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1 Larval Dytiscus sp. sinking its mandibles into a small fi sh in a laboratory aquarium (Photo courtesy of Siegfried Kehl 2012)
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As conspicuous predators throughout ontogeny, dytiscids are central to freshwater food webs, particularly in lentic systems such as wetlands and ponds. Adult and larval dytiscids are considered to be generalists, feeding on zooplankton, aquatic invertebrates, larval amphibians, and fish, but some dytiscid species selectively feed on certain prey ty...
Citations
... Several species of Rhantus are reported as predators of mosquito or chironomid larvae in field studies (e.g. Kögel 1987;Aditya & Saha 2006;Culler et al. 2014). Gut content analysis of Rhantus frontalis (Marsham, 1802) revealed the presence of different food objects (Chironomidae, Culicidae, ephemeroptera, algae and vascular plants), with a predominance of chironomids (Deding 1988). ...
†Rhantus villumi sp. nov. is described and illustrated on the basis of a single specimen from the earliest Eocene Fur Formation, Denmark. With an estimated age of ca. 55.4 Ma, it represents the oldest member of an extant genus of the family Dytiscidae. However, the presence of Rhantus in the early Eocene is only slightly older than previous estimates, and generally agrees well with phylogenetic analyses of the subfamily Colymbetinae. The presence of a predominantly temperate genus in the presumably warm Lagerstätte is briefly discussed, supporting the hypothesis of temporary cooling, as suggested by several other invertebrate records from the Fur Formation. It is suggested that the new species could feed on mosquito larvae, which are known from the Lagerstätte. Finally, a record of another Dytiscidae species from the same locality is mentioned, but, due to poor preservation and lack of diagnostic characters, this fossil remains unidentified to genus or species level.
... Diving beetles (Coleoptera: Dytiscidae) are important predators of aquatic communities in ponds lacking fish (Cobbaert et al. 2010, Culler et al. 2023. The genus Cybister Curtis, 1827 (a group of large beetles, with a body length of >20 mm) lives primarily in water bodies, such as ponds, wetlands, and paddy fields (Miller andBergsten 2016, Nakajima et al. 2020). ...
Diving beetles play an important role in fishless freshwater communities. The genus Cybister is included in the Japanese Red Data List owing to its diminished population size. The phylogenetic relationships and genetic structures of Cybister chinensis and Cybister brevis, whose populations are declining, and Cybister tripunctatus lateralis, whose population and distribution is increasing, are poorly understood and must be addressed in future conservation efforts. In this study, we investigated the flight behaviour and phylogeography of the three Cybister species. Cybistyer tripunctatus lateralis and C. brevis flew well in the spring, and the proportion of flight in C. tripunctatus lateralis increased again after the reproductive season. However, C. chinensis did not fly. Relatively, among the three species, C. tripunctatus lateralis has the largest forewings. Phylogenetic analysis based on mitochondrial DNA revealed that C. chinensis showed genetic differentiation between the eastern and western regions of Japan, whereas C. tripunctatus lateralis showed no regional trends. Furthermore, C. brevis showed an intermediate trend between the two species. These findings suggest that C. tripunctatus lateralis has been expanding the area of its distribution rapidly through flight dispersal in recent years. Cybister chinensis flies infrequently, raising concerns about metapopulation fragmentation.
... Dytiscidae larvae prey on live animals such as insects, amphibians, and fish (e.g., Ohba 2009a;Culler et al. 2014;Yamasaki et al. 2022), and are usually reared using prey collected from the field (Inoda and Kitano 2013). Consequently, research on alternative prey would contribute to ex-situ conservation in several aspects, including protection of field resources and manpower reduction, and can control for the variations in peak reproduction seasons. ...
