. endrachtensis (Australia); Platycephalotrema platycephali (Yin & Sproston, 1948) n. comb. from P. indicus (China) and P. fuscus (Australia); Platycephalotrema sinensis (Yamaguti, 1963) n. comb. from Cociella punctata (Cuvier) (China); Platycephalotrema thysanophrydis (Yamaguti, 1937) n. comb. from Inegocia japonica (Cuvier), Inegocia ochiaii Imamura, and Cociella crocodilus (Cuvier) (Japan, China). Other species requiring further study but potentially members of Platycephalotrema include Ancyrocephalus vesiculosus Murray, 1931, Haliotrema indicum Tripathi, 1957, Haliotrema swatowensis Yao, Wang, Xia, & Chen, 1998, and Haliotrema pteroisi Paperna, 1972. The primary features differentiating Platycephalotrema include species having: (1) tandem gonads (testis postgermarial); (2) two prostatic reservoirs, each emptying independently into the base of the male copulatory organ; (3) a dextral vaginal pore and large vaginal vestibule; (4) dorsal and ventral pairs of morphologically similar anchors; (5) a ventral bar with spatulate ends; (6) a dorsal bar with bifurcated ends, and (7) absence of an accessory piece. The new species are described, and P. thysanophrydis is redescribed based on newly collected and museum specimens.

Environmental drivers of parasite load and species richness in introduced parakeets in an urban landscape

Introduced species represent a threat to native wildlife worldwide, due to predation, competition, and disease transmission. Concurrent introduction of parasites may also add a new dimension of competition, i.e. parasite-mediated competition, through spillover and spillback dynamics. Urban areas are major hotspots of introduced species, but little is known about the effects of urban habitat structure on the parasite load and diversity of introduced species. Here, we investigated such environmental effects on the ectoparasite load, richness, and occurrence of spillback in two widespread invasive parakeets, Psittacula krameri and Myiopsitta monachus, in the metropolitan area of Rome, central Italy. We tested 231 parakeets and found that in both species parasite load was positively influenced by host abundance at local scale, while environmental features such as the amount of natural or urban habitats, as well as richness of native birds, influenced parasite occurrence, load, and richness differently in the two host species. Therefore, we highlight the importance of host population density and habitat composition in shaping the role of introduced parakeets in the spread of both native and introduced parasites, recommending the monitoring of urban populations of birds and their parasites to assess and manage the potential occurrence of parasite-mediated competition dynamics as well as potential spread of vector-borne diseases.

High resources and infectious disease facilitate invasion by a freshwater crustacean

It is well-established that both resources and infectious disease can influence species invasions, but little is known regarding interactive effects of these two factors. We performed a series of experiments to understand how resources and parasites can jointly affect the ability of a freshwater invasive zooplankton to establish in a population of a native zooplankton. In a life history trial, we found that both species increased offspring production to the same degree as algal resources increased, suggesting that changes in resources would have similar effects on both species. In a microcosm experiment simulating an invasion, we found that the invasive species reached its highest densities when there was a combination of both high resources and the presence of a shared parasite, but not for each of these conditions alone (i.e., a significant resource x parasite interaction). This result can be explained by changes in native host population density; high resource levels initially led to an increase in the density of the native host, which caused larger epidemics when the parasite was present. This high infection prevalence caused a subsequent reduction in native host density, increasing available resources and allowing the invasive species to establish relatively dense populations. Thus, in this system, native communities with a combination of high resource levels and parasitism may be the most vulnerable to invasions. More generally, our results suggest that parasitism and resource availability can have interactive, non-additive effects on the outcome of invasions.