Transcriptome-based phylogeny of the semi-aquatic bugs (Hemiptera: Heteroptera: Gerromorpha) reveals patterns of lineage expansion in a series of new adaptive zones

Key innovations enable access to new adaptive zones and are often linked to increased species diversification. As such, they have attracted much attention, yet their concrete consequences on the subsequent evolutionary trajectory and diversification of the bearing lineages remain unclear. The monophyletic group of water striders and relatives (Hemiptera: Heteroptera: Gerromorpha) represent a group of insects that transited to live on the water-air interface and diversified to occupy ponds, puddles, streams, mangroves and even oceans. This lineage offers an excellent model to study the patterns and processes underlying species diversification following the conquest of new adaptive zones. However, such studies require a reliable and comprehensive phylogeny of the infraorder. Based on whole transcriptomic datasets of 97 species and fossil records, we reconstructed a new phylogeny of the Gerromorpha that resolved inconsistencies and uncovered strong support for previously unknown relationships between some important taxa. We then used this phylogeny to reconstruct the ancestral state of a set of adaptations associated with water surface invasion (fluid locomotion, dispersal and transition to saline waters) and sexual dimorphism. Our results uncovered important patterns and dynamics of phenotypic evolution revealing how the initial event of water surface invasion enabled multiple subsequent transitions to new adaptive zones, representing distinct niches of water surfaces, and further diversification of the group. This phylogeny and the associated transcriptomic datasets constitute highly valuable resources, making Gerromorpha an attractive model lineage to study phenotypic evolution.

Hosts and transmission of Mycobacterium ulcerans: a systematic review

The control of Buruli ulcer (BU), a debilitating neglected tropical disease, is hampered by the inadequate understanding of the mode of transmission of its causative agent, Mycobacterium ulcerans (M. ulcerans). The DNA of M. ulcerans has been detected in some living organisms and non-living environmental samples of both aquatic and terrestrial sources. However, it is unclear whether the identified organisms support in vivo multiplication of the bacterium or play any role in its transmission. This paper identifies hosts of M. ulcerans, reviews progress made in unravelling the exact mode of transmission of M. ulcerans and identifies research gaps in this aspect of BU epidemiology. Using the search terms, ‘niche, Mycobacterium ulcerans’ and ‘mode of transmission, Mycobacterium ulcerans’ as well as defined inclusion criteria, information was obtained from the PubMed database and reviewed to assess their importance to the research question. Aquatic bugs of the genera Appasus and Diplonychus as well as Naucoris cimicoides and possums were identified to support in vivo multiplication of the bacterium. Bite of M. ulcerans contaminated Aedes notoscriptus, bite of aquatic bugs harboring or contaminated with M. ulcerans, and M. ulcerans contaminated skin-puncturing materials present in nature create opportunity for its transmission and infection. Appropriate protective measures may be useful to reduce the risk of exposure to M. ulcerans in BU endemic areas, and incorporation of trophic interactions of aquatic organisms known to support in vivo multiplication of M. ulcerans is needed in future research for better understanding of the spread of M. ulcerans in nature. French title: Hôtes et transmission de Mycobacterium ulcerans: une revue systématique Le contrôle de l'ulcère de Buruli (UB), une maladie tropicale négligée débilitante, est entravé par la compréhension insuffisante du mode de transmission de son agent causal, Mycobacterium ulcerans (M. ulcerans). L'ADN de M. ulcerans a été détecté dans certains organismes vivants et des échantillons environnementaux non vivants de sources aquatiques et terrestres. Cependant, il n'est pas clair si les organismes identifiés favorisent la multiplication in vivo de la bactérie ou jouent un rôle dans sa transmission. Cet article identifie les hôtes de M. ulcerans, passe en revue les progrès réalisés pour démêler le mode exact de transmission de M. ulcerans et identifie les lacunes de la recherche dans cet aspect de l'épidémiologie de l'UB. À l'aide des termes de recherche « niche, Mycobacterium ulcerans » et « mode de transmission, Mycobacterium ulcerans » ainsi que des critères d'inclusion définis, des informations ont été obtenues à partir de la base de données PubMed et examinées pour évaluer leur importance pour la question de recherche. Des punaises aquatiques des genres Appasus et Diplonychus ainsi que Naucoris cimicoides et possums ont été identifiées pour soutenir la multiplication in vivo de la bactérie. La piqûre d'Aedes notoscriptus contaminé par M. ulcerans, la piqûre d'insectes aquatiques hébergeant ou contaminés par M. ulcerans et les matériaux de perforation de la peau contaminés par M. ulcerans présents dans la nature créent une opportunité de transmission et d'infection. Des mesures de protection appropriées peuvent être utiles pour réduire le risque d'exposition à M. ulcerans dans les zones d'endémie UB, et l'incorporation d'interactions trophiques d'organismes aquatiques connus pour favoriser la multiplication in vivo de M. ulcerans est nécessaire dans les recherches futures pour une meilleure compréhension de la propagation de M. ulcerans dans la nature.