Dytiscus sharpi is defined as “Critically Endangered” in the Red List of Japan and designated as a “nationally endangered species of wild fauna and flora” of the Japanese “Conservation of Endangered Species of Wild Fauna and Flora” Act. In previous studies, tadpoles of Red List species (Rana ornativentris) were collected, and approximately 300 tadpoles were needed to raise one D. sharpi adult. A rearing experiment was performed to identify alternative prey for D. sharpi larvae. Larvae were reared on cultivable prey (Asellus hilgendorfii, goldfish, and crickets), and the quality of alternative prey was compared to that of tadpoles based on three criteria: adult size, survival rate, and development speed. Adult size, survival rate, and development speed values showed that alternative prey, i.e., A. hilgendorfii, goldfish, and crickets, were of adequate quality as larval prey according to all monitored parameters when compared to tadpoles. Dytiscus sharpi larvae can be raised using only cultivable prey, and multiple choices are available. The elimination of the need to overcollect endangered tadpoles from the field by using alternative prey for rearing will contribute to the conservation of both D. sharpi and R. ornativentris. This result would make ex-situ conservation of D. sharpi sustainable.
... Invertebrate assemblages in SSWs exhibit a wide variety of feeding habits, which contributes to the proper functioning and stability of these ecosystems (Calizza et al., 2019). In fishless SSWs, some of these invertebrates are top predators (Culler et al., 2014;Magnusson and Williams, 2009;Rennie and Jackson, 2005). Invertebrate assemblages include also grazers, filterers or zooplankton-feeders, which participate in the control of eutrophication effects and strongly contribute to maintain a clear-water state (McLaughlan and Aldridge, 2013;Mormul et al., 2018;Schum and Maly, 2000). ...
Small shallow lakes and ponds (SSWs) have high conservation value and support numerous ecosystem services. However, these small ecosystems face many threats, including eutrophication and internal biotic pressures like Cyprinidae or exotic bioturbators crayfish, which tend to shift biodiverse SSWs to a turbid state dominated by phytoplankton unfitted to numerous usages, and compromise the effectiveness of their restoration. The ecological quality of SSWs and the efficiency of their management still remain poorly evaluated because of the lack of adapted tools. To fill this gap, we propose a new multimetric index (BECOME) and a diagnostic tool (BECOMEd) both based on macrophyte and invertebrate communities. BECOME exhibits a high sensitivity to the impact of surrounding crops, urbanization and fertilized meadows, morphological alterations, and various internal biotic sources of alterations, in a wide variety of geological and climatic contexts. BECOME is especially innovative, because taking into account internal biotic sources of pressures neglected by most of the existing biological WFD-compliant indices for European lakes and ponds, despite their importance in SSW threats. BECOMEd allows to identify the major alteration sources and estimates their relative contribution to SSW degradation, helping managers to prioritize actions or to evaluate their effectiveness. The statistical design applied for the index construction has been fitted to develop biological index for ecosystems influenced by a wide amplitude of numerous environmental conditions. This design could be easily applied elsewhere in the world, for SSWs but also for other types of ecosystems.
... Prior studies have shown that predation can happen (including cannibalism) among all of our predator groups, and is dependent on factors like body size, age, food scarcity, and predator density (Anholt 1994, Bofill and Yee 2019, Culler et al. 2014, Culler and Lamp 2009, Deding 1988, Hicks 1994, Hopper et al. 1996, Johnson and Jakinovich 1970, Van Buskirk 1989and 1992, Wissinger 1988, Yee 2010. We hypothesized that IGP would occur more often in the absence of mosquito larvae as prey. ...
... Photoperiod ranged from 12 h, 20 min of daylight in mid-September to 10 h, 55 min in early November of 2019 (timeanddate.com). Insects are ectothermic, therefore lower temperatures likely lower their overall activity as well (Culler et al. 2014, Gresens et al. 1982, Inoda et al. 2007). Past work has described how predatory aquatic insect foraging and reproduction behaviors can be affected by ambient temperature (Pandian et al. 1979, De Block and Stoks 2003, Calosi et al. 2007, Inoda et al. 2007) and photoperiod (Norling 1984, Johansson andRowe 1999). ...
