Karyotypes and sex determination of ten species of phytoseiid mites (acarina: Mesostigmata)

The chromosomal picture was studied on early cleayage divisiona of 10 phytoseiid mites, using the aceto-orcein smear technique. Eggs of 9 species have either a haploid (4) or a diploid (8) number of chromosomes:Amblyseius rubini Swirski & Amitai,A. swirskii Athias,A. hibisci Chant,A. ohilenensis (Dosse),A. largoensis (Muma),Typhlodromus athiasae Porath and SwirskiT. rhenanus (Oud.) sensu latiore,Phytoseiulus persimilis Athias, andI phiseius degeneraus (Berlese).Typhlodromus oceidentalis Nesbitt has 3 and 6 chromosomes. In sections and smears of post embryonic stages belonging to mites representative of the four genera, a haploid number was found in males, whereas in females somatic cells contained 2n and ovaries n as well as 2n. Thus it is shown that sex is determined by the haplo-diploid (arrhenotokous) mechanism. Males differ from females in the structure of the interphase nuclei belonging to the central nervous system. Contribution from The Volcani Institute of Agricultural Research (NUIA.) Bet Dagan, Israel, 1968 Series, No. 1331-E.     

Fine structure of the spermatophore and spermatozoa in inseminated females of Pergamasus mites (Acari: Gamasida: Pergamasidae)

This study describes the spermatophore of Pergamasus mites after transfer into the female endogynial sac and modifications of the structure of the female-penetrating spermatozoa. The spermatophore is saccular and contains largely unmodified spermatozoa and variously structured secretions. The spermatozoa that leave the spermatophore reach the inner (proximal) end of the vaginal duct where they presumably escape from the genital tract to continue their route through the hemocoel into the ovarian tissue where fertilization occurs. During this transit, the structure of such spermatozoa changes considerably, in particular when in contact with the ovary. These alterations include modifications of the cell periphery and of certain inclusion bodies. Furthermore, the spermatozoa form protrusions that fit into corresponding invaginations of the somatic tissue of the ovary.     

On the ultrastructure and functional morphology of the male chelicerae (gonopods) in Parasitina and Dermanyssina mites (Acari: Gamasida)

Males of Parasitina and Dermanyssina (Gamasida = Mesostigmata) have chelicerae modified to function as gonopods. The slit-like spermatotreme in the movable digit of the chela in males of Parasitina was studied in three species: in Pergamasus quisquiliarum and Holoparasitus sp. a rather simple slit is indeed present, whereas in Vulgarogamasus kraepelini the structure is represented by a fine duct traversing the movable digit. The spermatodactyl studied in two phytoseioid species (Phytoseiulus persimilis, Blattisocius dentriticus) of Dermanyssina is a slender process arising from the movable digit and containing a fine duct which is formed by cuticular folds. The spermatodactyl of these species thus differs remarkably from that described in Veigaia sp. The diversity of these structures seen in the few taxa studied up to now is discussed under functional and systematic aspects.     

Karyotypes and sex-determination in spider mites (Tetranychidae)

The chromosomes of 13 species of spider mites (Tetranychidae) are determined using the aceto-orcein squash technique in order to establish the haplo-diploid sex-determination. 12 species showed the existence of haploid and diploid eggs:Neotetranychus rubi (Trägårdh) with 7 and 14 chromosomes;Eurytetranychus buxi (Garman) with 5 and 10;Bryobia sarothamni (Geijskes),Eotetranychus tiliarium (Joh. Hermann) andE. carpini (Oudemans) with 4 and 8;Panonychus ulmi (Koch),Schizotetranychus schizopus (Zacher),Oligonychus ununguis (Jacobi).Tetranychus hydrangeae Pritch. & Baker, T.pacificus McGregor,T. urticae Koch andT. cinnabarinus (Boisduval) with 3 and 6 chromosomes.The progeny of virgin females in 7 different species consisted of eggs with the haploid complement. One species was shown to be thelytokous, viz.Tetranycopsis horridus (Canestrini & Franzago), having a diploid number of 4 chromosomes. Some eggs of an inbred line ofT. urticae showed a patchwork quilt of odd polyploidy in embryonic tissue.     

Nasal mites (Gamasida: Rhinonyssidae) of Paroaria coronata (Miller) (Passeriformes: Emberezidae)

With the aim of identifying the species of nasal mites of Paroaria coronata (red-crested cardinal), the nasal cavity of 40 birds were examined. The nasal mites were identified as Ptilonyssus sairae de Castro and Sternostoma pirangae Pence, with 50% and 7.5% of prevalence, respectively. This is the first record of these mite species parasitizing P. coronata. This report also amplifies the area of occurrence of S. pirangae for Brazil and that of P. sairae for Rio Grande do Sul, Brazil.     

