A synopsis of the genus Cylindrostethus Fieber 1861 (Insecta: Hemiptera: Gerridae).

Cylindrostethus Fieber, 1861 is one of the most striking genera of water striders (Insecta: Hemiptera: Gerridae) and has Pantropical distribution. Members of this group can be recognized by the very long, cylindrical body; the short antennomere IV; the short labium not reaching the mesosternum; and by characteristics of the abdomen of males and females. Although Neotropical representatives of the genus have been revised, there are pending taxonomic issues related to this fauna, and that of the Eastern Hemisphere has been barely studied in recent years. Here, we present a short note about the authorship of Cylindrostethus, an updated key to all species of the genus, a new synonymy, and the description of a previously unknown macropterous male of C. hungerfordi Drake and Harris.

Inkjet-Assisted Electroformation of Magnetically Guidable Water Striders for Interfacial Microfluidic Manipulation.

Gerridae, colloquially called water striders, are a peculiar class of insects characterized by the extraordinary ability to walk on the surface of water bodies. Owing to this capacity, they constitute an ideal source of inspiration for designing untethered microdevices capable of navigating the interface between two fluids. Such steerable micrometric objects can be of great interest for various applications, ranging from the handling of floating objects to the remote control of microreactions and the manipulation of self-assembled monolayers. This paper describes the realization of artificial water striders via an inkjet-assisted electroforming approach. Inkjet deposition patterns the negative mask, which is subsequently filled with different layers of metals through electroforming. One of such layers is the magnetic alloy NiFe, which allows wireless propulsion of the striders by means of externally applied magnetic fields. The magnetic actuation tests prove good maneuverability at the water-air and silicone oil-air interfaces, with superior control over the speed and position of the devices. The surface of the devices is modified to tune its superficial energy in order to maximize buoyancy on these different combinations of fluids. A magnetic field-controlled strider manipulates a droplet and demonstrates collecting oil microdroplets and synthesizing platinum nanoparticles by chemical microreactions. Finally, the remotely operated microrobot could be employed in laboratories as a real avatar of chemists.

New Species, New Records, and Updated Key to the Paravelia (Hemiptera: Heteroptera: Veliidae) from Brazil.

The broad-shouldered water-strider genus Paravelia Breddin, 1898 (Hemiptera: Heteroptera: Veliidae: Veliinae) is currently represented in Brazil by 38 species. Although the diversity of the genus in the country is relatively well known, eight states remain with no records of any species: Acre, Alagoas, Ceará (CE), Paraíba, Paraná, Pernambuco (PE), Piauí (PI), and Tocantins. Aiming to fill these gaps, several expeditions were carried out at conservation areas of the Caatinga biome between 2018 and 2021: Aiuaba Ecological Station (CE), Catimbau National Park (PE), and Serra das Confusões National Park (PI). Paravelia luisi sp. nov., a new species from PE, is described and illustrated. In addition, new records of P. bilobata Rodrigues, Moreira, Nieser, Chen & Melo, 2014, P. digitata Rodrigues & Moreira, 2016, and P. nieseri Moreira & Barbosa, 2012, and an updated key to the Brazilian species of Paravelia are provided. This study increases the number of species of Paravelia known in Brazil to 39 and provides the first records of the genus from three states: PE, with two species, and CE and PI, with one species each.

Environmental and Seasonal Effects on Gerridae Assemblages (Heteroptera: Gerromorpha) from a Stream in Brazilian Savannah.

