Aquatic Heteropterans Research Articles

Unravelling the environmental correlates influencing the seasonal biodiversity of aquatic Heteropteran assemblages in northern Africa

Heteropteran communities form a key component of aquatic ecosystems but have not been widely studied compared to other freshwater faunal groups. This research examined the environmental parameters influencing the diversity, seasonal distribution and structure of aquatic Heteroptera assemblages in the Mediterranean region of Tunisia, northern Africa. Heteropterans were most abundant during spring and summer, coinciding with the emergence of several species and the most favorable environmental conditions for benthic aquatic fauna. Three-way multivariate analyses (combining community composition data from all sites and seasons) highlighted the longitudinal spatial organization of Heteropteran communities. Headwater regions were dominated by halophobic sensitive taxa, and lowland sites were characterized by high salinity resistant taxa (halophilic taxa). The longitudinal organization was driven by gradients of mineralization (salinity and electrical conductivity) and oxygen (DO, COD and BOD) concentrations. Taxonomic composition differed between river catchments, with significantly higher diversity (taxa richness) in the streams with adjacent riparian forest cover. These sites were characterized by the presence of endemic species, such as Velia africana and Velia eckerleini, and rare species, Notonecta meridionalis, and Aquarius najas. Results recorded highlight the importance of aquatic vegetation and water quality in driving the seasonal and spatial variability of Heteropterans, and provide important information to inform the management and conservation of freshwater biodiversity in Northern Africa.

Species Composition of Aquatic (Nepomorpha) and Semiaquatic (Gerromorpha) Heteroptera (Insecta: Hemiptera) in Kaeng Krachan National Park, Phetchaburi Province, Thailand

The species composition of aquatic (Nepomorpha) and semiaquatic (Gerromorpha) Heteroptera were examined from protected and unprotected study sites in three streams associated with Kaeng Krachan National Park. At each stream, both quantitative and qualitative sampling methods were used during seven collecting events (November 2018 to June 2020). A total of 11 families, representing 33 genera and 60 species, were collected in this study, with more Nepomorpha families but higher species richness in Gerromorpha. The species richness of both protected and unprotected sampling sites were lowest during the fifth sampling event. Nevertheless, there was no significant difference in richness between protected and unprotected sampling sites for any sampling event based on a paired t-test analysis. Based on an nMDS analysis, the patterns of species composition of aquatic and semiaquatic heteropterans were unclear among protected and unprotected sampling sites. The use of aquatic and semiaquatic Heteroptera as bioindicators for habitat quality is still uncertain. Additional physiochemical characters of the water and physical characters of the stream may lead to a clearer picture of the relationship between aquatic and semiaquatic Heteroptera and stream habitat quality.

New data on Corixidae and Hebridae (Heteroptera) of Kazakhstan

The species Sigara (Subsigara) oxiana Jansson, 1983 (Corixidae) is recorded for the first time from Kazakhstan. New data on the distribution of two species, which are rare in Kazakhstan, Sigara (Subsigara) fossarum (Leach, 1817) and Hebrus (Hebrus) pilipes Kanyukova, 1997 (Hebridae) are also provided. Additional data on sampling localities of Callicorixa producta producta (Reuter, 1880), Corixa affinis Leach, 1817 and Corixa punctata (Illiger, 1807) in Kazakhstan are reported. Additions to the bibliography on aquatic and semiaquatic heteropterans of the Kazakh fauna are given.

The Heteropterans (Gerromorpha and Nepomorpha) of Andean lakes from Colombia

The Nepomorpha and Gerromorpha heteropterans are highly diverse, mainly in Neotropical aquatic ecosystems; however, their composition in the lakes of the Tropical Andes is poorly known. This article presents the composition of aquatic and semiaquatic bugs and their geographical and altitudinal distribution in eight lentic ecosystems from the Cundinamarca department, Colombia. The similar aquatic heteropteran composition between these Andean lakes and its relationship with the geographical and altitudinal range from 1,585 to 3,700 m.a.s.l. in the Eastern Andes are also analyzed. To carry out this work, the collections and pertinent literature are reviewed, and biota similarity is compared by applying a upgma analysis. The results show the predominance of Nepomorpha with a total of 12 species, four genera, and two families: Corixidae (6), and Notonectidae (6). The second most common suborder is Gerromorpha with eight species, seven genera, and five families: Gerridae (3), Veliidae (2), Hebridae (1), Hydrometridae (1), and Mesoveliidae (1). The biota similarity is related to páramo ecosystems and forest type. This article is the first to consider aquatic and semiaquatic heteropterans as biota from the Andean and High Andean lakes in Colombia.

