Clarification of the Rhipicephalus sanguineus group (Acari,Ixodoidea, Ixodidae). I. R. sulcatus Neumann, 1908 and R. turanicus Pomerantsev, 1936

For many years the biosystematic status of several species in the Rhipicephalus sanguineus group has been confused, with the result that they have often been misidentified. Over the years some 18 of these species have been synonymised with R. sanguineus (Latreille, 1806) itself. More recently four new species in the group have been described: R. guilhoni Morel & Vassiliades, 1963; R. moucheti Morel, 1964; R. bergeoni Morel & Balis, 1976; and R. camicasi Morel, Mouchet & Rodhain, 1976.The literature on this group is critically reviewed and the main systematic problems analysed. R. sulcatus Neumann, 1908 and R. turanicus Pomerantsev, 1936 are two species that were confused both morphologically and ecologically. This has resulted in erroneous conclusions regarding their host relationships and distributions. Integrated biological, morphological and ecological studies on these two species have been conducted. Cross-breeding experiments have proved that both are distinct taxonomic entities. Interbreedings between African and Cypriot strains of R. turanicus demonstrated marked heterosis.A scanning electron microscope was used to determine the main diagnostic morphological differences between the larvae, nymphae and adults of R. sulcatus and R. turanicus, and the morphological similarities between African and Cypriot strains of R. turanicus. Rhipicephalus sulcatus occurs widely in the Afrotropical region in wetter ecological habitats and most frequently parasitises hares, dogs and jackals. R. turanicus occurs more-or-less throughout the Afrotropical region in a wide range of climatic biotopes, as well as in parts of southern Europe, Arabia and Asia, and is most abundant in the late rainy/early dry seasons. It occurs on a wide range of domesticated and wildlife hosts, including ground-feeding birds.     

Ticks (Acari:Ixodidae) of the Blue and White Nile ecosystems in the Sudan with particular reference to theRhipicephalus sanguineus group

Twenty-four adult ixodid tick species, infesting livestock and some wildlife hosts along the Blue and White Nile in the Sudan, were identified. Three species,Boophilus geigyi, Rhipicephalus camicasi andR. bergeoni, were recorded for the first time from the Sudan. Tick numbers on indigenous breeds of cattle (Bos indicus) were relatively low, ranging between 17.1 and 40.5 per animal. Young cattle grazing with the herd carried significantly fewer ticks than older animals. With the exception ofB. annulatus andR. simus, which have extended their distribution further north into Blue Nile, Gezira and Khartoum Provinces, the distribution patterns of the most important cattle ticks have been relatively unchanged over the past 30 years.TheRhicicephalus sanguineus group was represented by six species.R. camicasi was the only species present on cattle, sheep and goats in the north in Kassala and Khartoum Provinces, whereas this species occurred sympatrically withR. guilhoni andR. turanicus further south in Gezira and Blue Nile Provinces. In the Southern Region of the Sudan onlyR. turanicus andR. guilhoni were present, the latter being by far the predominant species, with peak activity towards the end of the rains in the Jonglei Canal Area.R. bergeoni was collected once, from cattle near the Ethiopian border in Blue Nile Province, whereasR. sanguineus sensu stricto was collected throughout the study area, from domestic dogs only. Finally,R. sulcatus was found once on a hare.The distributions of the common tick species are correlated with the occurrence of tick-borne diseases of domestic animals and recommendations for the control of tick-borne diseases and their vectors in the Sudan are given.     