Our aim here was to assess the seasonal (dry, ebb, and rainy seasons), spatial (upstream, intermediate, and downstream), and environmental effects on the dynamics of Gerridae assemblages (Heteroptera: Gerromorpha) in a Cerrado stream, in central-western Brazil. We sampled the insects on the water line between May 2011 and April 2014 with an 18 cm diameter sieve. We used the scanning method in 100 m of stream in each sampled locality. We sampled 3690 individuals of 19 species. There was a seasonal difference in abundance, which was a result of a lower abundance in the rainy season, but this did not differ between different environments. The estimated species richness was lower upstream and in the rainy season. Species composition was different between the upstream and downstream portions. It was also different among all seasons, with the greatest difference occurring between the rainy and dry seasons. The abiotic factors were responsible for structuring the assemblages in different seasons. The observed differences among seasons in abundance, richness, and species composition have implications for conservation since changes in the structure of the vegetation in the stream edges change the hydrological cycle of streams, and consequently the diversity of the Gerridae assemblages. There was variation in richness and composition between such small distances (upstream and downstream). This shows how sensitive this system can be, and how important elements of the stream's trophic, with the Gerromorpha, can be easily altered.

Leg length and bristle density, both necessary for water surface locomotion, are genetically correlated in water striders.

Access to hitherto unexploited ecological opportunities is associated with phenotypic evolution and often results in significant lineage diversification. Yet our understanding of the mechanisms underlying such adaptive traits remains limited. Water striders have been able to exploit the water-air interface, primarily facilitated by changes in the density of hydrophobic bristles and a significant increase in leg length. These two traits are functionally correlated and are both necessary for generating efficient locomotion on the water surface. Whether bristle density and leg length have any cellular or developmental genetic mechanisms in common is unknown. Here, we combine comparative genomics and transcriptomics with functional RNA interference assays to examine the developmental genetic and cellular mechanisms underlying the patterning of the bristles and the legs in Gerris buenoi and Mesovelia mulsanti, two species of water striders. We found that two duplication events in the genes beadex and taxi led to a functional expansion of the paralogs, which affected bristle density and leg length. We also identified genes for which no function in bristle development has been previously described in other insects. Interestingly, most of these genes play a dual role in regulating bristle development and leg length. In addition, these genes play a role in regulating cell division. This result suggests that cell division may be a common mechanism through which these genes can simultaneously regulate leg length and bristle density. We propose that pleiotropy, through which gene function affects the development of multiple traits, may play a prominent role in facilitating access to unexploited ecological opportunities and species diversification.

New species and new records of semiaquatic bugs (Arthropoda, Insecta, Hemiptera, Heteroptera, Gerromorpha) from French Guiana.

Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are predatory insects that occupy a wide range of freshwater and marine habitats, with some secondary transitions to terrestrial life. They currently represent more than 2100 species distributed through all continents, except for Antarctica, and are especially rich in the Neotropical and Oriental regions. Although the fauna from the former region is relatively well known, some areas remain almost unexplored. Such is the case of French Guiana, where only a few species have been previously recorded, several of which based on collections made in the 19th and early 20th centuries. As a result of material recently collected in the territory, the descriptions of Rhagoveliadepressa Rodrigues, Khila & Moreira, sp. nov., R.tantilloides Rodrigues, Khila & Moreira, sp. nov. and Steinoveliavittata Rodrigues, Khila & Moreira, sp. nov. (Veliidae) are presented here. New records for 28 species are also provided, of which Cylindrostethushungerfordi Drake & Harris, 1934, Neogerrismagnus (Kuitert, 1942), Rheumatobatesmangrovensis (China, 1943), R.trinitatis (China, 1943), Ovatametraobesa Kenaga, 1942, Telmatometrafusca Kenaga, 1941, T.parva Kenaga, 1941 (Gerridae), Mesoveliaamoena Uhler, 1894 (Mesoveliidae), Rhagoveliabrunae Magalhães & Moreira, 2016, R.elegans Uhler, 1894, R.ephydros (Drake & Van Doesburg, 1966), R.equatoria D. Polhemus, 1997, R.evidis Bacon, 1948, R.guianana D. Polhemus, 1997, R.tenuipes Champion, 1898, Oioveliacunucunumana (Drake & Maldonado-Capriles, 1952), Striduliveliaalia (Drake, 1957), S.stridulata (Hungerford, 1929), and S.tersa (Drake & Harris, 1941) (Veliidae) are reported from French Guiana for the first time.