Identifying a “pseudogene” for the mitochondrial DNA COI region of the corixid aquatic insect, Hesperocorixa distanti (Heteroptera, Corixidae)

DNA barcoding has been actively used as a method for species identification, and it will become an increasingly important method in the future. However, DNA barcoding can occasionally encounter a major problem, namely “nuclear mitochondrial DNA pseudogenes (NUMTs)”. In this paper, we report the discovery of a pseudogene in the mitochondrial COI region from aquatic heteropterans. PCR with Folmer’s universal primer set produced two different lengths of DNA sequences: a standard 658 bp sequence and a slightly shorter 652 bp sequence. The presence of an “indel” and “stop codon” in the shorter sequence made them separable. We recommend using the “HCOoutout” primer as a downward primer for amplification of the COI region of aquatic heteropterans, especially corixid water bugs.

Detection of an endangered aquatic heteropteran using environmental DNA in a wetland ecosystem.

The use of environmental DNA (eDNA) has recently been employed to evaluate the distribution of various aquatic macroorganisms. Although this technique has been applied to a broad range of taxa, from vertebrates to invertebrates, its application is limited for aquatic insects such as aquatic heteropterans. Nepa hoffmanni (Heteroptera: Nepidae) is a small (approx. 23 mm) aquatic heteropteran that inhabits wetlands, can be difficult to capture and is endangered in Japan. The molecular tool eDNA was used to evaluate the species distribution of N. hoffmanni in comparison to that determined using hand-capturing methods in two regions of Japan. The eDNA of N. hoffmanni was detected at nearly all sites (10 eDNA-detected sites out of 14 sites), including sites where N. hoffmanni was not captured by hand (five eDNA-detected sites out of six captured sites). Thus, this species-specific eDNA technique can be applied to detect small, sparsely distributed heteropterans in wetland ecosystems. In conclusion, eDNA could be a valuable technique for the detection of aquatic insects inhabiting wetland habitats, and could make a significant contribution to providing distribution data necessary to species conservation.

Characterizing a novel predator\u2013prey relationship between native Diplonychus esakii (Heteroptera: Belostomatidae) and invasive Gambusia affinis (Teleostei: Poeciliidae) in central China

A considerable body of the literature considers the potential impact of exotic predators on native prey organisms, while comparatively, few studies have asked whether and how native predators include novel prey types into their diet spectrum. Here, we asked whether the native aquatic heteropteran Diplonychus esakii preys on the highly invasive western mosquitofish (Gambusia affinis), which has been introduced to southern China and threatens native fish species through competition and predation on their fry. We conducted 48-h prey choice experiments under semi-natural conditions. In a ‘no-choice’ experiment (one predator and one potential prey; n = 200), we found the heteropterans to prey more on large-bodied fish, a pattern that was also described for other belostomatids, while prey sex had no effect on capture rates. Moreover, large-bodied heteropterans caught more fish than small-bodied individuals. However, overall capture rates in our study were low (11.5–30%) compared to studies on other belostomatids, which explains why subsequent binary prey choice experiments using one predator and two prey—either large and small females or male and female (with smaller sample sizes of n = 20 and 30, respectively)—did not confirm the results of our first experiment. Our study exemplifies how a pattern of body size-dependent predation can arise in a novel (not coevolved) predator–prey interaction. We tentatively argue that the observed pattern could be driven by intrinsic features of the predator, namely, altered prey preferences with increasing age coupled with a general preference for large-bodied prey, or changing nutritional needs at different developmental stages.