Mosquito larvicides are used across a variety of aquatic habitats, although when applied they likely affect other aquatic organisms. The removal or impairment of top insect predators via larvicides could be beneficial to mosquitoes by allowing their populations to rebound once pesticide levels dissipate. Our goal was to determine if two larvicide types, growth regulators (IGRs) and surface films (SFs), harm non-target aquatic insect communities, and if these chemicals influence the ability of predatory aquatic insects to regulate mosquitoes. We surveyed aquatic sites before and after IGR and SF-application, then compared changes in insect community structure. Evenness was lower in SF treated habitats, and when analyzing prey/controphic taxa only, evenness and diversity changed in untreated reference areas, suggesting that differences measured were due to other environmental factors, not larvicide presence. A field experiment was then conducted by exposing specific predatory aquatic insects to varying doses of IGRs and SFs and then placing them in mesocosms containing mosquito larvae. Surface films were directly lethal to adult dytiscids at recommended and high concentrations. Although we found no significant differences in mosquito emergence among all treatment levels, there was a trend of negative controls (no predator mesocosms) and SF-treated predators allowing the most mosquitoes to emerge compared to positive controls (predators not exposed to larvicides) and IGR-treated predators. Thus, these larvicides may have minimal effects on mosquito larvae predators, but the direct effects of surface films on insects that interact with the water's surface require further investigation.
... This allowed larger prey to pass through the cage while providing visual and chemical cues to experimental organisms, but preventing fish from consuming them. Fish were represented by thee 15-20 cm long individuals tof the crucian carp Carassius auratus (Cyprinidae) which is an invasive, omnivorous predator of aquatic insects, typically found in European lentic habitats 53 55 . Ensuring that each species experienced a block was more important than having 11 consecutive sampling events in the same blocks because there could have been a significant effect of a block on insect behaviour. ...
Habitat selection, the choice of a habitat based on its perceived quality, is a key mechanism structuring freshwater communities. To date, individual variability in habitat selection has been neglected, and specialisation has never been considered in this type of studies. We examined the individual differences in the habitat selection of backswimmers (Notonectidae) and diving beetles (Dytiscidae). From each family, we selected one habitat generalist able to coexist with fish ( Notonecta glauca , Dytiscus marginalis ), and one species specialised to fishless habitats ( Notonecta obliqua , Acilius sulcatus ). We performed a mesocosm experiment quantifying the consistency in individuals’ decisions in response to fish and vegetation structure, in relation to sex and specialisation. Neither the overall pattern of preferences nor consistency in individuals’ decisions differed between specialists and generalists or between the sexes, but both were consistent within families. At the population level, backswimmers preferred fishless pools with submersed and floating macrophytes, while diving beetles showed no clear preferences. Individual decisions of backswimmers were consistent and likely driven by conspecific/heterospecific attraction. In diving beetles, individual decisions were primarily density-dependent. Our results reinforce the significance of habitat selectivity for aquatic community assembly, while suggesting a range of mechanisms driving variability in individual behaviour.
... In this study, we focus on diving beetles (Dytiscidae), a family of aquatic insects in which most species utilize aquatic vegetation for various purposes, including escape from predators and ovipositing (Nilsson and Holmen, 1995). Dytiscids are predaceous during at least part of their life cycle, and their dynamics have important cascade effects on local invertebrate communities in freshwater ecosystems (Culler et al., 2014). In our study, we address the following questions: (1) How does the quantity of refuges, i.e. emergent plant cover, affect diving beetle species richness and abundance? ...
... Fish are known to have strong negative effects on dytiscid species richness and abundance (Liao et al., 2020). In fishless aquatic habitats, however, dytiscids are top predators in the food chain, despite that they are not completely free from other predators (Culler et al., 2014). Emergent plants can serve as dytiscid refuges, providing sanctuary from predators (Nilsson et al., 1994) and reducing attacking rate and success (Yee, 2010;Ghosh et al., 2017). ...