Chemoreception in four species of water mites (Acari: Hydrachnida): behavioural and morphological evidence

Silver nitrate staining of the solenidial and eupathidial sensilla on the palpi, tarsi and tibiae of legs I and II of Arrenurus acutus, Geayia ovata, Mideopsis reelfootensis and Albia caerulea, along with ultrastructural studies, showed that these setae have a porous shaft cuticle. These setae are hollow and contain dendrites in their lumens and more than one neuron is associated with each setae. Behavioural experiments supported the involvement of these sensilla in the perception of chemical cues from prey and sexual partners.     

Chemoreception in four species of water mites (Acari: Hydrachnida): behavioural and morphological evidence

Silver nitrate staining of the solenidial and eupathidial sensilla on the palpi, tarsi and tibiae of legs I and II of Arrenurus acutus, Geayia ovata, Mideopsis reelfootensis and Albia caerulea, along with ultrastructural studies, showed that these setae have a porous shaft cuticle. These setae are hollow and contain dendrites in their lumens and more than one neuron is associated with each setae. Behavioural experiments supported the involvement of these sensilla in the perception of chemical cues from prey and sexual partners.     

Competitive interactions among four pest species of earth mites (Acari: Penthaleidae)

Earth mites are major winter pests of a variety of crops and pastures in southern Australia. Competition between four earth mite species was investigated using field and shadehouse experiments. The influence of different plant hosts on the frequency and intensity of competitive interactions also were examined. This information is important, because control attempts that eradicate one species of mite could be directly followed by an increase in abundance of another earth mite species. There were strong effects of intraspecific competition on the reproductive rate of species, while interspecific interactions between Halotydeus destructor (Tucker) and Penthaleus species and between the three Penthaleus species also were detected. Competitive abilities were altered on the different plant types. On pasture, the competitive advantage swayed between Penthaleus major (Dugés), H. destructor, and Penthaleus falcatus (Qin & Halliday). Penthaleus sp. x was the strongest competitor in a mixture of wheat, Triticum aestivum (L.), and oats, Avena sativa (L.), whereas on canola, Brassica napus (L.), and bristly ox-tongue, Picris echioides (L.), P. falcatus, and H. destructor were superior competitors. These results suggest that competition is a strong force influencing the abundance of earth mites in the field and that host plant factors are important in shaping the type of interactions. This highlights the importance of identifying mite species when considering control options and suggests that effective control recommendations need to be developed for each individual species.     

Effect of prey density on sex ratio of two predacious mites, Phytoseiulus persimilis and Amblyseius womersleyi (Acari: Phytoseiidae)

The sex ratios of two phytoseiid mites, Phytoseiulus persimilis and Amblyseius womersleyi, were observed under various prey conditions. Upon consumption of abundant prey, both phytoseiids produced progeny in a female-biased sex ratio (approximately 0.8 females). When few prey were consumed, the sex ratio was lowered to 0.5 (the unbiased sex ratio). Under the conditions in which the unbiased sex ratio was observed, male and female progeny appeared in an alternating sequence. To determine the change in the sex ratio and the sequence of progeny, the size of eggs deposited by females under various prey conditions was first compared. Survivorship and developmental rate of progeny (immatures) hatched under ample and poor prey conditions were also examined. The eggs deposited under poor prey conditions were smaller than those deposited under ample prey conditions. This is an indication that the phytoseiid females did not invest extra energy into the eggs to secure survival of their progeny under poor prey conditions. The male and female progeny from the small eggs developed slowly, probably due to the small egg size. However, hatchability of the small eggs and survival of the immatures were the same as those of the normal eggs when the immatures were reared under ample prey conditions. The immature survivorship was little affected by the prey consumption rate of their mothers when the immatures were reared under poor prey conditions. We concluded that the sex ratio of phytoseiid mites is not determined by the characteristics of the progeny, but by the nutritious condition of the females.Exp Appl Acarol 22: 709723 © 1998 Kluwer Academic Publishers     

Ultrastructural Study of Spermatogenesis in Gamasid Mites (Acari,Gamasida)

Structural alterations accompanying the development of germ cells in representatives of two families of gamasid mites: Pergamasidae (Pergumasus barbarus. P. truatellus) and Parasitidae (Porrhostaspis lunulata) were examined by scanning electron microscopy. Spermatogenesis occurs in cysts containing two (P. lunuluta) or four spermatogonia (P. barbarus and P. truatellus) prior to meiosis. later arranged in a tetrahedral pattern. Meiosis produces 8 and 16 spermatids per cyst, respectively. Spermatids are located radially and elongate synchronously. Dimples appear at their acrosomal ends, soon replaced by peg-like structures surrounded by superficial ridges. The number of ridges which correspond to longitudinal ribbons can vary between and within species as well as between spermatids occupying one cyst. Our observations suggest some unknown mechanism which allows the spermatozoa to enter vasa deferentia in a unidirectional orientation.     