Impacts of oil palm plantations on changes in environmental heterogeneity and Heteroptera (Gerromorpha and Nepomorpha) diversity

This study evaluates the effects of oil palm plantations on environmental heterogeneity and diversity (α and β) of aquatic Heteroptera (semi-aquatic and aquatic species) in Amazon streams. We assessed eight streams located in forested areas and 12 in oil palm plantations. As expected, oil palm areas had lower environmental heterogeneity, despite the presence of riparian vegetation. Heteropteran communities differed in forest and oil palm areas, however, only semi-aquatic bugs were affected by environmental variables. Streams in oil palm plantations had lower α-diversity and distinct community structures when compared to forest sites. Oil palm plantation did not affect the β-diversity of semi-aquatic bugs, however, there was increased β-diversity of aquatic bugs in these areas. These results reflect the impacts of environmental heterogeneity generated by plantations next to riparian vegetation, inducing local diversity loss. Effects on β-diversity differed among groups of Heteroptera, mainly due to the differences in the life histories of each group. Semi-aquatic bugs seem to undergo environmental filtering, while aquatic bugs can be structured by limiting similarity. Thus, the management and land conservation strategies adopted to preserve ecosystems within oil palm plantations were insufficient for the protection of aquatic heteropteran communities. In summary, such conservation policies should account for the particularities of different groups of the aquatic ecosystem; especially for aquatic fauna, which are usually overlooked in conservation policies for the Brazilian Amazon.

Study of nucleolar behavior during spermatogenesis in Martarega brasiliensis (Heteroptera, Notonectidae).

Few cytogenetic studies have been undertaken using aquatic heteropterans and the nucleolar behavior of these insects has been described in only four species, Limnogonus aduncus, Brachymetra albinerva, Halobatopsis platensis, and Cylindrostethus palmaris. The nucleolus is a cellular structure related to biosynthetic activity and it exhibits a peculiar behavior in the heteropterans of the Triatominae subfamily; it persists during all stages of meiosis. Thus, this study aims to analyze spermatogenesis in Martarega brasiliensis, with an emphasis on nucleolar behavior. Twenty M. brasiliensis adult males were used and collected from the Municipal reservoir in the city of São José do Rio Preto, São Paulo, Brazil. The species were fixed in methanol:acetic acid (3:1), then dissected, and the testicles were extracted, torn apart, and impregnated with silver ions. During prophase, the nuclei of M. brasiliensis were composed of the nucleolus and nucleolar corpuscles, which varied in number from one to four, emphasizing that this insect has great synthetic activity during meiosis. The analysis of cells in metaphase I showed that M. brasiliensis presents a nucleolar organizing region in at least one autosome. Furthermore, the phenomenon of nucleolar persistence was not observed. All spermatids presented nucleolar markings that varied in number and position according to the stage of elongation. Moreover, it was also possible to highlight the presence of a vesicle in spermatids. Thus, this paper describes the nucleolar behavior of M. brasiliensis and highlights important characteristics during spermatogenesis, thus, increasing the knowledge about the biology of these aquatic heteropterans.

Distribution of water bugs (Heteroptera: Nepomorpha, Gerromorpha) over latitudinal zones in the northeast of European Russia

Data on the taxonomic composition of water bugs (Heteroptera: Nepomorpha, Gerromorpha) in the northeast of European Russia are given. A total of 34 water-bug species, which belong to 16 genera and 8 families, are recorded. The species diversity of Nepomorpha and Gerromorpha changes northwards: 33 occur in the taiga zone and only 8 species occur in the tundra zone. The bulk of the fauna consists of Eurosiberian (29%) and trans-Eurasian (26%) species; in latitude-related terms, the temperate group is most richly represented (64%). The species composition of the aquatic and semiaquatic heteropteran fauna of the region is especially similar to that of the tundra and taiga zones of Western Siberia.