A New Species of Small Water Strider in the Genus Microvelia (Hemiptera: Heteroptera: Veliidae) from Aichi Prefecture, Honshu, Japan.

A new species of small water strider (Hemiptera: Heteroptera: Veliidae), Microvelia pilosa sp. nov., is described from Aichi Prefecture, Honshu, Japan. It belongs to the subgenus Picaultia Distant, 1913 within the genus Microvelia Westwood, 1834, and is similar to Microvelia japonica Esaki and Miyamoto, 1955 and Microvelia douglasi douglasi Scott, 1874. The new species can be distinguished from these two taxa by its blackish-brown body, small punctures on the pronotum, and arcuate right paramere that is slender only in the distal part. Our molecular phylogenetic analysis using the mitochondrial COI gene revealed that M. pilosa sp. nov. is genetically separated from some of the other Japanese Microvelia and is most closely related to M. japonica.

Dispersal and Migration Patterns of Freshwater Semiaquatic Bugs.

Semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha) are mostly wing-polymorphic species with flight dispersal as an important life history trait, but the specific flight ability and dispersal pattern remain unexplored in most species. This report presents the results of a long-term survey based on the individual marking of more than 23,000 specimens of eight water striders (Gerridae) and a water cricket Velia caprai (Veliidae). Three distinct lentic habitats were sampled (solitary fishponds, systems of nearby fishponds and systems of small, often temporary pools) and one lotic habitat-a small forest stream. Recaptures revealed that three gerrid species tend to stay at the breeding site, but can differ in dispersal via the water surface. Reproductive flightless females disperse most actively via the water surface, possibly bypassing the trade-off between dispersal and reproduction. One species has a sex-dependent dispersal pattern, with females being rather philopatric, whereas males often disperse. Three other gerrid species are highly dispersive and tend to change breeding site. V. caprai, the only lotic species included in this survey, tend to move upstream and possibly compensate for the downstream drift.

Efecto de las aguas jabonosas sobre el comportamiento de hemípteros semiacuáticos (Gerromorpha) de dos ecosistemas acuáticos neotropicales / Effect of soapy water on the behavior of semiaquatic hemipterans (Gerromorpha) from two neotropical aquatic ecosystems

Resumen Introducción: Los hemípteros semiacuáticos son insectos que podrían ser de los mejores indicadores de la calidad del ambiente acuático, específicamente en cuanto al contenido de sustancias que rompen la tensión superficial. Sin embargo, no existen estudios que evalúen cómo estos insectos se ven afectados por cambios en la tensión superficial del agua. Objetivo: Determinar el efecto que tienen las aguas jabonosas sobre la capacidad de locomoción de tres especies de hemípteros semiacuáticos neotropicales. Métodos: Desde agosto hasta noviembre 2020, realizamos experimentos ex situ, con nueve grupos de diez individuos de la familia Veliidae (N = 90) y Gerridae (N = 90), en donde cada grupo individualmente, fue sometido a la entrada de aguas jabonosas durante tres minutos. Para esto, diseñamos un acuario que consistía en tres cajas de plástico a diferentes alturas, conectadas entre sí, de modo que se generaba un flujo de corriente. Utilizamos jabón en polvo para ropa, jabón líquido para manos, y jabón en barra para platos. De cada tipo de jabón preparamos una concentración baja (9 ppm), media (50 ppm) y alta (200 ppm). Mediante grabaciones, registramos el tiempo que duraron los hemípteros en el agua, así como su capacidad para salir de la misma, y si se hundían o no. Resultados: Encontramos que, sin importar el tipo de jabón, el tiempo que permanecen los hemípteros en el agua contaminada, se reduce drásticamente conforme aumenta la concentración, pero dicho impacto varía según la especie, siendo Rhagovelia solida (familia Veliidae) menos afectada por la contaminación en comparación con Platygerris caeruleus y Potamobates unidentatus (familia Gerridae). Conclusión: El uso de estos táxones como indicadores del grado de contaminación de los ríos por detergentes y jabones, puede ser muy útil, sobre todo si se toma en cuenta las diferencias de sensibilidad según la familia o género del grupo.