... It is predictable that dytiscids seek shelter within emergent plants in ponds with fish. In ponds without fish, dytiscids are not free from predators (Culler et al., 2014). Other predators of dytiscids include aquatic insects (Larson, 1990), amphibians (Fasola and Canova, 1992), waterbirds (Thomas, 1982), and mammals (Haberl, 2002; Table 1). ...
Aquatic plants are important prey refuges for aquatic organisms, and their species richness is positively related with aquatic invertebrate species richness. Yet, it is unclear how the quantity of refuges, i.e. aquatic vegetation cover, affect aquatic invertebrate assemblages and their habitat use under different levels of predation risk (e.g. in the presence or absence of fish), nor at different scales (i.e. microhabitat and pond scales). Here, we investigated how provision of refuges affects diving beetle (Dytiscidae) species richness and abundance in the presence and absence of fish predators. We sampled diving beetles (Dytiscidae) with 1-L activity traps and estimated emergent plant cover at both the pond and microhabitat scales. We found that plant cover affected dytiscid populations differently: At the pond scale, dytiscid presence was positively correlated with increasing plant cover, both with and without fish, indicating the importance of emergent plants for aquatic biodiversity. At the microhabitat scale, dytiscid species richness and abundance were positively correlated to increasing plant cover in ponds with fish, but there was no such relationship in ponds without fish, emphasizing that the level of predation risk can alter prey species’ use of prey refuges. Our findings provide evidence that the availability of both vegetated and non-vegetated microhabitats can benefit aquatic invertebrates. We suggest maintaining variation in the provision of emergent plant cover, to retain high habitat heterogeneity in urban ponds and to enhance freshwater biodiversity.
... As many species of dytiscid have a poor capacity of co-existing with fish (Culler et al. 2014;Liao et al. 2020), ponds with fish may become sink-habitats, especially when a pond lacks habitat heterogeneity. The high variation in community dissimilarity between ponds with fish ( Fig. 3d; Online Appendices 2 and 3) suggests that predation has filtered dytiscid species. ...
Context
Structural and functional connectivity, as subconcepts of landscape connectivity, are key factors in biodiversity conservation and management. Previous studies have focused on the consequences of connectivity for populations of terrestrial organisms, which may not be appropriate for aquatic organisms.
Objectives
As landscape connectivity critically affects the potential value of ponds for biodiversity, here we used diving beetles (Dytiscidae), an indicator taxon of wetland biodiversity, to investigate how structural connectivity affects functional connectivity to aquatic invertebrates in an urban landscape.
Methods
We assessed pairwise similarities of dytiscid community, i.e. the variation of species composition between clustered and isolated ponds in the Helsinki Metropolitan Area, Finland. We investigated how dytiscid community similarity is affected by Euclidean distances between ponds, as an indicator of structural connectivity.
Results
We found that clustered ponds shared more species than isolated ponds. Dytiscid species community similarity responded negatively to increasing Euclidean distance between ponds. Effectively dispersing species were widely distributed across the landscape, while poor dispersers were scarcely distributed in the same landscape.
Conclusions
Structural connectivity determines which species are able to disperse successfully, with poor dispersers restricted to well-connected ponds. The different responses of effective dispersers and poor dispersers to the same structural connectivity indicate that functional connectivity determines species composition. We recommend providing well-connected aquatic habitats in urban landscapes and the implementation of measures to reduce isolation of wetland assemblages. Even clustered ponds need dispersal from other habitats to ensure their contribution to urban biodiversity.
... Large predatory macroinvertebrates are top predators in aquatic, fishless ecosystems (Wellborn, Skelly & Werner, 1996;Cobbaert, Bayley & Greter, 2010;Culler, Ohba & Crumrine, 2014;Úbeda et al., 2019). Predation in nature is a complex phenomenon, however, particularly where predatory invertebrates hunt vertebrates. ...