Trichoptera — the newest insect order host of temnocephalans (Platyhelminthes, Temnocephalida) and the description of a new species of Temnocephala from Brazil

Trichoptera Kirby, 1813, is the second order of Insecta Linnaeus, 1758 (after Hemiptera Linnaeus, 1758) to be found hosting temnocephalans anywhere in the world. Temnocephalans were found on caddisfly larvae from the genus Barypenthus Burmeister, 1839 while collecting aquatic insects from a small creek in Serra do Cipó, State of Minas Gerais, Brazil. Thirty-six larvae and their cases were examined, of which 20 (55.5%) were positive for specimens of Temnocephala Blanchard, 1849. Juvenile and adult temnocephalans were always devoid of body pigmentation and were living on the dorsal and ventral body surfaces of the larvae. The eye pigmentation was deep red, disappearing in specimens fixed in ethanol. Eggs were found in larger numbers on the dorsal thoracic segments. The most distinctive characters of the temnocephalans found on caddisfly larvae were found in the cirrus and the vagina. The comparison of the general anatomy and, in particular, the morphology of the cirrus and the vagina with those of Temnocephala curvicirri Amato & Amato, 2005, described from aquatic heteropterans (Belostoma spp.), from the State of Rio Grande do Sul, which is revisited, showed that although these characters are of the same type and nature they are not equal, differing primarily in size and morphology of the cirrus and the muscularity of the middle portion of the vagina. The egg deposition sites are different and the cirrus and the vagina are characterized for the first time as being ‘complex’.

Population responses of two omnivorous fish species to impoundment of a Brazilian tropical river

Brycon gouldingi and B. falcatus were the most abundant and widespread of five species of the genus captured in a sampling study encompassing 5 years (1995–2000) in the upper Rio Tocantins, where the river was impounded by the Serra da Mesa hydroelectric dam. Given that impoundments constitute a disturbance to which species will show demographic and biological responses, we assessed such responses of these two omnivorous fishes, whose genus is regarded as vulnerable to impoundments. Both species increased greatly in numbers during the initial reservoir filling period. Brycon gouldingi had higher abundance values than B. falcatus in all sampling months, except in the pre-impoundment period. Both species showed a significant weight increment relative to body length during the time they remained in the reservoir. No reproductive individuals of B. gouldingi were recorded in the study area, but those few of Brycon falcatus were found in both wet and dry seasons, suggesting a more opportunistic strategy of reproduction. Both species were omnivorous and overlapped broadly in diet. The proportions of dietary items, however, varied in relation to fish size class and water dynamics (lotic versus lentic sites). Terrestrial arthropods composed a larger proportion of the diet of smaller-sized individuals and those from lentic sites, whereas seeds and fruits contributed more to the diet of both larger-sized individuals and those from lotic environments. Except for fish and aquatic heteropterans, which were consumed mainly in the reservoir, all other food items were allochthonous, indicating the dependence of these two species of Brycon on the terrestrial environment. The two species responded similarly to the alterations imposed by the impoundment of the upper Tocantins, although reproduction/recruitment pattern was slightly different between species. As observed in other regions of Brazil, impoundments and deforestation appear to produce negative cumulative effects on species of Brycon. These impacts call for greater efforts to conserve and manage members of this diverse and widespread genus.

Aquatic insects as umbrella species for ecosystem protection in Death Valley National Park

Under the United States Endangered Species Act (ESA), critical habitat for listed species is also protected. Many aquatic insects protected under the ESA are habitat-restricted, mainly to springs. Some of these species do not co-occur with ostensibly more charismatic vertebrates, and have the potential to act as umbrella species for aquatic ecosystems. We suggest that the flightless creeping water bug Ambrysus funebris La Rivers (Insecta: Heteroptera: Naucoridae) has the potential to be such a species. Endemic to a spring system in Death Valley National Park, it co-occurs with eight other endemic aquatic invertebrate species, but with no vertebrates. Therefore, its protection would facilitate protection of this desert oasis. Ambrysus funebris is a candidate for protection under the ESA because of its endemicity, a decline in abundance, and habitat degradation. To facilitate its use as an umbrella species, we report the first illustrated descriptions of the five nymphal instars of Ambrysus funebris La Rivers. Recommendations on its conservation and role as an umbrella species for conserving its habitat are presented. A synopsis of aquatic insect species protected or listed as candidates under the ESA indicates that spring-endemics predominate. We also present a list of potentially threatened and unprotected aquatic heteropterans in the western United States.