Gerromorpha (Hemiptera: Heteroptera) from the Metropolitan Region of Santarém, Brazil, including three new species of Microvelia Westwood, 1834 (Veliidae: Microveliinae)

Gerromorpha (Hemiptera: Heteroptera) comprises more than 2100 species of semiaquatic bugs, most of which have the ability to walk on the surface of the water. So far, 238 species have been recorded from Brazil, but several portions of the country remain poorly explored. The Metropolitan Region of Santarém (MRS), Pará State, Brazil, lacks faunistic and taxonomic studies concerning this group and the local fauna is under threat due to human actions. Aiming to fill gaps concerning the diversity and distribution of Gerromorpha in the Amazon, a survey of the semi-aquatic bugs from the MRS is presented. Collections were made in 33 aquatic ecosystems in the different phytophysiognomies within this area from July 2019 to October 2020. As a result, a checklist with 44 species recorded from the three municipalities of the MRS is presented. Furthermore, three new species of the genus Microvelia Westwood, 1834 (M. belterrensis sp. nov., M. hamadae sp. nov. and M. sousorum sp. nov.) are described, two species are recorded for the first time from Brazil (Microvelia aschnakiranae Makhan, 2014 and Rhagovelia graziae Galindo-Malagón, Morales & Moreira, 2021), two from Pará State (Microvelia longipes Uhler, 1894 and Paravelia dilatata Polhemus & Polhemus, 1984) and 15 from the MRS (Brachymetra lata Shaw, 1933, B. shawi Hungerford & Matsuda, 1957, Tachygerris adamsoni (Drake, 1942), Microvelia pulchella Westwood, 1834, Rhagovelia brunae Magalhães & Moreira, 2016, R. evidis Bacon, 1948, R. jubata Bacon, 1948, Callivelia conata (Hungerford, 1929), Oiovelia cunucunumana Drake & Maldonado-Capriles, 1952, Paravelia bullialata Polhemus & Polhemus, 1984, Stridulivelia alia (Drake, 1957), S. stridulata (Hungerford, 1929), S. strigosa (Hungerford, 1929), S. tersa (Drake & Harris, 1941) and S. transversa (Hungerford, 1929)).

A review of Cryphocricos Signoret, 1850 (Naucoridae: Cryphocricinae) with descriptions of three new species

The genus Cryphocricos Signoret, 1850 was recently determined in a molecular phylogeny to be distantly related to other taxa of the subfamily Cryphocricinae to the extent that it is now once again the sole member of the subfamily. This exclusively New World group of aquatic bugs lives in fast and usually turbulent current and respires by means of a plastron. Efforts to identify morphological features to distinguish among the species have largely fallen short, and some species have been established based on features that exhibit a high degree of intraspecific variation overlapping those of other species. Presented here is a review of the 13 described species with discussions of their features and photos of type specimens, and three new species from Venezuela and Colombia are described. Also presented is a diagnostic attribute unique to the enigmatic Cryphocricos barozzii Signoret, 1850.

Water bugs (Hemipera: Heteroptera: Nepomorpha & Gerromorpha) of Chile: phylogenetic and biogeographic considerations, and a catalog of the fauna

The Chilean fauna of water bugs comprises seven species of semi-aquatic bugs (Heteroptera: Gerromorpha), representing five genera, three tribes, four subfamilies and four families; and 27 species and one subspecies of aquatic bugs (Heteroptera: Nepomorpha), representing four subgenera, eight genera, three tribes, seven subfamilies, and five families. We compare the fauna with neighboring countries and find that several otherwise widespread and abundant taxa are missing in Chile, but that Chepuvelia usingeri China, 1963 (Macroveliidae), Microvelia chilena Drake & Hussey, 1955 (Veliidae), Limnocoris dubiosus Montandon, 1898 (Naucoridae), Nerthra (Nerthra) parvula (Signoret, 1863), N. (N.) undosa Nieser & Chen, 1992, N. (Rhinodermacoris) praecipua Todd, 1957 (Gelastocoridae), and Sigara (Tropocorixa) termasensis (Hungerford, 1928a) (Corixidae) are endemic to the country. To this list, we add †Nerthra (Nerthra) subantarctica Faúndez & Ashworth, 2015, even though the species is only known from a subfossil. We can also inform that while water bugs are found in the archipelagoes of southern Chile, no species has been reported from the Juan Fernandez Islands, Easter Island and other off-shore islands. Several of the Chilean species are without any close extant relatives, such as C. usingeri and Aquarius chilensis (Berg, 1881) (Gerridae), or with relatives in Oceania (N. praecipua), suggesting that historical events such as dispersal and extinction have had a major influence on the composition of the Chilean fauna.