The “tropical lineage” of the brown dog tick Rhipicephalus sanguineus sensu lato identified as Rhipicephalus linnaei ()

The brown dog tick (Rhipicephalus sanguineus) parasitises dogs. Over the past decade, two distinct lineages have been recognised – R. sanguineus sensu lato “temperate lineage” and R. sanguineus sensu lato “tropical lineage”. The nominal taxon R. sanguineus (Latreille, 1806) was recently associated with the “temperate lineage”. We here identify the “tropical lineage” as Rhipicephalus linnaei (Audouin, 1826) using material from Australia, where no other Rhipicephalus species parasitises dogs. Whole genome sequencing of R. linnaei from Australia, Fiji and Laos, and assembly of their complete mitochondrial DNA (~15 kb) confirms the genetic identity and distinctness from all other known species within the brown dog tick species complex. Designation of the species R. linnaei is unequivocally supported by material available through the Australian National Insect Collection, Australia. Accordingly, we are formally justified in using R. linnaei for the “tropical lineage”.     

Mitochondrial DNA analysis of Rhipicephalus sanguineus s.l. from the western Iberian peninsula

Rhipicephalus sanguineus Latreille (1806) (Ixodida: Ixodidae) is considered to be the most widely distributed tick and to have a vast range of habitats and hosts, including livestock, pets and wildlife. In addition to morphological differences, recent investigations using approaches based on molecular genetic markers have revealed the existence of different R. sanguineus lineages in different geographic regions. In this study, 475 ticks collected from dogs in the western Iberian peninsula were studied both morphologically and genetically, using 12S and 16S rDNA and COI gene markers in order to clarify the controversy over the systematic status of R. sanguineus sensu lato in Western Europe, and to compare the present data with those sourced from studies conducted in other regions of the world. Despite the high morphometric variability, particularly on spiracles in both genders and in female genitalia, data obtained with different genetic molecular markers show very low variability, suggesting the existence of a unique species. In addition, the phylogenetic analysis showed genetic uniformity, supporting the existence of a well‐defined clade consisting of R. sanguineus s.l. specimens from Western Europe that are distinct from R. sanguineus s.l. from Africa. Furthermore, these data corroborate the existence of a polymorphic species in Western Europe, which requires to be consensually redescribed in view of its medical and veterinary importance in pathogen transmission.     

Synergism of thymol,carvacrol and eugenol in larvae of the cattle tick,Rhipicephalus microplus,and brown dog tick,Rhipicephalus sanguineus

The effects of combinations of the monoterpenes thymol and carvacrol and the phenylpropanoid eugenol in larvae of Rhipicephalus microplus (Canestrini, 1888) (Acari: Ixodidae) and Rhipicephalus sanguineus sensu lato (s.l.) (Acari: Ixodidae) were assessed by the larval packet test. The CompuSyn program was used to make qualitative assessments of the effects (synergistic, additive and antagonistic) of the associations. The effects of all combinations tested against R. microplus larvae were synergistic, with combination indices (CIs) <0.70. When tested against R. sanguineus, eight of the mixtures showed a synergistic effect (CI < 0.70); only the carvacrol + thymol mixture at LC₅₀ presented a moderate synergistic effect, with CIs between 0.70–0.90. This study is the first to determine the effects of the interactions of these substances in the control of these two tick species. The combinations of carvacrol + thymol, carvacrol + eugenol and thymol + eugenol have synergistic effects in R. microplus and R. sanguineus s.l. larvae.     

Rickettsial infections of dogs, horses and ticks in Juiz de Fora, southeastern Brazil, and isolation of Rickettsia rickettsii from Rhipicephalus sanguineus ticks

The present study was performed in an area endemic for Brazilian spotted fever (BSF) in Juiz de Fora, state of Minas Gerais, Brazil, during the years 2007 and 2008, when fatal cases of BSF (caused by Rickettsia rickettsii) were reported. Adult ticks (Acari: Ixodidae) identified as Rhipicephalus sanguineus (Latreille) and Amblyomma cajennense (Fabricius) were collected from dogs and horses, respectively, and tested by polymerase chain reaction (PCR). Overall, 13.1% of the Rh. sanguineus ticks and none of the A. cajennense were found to be infected with R. rickettsii. Two isolates of R. rickettsii were successfully established in Vero cell culture from two Rh. sanguineus ticks. An indirect immunofluorescence assay (IFA) using R. rickettsii antigens detected blood serological reaction to R. rickettsii in 67.9% (53/78) of dogs and 41.0% (16/39) of horses living in the study area. Larval offspring from two Rh. sanguineus engorged females, naturally infected by R. rickettsii, were reared to adult stage in the laboratory. All active stages (larvae, nymphs, adults) remained 100% infected by R. rickettsii, which was efficiently transmitted to naïve rabbits. Overall, the results of the present study indicate a potential risk for transmission of R. rickettsii to humans by Rh. sanguineus, an occurrence yet to be documented in Brazil.     