A comparative study of predation of three aquatic heteropteran bugs on Culex quinquefasciatus larvae

The aquatic bugs Anisops bouvieri Kirkaldy 1704 (Heteroptera: Notonectidae), Diplonychus (=Sphaerodema) rusticus Fabricius 1781, and Diplonychus annulatus Fabricius 1781 (Heteroptera: Belostomatidae) are common members of the freshwater insect communities of the East Calcutta Wetlands along the eastern fringe of Kolkata, India. These insects are established predators of dipteran larvae and other organisms. A comparative account of their predatory efficiency was made using larvae of Culex quinquefasciatus Say 1823 in the laboratory. It was revealed that a single adult of A. bouvieri could consume 28–34 fourth-instar mosquito larvae per day, D. rusticus 11–87 fourth-instar mosquito larvae per day, and D. annulatus 33–122 fourth-instar mosquito larvae per day, depending upon the prey and predator densities. The mean predation rate of A. bouvieri and D. annulatus remained stable over a 6-day feeding period but varied for D. rusticus. The predatory impact (PI) values were 14.77–17.31, 46.9–55.73, and 61.74–72.72 larvae/day for A. bouvieri, D. rusticus, and D. annulatus, respectively. Compared to these, the clearance rate (CR) value range was 9.06–13.25 for A. bouvieri, 13.64–15.99 for D. rusticus, and 13.50–16.52 larvae l/day/predator for D. annulatus. The values of mutual interference, “m,” remained 0.06–0.78 for A. bouvieri, 0.003–0.25 for D. rusticus, and 0.09–0.27 for D. annulatus, and did not vary between the days. The difference in predatory efficiency, CR, and PI values varied significantly among the three predators, indicating the possible difference in the function as predators occupying the same guild. It can be assumed that these predators play an important role in larval population regulation of mosquitoes and thereby impart an effect on species composition and interactions in the aquatic insect communities of the wetlands and other similar habitats where they occur.

The role of sexual harassment in cave and surface dwelling populations of the Atlantic molly, Poecilia mexicana (Poeciliidae, Teleostei)

Sexual coercion is a common behaviour for males trying to compensate for being inferior in male competition and/or female choice. We measured the cost of male sexual harassment for females as reduced feeding time in three populations of the Atlantic molly (Poecilia mexicana). Of these populations, one originated from a typical river habitat, another from a lightless cave chamber and the third one from a small, milky creek outside the cave. We gave hungry females an opportunity to feed in the presence of either another female or a male. We found the following: (1) male sexual harassment represents a cost in the river dwelling population and both small and large males significantly reduce female feeding time; and (2) sexual harassment was not detected in the other two populations (cave and cave entrance). In the cave molly, small males are at a disadvantage in female choice, but predation by an aquatic heteropteran selects against large male body size.

Secretory PITS in Backswimmers (Heteroptera: Notonectidae).

In studies of several families of aquatic heteropterans we have found exoskeletal pits not described in the literature. These structures are associated with the lateral margins of the pronotum and/or the dorsal surface, posterior to the scutellum in notonectids, nepids, and corixids. The function of these pits is unknown, but we presumed that they might be either sensory or secretory in nature. We undertook this study of the microscopy of pits in the notonectid, Buenoa margaritacea to learn if either of these functions is consistent with the fine structure.For TEM, adult insects were submerged in 1.0% paraformaldeyde and 2.0% glutaraldehyde in 0.02M sodium cacodylate buffer with 0.01% calcium chloride at a pH of 7.2, then dissected with a razor blade cleaned with acetone. Tissues were fixed overnight at 4°C in paraformaldehyde and glutaraldehyde, then fixed in 1% osmium tetroxide in cacodylate buffer, dehydrated in a graded series of acetone, embedded in Spurr resin and polymerized at 70°C for 21 hours. Blocks were thin sectioned with a diamond knife, and sections were stained with uranyl acetate and lead citrate. Whole specimens for SEM were similarly fixed, dehydrated in an ethanol series and critical point dried. SEM micrographs of internal pit anatomy were produced by adhering 500nm sections to a glass coverslip, then removing the embedding resin by incubation for 5 minutes in a saturated solution of potassium hydroxide in absolute ethanol, followed by three 20 minute rinses in absolute ethanol and air drying. Cover slips were attached to an aluminum specimen stub and sputter coated for 60 seconds with gold/palladium as were whole insects .