Abstract Introduction: Semiaquatic hemipterans are insects that may be among the best indicators of the quality of the aquatic environment, specifically in terms of the content of substances that break surface tension. However, no studies are evaluating how these insects are affected by changes in the surface tension of the water. Objective: To determine the effect of soapy water on the locomotion ability of three species of neotropical semiaquatic hemipterans. Methods: From August to November 2020, we conducted ex situ experiments, with nine groups of ten individuals of the family Veliidae (N = 90) and Gerridae (N = 90), where each group individually, was subjected to the entry of soapy water for three minutes. For this, we designed an aquarium consisting of three plastic boxes at different heights, connected to each other, so that a current flow was generated. We used powdered laundry soap, liquid hand soap, and bar soap for dishes. For each type of soap we prepared a low (9 ppm), medium (50 ppm) and high (200 ppm) concentration. By means of recordings, we recorded the time the hemipterans spent in the water, as well as their ability to get out of the water, and whether or not they sank. Results: We found that, regardless of the type of soap, the time spent by hemipterans in contaminated water decreases drastically as the concentration increases, but the impact varies by species, with Rhagovelia solida (family Veliidae) being less affected by pollution compared to Platygerris caeruleus and Potamobates unidentatus (family Gerridae). Conclusions: The use of these taxa as indicators of the degree of contamination of rivers by detergents and soaps can be very useful, especially if we take into account the differences in sensitivity according to the family or gender of the group.

A new species of emMicrovelia/em Westwood, 1834 (Hemiptera: Heteroptera: Veliidae) from southeastern Brazil.

Microvelia joceliae Magalhães Moreira, sp. nov. is described and illustrated based on material from Parque Natural Municipal das Andorinhas, Minas Gerais State, in southeastern Brazil. The new species can be distinguished from congeners occurring in the region by the pronotum of the apterous form covering almost the entire thorax dorsally, proepisternum with black denticles, male abdominal segments V-VII ventrally depressed, shape of the asymmetrical parameres, and female abdominal laterotergites reflected over the mediotergites and almost touching over segments V-VII.

The Microbiome of Neotropical Water Striders and Its Potential Role in Codiversification.

Insects host a highly diverse microbiome, which plays a crucial role in insect life. However, the composition and diversity of microbiomes associated with Neotropical freshwater insects is virtually unknown. In addition, the extent to which diversification of this microbiome is associated with host phylogenetic divergence remains to be determined. Here, we present the first comprehensive analysis of bacterial communities associated with six closely related species of Neotropical water striders in Panama. We used comparative phylogenetic analyses to assess associations between dominant bacterial linages and phylogenetic divergence among species of water striders. We found a total of 806 16S rRNA amplicon sequence variants (ASVs), with dominant bacterial taxa belonging to the phyla Proteobacteria (76.87%) and Tenericutes (19.51%). Members of the α- (e.g., Wolbachia) and γ- (e.g., Acinetobacter, Serratia) Proteobacteria, and Mollicutes (e.g., Spiroplasma) were predominantly shared across species, suggesting the presence of a core microbiome in water striders. However, some bacterial lineages (e.g., Fructobacillus, Fluviicola and Chryseobacterium) were uniquely associated with different water strider species, likely representing a distinctive feature of each species' microbiome. These findings indicate that both host identity and environmental context are important drivers of microbiome diversity in water striders. In addition, they suggest that diversification of the microbiome is associated with diversification in water striders. Although more research is needed to establish the evolutionary consequences of host-microbiome interaction in water striders, our findings support recent work highlighting the role of bacterial community host-microbiome codiversification.