Abnormal development of Rhipicephalus sanguineus (Ixodidae)

Three malformed Rhipicephalus sanguineus specimenswere noticed in a tick laboratory colony. These specimens had different degreesof twining, from an almost fused individual (with two anal pores) to apartiallyfused adult male, with four spiracular plates. One female was a heart-shapedspecimen, with both body halves fused along a longitudinal axes, with fourspiracular plates and two anal pores.     

Off‐host aggregation in the non‐fed,female brown dog tick,Rhipicephalus sanguineus (Latreille), is induced by tick excreta and enhanced by low relative humidity

We report that Rhipicephalus sanguineus (Ixodida: Ixodidae) faeces and its main component, guanine, act as assembly pheromones in short‐range Petri plate bioassays. Arrestment activity in response to guanine was lower than that in response to natural excreta, indicating the presence of other active ingredients in natural excreta. The selective removal of appendages was used to establish the important roles played by the palps and the front pair of legs in the detection of the pheromone. Reaction to chemically pure guanine at varying concentrations occurred without a dose response; thus only the presence of guanine, not a critical amount, is required to induce assembly. Higher speed and intensity of clustering occurred at 33% relative humidity (RH). We conclude that female adults of R. sanguineus are more prone to assemble under dry conditions that match the arid microhabitats preferred by this species and that this tendency allows this tick to reside in human dwellings and dog kennels that maintain standards of comfort at 30–50% RH. Cleaning or removing tick excreta‐covered surfaces on which ticks aggregate from within and around human dwellings may prove useful as a means of interfering with the establishment of off‐host clusters of R. sanguineus.     

Polymorphic chromosomal inversions in Anopheles moucheti,a major malaria vector in Central Africa

Anopheles moucheti Evans (Diptera: Culicidae) is a major vector of malaria in forested areas of Central Africa. However, few genetic tools are available for this species. The present study represents the first attempt to characterize chromosomes in An. moucheti females collected in Cameroon. Ovarian nurse cells contained polytene chromosomes, which were suitable for standard cytogenetic applications. The presence of three polymorphic chromosomal inversions in An. moucheti was revealed. Two of these inversions were located on the 2R chromosome arm. The homology between the 2R chromosome arms of An. moucheti and Anopheles gambiae Giles was established by fluorescent in situ hybridization of six An. gambiae genic sequences. Mapping of the probes on chromosomes of An. moucheti detected substantial gene order reshuffling between the two species. The presence of polytene chromosomes and polymorphic inversions in An. moucheti provides a new basis for further population genetic, taxonomic and ecological studies of this neglected malaria vector.     

Seasonal dynamics of the brown dog tick,Rhipicephalus sanguineus,on a confined dog population in Italy

This study evaluated the seasonal dynamics of Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) on naturally infested dogs in a private shelter in southern Italy. From March to May 2008, 39 autochthonous mixed‐breed young dogs and 10 beagles were enrolled in the study. From March 2008 until March 2009, every 21 ± 2 days, 11 body sites of each dog were checked for ticks. At each follow‐up, the number of ticks, their developmental stage, sex and location on the dog's body were recorded. Adult ticks were found throughout the year, but immatures were absent in January and February. The adult tick population increased from July to August, whereas the load of immatures increased in early July and peaked in September, which suggests that R. sanguineus develops one generation per year in this area. The mean number of immature ticks per infested dog was higher than that of adults from March to October 2008. Ears, interdigital areas and armpits were the most frequent attachment sites of adult ticks. At the last follow‐up, a total of 2266 ticks were collected and identified as R. sanguineus. The results suggest that R. sanguineus develops one generation per year in the study area, but that it infests dogs in all seasons. This information should be taken into account when planning control programmes against this tick species and the pathogens it transmits.     