The community of Odonata and aquatic Heteroptera (Gerromorpha and Nepomorpha) in a rehabilitated wetland: the Laguna de la Nava (Palencia, Spain)

Dragonfly larvae and aquatic heteropteran nymphs and adults of the Laguna de La Nava de Fuentes (Palencia, Spain), a wetland rehabilitated with the intention of recovering a portion of the former Laguna de La Nava, were sampled monthly in a one year period from July 1991 to June 1992. An ecological and phenological study of the 26 identified species (9 Odonata and 17 Heteroptera) and of the whole community has been made. This is followed by a discussion of the degree of maturity reached by the wetland, based on the monitoring values of the autoecology of the collected species.

Role of Belostoma bakeri (Heteroptera) in the trophic ecology of a fishless desert spring

We examined the foraging and production ecology of a top predator (Belostoma bakeri, Belostomatidae) in the fishless, thermally constant aquatic ecosystem of Montezuma Well, Arizona. Our results highlight the importance of prey behavior in energy flow in aquatic ecosystems. B. bakeri captured more amphipods (Hyalella montezuma) than damselfly nymphs (Telebasis salva) in laboratory experiments; H. montezuma spent significantly more time moving than damselfly nymphs did. Also, B. bakeri captured significantly more adult (≥ 3 mm) amphipods than juveniles (<3 mm) in the light but not in dark treatments. Production by B. bakeri was 2.8 g dw m−2 yr−1 (±2 SE = 0.3). Mean annual standing stock was 0.214 g m−2, annual P:B̄ ratio was 13.3, cohort P:B̄ was 4.7, and annual energy production was 5.88 × 104 J m−2 yr−1. Ecological efficiency was 13.2% between primary producers and amphipods in Montezuma Well, 5.1% between amphipods and damselfly nymphs, and 2.7% between lower levels and aquatic heteropterans. Production by B. bakeri made up 25% of the total energy incorporated in secondary consumer production and accounted for 72% of the production by the top predators in Montezuma Well.

Handling time and multi-prey capture by a water bug

Some aquatic heteropterans that spend a relatively long time handling a prey item, such as the belostomatid Diplonychus indicus Venk. & Rao, can handle prey in such a way that they can capture another item without having to abandon their previous catch. Diplonychus indicus can handle up to three prey items simultaneously. Handling times and inter-catch intervals varied with the number of prey items in the queue. No significant differences between handling times for the first item in a queue were found whatever the length of the queue, but handling times were significantly longer for the first items in a queue than for the following items. Inter-catch intervals were significantly longer when prey were treated one by one than when there were more items in the queue. These data do not support Juliano's (1989, Anim. Behav. 38, 757–770) queueing model.

Feeding by the aquatic heteropteran, Diplonychus rusticum (Belostomatidae): an effect of prey density on meal size

The behaviour of Diplonychus rusticum feeding on chironomid larvae has been investigated under laboratory conditions. Changes in the percentage of material extracted from prey indicated that feeding for the first two minutes enabled the predator to obtain approximately 33% of the available food; feeding for 10 minutes resulted in only 60% extraction. Comparing the percentage of each prey consumed by D. rusticum exposed to various prey densities, it was apparent that predators were more ‘wasteful’ and ate less of each prey as chironomid density increased. Because the rate of food intake declined as a greater proportion of each prey was extracted, predators exposed to high chironomid densities reduced the amount of each prey consumed thereby conforming to a simple optimal feeding model.