Revision of the American genus Steinovelia Polhemus amp; Polhemus, 1993 (Heteroptera: Gerromorpha: Veliidae).

The genus Steinovelia Polhemus Polhemus, 1993 is distributed from southeastern Canada to northeastern Argentina and has been considered to contain five valid species: S. permista (Drake, 1951a), S. placida (Drake, 1951a), S. stagnalis (Burmeister, 1835), S. vinnula (Drake, 1951b) and S. virgata (White, 1879a). We present here a revision of the genus with redescriptions of S. permista, S. stagnalis, S. vinnula, and S. virgata, the synonymy of S. placida with S. virgata, a key, distribution maps, and photographs of all species.

Veliidae (Insecta: Heteroptera: Gerromorpha) from Colombia: Description of a new species and of the male of Euvelia meta Molano, Moreira & Morales, 2016

Abstract Stridulivelia (Aenictovelia) chocoana sp. nov. (Heteroptera: Veliidae: Veliinae) is described based on specimens from the Colombian department of Chocó. The new species is diagnosed by pronotal humeral angles, body length, male hind trochanter and paramere shape. Furthermore, we describe and illustrate the previously unknown male of Euvelia meta Molano, Moreira & Morales, 2016 (Heteroptera: Veliidae: Microveliinae) and its range is extended to Amazonas and Vichada departments.

Cooption of the pteridine biosynthesis pathway underlies the diversification of embryonic colors in water striders.

Naturalists have been fascinated for centuries by animal colors and color patterns. While widely studied at the adult stage, we know little about color patterns in the embryo. Here, we study a trait consisting of coloration that is specific to the embryo and absent from postembryonic stages in water striders (Gerromorpha). By combining developmental genetics with chemical and phylogenetic analyses across a broad sample of species, we uncovered the mechanisms underlying the emergence and diversification of embryonic colors in this group of insects. We show that the pteridine biosynthesis pathway, which ancestrally produces red pigment in the eyes, has been recruited during embryogenesis in various extraocular tissues including antennae and legs. In addition, we discovered that this cooption is common to all water striders and initially resulted in the production of yellow extraocular color. Subsequently, 6 lineages evolved bright red color and 2 lineages lost the color independently. Despite the high diversity in colors and color patterns, we show that the underlying biosynthesis pathway remained stable throughout the 200 million years of Gerromorpha evolutionary time. Finally, we identified erythropterin and xanthopterin as the pigments responsible for these colors in the embryo of various species. These findings demonstrate how traits can emerge through the activation of a biosynthesis pathway in new developmental contexts.

The genome of the water strider Gerris buenoi reveals expansions of gene repertoires associated with adaptations to life on the water.

BACKGROUND: Having conquered water surfaces worldwide, the semi-aquatic bugs occupy ponds, streams, lakes, mangroves, and even open oceans. The diversity of this group has inspired a range of scientific studies from ecology and evolution to developmental genetics and hydrodynamics of fluid locomotion. However, the lack of a representative water strider genome hinders our ability to more thoroughly investigate the molecular mechanisms underlying the processes of adaptation and diversification within this group. RESULTS: Here we report the sequencing and manual annotation of the Gerris buenoi (G. buenoi) genome; the first water strider genome to be sequenced thus far. The size of the G. buenoi genome is approximately 1,000 Mb, and this sequencing effort has recovered 20,949 predicted protein-coding genes. Manual annotation uncovered a number of local (tandem and proximal) gene duplications and expansions of gene families known for their importance in a variety of processes associated with morphological and physiological adaptations to a water surface lifestyle. These expansions may affect key processes associated with growth, vision, desiccation resistance, detoxification, olfaction and epigenetic regulation. Strikingly, the G. buenoi genome contains three insulin receptors, suggesting key changes in the rewiring and function of the insulin pathway. Other genomic changes affecting with opsin genes may be associated with wavelength sensitivity shifts in opsins, which is likely to be key in facilitating specific adaptations in vision for diverse water habitats. CONCLUSIONS: Our findings suggest that local gene duplications might have played an important role during the evolution of water striders. Along with these findings, the sequencing of the G. buenoi genome now provides us the opportunity to pursue exciting research opportunities to further understand the genomic underpinnings of traits associated with the extreme body plan and life history of water striders.