Experimental evaluation of birds as disseminators of the cosmopolitan tick Rhipicephalus sanguineus (Acari: Ixodidae)

Rhipicephalus sanguineus is believed to be the most widespread tick species of the world and its dissemination seems to rely on the diffusion of its main host, the dog. Empirical observations indicate that several bird species in urban areas regularly steal dog food. Such circumstances create a chance for R. sanguineus ticks to climb on birds and carry ticks to another site. In this work we evaluated experimentally the likelihood of birds (chicks) to either feed and/or carry R. sanguineus ticks from an infested site to another and to infest a host (rabbit) in the new location. Chicks were not suitable hosts for R. sanguineus ticks. Not a single adult tick engorged on chicks, yield as well as weight of engorged larvae and nymphs were very low and feeding period of these ticks was very long. However, a few larvae and, chiefly, nymphs were delivered to a new location either mechanically or after attachment and engorging total or partially on chicks. A few of these ticks fed successfully on rabbits. Further evidence on the capacity of birds to introduce R. sanguineus into non-infested dog settings should be provided by systematic examination of birds from urban areas, close to tick infested households.     

In vitro organogenesis in two dioecious species,Rumex acetosella L. and R. acetosa L. (Polygonaceae)

Callus cultures were established from dioecious plant species Rumex acetosella and R. acetosa, using cotyledons, hypocotyls and stem tips of aseptically germinated seedlings as primary explants. Cultures were also established from male and female R. acetosella adult plants, starting from vegetative lateral buds. Cell division was induced using a high 2,4-D concentration, while bud induction and multiplication were stimulated on a medium with high BAP/IAA ratio. Cotyledon fragments of both species produced only rhizogenic calli. Hypocotyl-derived calli of R. acetosella produced buds, while those of R. acetosa showed no bud forming response under these conditions. Bud multiplication occurred in stem tip cultures of both species and in lateral bud cultures of R. acetosella. Calli derived from male plants produced more buds than those from female. Shoots were easily rooted using IBA, and plantlets were effectively transferred to soil. Flowering was not induced in culture. The sex of regenerated male and female plants was not altered by the culture conditions.     

Complete Mitochondrial Genome Sequence Data Provides Genetic Evidence That the Brown Dog Tick Rhipicephalus sanguineus (Acari: Ixodidae) Represents a Species Complex

Ticks are blood-sucking ectoparasites of great medical and veterinary significance that can transmit bacteria, protozoa, fungi and viruses, and cause a variety of human and animal diseases worldwide. In the present study, we sequenced the complete mitochondrial (mt) genome of Rhipicephalus sanguineus from China (RSC) and compared with that of R. sanguineus from USA (RSU). Nucleotide sequence difference in the full mt genome was 11.23% between RSC and RSU. For the 13 protein-coding genes, comparison revealed sequence divergences at both the nucleotide (9.34-15.65%) and amino acid (2.54-19.23%) levels between RSC and RSU. In addition, sequence comparison of the conserved mt cox1 and cytb genes among multiple individual R. sanguineus revealed substantial nucleotide differences between RSC and RSU but limited sequence variation within RSC. Phylogenetic analysis of ticks based on the amino acid sequence data of 13 protein-coding genes revealed that R. sanguineus from China and R. sanguineus from USA represent sister taxa (likely separate species). Taken together, the findings support the recently proposal that R. sanguineus tick may represents a species complex of at least two closely related species.     