The disappearance and deterioration of amphibian breeding habitats is a major cause of their global extinction. In Europe, this problem affects the yellow‐bellied toad Bombina variegata , which inhabits small ponds in the early stages of succession, where no predatory invertebrate species normally occur. Nonetheless, as habitats, small temporary ponds are highly endangered, a situation that is intensifying with urban spread.
A system of 13 pairs of artificial ponds was constructed in 2012 for the breeding of B. variegata with the aim of reconnecting disjunct populations. During the 2 years of the study, one of the twin ponds was regularly cleared of emergent vegetation and invertebrates. The survival rates of the tadpoles released in the cleared and uncleared ponds were analysed.
The survival rate of the tadpoles released into the cleared ponds was higher than of those introduced into the uncleared ones. Tadpole survival rates were also higher in new, single ponds, constructed in 2013.
The lower survival rates of the introduced tadpoles are best explained by the presence of predatory aquatic invertebrates, particularly the large diving beetle Dytiscus marginalis . Experimentally obtained consumption rates indicate that one Dytiscus larva is capable of destroying a typical clutch of B. variegata tadpoles within a few hours, much faster than any of the other insect predators tested.
The impact of freshwater invertebrates on tadpoles is frequently studied but rarely quantified. For conservation measures to be effective, quantitative standards need to be applied that describe the impact of predation in a predictable manner.
Construction of artificial small ponds is broadly accepted as an important conservation measure compensating for the disappearance of natural amphibian breeding sites. This function of artificial ponds may be substantially enhanced by the periodic removal of invertebrate predators.
... In the present study some predaceous insects were found associated with mosquito larvae in different habitats this was also mentioned by McDonald and Buchanan (1981) who found that the mosquito's larvae which colonized the man-made ponds followed by predaceous Coleoptera, Hemiptera and Odonata. During our study, diving beetles (Coleoptera: Dytiscidae) was also collected from wetlands and rice fields this is in agreement with Bay (1974), Bellini et al., 2000), Berman et al., 2000), Bosi (2001), Lundkvist et al., (2003), Chandra et al., (2008), Lamp (2009) andCuller et al., (2015). ...
Mosquito larvae and their predators were surveyed from different breeding sites in El-Fayoum Governorate. The physiochemical characters of water and environmental factors that effect on mosquito larvae were studied. Biochemical and toxicological effects of the two photosensitizing compounds; eosin yellow lactone and phloxine B (xanthene dye) were evaluated against the third instar larvae of the most dominant mosquito species and their predators. The surveyed results revealed the occurrence of six mosquito species in the study area: one aedine, Aedes caspius, two anopheline, Anopheles pharoensis, An. sergenti, and three culicines, Culex pipien, Cx. antennatus, and Culiseta longiareolata. The most dominant species was Cx. pipiens with a total number of 3571 larvae followed by Ae. caspius and An. phareonsis with a total number of 670, 452 collected larvae, respectively. The two commonly collected predators were Pantala flavescens (Odonata) and Caenis macrura (Ephemeroptera) naiads. The results explained that both eosin yellow and phloxine B can be used as larvicide. However, eosin was more efficient than phloxine against Cx. pipiens with LC50 equal to (0.025 and 0.053 ppm) and An. pharoensis (0.023 and 0.016 ppm, respectively. On the other hand, the phloxine was more effective than eosin against Ae. caspius (0.016 and 0.024 ppm, respectively. Also, the results investigated that phloxine was more efficient than eosin against Cx. pipiens in dark and there was a significant difference between their toxicity in sunlight and in the absence of direct light. In addition, phloxine was less toxic against P. flavescens than eosin with LC50 of 1.822 and 1.044 ppm, respectively) and the mayfly (C. macrura) was more sensitive to the both photosensitizers with LC50 equal to 0.003 and 0.006 ppm for eosin and phloxine, respectively. The biochemical studies indicated the increasing in the levels of glutathione S-transferase after treatment with eosin and phloxine and there is a significant decrease in peroxidase levels after treatment with both eosin and phloxine.