Karyotypes of eight species of phytoseiid mites of the genus Amblyseius Berlese (Acarina: Mesostigmata)

Chromosome studies, using the aceto-orcein smear technique, were made on embryonic tissue of eight Amblyseius Berlese species of the family Phytoseiidae. A haploid number of 4 chromosomes and a diploid of 8 were found.     

Temperature-dependent population growth of three species of stored product mites (Acari: Acaridida)

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions. In this study we investigated the effect of temperature, ranging from 5 to 35°C, on the population growth of three important mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of mites was observed after 3 weeks of cultivation, or after 6 weeks for those kept at low temperatures (5, 10, 12.5, and 15°C). The rate of increase was calculated for each temperature and species. The obtained data were fitted with polynomial models. The mite population growth rates increased with increasing moderate temperatures until 25°C, when r _m -values were 0.179, 0.177 and 0.190 for A. siro, A. ovatus and T. putrescentiae, respectively. The lower development threshold was 10.2°C in all three species. Estimated upper temperature threshold was higher in T. putrescentiae (49°C) than in A. siro and A. ovatus (38°C). Simulation of the rate of population increase under ideal conditions, using real temperature records obtained from Czech grain stores, showed that the pest mite populations increase only during 3.5 months within a typical 9-month storage season in Central Europe. These results indicate that control of mites, be it chemical, physical or biological, is recommended during the months when allergens and pests are produced, i.e. from September to mid November and in May.     

Geographical variation in the species Montivagum dihumerale and speciation in chigger mites (Acari: Trombiculidae)

Intraspecific morphological variation of the chigger mite species Montivagum dihumerale (Traub et Nadchatram, 1967) is studied. Eco-geographic rules of the variation are revealed. General size of mites is found to be increased along with the rise of the high-mountain character of the landscape in the collection localities. The numbers of idiosomal setae are varied independently from the size parameters and geographically close populations are proved to be the most similar by these characters. At the same time, numbers of the setae of different types play the leading role in the discrimination of closely related Montivagum species, while the eco-geographical rules have not been found in this genus at the level of interspecific differences. As a result, the hypothesis is set up, that a significant degree of isolation of local populations separated from each other by high mountain ranges of the Central Asia is the main factor of speciation in the genus Montivagum. Regional character of this speciation mode is confirmed by the comparison with other chigger mites taxa.     

Three new species of picobiine mites (Acari: Syringophilidae) parasitising African flycatchers (Aves: Muscicapidae)

Three new species of quill mites of the subfamily Picobiinae Johnston & Kethley, 1973 (Acari: Syringophilidae) are described from African flycatchers (Passeriformes: Muscicapidae): Picobia cichladusa n. sp. on Cichladusa arquata Peters and P. myrmecocichla n. sp. on Myrmecocichla arnotti (Tristram), both from Tanzania, and P. echo n. sp. on Cossypha heuglini Hartlaub from the Democratic Republic of the Congo.     

Further studies on water mites from Korea,with description of two new species (Acari,Hydrachnidia)

New records of water mites (Acari: Hydrachnidia) from streams in South Korea are presented. Two species are described as new to science: Torrenticola neodentifera sp. n. (Torrenticolidae) and Atractides ermilovi sp. n. (Hygrobatidae). Five species are reported as first records for Korea: Wandesia (Wandesia) reducta Tuzovskij, 1987, Wandesia (Wandesia) cf. rara Tuzovskij, 1990, Sperchon (Sperchon) orientalis Tuzovskij, 1990, Feltria (Feltria) kuluensis Tuzovskij, 1988 and Atractides (Atractides) constrictus (Sokolow, 1934). The latter species is redescribed and elevated to species rank based on new material from the Russian Far East.     

Further studies on karyotypes and sex determination of phytoseiid mites (Acarina: Mesostigmata)

Chromosome studies were made on embryonic tissues of eggs of 15 species of predaceous mites of the family Phytoseiidae belonging to six genera: Amblyseius Berlese, Seiulus Berlese, Typhlodromus Scheuten, Phytoseiulus Evans, Phytoseius Ribaga and Paragigagnathus Amitai et Grinberg. In 14 species, the chromosome numbers n=4, 2n=8 were found. In cytological studies of post-embryonic stages based on these results, the haplo-diploid (arrhenotokous) mechanism was established. In the species Amblyseius deleoni Muma et Denmark, which was found to be thelytokous, only metaphases with 8 chromosomes were found.     

Astigmatid mites (Acari: Sarcoptiformes) of forensic interest

This paper reviews the occurrence of mites of the infraorder Astigmata in situations involving the legal system, particularly in the area of medicocriminal entomology. Species in the families Acaridae, Lardoglyphidae and Histiostomatidae are encountered in stored food products and in vertebrate carrion, including human remains. Some of these species are incidentals, whereas others are obligate necrophages. Phoretic associations between these mites and insects allows for rapid dispersal and colonization of such patchy resources.