Potential of the insect growth regulator, fluazuron, in the control of Rhipicephalus sanguineus nymphs (Latreille, 1806) (Acari: Ixodidae): determination of the LD95 and LD50

Conventional pesticides have suffered two main drawbacks: (a) broad spectrum of action and (b) selection of target species resistant to the different active ingredients. Thus compounds that are less harmful to the environment and to human health, more specific and that do not induce resistance need to be developed. One alternative are insect growth regulators, such as fluazuron. The present study examined the efficacy of fluazuron (active ingredient of the acaricide Acatak®) and the sensitivity of Rhipicephalus sanguineus nymphs exposed to different doses of this chemical, and determined the lethal doses of fluazuron: 95% – LD₉₅ and 50% – LD₅₀. Different doses of fluazuron were applied in duplicates on the dorsal region of hosts (“pour on”). Distilled water was used in the control group. On the first day after the treatment with fluazuron, hosts were artificially infested with R. sanguineus nymphs. After engorgement, nymphs were removed, placed on Petri dishes, identified, and maintained in BOD incubator for 15 days. Dead R. sanguineus nymphs after the treatment with 13 different doses of fluazuron were quantified and the LD₉₅ was estimated to be 100 mg/kg and LD₅₀, 19.544 mg/kg (12.478–22.636), with a confidence interval of 95%. Nymphs of R. sanguineus were sensitive to fluazuron at various levels, indicating that this insect growth regulator (IGR) may be used to control this parasite in this stage of its biological cycle, reducing the significant damage it causes.     

Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater

The Branchiura of freshwater habitats, consisting of the valid genera Argulus, Chonopeltis, Dipteropeltis, and Dolops, presently contains 113 valid species and 12 undescribed species. The entire group is composed of ectoparasitic species that usually live on fishes. The highest diversity of genera and species occurs in the Afrotropical and Neotropical regions. The diversity of the freshwater species surpasses that of species in marine and brackish waters, but this could be due to inadequate study of the fauna of the latter habitats. One species, Argulus japonicus, has been introduced from east/southeast Asia to all other continents, except Antarctica. Studies of higher level relationships place the Branchiura with either Pentastomida or Ostracoda. Hypotheses about phylogenetic relationships of either the genera or species in this group have not been proposed. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment The present paper was intended as a very brief overview of the known diversity of the Branchiura in freshwaters only, and regrettably is deficient in mention of much information and many relevant citations pertaining to the group.     

A new species of Notodiaptomus Kiefer, 1936 (Copepoda,Diaptomidae) from the Amazon and Orinoco River Basins

A new species of Notodiaptomus, Notodiaptomus simillimus sp. nov., based on the female originally but erroneously assigned to Rhacodiaptomus calatus, and the corresponding newly discovered male, is described and illustrated in detail. The designation of the female as a new species of Notodiaptomus, and the recognition of the corresponding new male, is based on detailed morphological and biometrical studies, analysis of the known distribution and material from laboratory cultures. Morphological analysis demonstrated that the female shares the form of the external genital area and setal armature of the exopod 2 of leg 5 with other species of Notodiaptomus but they differ from those exhibited by species of Rhacodiaptomus. The distributions of the female and male assigned to Notodiaptomus simillimus sp. nov. overlap and include the Atabapo and Guaviare Rivers and Lago Calado. On the other hand, the distributions of the males and females originally assigned to R. calatus are disjunct and where they overlap, that is, in Lago Calado, each is accompanied by its respective mate. Laboratory cultures showed that, as expected, copulation did not occur between males and females described originally as R. calatus. This experiment demonstrated the existence of reproductive isolating mechanisms between these females and males, and confirmed the existence of two distinct genetic pools, i.e. two different species, the original males being of the valid R. calatus and the female a new Notodiaptomus. This female and the corresponding newly discovered male are N. simillimus. The new species is closely related to N. coniferoides.