Contributions to the knowledge of water bugs in Mindoro Island, Philippines, with a species checklist of Nepomorpha and Gerromorpha (Insecta, Hemiptera, Heteroptera)

This survey aims to provide an updated species checklist of aquatic and semi-aquatic bugs in the intra-Philippine biogeographic Region of Mindoro. An assessment survey of water bugs (Hemiptera, Heteroptera) was conducted mostly by manual collection in selected areas of Oriental Mindoro from 2017 to 2018, in which some of the collecting activities were undertaken by graduate students of Ateneo de Manila University. Twenty-nine aquatic and semi-aquatic heteropteran species were documented and some are known island-endemic species or subspecies, including Enithares martini mindoroensis Nieser & Zettel, 1999, Hydrotrephes stereoides mindoroensis Zettel, 2003, Aphelocheirus freitagi Zettel & Pangantihon, 2010, Rhagovelia mindoroensis Zettel, 1994, Rhagovelia raddai Zettel, 1994, Rhagovelia potamophila Zettel, 1996 and Strongylovelia mindoroensis Lansbury & Zettel, 1997, which were found in new areas in the Region. In addition, there are also new records for the Island that have already been documented in other parts of the Philippines, such as the Philippine-endemic Ochterus magnus Gapud & San Valentin, 1977 and Hebrus philippinus Zettel, 2006 and the widely-distributed backswimmers Anisops nigrolineatus Lundblad, 1933 and Anisops rhomboides Nieser & Chen, 1999. Several undescribed specimens and potentially new species are also discussed in this paper. Further surveys in the other parts of Mindoro and in the other regions of the Philippines, are encouraged to produce a comprehensive baseline data of heteropteran species richness in the country.

Aquatic Hemiptera in Southwest Cameroon: Biodiversity of Potential Reservoirs of Mycobacterium ulcerans and Multiple Wolbachia Sequence Types Revealed by Metagenomics

Buruli ulcer (BU), caused by Mycobacterium ulcerans, is a neglected tropical disease associated with freshwater habitats. A variety of limnic organisms harbor this pathogen, including aquatic bugs (Hemiptera: Heteroptera), which have been hypothesized to be epidemiologically important reservoirs. Aquatic Hemiptera exhibit high levels of diversity in the tropics, but species identification remains challenging. In this study, we collected aquatic bugs from emerging foci of BU in the Southwest Region of Cameroon, which were identified using morphological and molecular methods. The bugs were screened for mycobacterial DNA and a selection of 20 mycobacteria-positive specimens from the families Gerridae and Veliidae were subjected to next-generation sequencing. Only one individual revealed putative M. ulcerans DNA, but all specimens contained sequences from the widespread alpha-proteobacterial symbiont, Wolbachia. Phylogenetic analysis placed the Wolbachia sequences into supergroups A, B, and F. Circularized mitogenomes were obtained for seven gerrids and two veliids, the first from these families for the African continent. This study suggests that aquatic Hemiptera may have a minor role (if any) in the spread of BU in Southwest Cameroon. Our metagenomic analysis provides new insights into the incursion of Wolbachia into aquatic environments and generated valuable resources to aid molecular taxonomic studies of aquatic Hemiptera.

Aquatic Hemiptera in Southwest Cameroon: Biodiversity of Potential Reservoirs of Mycobacterium ulcerans and Multiple Wolbachia Sequence Types Revealed by Metagenomics

Buruli ulcer (BU), caused by Mycobacterium ulcerans, is a neglected tropical disease associated with freshwater habitats. A variety of limnic organisms harbor this pathogen, including aquatic bugs (Hemiptera: Heteroptera), which have been hypothesized to be epidemiologically important reservoirs. Aquatic Hemiptera exhibit high levels of diversity in the tropics, but species identification remains challenging. In this study, we collected aquatic bugs from emerging foci of BU in the Southwest Region of Cameroon, which were identified using morphological and molecular methods. The bugs were screened for mycobacterial DNA and a selection of 20 mycobacteria-positive specimens from the families Gerridae and Veliidae were subjected to next-generation sequencing. Only one individual revealed putative M. ulcerans DNA, but all specimens contained sequences from the widespread alpha-proteobacterial symbiont, Wolbachia. Phylogenetic analysis placed the Wolbachia sequences into supergroups A, B and F. Circularized mitogenomes were obtained for seven gerrids and two veliids, the first from these families for the African continent. This study suggests that aquatic Hemiptera may have a minor role (if any) in the spread of BU in Southwest Cameroon. Our metagenomic analysis provides new insights into the incursion of Wolbachia into aquatic environments and generates valuable resources to aid molecular taxonomic studies of aquatic Hemiptera.