The achaete-scute complex contains a single gene that controls bristle development in the semi-aquatic bugs.

The semi-aquatic bugs (Heteroptera, Gerromorpha) conquered water surfaces worldwide and diversified to occupy puddles, ponds, streams, lakes, mangroves and even oceans. Critical to this lifestyle is the evolution of sets of hairs that allow these insects to maintain their body weight on the water surface and protect the animals against wetting and drowning. In addition, the legs of these insects are equipped with various grooming combs that are important for cleaning and tidying the hair layers for optimal functional efficiency. Here we show that the hairs covering the legs of water striders represent innervated bristles. Genomic and transcriptomic analyses revealed that in water striders the achaete-scute complex, known to control bristle development in flies, contains only the achaete-scute homologue (ASH) gene owing to the loss of the gene asense. Using RNA interference, we show that ASH plays a pivotal role in the development of both bristles and grooming combs in water striders. Our data suggest that the ASH locus may have contributed to the adaptation to water surface lifestyle through shaping the hydrophobic bristles that prevent water striders from wetting and allow them to exploit water surface tension.

Water striders (Heteroptera: Gerromorpha: Gerridae) of Romania with an update on the distribution of Gerris gibbifer and G. maculatus in southeastern Europe.

The Romanian fauna comprises two species of Aquarius Schellenberg, 1800, eight species of Gerris Fabricius, 1794 and one species of Limnoporus Stål, 1868, and we hereby update the distribution and provide insights on the phenology and ecology of all eleven species in this country. We furthermore update the distribution of the two closely related species Gerris gibbifer Schummel, 1832 and G. maculatus Tamanini, 1946 in southeastern Europe. Gerris maculatus is recorded for the first time from Hungary, Montenegro and Slovenia, and the first detailed localities from Romania and Serbia are given. All bibliographic records of G. gibbifer from Romania, Macedonia and Serbia are based on misidentification and this species is thus excluded from the faunal lists of these countries. Both G. gibbifer and G. maculatus occur in Croatia, Hungary, Ukraine, and probably Slovenia.

A new species of Metrobates Uhler, 1871 (Hemiptera: Heteroptera: Gerridae) from Colombia.

A new species of Metrobates Uhler, 1871 (Trepobatinae: Metrobatini) from Colombia is described. Metrobates sanciprianensis sp. nov. resembles M. fugientis Drake Harris but is distinguished by the shape of the parameres and the lack of a spine on the fore femur. In addition, M. amblydonti Nieser is redescribed and a key to males of the species of Metrobates in Colombia is presented.

The role of ecology, neutral processes and antagonistic coevolution in an apparent sexual arms race.

Some of the strongest examples of a sexual 'arms race' come from observations of correlated evolution in sexually antagonistic traits among populations. However, it remains unclear whether these cases truly represent sexually antagonistic coevolution; alternatively, ecological or neutral processes might also drive correlated evolution. To investigate these alternatives, we evaluated the contributions of intersex genetic correlations, ecological context, neutral genetic divergence and sexual coevolution in the correlated evolution of antagonistic traits among populations of Gerris incognitus water striders. We could not detect intersex genetic correlations for these sexually antagonistic traits. Ecological variation was related to population variation in the key female antagonistic trait (spine length, a defence against males), as well as body size. Nevertheless, population covariation between sexually antagonistic traits remained substantial and significant even after accounting for all of these processes. Our results therefore provide strong evidence for a contemporary sexual arms race.